1 Division of Nephrology, Department of Internal Medicine, University of Arkansas for Medical Sciences and John McClellan Memorial Veterans Hospital, Little Rock, Arkansas 72205; 2 Department of Pathology, Duke University Medical Center Durham, North Carolina 27710; 3 Laboratory of Metabolism, National Cancer Institute, Bethesda, Maryland 20892; and 4 Department of Geriatrics, University of Arkansas for Medical Sciences and John McClellan Memorial Veterans Hospital, Little Rock, Arkansas 72205
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Regulation of fatty acid
-oxidation (FAO) represents an important mechanism for a sustained
balance of energy production/utilization in kidney tissue.
To examine the role of stimulated FAO during ischemia, Etomoxir
(Eto), clofibrate, and WY-14,643 compounds were given 5 days prior to
the induction of ischemia/reperfusion (I/R) injury. Compared
with rats administered vehicle, Eto-, clofibrate-, and WY-treated rats
had lower blood urea nitrogen and serum creatinines following I/R
injury. Histological analysis confirmed a significant amelioration of
acute tubular necrosis. I/R injury led to a threefold reduction of mRNA
and protein levels of acyl CoA oxidase (AOX) and cytochrome P4A1, as
well as twofold inhibition of their enzymatic activities. Eto treatment
prevented the reduction of mRNA and protein levels and the inhibition
of the enzymatic activities of these two peroxisome
proliferator-activated receptor-
(PPAR
) target genes during I/R
injury. PPAR
null mice subjected to I/R injury demonstrated
significantly enhanced cortical necrosis and worse kidney function
compared with wild-type controls. These results suggest that
upregulation of PPAR
-modulated FAO genes has an important role in
the observed cytoprotection during I/R injury.
carnitine palmitoyltransferase; fatty acid oxidation; ischemia/reperfusion
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
THE PROCESS of -oxidation of long-chain fatty acids
(LCFA) occurs predominantly in the S3 segment of the proximal tubule and represents an important mechanism for energy production in the
kidney cortex. Fatty acid
-oxidation (FAO) enzymes exist in the
mitochondria, peroxisomes, and microsomes of this nephron segment (1,
14, 15). We have recently shown that the inhibition of carnitine
palmitoyltransferases (CPTs), mitochondrial enzymes involved in FAO,
protects proximal tubules against hypoxia-induced cell death (21).
Recent studies suggest that inhibitors of mitochondrial CPT I activity
can work also as direct ligands for a peroxisome proliferator-activated
receptor-
(PPAR
) (5, 10, 27). Ligand-mediated activation of this
novel nuclear transcription factor upregulates the activity of the
peroxisomal enzyme acyl CoA oxidase (AOX) and microsomal
cytochrome P-450 (CYP). This regulation occurs through binding
of the ligand-receptor complex to a peroxisome proliferator responsive
element in target genes (4, 9, 31).
Given the existing information of the rapid inhibition of enzymatic
activities of microsomal and peroxisomal FAO enzymes during ischemia/reperfusion (I/R) injury to the kidney (6, 7, 23, 29),
in the present studies the role of the stimulation of FAO enzymes on
kidney function, enzymatic activity, protein levels, and expression of
peroxisomal and microsomal FAO enzymes following I/R injury to the
kidney was investigated. For these studies we used Etomoxir (Eto,
2-[6-(4-chlorophenoxy)hexyl]-oxiranecarboxylate), a compound that irreversibly binds to the active catalytic site of CPT
I, thereby inhibiting its activity, but also upregulates FAO in
peroxisomes and microsomes (16, 26). We also used clofibrate and
[4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid
(WY-14,643), two compounds known to stimulate FAO. The studies
presented here extend the observations on the beneficial effect of
manipulating FAO enzymes during hypoxia in isolated proximal tubules.
In addition, these studies suggest that preservation of kidney function
during ischemia may involve increased mRNA, protein levels, and
enzyme activity of peroxisomal AOX and microsomal CYP4A1 enzymes.
Histological analysis of kidney tissue of Eto-treated animals compared
with untreated animals demonstrated significant protection against the
development of acute tubular necrosis (ATN) after I/R injury. Additional studies that support the protective role of induction of
PPAR-regulated enzymes on kidney function were obtained in PPAR
null mice. These studies demonstrate greater kidney dysfunction associated with severe cortical necrosis during I/R injury in PPAR
null animals compared with wild-type controls. We propose that
metabolic modulation of the expression of FAO enzymes has an important
role in determining preservation of kidney function during acute
ischemic renal failure.
![]() |
EXPERIMENTAL PROCEDURES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Induction of ATN. Male Sprague-Dawley rats weighing 200-250 g were obtained from Harlan. Rats were fed ad libitum with a Pro Lab diet (Purina) and housed in an animal facility at 21°C. Under anesthesia using Nembutal (50 mg/kg body wt), we exposed the retroperitoneal cavity via a lumbar incision, and both renal arteries were identified and freed by blunt dissection. Microvascular clamps were placed on both renal arteries to effect complete cessation of blood flow. The core temperature of these animals was maintained at 37°C by placing them on a homeothermic table. After 45 min, the clamps were removed with return of blood flow to the kidneys. Visual inspection corroborated successful reperfusion with a change in the color of the kidneys from dark blue to bright red after releasing the clamps. Postsurgery, the animals were kept for at least 3 h in a 37°C incubator to ensure that postoperative recovery was satisfactory.
Administration of Eto, clofibrate, and WY-14,643 compounds. Sham-operated animals and rats subjected to I/R were treated with Eto for 5 days (25 mg/kg body wt). Eto sodium (Research Biochemicals International, Natick, MA) was dissolved in distilled water and administered intraperitoneally. Clofibrate (150 mg/kg body wt, Sigma) and WY-14,643 (45 mg/kg body wt, Chemsyn Science Laboratories) were dissolved in corn oil and given intraperitoneally for 5 days. The last injection was given 4 h before the induction of ischemic injury.
Measurement of renal function. Tail vein blood was obtained before induction of ATN, after 45 min of ischemia, and after 24, and 48 h of reperfusion for measurement of serum creatinine, blood urea nitrogen (BUN), and electrolytes.
Fluorometric assay of palmitoyl CoA oxidase activity. Kidney homogenates were prepared in SET buffer (0.25 M sucrose, 1 mM EDTA, and 10 mM Tris · HCl, pH 7.40). Palmitoyl CoA oxidase activity was assayed fluorometrically with homovanillic acid in the presence of peroxidase to give a fluorescent dimer (32). The assay was performed in a final volume of 500 µl containing 5 mM homovanillate, 0.1 mg peroxidase type II, 0.02 mM FAD, 0.1 mM palmitoyl CoA, and 80 mM glycylglycine, pH 8.30. The reaction was started by adding 50 µl of sample homogenate (0.1-0.2 mg of proteins) into the reaction mixture, which was incubated at 26°C. At 5, 10, 20, and 40 min, 75 µl of the mixture was transferred into 1.5 ml of 0.5 M sodium bicarbonate buffer (pH 10.7) and read immediately, utilizing a fluorescence spectrometer at excitation wavelength of 325 nm and emission wavelength of 425 nm. A blank without the substrate (palmitoyl CoA) was set up for each sample assay. The enzyme activity was expressed as arbitrary units per milligram of protein per minute. The protein content of homogenates was assayed with Bio-Rad reagents as described by the manufacturer.
CYP4A1 enzyme activity assay. Microsomal fractions from kidney
cortex homogenates were prepared by differential centrifugation between
10,000 g and 100,000 g, and the final protein
concentration was adjusted to 5-10 mg/ml. The preparation was used
immediately for the assay. CYP4A activities were measured by monitoring
the conversion of 14C-labeled lauric acid into
-hydroxylauric acids in 1 ml of 50 mM Tris-HCl (pH 7.4)
in the presence of 0.2 mM NADPH at 37°C for 5 min (8). The reaction
was stopped by adding 0.20 ml of 1 N HCl and vortexing. The lipids were
extracted with 0.5 ml of ether twice, dried in a stream of nitrogen
gas, and then separated by thin-layer chromatography (TLC) using
benzene:ether:ethanol:formic acid (90:10:1:0.2) as described previously
(22). The bands corresponding to lauric acid and
-hydroxylauric
acids were scraped separately and counted. The enzymatic activity was
expressed as nanomoles of
-hydroxylauric acid produced per minute
per milligram of microsomal protein.
Western blot analysis. Rat kidney cortex tissue from every
experimental condition was homogenized with glass Teflon homogenizer in
ice-cold SET buffer (0.25 M sucrose, 1 mM EDTA, and 10 mM Tris HCl, pH
7.4). Organelles were isolated by differential
centrifugation. Mitochondria and microsome fractions were collected at
10,000 g (10 min) and 40,000 g (60 min). The
supernatant of 40,000 g was considered as cytosol in these
experiments. All of these fractions were used immediately or kept at
70°C. Eighty micrograms of protein of each microsome
fraction or cytosol fraction was precipitated with 70% ice-cold
acetone. The pellets were solubilized in 20 µl of SDS sample buffer
and heated in boiling water for 3 min. SDS-PAGE was conducted with 10%
gels in a Bio-Rad mini-Gel II apparatus at 200 V for 36 min. Protein
was transferred to polyvinylidene difluoride (PVDF)
membrane in Tris-glycine buffer and rinsed with Tris-buffered saline
twice, then blocked in 4% dry milk in Tris-Tween-buffered saline for 1 h at room temperature.
To measure changes in CYP4A1 protein levels by Western blot analysis, the membranes were incubated with goat anti-rat CYP4A1 serum obtained from Daiichi Pure Chemicals (1:500 in 4% dry milk) for 2 h at room temperature. Peroxidase-conjugated rabbit anti-goat IgG (1:10,000 dilution with 4% dry milk) was used as the secondary antibody, followed by ECL staining (Amersham). To measure changes in AOX protein, rabbit antiserum raised against rat AOX was used (19). The primary antibody was diluted 1:10,000 in 4% dry milk with incubation was at room temperature for 4 h. Peroxidase-conjugated goat anti-rabbit IgG (Bio-Rad) was used as the secondary antibody (1:5,000 dilution in 4% dry milk), and the AOX protein was visualized by ECL staining. Western blot images were analyzed and quantitated with Adobe Photoshop 3.0 and the NIH imager program.
Northern blots. Rat kidney total RNA was purified by Polytron sonic disruption of frozen kidney tissue in TRIzol reagent as described by the manufacturer (GIBCO-BRL, Life Technologies), and 30 µg was electrophoresed on a 1% agarose gel containing 2.2 M formaldehyde, transferred to a nitrocellulose membrane using 20 × SSC (3 M NaCl, 0.3 M sodium citrate, pH 7), and fixed to the membrane by baking at 80°C for 2 h in a vacuum oven. Membranes were then prehybridized in a hybridization buffer containing 50% formamide, 6× SSPE, 5× Denhardt's solution, 100 µg/ml salmon sperm DNA, and 0.5% SDS. Hybridization probes were labeled with [32P]dCTP through random priming. Three cDNA probes were used for sequential Northern blot analysis. These cDNA probes encode rat peroxisomal AOX, rat microsomal CYP4A1, and GAPDH (20). The sizes of these probes were 1,037, 2,200, and 905 bp, respectively. GAPDH was used as a control. After overnight hybridization at 65°C, the nitrocellulose membranes were washed once for 30 min with 2× SSC/0.5% SDS and then twice with 0.1× SSC/0.1% SDS for 30 min. Autoradiography periods ranged from 24-96 h, depending on the signal strength.
Histopathological assessment. Kidneys were bisected, fixed in 3.7% phosphate-buffered neutral formaldehyde, dehydrated with serial alcohols, and embedded in paraffin. Three-micrometer-thick paraffin sections were stained with hematoxylin and eosin and a periodic acid-Schiff (PAS) method (17). The 12 morphological features described by Solez and coworkers (28) were evaluated in a masked fashion as follows: leukocyte accumulation in the vasa recta, tubular necrosis (presence of necrotic cells, apparently denuded areas of tubular basement membrane, or ruptured tubular basement membranes); tubular regeneration; mitotic figures in tubular cells; dilatation of Bowman's space with retraction of the glomerular tuft ("acute glomerular ischemia"); loss of PAS-positive tubular brush border; "tubularization" of the parietal epithelium of Bowman's capsule; tubular casts; interstitial inflammation; interstitial edema; tubular dilatation; and prominence of the juxtaglomerular apparatus. The morphological changes were graded on a scale from 0 to 2, where 0 = none, 0.5 = minimal, 1 = mild, 1.5 = moderate, and 2 = marked (11).
I/R on PPAR (
/
)
and wild-type mice. Male mice, homozygous wild-type (+/+) or
PPAR
null (
/
), pure Sv1129 background, 10-12 wk
of age (13), were housed in plastic cages in a temperature- and
light-controlled environment. Groups of mice (3 mice/group) were
subjected to either sham or I/R injury. Mice were preanesthetized with
isoflurane in a bell jar and then anesthetized using isoflurane discharged through a veterinary small animal flowmeter at 1.5% isoflurane mixed with oxygen. Temperature was regulated through a
servo-controlled heating pad and light, with use of a rectal temperature probe. The skin corresponding to the abdominal area was
shaved and cleaned. A midline incision was made. The left renal hilum was exposed by gentle traction under loop (×3.5)
magnification. The left hilum was encircled with a 5-0 silk and
polyethylene PE-90 tubing. Ischemia of the left
kidney was confirmed by visualization of color change of the kidney
parenchyma. The right renal hilum was similarly exposed and occluded.
Occlusion was carried out for 45 min while the mouse continued under
isoflurane anesthesia and temperature regulation. After
45 min of ischemia, the clamps were removed, and visual
confirmation of reperfusion was made. The abdomen was closed with
running 4-0 silk, and the mouse was awakened. Animals were kept in
metabolic cages for the remaining time of the experiment and killed
after 24 h of reperfusion. Serum creatinine levels were measured using
tail vein blood to monitor changes in renal function. One kidney from
each mouse was placed into buffered fixative for histological examination.
Statistical analysis. All experiments were performed in at least four animals per each condition. Statistical significance was determined by the paired Student's test. P < 0.05 was considered statistically significant.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Kidney function was evaluated in animals subjected to sham surgery
(controls) and to I/R by determining blood urea nitrogen (BUN) and
serum creatinine levels. Compared with rats administered vehicle, rats
administered Eto prior to I/R had significantly lower serum creatinine
and BUN levels (Fig. 1,
A and B). Because oxirane compounds like Eto have been
shown to be direct ligands for PPAR (5), we next performed studies
in animals pretreated for 5 days with fibrate compounds prior to I/R
injury. Two known PPAR
activators, clofibrate and WY-14,643 had an
effect similar to Eto in protecting kidney function during acute
ischemic renal failure. Figure 1C shows that serum creatinine
levels were much higher in rats administered vehicle (corn oil)
subjected to I/R compared with clofibrate and WY-treated rats. Because
of the marked improvement on kidney function using Eto
and the observation of increased mRNA and protein levels of FAO in
kidney tissue using clofibrate and WY (results not shown), the next
series of experiments was conducted using Eto-treated animals prior to
I/R injury.
|
In addition to biochemical assessment of kidney function,
histopathological alterations in the kidneys were evaluated 24 h after
renal perfusion was reestablished, as described in EXPERIMENTAL PROCEDURES. The morphological changes were graded on a scale from 0 to 2 where 0 = none, 0.5 = minimal, 1 = mild, 1.5 = moderate, and 2 = marked as described (28). The results, shown in Fig. 2 and Table
1, demonstrate that rats pretreated with
Eto when subjected to I/R injury exhibited minimal to mild tubular
necrosis compared with rats not receiving Eto, which exhibited marked
tubular necrosis (P < 0.005). The number of casts and the
degree of tubular dilatation were significantly reduced by pretreatment
with Eto (P < 0.05), as would be expected for rats with less
ATN. Thus histological changes correlated with preservation of kidney
function (lower serum creatinine and BUN) in animals treated with Eto.
|
|
To confirm that Eto administered intraperitoneally was capable of
inhibiting renal CPT, CPT activity was measured following I/R in
vehicle- or Eto-treated animals. CPT I activity did not change
significantly during ischemia; baseline CPT I activity went
from 1,195 ± 34 to 1,092 ± 40 dpm · min1 · mg
protein
1 at the end of
I/R. Pretreatment with Eto for 5 days prior to ischemia
resulted in marked reduction (65%) in the levels of CPT I activity
compared with ischemic animals pretreated with vehicle alone (Fig.
3). Thus the concentration and route of
administration of Eto used in these studies effectively inhibited
kidney CPT activity.
|
Previous studies have demonstrated that I/R injury is accompanied by a
reduction in the activities of AOX and CYP4A1. Therefore, to examine
the potential effect of Eto on stimulating FAO in the kidney during I/R
we evaluated mRNA, protein levels and enzymatic activities of palmitoyl
CoA oxidase. Northern blot analyses of AOX and CYP4A1 mRNAs (Fig.
4, A-C)
demonstrated that both mRNAs were reduced by I/R and that pretreatment
with Eto restored the levels to those of control rats. Western blot
analyses of kidney proteins demonstrated similar changes in protein
levels of AOX and CYP4A1 (Fig.
5, A-C).
Enzymatic activity (Fig. 6) paralleled the
changes in mRNA and protein levels.
|
|
|
To more directly determine the role of PPAR in I/R injury, PPAR
null mice were subjected to I/R injury and compared with wild-type mice
treated in an identical manner. PPAR
null mice have been shown to
lack the induction of AOX and CYP4A1 gene transcription when
administered peroxisome proliferators or CPT inhibitors (3, 13).
Compared with wild-type mice, the PPAR
null mice exhibited significantly greater kidney dysfunction after I/R injury, as assessed
by higher serum creatinine levels and enhanced tubular necrosis at the
corticomedullary junction (Fig. 7,
A-C). No differences in baseline creatinines were
observed between sham-operated wild-type and null mice.
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Previous studies demonstrated the inhibition of peroxisomal enzymes
including AOX and CYP4As during renal ischemia. This inhibition was initially attributed to excessive accumulation of hydrogen peroxide
(7, 29). Those studies showed that progressive amounts of
ischemia from 30 to 90 min led to 40-50% inhibition of
AOX enzyme activity. Reperfusion for 24 h following 90 min of
ischemia led to a further decrease (37 and 63%, respectively)
in the amount of 72- and 52-kDa protein subunits of AOX compared with
controls. Similar observations were reported for CYP4A protein and
enzyme activity (29). Our studies also showed ~50% reduction in
enzyme activities of both AOX and CYP4A1 after 45 min of
ischemia and 24 h of reperfusion, consistent with previous
studies (7, 29). Those earlier studies also concluded that inhibition
of peroxisomal -oxidation enzymes was caused by I/R-induced
proteolysis. Our data revealed a significant reduction (60%) in the
protein levels of AOX, as well CYP4A1 in the rat kidney. In addition, a
concomitant reduction in the mRNA levels of these two genes was
detected after I/R in our studies. Therefore, our results suggest that
the inhibition of enzymatic activity of AOX and CYP4A1 which
accompanies ischemic acute renal failure (ARF) can also occur as a
result of reduced mRNA levels and subsequent decreased protein
synthesis of these two enzymes in the rat kidney.
Previous studies have documented changes in gene expression during ischemic and nephrotoxic renal failure (25). Reduced gene expression has been established for prepro-epidermal growth factor (preproEGF), Tamm-Horsfall protein (TH), and Kid-1 during ischemic ARF (18, 24, 37). These genes are expressed in the distal tubule. Our studies are the first to demonstrate ischemia-induced decreased expression of fatty acid oxidation genes, which are preferentially expressed in the proximal tubule (1). A general paradigm which could explain changes in gene expression is that regeneration following postischemic injury recapitulates renal development. Thus cells that enter the cell cycle after an ischemic insult express proteins such as vimentin (30, 36) that are expressed in those cell types only in early stages of renal development. With regard to the regulation of expression of genes encoding peroxisomal FAO enzymes, previous studies have demonstrated that mature oxidative enzyme levels are reached progressively over the first weeks of postnatal life in the developing proximal tubule and that thyroid hormones represent an essential factor in the acquisition of these metabolic patterns that characterize the fully differentiated proximal tubule (35). Thus the reduced expression of each of these peroxisomal FAO genes during renal injury may be a necessary component of the regenerative response that characterizes the "undifferentiated state" of the proximal tubule after I/R injury.
The mechanism by which Eto as well as clofibrate and WY compounds
restore mRNA, protein, and enzyme activities of palmitoyl CoA oxidase
and CYP4A1 close to those levels observed in animals not
subjected to I/R is likely mediated through PPAR. Eto, like other
oxirane compounds including tetradecylglycidate (TDGA), can directly
bind and activate PPAR
(5), leading to increased transcription of
genes encoding peroxisomal enzymes. We performed additional studies
(Fig. 1C) in which we observed significant protection of kidney
function during ischemia when animals were pretreated with
clofibrate or WY, two compounds known to induce mRNA levels of
peroxisomal and microsomal enzymes via activation of a PPAR
nuclear
receptor (13). Moreover, renal damage following I/R in PPAR
null
mice was more pronounced than in identically treated wild-type mice.
Together these data indicate PPAR
activation as the underlying
mechanism whereby Eto, clofibrate, and WY treatment results in
protection of renal function after ischemia.
One of the most important effects shown in this study is the remarkable
protection Eto affords against necrosis of the proximal tubule during
ischemia, as shown by the histological data. All kidneys of
rats subjected to I/R treated with vehicle (controls) exhibited marked
epithelial necrosis of tubules in the inner cortex/outer stripe of the
medulla, the zone corresponding to the S3 segment of the proximal
tubule (34). This confirms previous observations that S3 cells
selectively undergo progressive injury and death following I/R in the
rat (34). In contrast to the control animals, Eto-treated rats had only
mild necrosis of the tubular epithelial cells. This observation
confirms previous in vitro experiments that showed protection against
cell death during hypoxia in freshly isolated proximal tubules using
oxfenicine and glyburide, two compounds known to modulate FAO in kidney
tissue (21). In those studies, we demonstrated that CPT inhibition was
accompanied by inhibition of -fodrin proteolysis and decreased
accumulation of toxic amphiphilic metabolites. The present data
do not provide a definitive cellular mechanism by which preservation of
peroxisomal and microsomal FAO enzymes during I/R injury will
eventually prevent necrotic cell death. However, this cytoprotecion
could be the result of a complex interaction between FAO enzymes and
cytoskeletal proteins. Recent proposed models for the regulation of CPT
activity in the liver suggest an active role of calmodulin-dependent
kinases and cytoskeletal proteins (33).
In addition, an increase on acyl CoA activity leads to the increased
catabolism of long-chain fatty acyl CoA compounds. The accumulation of this LCFA metabolite along with long-chain
acylcarnitines could potentially lead to inhibition of the Na-K-ATPase
and ion transport in kidney cells during ischemia (21). On the
other hand, inhibition of CYP4A1 -oxidation of fatty acids during
ischemia could lead to lack of production of
20-hydroxyeicosatetraenoic acid (20-HETE). This compound has been shown
to cause vasoconstriction; therefore, having this compound produced by
stimulation of PPAR
and CYP4A1 enzyme has the potential to improve
glomerular filtration rate during ischemia.
Although the effects observed in in vivo organ studies are usually more
difficult to study than the effects observed in isolated tubules, we
demonstrated that in both models of ischemic injury (hypoxic tubules
and bilateral renal artery occlusion), protection of kidney function
and preservation of membrane integrity of proximal tubules is
associated with the preservation of FAO enzymes. These studies strongly
suggest that the induction of peroxisomal FAO during ischemic injury is
important to maintain structure and kidney function. This is
particularly important since nuclear receptors such as PPAR and
PPAR
are abundantly expressed in distinct nephron segments (2, 39).
These nuclear receptors could be modulated by tissue-specific
coactivators, corepressors (38), or various ligands including fatty
acids. Interestingly, fatty acids and prostaglandins have been shown to
be ligands for PPARs (12). Isolation and identification of
ischemic-induced regulation of levels of coactivators, corepressors, or
native endogenous PPAR ligands in the kidney should help to elucidate the molecular mechanisms by which I/R leads to downregulation of FAO
enzymes and help provide therapeutic strategies to overcome renal injury.
![]() |
ACKNOWLEDGEMENTS |
---|
We acknowledge Dr. Toshifumi Aoyama for providing acyl CoA antibodies.
![]() |
FOOTNOTES |
---|
This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grant R01-DK-52926 and a by a Veterans Affairs Merit Review Award to D. Portilla.
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests and other correspondence: D. Portilla, Dept. of Medicine, Division of Nephrology, Univ. of Arkansas for Medical Sciences 4301 West Markham, Slot 501, Little Rock, AR 72205-7199 (E-mail: portilladicier{at}exchange.vams.edu).
Received 20 November 1998; accepted in final form 15 November 1999.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Bell, DR,
Bars RG,
and
Elcombe CR.
Differential tissue-specific expression and induction of cytochrome P450IVA1 and acyl-CoA oxidase.
Eur J Biochem
206:
979-986,
1992[Abstract].
2.
Braissant, O,
Foufelle F,
Scotto C,
Dauca M,
and
Wahli W.
Differential expression of peroxisome proliferator activated receptors (PPARs): tissue distribution of PPAR,
and
in the adult rat.
Endocrinology
137:
354-366,
1996[Abstract].
3.
Djouadi, F,
Weinheimer CJ,
Saffitz JE,
Pitchford C,
Bastin J,
Frank Gonzalez J,
and
Kelly DP.
A gender-related defect in lipid metabolism and glucose homeostasis in peroxisome proliferator activated receptor alpha deficient mice.
J Clin Invest
102:
1083-1091,
1998
4.
Dreyer, C,
Krey G,
Keller H,
Givel F,
Helftenbein G,
and
Wahli W.
Control of the peroxisomal beta-oxidation pathway by a novel family of nuclear hormone receptors.
Cell
68:
879-887,
1992[ISI][Medline].
5.
Forman, BM,
Chen J,
and
Evans RM.
Hypolipidemic drugs, polyunsaturated fatty acids, and eicosanoids are ligands for peroxisome proliferator activated receptors and
.
Proc Natl Acad Sci USA
94:
4312-4317,
1997
6.
Gulati, S,
Singh AK,
Irazu C,
Orak J,
Rajagopalan PR,
Fitts CT,
and
Singh I.
Ischemia-reperfusion injury: biochemical alterations in peroxisomes of rat kidney.
Arch Biochem Biophys
295:
90-100,
1992[ISI][Medline].
7.
Gulati, S,
Ainol L,
Orak J,
Singh AK,
and
Singh I.
Alterations of peroxisomal function in ischemia-reperfusion injury of rat kidney.
Biochim Biophys Acta
1182:
291-298,
1993[ISI][Medline].
8.
Imaoka, S,
Tanaka S,
and
Funae Y.
and (
-1) Hydroxylation of lauric acid and arachidonic acid by rat renal cytochrome P-450.
Biochem Int
18:
731-740,
1989[ISI][Medline].
9.
Juge-Aubry, C,
Pernin A,
Favez T,
Burger AG,
Wahli W,
Meier CA,
and
Desvergne B.
DNA binding properties of peroxisome proliferator-activated receptor subtypes on various natural peroxisome proliferator response elements. Importance of the 5' flanking region.
J Biol Chem
272:
25252-25259,
1997
10.
Kaikaus, RM,
Sui Z,
Lysenko N,
Wu NY,
Ortiz de Montellano PR,
Ockner RK,
and
Bass NM.
Regulation of pathways of extramitochondrial fatty acid oxidation and liver fatty acid-binding protein by long chain monocarboxylic fatty acids in hepatocytes. Effect of inhibition of carnitine palmitoyltransferase I.
J Biol Chem
268:
26866-26871,
1993
11.
Kelleher, SP,
Robinette JB,
Miller F,
and
Conger JD.
Effect of hemorrhagic reduction in blood pressure on recovery from acute renal failure.
Kidney Int
31:
725-730,
1987[ISI][Medline].
12.
Kliewer, SA,
Forman BM,
Blumberg B,
Ong ES,
Borgmeyer U, DJ,
Mangelsdorf Umesono K,
and
Evans RM.
Differential expression and activation of a family of murine peroxisome proliferator-activated receptors.
Proc Natl Acad Sci USA
91:
7355-7359,
1994[Abstract].
13.
Lee, SST,
Pineau T,
Drago J,
Lee EJ,
Owens JW,
Kroetz DL,
Fernandez-Salguero PM,
Westphal H,
and
Gonzalez FJ.
Targeted disruption of the isoform of the peroxisome proliferator-activated receptor gene in mice results in abolishment of the pleiotropic effects of peroxisome proliferators.
Mol Cell Biol
15:
3012-3022,
1995[Abstract].
14.
LeHir, M,
and
Dubach UC.
Distribution of two enzymes of -oxidation of fatty acids along the rat nephron.
In: Biochemistry of Kidney Functions, edited by Morel F.. Amsterdam: Elsevier Biochemical, 1982, p. 82-94. (INSERM Symposium 21)
15.
LeHir, M,
and
Dubach UC.
Peroxisomal and mitochondrial -oxidation in the rat kidney. Distribution of fatty acyl coenzyme A oxidase and 3-hydroxyacyl-coenzyme A dehydrogenase activities along the nephron.
J Histochem Cytochem
30:
441-444,
1982[Abstract].
16.
Lopaschuk, GD,
Wall SR,
Olley PM,
and
Davies NJ.
Etomoxir, a carnitine palmitoyltransferase I inhibitor, protects hearts from fatty acids induced ischemic injury independent of changes in long chain acylcarnitine.
Circ Res
63:
1036-1043,
1988[Abstract].
17.
McManus, JFA
Histological and histochemical uses of periodic acid.
Stain Technol
23:
99-108,
1948[ISI].
18.
Norman, JT,
Bohman RE,
Fischmann G,
Bowen JW,
McDonough A,
Slamon D,
and
Fine LG.
Patterns of mRNA expression during early cell growth differ in kidney epithelial cells destined to undergo compensatory hypertrophy versus regenerative hyperplasia.
Proc Natl Acad Sci USA
85:
6768-6772,
1988[Abstract].
19.
Osumi, T,
Hashimoto T,
and
Ui N.
Purification and properties of acyl CoA oxidase from rat liver.
J Biochem
87:
1735-1746,
1980[Abstract].
20.
Peters, JM,
Zhou Y-C,
Ram PA,
Lee SST,
Gonzalez FJ,
and
Waxman DJ.
Peroxisome proliferator activated receptor- required for gene induction by dehydroepiandrosterone-3-
sulfate.
Mol Pharmacol
50:
67-74,
1996[Abstract].
21.
Portilla, D.
Carnitine palmitoyltransferase enzyme inhibition protects proximal tubules during hypoxia.
Kidney Int
52:
429-437,
1997[ISI][Medline].
22.
Prough, RA,
Okita RT,
Fan LL,
and
Masters BSS
The measurement of and (
-1) hydroxylation of fatty acids by mixed function oxidase systems.
Methods Enzymol
52:
319-324,
1978.
23.
Ruidera, E,
Irazu CE,
Rajagopalan PR,
Orak JK,
Fitts CT,
and
Singh I.
Fatty acid metabolism in renal ischemia.
Lipids
23:
882-884,
1988[ISI][Medline].
24.
Safirstein, R,
Megyesi J,
Saggi SJ,
Price PM,
Poon M,
Rollins BJ,
and
Taubman MB.
Expression of cytokine-like genes JE and KC is increased during renal ischemia.
Am J Physiol Renal Fluid Electrolyte Physiol
261:
F1095-F1101,
1991
25.
Safirstein, R,
Price PM,
Saggi SJ,
and
Harris RC.
Changes in gene expression after temporary renal ischemia.
Kidney Int
37:
1515-1521,
1990[ISI][Medline].
26.
Selby, PL,
and
Sherratt HSA
Substituted 2-oxiranecarboxylic acids: a new group of candidate hypoglycemic drugs.
Trends Pharmacol Sci
10:
495-500,
1989[ISI][Medline].
27.
Skorin, C,
Necochea C,
Johow V,
Soto U,
Grau AM,
Bremer J,
and
Leighton F.
Peroxisomal fatty acid oxidation and inhibitors of the mitochondrial carnitine palmitoyltransferase I in isolated rat hepatocytes.
Biochem J
281:
561-567,
1992[ISI][Medline].
28.
Solez, K,
Morel-Maroger L,
and
Sraer JD.
The morphology of "acute tubular necrosis" in man: analysis of 57 renal biopsies and a comparison with the glycerol model.
Medicine
58:
362-376,
1979[ISI][Medline].
29.
Tamura, Y,
Imaoka S,
Gemba M,
and
Funae Y.
Effects of ischemia-reperfusion on individual cytochrome P450 isoforms in the rat kidney.
Life Sci
60:
143-149,
1997[ISI][Medline].
30.
Toback, FG.
Control of renal regeneration after acute tubular necrosis.
In: Nephrology, edited by Robinson RR.. New York: Springer-Verlag, 1984, p. 748-762.
31.
Tugwood, JD,
Isemann I,
Anderson RG,
Bundell KR,
McPheat WL,
and
Green S.
The mouse peroxisome proliferator activated receptor recognizes a response element in the 5' flanking sequence of the rat acyl CoA oxidase gene.
EMBO J
11:
433-439,
1992[Abstract].
32.
Vamecq, J.
Fluorometric assay of peroxisomal oxidases.
Anal Biochem
186:
340-349,
1990[ISI][Medline].
33.
Velasco, G,
Geelen MJH,
Gómez del Pulgar T,
and
Guzmán M.
Malonyl-CoA-independent acute control of hepatic carnitine palmitoyl-transferase I activity. Role of Ca2+/calmodulin-dependent protein kinase II and cytoskeletal components.
J Biol Chem
273:
21497-21504,
1998
34.
Venkatachalam, MA,
Bernard DB,
Donohue JF,
and
Levinsky NG.
Ischemic damage and repair in the rat proximal tubule: differences among the S1, S2 and S3 segments.
Kidney Int
14:
31-49,
1978[ISI][Medline].
35.
Wijkhuisen, A,
Djouadi F,
Vilar J,
Merlet Benichou C,
and
Bastin J.
Thyroid hormones regulate development of energy metabolism enzymes in rat proximal convoluted tubule.
Am J Physiol Renal Fluid Electrolyte Physiol
268:
F634-F642,
1995
36.
Witzgall, R,
Brown D,
Schwarz C,
and
Bonventre JV.
Localization of proliferating cell nuclear antigen vimentin, c-fos, and clusterin in the postischemic kidney: evidence for a heterogeneous genetic response among nephron segments, and a large pool of mitotically active and dedifferentiated cells.
J Clin Invest
93:
2175-2188,
1994[ISI][Medline].
37.
Witzgall, R,
O'Leary E,
Gessner R,
Ouellette AJ,
and
Bonventre JV.
Kid-1, a putative renal transcription factor: regulation during ontogeny and in response to ischemia and toxic injury.
Mol Cell Biol
13:
1933-1942,
1993[Abstract].
38.
Wu, Z,
Puigserver P,
Andersson U,
Zhang C,
Adelmant G,
Mootha V,
Troy A,
Cinti S,
Lowell B,
Scarpulla RC,
and
Spiegelman BM.
Mechanisms controlling mitochondrial biogenesis and respiration through the thermogenic coactivator PGC-1.
Cell
98:
115-124,
1999[ISI][Medline].
39.
Youfei, G,
Zhang Y,
Davis L,
and
Breyer MD.
Expression of peroxisome proliferator-activated receptors in urinary tract of rabbits and humans.
Am J Physiol Renal Physiol
273:
F1013-F1022,
1997