Norepinephrine induces alveolar epithelial apoptosis mediated by alpha -, beta -, and angiotensin receptor activation

H. Erhan Dincer1, Nupur Gangopadhyay2, Rongqi Wang3, and Bruce D. Uhal2

1 Division of Pulmonary and Critical Care Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53226; 2 Department of Physiology, Michigan State University, East Lansing, Michigan 48824; and 3 Department of Pathology, Northwestern University, Chicago, Illinois 60085


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Norepinephrine (NE) induces apoptosis in cardiac myocytes, and autocrine production of angiotensin (ANG) II is required for apoptosis of alveolar epithelial cells (AECs) (Wang R, Zagariya A, Ang E, Ibarra-Sunga O, and Uhal BD. Am J Physiol Lung Cell Mol Physiol 277: L1245-L1250, 1999; Wang R, Alam G, Zagariya A, Gidea C, Pinillos H, Lalude O, Choudhary G, and Uhal BD. J Cell Physiol 185: 253-259, 2000). On this basis, we hypothesized that NE might induce apoptosis of AECs in a manner inhibitable by ANG system antagonists. Purified NE induced apoptosis in the human A549 AEC-derived cell line or in primary cultures of rat AECs, with EC50 values of 200 and 20 nM, respectively. Neither the alpha -agonist phenylephrine nor the beta -agonist isoproterenol could mimic NE when tested alone but when applied together could induce apoptosis with potency equal to NE. Apoptosis and net cell loss (47-59% in 40 h) in response to NE was completely abrogated by the ANG-converting enzyme inhibitor lisinopril or the ANG II receptor antagonist saralasin, each at concentrations capable of blocking Fas- or tumor necrosis factor-alpha -induced apoptosis. These data suggest that NE induces apoptosis of human and rat AECs through a mechanism involving the combination of alpha - and beta -adrenoceptor activation followed by autocrine generation of ANG II.

catecholamine; angiotensin II; lung injury; pulmonary edema; type II pneumocyte


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

PULMONARY ALVEOLAR EPITHELIAL CELLS (AECs) have varied and important roles in lung homeostasis, one of which is the replacement of epithelial cells lost to lung injury (21). Repair of the alveolar epithelium is accomplished by the regulated proliferation and differentiation of type II AECs (37). Incomplete or delayed alveolar repair leads to acceleration of collagen deposition and lung fibroblast proliferation in animal models (41, 48). For these reasons, type II pneumocytes are thought to be crucially important in the pathogenesis of lung fibrosis (34, 48).

Apoptosis of unneeded cells during lung development or during resolution of lung injury is a normal physiological process, but inappropriate stimulation or delay of apoptosis may play a role in the pathogenesis of lung disease (9). For example, the repair process after acute lung injury requires elimination of excess mesenchymal and inflammatory cells from the alveolar space and wall. Failure to clear these cells by apoptosis could accelerate the progression to fibrosis or delay its resolution (7, 9, 29). As examples of excessive apoptosis, acute fulminant hepatitis and death occurred after intraperitoneal injection of a Fas-activating antibody into adult mice (26). Moreover, intratracheal instillation of the same antibody into normal mice caused epithelial cell apoptosis followed by lung fibrosis (12), consistent with the notion that the loss of epithelial integrity is a key event in fibrogenesis.

The influence of circulating catecholamines on the proliferation or death of AECs is largely unknown. Although high serum levels of norepinephrine (NE) have some beneficial effects in the lung, such as the stimulation of lung liquid clearance (28), high sympathetic drive may also cause pulmonary edema (28). In heart failure, apoptosis of cardiac myocytes in response to NE is believed to be an important component of the progression of cardiac fibrosis (6, 14, 18). Moreover, cardiomyocyte apoptosis in response to NE is mediated by beta -adrenergic receptors and is inhibited by the beta -adrenergic antagonist propranolol.

For these reasons, we hypothesized that NE might induce apoptosis of AECs as it does in cardiac myocytes. Moreover, on the basis of recent work in which Wang and colleagues found a requirement for autocrine production of angiotensin (ANG) II in the signaling of AEC apoptosis in response to Fas (44) or tumor necrosis factor (TNF)-alpha (42), we further theorized that AEC apoptosis in response to NE might also involve autocrine generation of ANG II. We report here that NE induces apoptosis in cultured AECs by a mechanism that involves the combination of alpha - and beta -adrenoceptors as well as autocrine ANG II production.


    METHODS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Reagents and materials. Norepinephrine (NE), isoproterenol (Iso), phenylephrine (PE), propranolol, prazosin, atenolol, lisinopril, and saralasin were obtained from Sigma (St. Louis, MO). Fluorescein-conjugated annexin V was obtained from PharMingen (San Diego, CA). Z-Val-Ala-Asp-fluoromethylketone (ZVAD-fmk) was obtained from Kamiya Biomedical (Seattle, WA).

Cell culture. The human lung adenocarcinoma cell line A549 was obtained from the American Type Culture Collection and cultured in Ham's F-12 medium supplemented with 10% fetal bovine serum. Primary AECs were isolated from adult male Wistar rats as described earlier (38, 40). The primary cells were studied on day 2 of culture, a time at which they are type II cell-like by accepted morphological and biochemical criteria (38). All primary cell preparations were of >90% purity as assessed by acridine orange staining as previously described (40). All cells were seeded on 12-mm sterile coverslips in 24-well chambers at subconfluent densities of 80-90% in serum-free Ham's F-12 medium. Test reagents were diluted with Ham's F-12 medium. The cells were exposed to propranolol, ZVAD-fmk, and antagonists of the renin-ANG system 30 min before exposure for 20 h to NE, Iso, or PE.

Quantitation of apoptosis and cell loss. Detection of apoptotic cells with propidium iodide was conducted as described earlier (39, 42) after digestion of ethanol-fixed cells with DNase-free RNase in PBS containing 5 µg/ml of propidium iodide. In these assays, detached cells were retained by centrifugation of the 24-well culture vessels during fixation with 70% ethanol. Cells with discrete nuclear fragments containing condensed chromatin were scored as apoptotic. As in earlier publications (42, 44), the induction of apoptosis was verified by annexin V binding and abrogation of nuclear fragmentation by caspase inhibition with ZVAD-fmk.

In Figs. 1, 3, and 4, nuclear fragmentation data are expressed as the percentage of positive cells relative to the control (untreated) group, which was set to 100% in each assay. This manner of expression reflects the fact that the nuclear fragmentation assay, although specific for apoptosis (42, 45), detects only the very late and rapid stage of karyorrhesis and thus underestimates the true apoptotic index by three- to fourfold (see Fig. 2 for comparison to the annexin V binding assay). The actual numbers of cells displaying nuclear fragments are provided in Figs. 2-4.


View larger version (24K):
[in this window]
[in a new window]
 
Fig. 1.   Norepinephrine (NE) induces apoptosis in human and rat alveolar epithelial cells (AECs) in a dose-dependent manner. The human AEC line A549 and primary rat AECs were exposed for 20 h in serum-free cell culture medium to the indicated concentrations of NE and to propranolol (PR; 10 µM) administered in the presence of 1 µM NE. Total cells (adherent plus detached) were analyzed, and the fraction of apoptotic cells was scored with propidium iodide as described in METHODS. See Fig. 2 for detection method and absolute values. * P < 0.001 vs. 0.0 dose by ANOVA and Student-Newman-Keuls test.



View larger version (23K):
[in this window]
[in a new window]
 
Fig. 2.   Fluorescence assays of apoptosis in primary rat AECs as assessed by propidium iodide (PI) and annexin V binding. Primary cultures of rat AECs were exposed to NE in serum-free medium as in Fig. 1. Total cell population (adherent plus detached) was subjected to detection of apoptotic cells with fluorescein-labeled annexin V or with PI (see METHODS for details). Inset: fragmented nuclei. Annexin V+, annexin V positive. With the annexin V method, actual values for control (CTL) and NE treatment were 7.8 ± 1.1 and 30.0 ± 4.6%, respectively. With the PI method (an underestimate of the true apoptotic index; see METHODS), actual values for control and NE treatment were 0.9 ± 0.2 and 4.8 ± 0.2, respectively, for A549 cells and 2.4 ± 0.2 and 13.0 ± 0.6%, respectively, for primary rat AECs. * P < 0.01 vs. 0.0 dose (CTL) by Student's t-test.



View larger version (15K):
[in this window]
[in a new window]
 
Fig. 3.   NE-induced apoptosis of primary rat AECs and the human A549 cell line is mediated by the combination of alpha - and beta -adrenoceptor activation. A: primary cultures of rat AECs were exposed to the indicated concentrations (in µM) of NE, phenylephrine (PE), isoproterenol (ISO), prazosin (PRAZ; 10 µM), or atenolol (ATEN; 1 µM), all applied in serum-free medium as in Fig. 1. B: human A549 cells were exposed to the indicated concentrations (in µM) of NE, PE, or ISO applied in serum-free medium as in Fig. 1. Total cell population (adherent plus detached) was subjected to detection of apoptotic cells (see METHODS for details). Actual values in the PI assay for control and 1 µM NE treatment were 0.9 ± 0.2 and 3.9 ± 0.3%, respectively, for A549 cells and 2.0 ± 0.3 and 10.5 ± 0.7%, respectively, for primary rat AECs. ** P < 0.01 vs. 0.0 dose (CTL) by ANOVA and Student-Newman-Keuls test.



View larger version (15K):
[in this window]
[in a new window]
 
Fig. 4.   Antagonists of the renin-angiotensin system abrogate NE-induced apoptosis of A549 cells or primary rat AECs. A: human A549 cells were exposed to NE (1 µM) in the presence of the angiotensin-converting enzyme inhibitor lisinopril (LISIN; 500 ng/ml), the nonselective angiotensin II receptor antagonist saralasin (SARAL; 50 µg/ml), or the broad-spectrum caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVAD; 60 µM), all applied 30 min before NE. B: primary cultures of rat AECs were exposed to NE (1 µM) in the presence of the angiotensin-converting enzyme inhibitor LISIN (500 ng/ml) or the nonselective angiotensin II receptor antagonist SARAL (50 µg/ml) as in A. Apoptosis was detected as in Fig. 1 (see METHODS). Actual values in the PI assay for control and 1 µM NE treatment were 0.8 ± 0.2 and 2.8 ± 0.3%, respectively, for A549 cells and 2.0 ± 0.2 and 7.8 ± 0%, respectively, for primary rat AECs. ** P < 0.001 vs. CTL by ANOVA and Student-Newman-Keuls test.

Cell loss over 20 or 40 h of culture was quantitated by cell counts of the adherent and detached cell populations. These were obtained after centrifugation of the culture vessels without prior washing as described above. Thus detached cells (routinely <10% of the total cell number) were included in the cell loss data. The fraction of the total cell number composed of detached cells did not change significantly under the treatment conditions reported (data not shown). Total cell counts (attached plus detached) were scored over a minimum of four separate microscopic fields from each of at least three culture vessels per treatment group. Data from each treatment group were compiled and analyzed by ANOVA followed by Student-Newman-Keuls post hoc analysis.


    RESULTS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Purified NE induced apoptosis of cultured human (A549) and rat AECs in a concentration-dependent manner (Fig. 1). In both cell culture models, the induction of apoptosis was maximal at 1 µM NE, but the primary rat AECs were more sensitive (EC50 = 20 nM) than the A549 cell line (EC50 = 200 nM). The beta -adrenergic antagonist propranolol (10 µM) completely blocked the apoptosis induced by 1 µM NE. At the maximally stimulatory dose of NE (1 µM), the percentage of primary rat AECs undergoing apoptosis at any given time was at least 30% as detected by annexin V binding (Fig. 2), a fraction sufficient to result in a net cell loss of 50% or more in 40 h (see below).

The apoptotic effect of 1 µM NE on primary rat AECs could not be reproduced by stimulation of beta -adrenergic receptors alone with an equivalent dose of Iso (1 µM; Fig. 3A) nor by stimulation of alpha -adrenergic receptors alone with PE. In contrast, NE applied at the same doses as PE (0.01 and 0.1 µM; compare Figs. 1 and 3) was sufficient to cause a significant induction of apoptosis. However, when the cultured AECs were challenged with Iso and PE together (Fig. 3), the stimulation of apoptosis was equal to that induced by NE at the same total agonist concentration (actually 1.1 µM total agonist). These data suggest that the proapoptotic effect of NE on AECs is mediated through the combined activation of alpha - and beta -adrenoceptors simultaneously. Consistent with that interpretation, the apoptotic effect of 1 µM NE could be abrogated (Fig. 3A) by either the alpha 1-antagonist prazosin (10 µM) or the beta 1-antagonist atenolol (1 µM). Qualitatively similar results were obtained for the cell line A549 (Fig. 3B).

Apoptosis of A549 cells in response to NE was also abrogated by the broad-spectrum caspase inhibitor ZVAD-fmk, the ANG-converting enzyme (ACE) inhibitor lisinopril or the ANG receptor antagonist saralasin (Fig. 4A). Essentially identical results were obtained for primary rat AECs (Fig. 4B). These data are consistent with recent work from this laboratory indicating a requirement for autocrine production of ANG II for the execution of apoptosis in AECs in response to Fas ligand (39) or TNF-alpha (37).

The induction of apoptosis by NE at 1 µM was sufficient to result in a net cell loss of 49 and 56% of A549 cells (Fig. 5A) and primary rat AECs (Fig. 5B), respectively, each over 40 h of incubation. The method used for cell counting (see METHODS) ensured that cell loss due to detachment did not confound the assay; in any case, no significant differences in the number of detached versus adherent cells were noted under any treatment condition (data not shown). The combination of PE and Iso was equally as potent as 1 µM NE in promoting the cell loss as it was in inducing apoptosis (Fig. 3). Moreover, the net cell loss induced by NE over 40 h could be completely blocked by the same antagonists of the renin-ANG system that blocked nuclear fragmentation, i.e., lisinopril or saralasin. This was the case in either A549 cells (Fig. 5A) or primary rat AECs (Fig. 5B). The net cell loss also was abrogated by the beta -antagonist propranolol (10 µM) or by the caspase inhibitor ZVAD-fmk (Fig. 5B). The latter result confirms that the net cell loss was due to apoptosis (24).


View larger version (21K):
[in this window]
[in a new window]
 
Fig. 5.   Antagonists of the renin-angiotensin system abrogate NE-induced net cell loss of A549 cells or primary rat AECs. A: human A549 cells were exposed to NE (1 µM), PE (0.1 µM), and ISO (1 µM) as in Figs. 1 and 3 in the presence of the angiotensin-converting enzyme inhibitor LISIN (500 ng/ml) or the nonselective angiotensin II receptor antagonist SARAL (50 µg/ml). B: primary cultures of rat AECs were exposed to NE (1 µM), PE (0.1 µM), ISO (1 µM), or propranolol (PROP; 10 µM) as in A in the presence of the angiotensin-converting enzyme inhibitor LISIN (500 ng/ml), the nonselective angiotensin II receptor antagonist SARAL (50 µg/ml), or the broad-spectrum caspase inhibitor ZVAD (60 µM). Inhibitors were applied 30 min before agonists; total cell number (attached plus detached) was scored after 40 h of exposure (see METHODS). ** P < 0.001 vs. CTL by ANOVA and Student-Newman-Keuls test.


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Type II AECs have roles in antioxidant defense, immunomodulation, surfactant synthesis, and injury repair (37). These cells are believed to be a critical player in the pathogenesis of pulmonary fibrosis (34). It is also known that apoptosis is an important regulator of AEC population size (37) and is a prominent feature of the fibrotic lung in vivo (2). Catecholamine-induced apoptosis has been studied in cardiac myocytes (6), brown adipose tissue (17), Cajal-Retzius cells (25), pheochromocytoma cells (4), glioma cells (5), lymphocytes (15), and hepatocytes (49). Increased levels of serum NE in congestive heart failure are believed to be cardiotoxic in circumstances involving relative hypoxia, calcium overload, elevation of cAMP, activation of alpha - or beta -adrenergic receptor, and the formation of oxidative catecholamine metabolites (19, 27, 30). A recent study by Communal et al. (6) showed that NE (10 µM) induced apoptosis in rat ventricular myocytes by activation of the beta -adrenergic pathway, which is speculated to contribute to myocardial fibrosis and heart failure.

In the same study, the effect of NE was mimicked by Iso but was blocked by propranolol, findings that suggested that NE-induced apoptosis of cardiac myocytes is mediated primarily by beta -adrenoceptors. In contrast, the blockade of NE-induced apoptosis of AECs by the alpha 1-antagonist prazosin or the beta 1-antagonist atenolol (Fig. 3) together with the ability of PE and Iso to induce apoptosis when applied jointly but not separately supports the contention that both alpha - and beta -receptor activation are required simultaneously for NE-induced apoptosis of AECs. Moreover, the ability of atenolol to block the apoptotic response to NE suggests the involvement of beta 1-receptors; this, in turn, sheds light on the failure of Iso to elicit a response when applied alone. The mechanistic basis for this cell type-specific difference in apoptosis signaling is an interesting topic for future inquiry.

Here we also showed that ACE inhibition or ANG II receptor antagonism can completely abrogate NE-induced apoptosis as it does for AEC apoptosis in response to Fas activation (8, 39, 44), TNF-alpha (42), or the pneumotoxic benzofuran antiarrythmic agent amiodarone (3). Taken together, these data support the hypothesis that autocrine production of ANG II by AECs and its binding to ANG II receptors may be a common event required for the execution of apoptosis regardless of the initiating stimulus. Data from other cell types suggest that possible candidates for a signal transduction mechanism common to NE, Fas, and TNF-alpha might include p53, p21 (WAF1), and/or associated DNA damage (16, 20, 23, 24). Although the molecular linkage between proapoptotic stimuli and autocrine production of ANG II by AECs is not yet known, preliminary results suggest that the linkage does not include autocrine synthesis of Fas ligand or TNF-alpha ; neutralizing antibodies capable of blocking Fas- or TNF-induced apoptosis in AECs had no effect on NE-induced apoptosis (data not shown).

Regardless, a role for catecholamines in acute respiratory distress syndrome (ARDS) has been suggested by a variety of studies. NE is increased greatly in the serum in endotoxin-induced experimental ARDS and in models of neurogenic edema (13, 35). In experimental neurogenic edema induced by bicuculline injection (35), plasma NE rose from a basal level of ~100 pg/ml to well over 30,000 pg/ml (~0.15 µM), well within the range necessary for maximal induction of apoptosis in primary cultures of AECs (Fig. 1, right). The high serum level of NE is thought to be meaningful as an indicator for the early diagnosis of ARDS (11, 13). It is believed that in rats with septic shock, endogenous release of catecholamines stimulates lung epithelial clearance of liquid through a beta -adrenoceptor-mediated stimulation of active sodium transport (28). Similarly, the effect of catecholamines to increase edema clearance was also observed in guinea pigs at birth (10). The findings that the moderately beta -selective agonists Iso and terbutaline could mimic the effect of endogenous catecholamines (32) have led to the suggestion that increased lung edema clearance is mediated by beta 2-receptors. However, the selectivity of these agonists for the beta 2-receptor is not absolute, and recent work (31) has shown that the beta 1-selective agonist denopamine can promote edema clearance at the same doses (10-6 to 10-3 M). These concentrations are an order of magnitude higher than those required by NE for induction of AEC apoptosis (see Fig. 1).

In addition to their positive effect, adrenergic agonists have also been suggested to play a negative role in lung injury. In animal models, high-dose epinephrine injections (30 µg/kg) may cause pulmonary edema and death (33). A recent study (1) examining the effect of catecholamines on endotoxin-induced lung injury revealed that administration of the alpha 1-adrenergic agonist PE before endotoxin significantly increased the expression of TNF-alpha and macrophage inflammatory protein-2 mRNAs by lung neutrophils compared with endotoxin alone. In contrast, alpha 2-adrenergic stimulation prevented endotoxin-induced increases in lung myeloperoxidase and lung neutrophil cytokine mRNA levels (1).

An inhibitory effect of ACE inhibitors on lung fibrogenesis has been documented (22, 46, 47). A more recent study (43) in which the fibrogenic effect of intratracheal administration of bleomycin was blocked with equal potency by the ACE inhibitor captopril or the caspase inhibitor ZVAD-fmk supports the contention that at least part of the antifibrotic effect of captopril was due to its ability to block bleomycin-induced apoptosis of AECs. By the same rationale, it will be interesting to determine whether acute lung injury might be induced in experimental animals by intratracheal instillation of NE in a manner inhibitable by antagonists of the renin-ANG system.

In summary, NE caused dose-dependent apoptosis of human and rat AECs that is mediated by a combined effect of alpha - and beta -adrenoceptors and, indirectly, ANG receptor activation. NE-induced apoptosis of AECs was abrogated by antagonists of the renin-ANG system, suggesting that autocrine production of ANG II is required for AEC apoptosis in response to NE. These findings are consistent with recent demonstrations (42, 44) of a requirement for ANG II generation for the execution of apoptosis in response to Fas or TNF-alpha . They also raise the possibility that apoptosis of AECs may be a contributing factor in the pathogenesis of acute lung injuries such as ARDS and neurogenic edema in which circulating NE is known to be greatly elevated. The relevance of these findings to lung injury mechanisms in vivo is currently being evaluated.


    ACKNOWLEDGEMENTS

This work was supported by National Heart, Lung, and Blood Institute Grant HL-45136 (to B. D. Uhal) and by the Research Foundation, Michigan State University (East Lansing, MI).


    FOOTNOTES

Address for reprint requests and other correspondence: B. D. Uhal, Dept. of Physiology, Michigan State Univ., 310 Giltner Hall, East Lansing, MI 48824 (E-mail: uhal{at}msu.edu).

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. Section 1734 solely to indicate this fact.

Received 27 December 2000; accepted in final form 11 April 2001.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Abraham, E, Kaneko DJ, and Shenkar R. Effects of endogenous and exogenous catecholamines on LPS-induced neutrophil trafficking and activation. Am J Physiol Lung Cell Mol Physiol 276: L1-L8, 1999[Abstract/Free Full Text].

2.   Barbales, RH, Xie SS, and Hsu S. Apoptosis is a major pathway responsible for the resolution of type II pneumocytes in acute lung injury. Am J Pathol 149: 845-852, 1996[Abstract].

3.   Bargout, R, Jankov A, Dincer E, Ibarra-Sunga O, Komodromos T, Filippatos G, and Uhal BD. Amiodarone induces apoptosis in human and rat alveolar epithelial cells in vitro. Am J Physiol Lung Cell Mol Physiol 278: L1039-L1044, 2000[Abstract/Free Full Text].

4.   Burke, WJ, Schmitt CA, Miller C, and Li SW. Norepinephrine transmitter metabolite induced apoptosis in differentiated rat pheochromocytoma cells. Brain Res 760: 290-293, 1997[ISI][Medline].

5.   Canova, C, Baudet C, Chevalier G, Brachet P, and Wion D. Noradrenaline inhibits the programmed cell death induced by 1,25 dihydroxyvitamin D3 in glioma. Eur J Pharmacol 319: 365-368, 1997[ISI][Medline].

6.   Communal, C, Singh K, Pimentel DR, and Colucci WS. Norepinephrine stimulates apoptosis in adult rat ventricular myocytes by activation of the beta -adrenergic pathway. Circulation 98: 1329-1334, 1998[Abstract/Free Full Text].

7.   Cox, G, Crossley J, and Zing Z. Macrophage engulfment of apoptotic neutrophils contributes to the resolution of acute pulmonary inflammation in vivo. Am J Respir Cell Mol Biol 12: 232-237, 1995[Abstract].

8.   Deas, O, Dumont C, Mollereau B, Metivier D, Pasquier C, Bernard-Pomier G, Firsch F, Charpentier B, and Senik A. Thiol mediated inhibition of Fas and CD2 apoptotic signaling in activated human peripheral T cells. Int Immunol 9: 117-125, 1997[Abstract].

9.   Fine, A, Janssen-Heininger Y, Soultanakis RP, Swisher S, and Uhal BD. Apoptosis in lung pathophysiology. Am J Physiol Lung Cell Mol Physiol 279: L423-L427, 2000[Abstract/Free Full Text].

10.   Finley, N, Norlin A, Baines DL, and Folkesson HG. Alveolar epithelial fluid clearance is mediated by endogenous catecholamines at birth in guinea pigs. J Clin Invest 101: 972-981, 1998[Abstract/Free Full Text].

11.   Fowler, AA, Hamman RF, Good JT, Benson KN, Baird M, Eberle DJ, Petty TL, and Hyers TM. Adult respiratory distress syndrome: risk with common predispositions. Ann Intern Med 98: 593-597, 1983[ISI][Medline].

12.   Hagimoto, N, Kuwano K, Miyazaki H, Kunitake R, Fujita M, Kawasaki M, Kanika Y, and Hara N. Induction of apoptosis and pulmonary fibrosis in mice in response to ligation of FAS antigen. Am J Respir Cell Mol Biol 17: 272-278, 1997[Abstract/Free Full Text].

13.   Hofford, JM, Milakofsky L, Pell S, and Vogel W. A profile of amino acid and catecholamine levels during endotoxin-induced acute lung injury in sheep: searching for potential markers of the adult respiratory distress syndrome. J Lab Clin Med 128: 545-551, 1996[ISI][Medline].

14.   Iwase, M, Bishop SP, Uechi M, Vatner DE, Shannon RP, Kudej RK, Wight DC, and Wagner TE. Adverse effects of chronic endogenous sympathetic drive induce by cardiac GS alpha overexpression. Circ Res 78: 517-524, 1996[Abstract/Free Full Text].

15.   Josefsson, E, Bergquist J, Ekman R, and Tarkowski A. Catecholamines are synthesized by mouse lymphocytes and regulate function of these cells by induction of apoptosis. Immunology 88: 140-146, 1996[ISI][Medline].

16.   Leri, A, Claudia P, Li Q, Wang X, Reiss K, Wang S, Malhotra A, Kajstura J, and Anversa P. Stretch-mediated release of angiotensin II induces myocyte apoptosis by activating p53 that enhances the local renin-angiotensin system and decreases the Bcl-2-to-Bax protein ratio in the cell. J Clin Invest 101: 1326-1342, 1998[Abstract/Free Full Text].

17.   Lindquist, JM, and Rehnmark S. Ambient temperature regulation of apoptosis in brown tissue. Erk2 promotes norepinephrine-dependent cell survival. J Biol Chem 273: 30147-30156, 1998[Abstract/Free Full Text].

18.   Linz, V, Wiemer G, Schaper J, Zimmermann R, Nagasawa K, Unger T, and Scholkens BA. Angiotensin converting enzyme inhibitors, left ventricular hypertrophy and fibrosis. Mol Cell Biochem 147: 89-97, 1995[ISI][Medline].

19.   Mann, DL, Kent RL, Parsons P, and Copper G IV. Adrenergic effects on the biology of adult mammalian cardiocyte. Circulation 85: 790-804, 1992[Abstract].

20.   Martinsons, A, Rudzite V, Bratslavska O, and Saulite V. The influence of kynurenine, neopterin, and norepinephrine on tubular epithelial cells and alveolar fibroblasts. Adv Exp Med Biol 467: 347-352, 1999[ISI][Medline].

21.   Mason, RJ, and Williams MC. Type II alveolar epithelial cells. In: The Lung: Scientific Foundations, edited by Crystal RG, and West JB.. New York: Raven, 1991, p. 235-246.

22.   Molteni, A, Ward W, Ts'ao C, Solliday N, and Dunne M. Monocrotaline-induced pulmonary fibrosis in rats: amelioration by captopril and penicillamine. Proc Soc Exp Biol Med 180: 112-120, 1985[Abstract].

23.   Morrissey, JJ, Ishidoya S, McCracken R, and Klahr S. The effect of ACE inhibitors on the expression of matrix genes and the role of p53 and p21 (WAF1) in experimental renal fibrosis. Kidney Int 54: 583-587, 1996.

24.   Mundle, S, Gregory S, Preisler H, and Raza A. Enzymatic programming of apoptotic cell death. Pathobiology 64: 161-170, 1996[ISI][Medline].

25.   Naqui, SZ, Harris BS, Thomaidou D, and Parnavelas JG. The noradrenergic system influences the fate of Cajal-Retzius cells in the developing cerebral cortex. Brain Res 113: 75-82, 1999.

26.   Ogasawara, J, Watanabe-Fukunaga R, Adachi M, Matsuzawa A, Kasugai T, Kitamura Y, Itoh N, Suda T, and Nagata S. Lethal effect of the anti-Fas antibody in mice. Nature 364: 806-809, 1993[ISI][Medline].

27.   Opie, LH, Walpoth B, and Barsacchi R. Calcium and catecholamines: relevance to cardiomyopathies and significance in therapeutic strategies. J Mol Cell Cardiol 17, Suppl 2: 21-34, 1985[ISI][Medline].

28.   Pittet, JF, Wiener-Kronish JP, McElroy MC, Folkesson HG, and Matthay MA. Stimulation of lung epithelial liquid clearance by endogenous release of catecholamines in septic shock in anesthetized rats. J Clin Invest 94: 663-671, 1994[ISI][Medline].

29.   Polonovsky, VA, Chen B, Henke C, Snover D, Wendt C, Ingbar DH, and Bitterman PB. Role of mesenchymal cell death in lung remodeling after injury. J Clin Invest 92: 388-397, 1993[ISI][Medline].

30.   Rona, G. Catecholamine cardiotoxicity. J Mol Cell Cardiol 17: 291-306, 1985[ISI][Medline].

31.   Sakuma, T, Tuchihara T, Ishigaki M, Osanai K, Nambu Y, Toga H, Takahashi K, Kurihara T, and Matthay M. Denopamine, a beta 1-adrenergic antagonist, increases alveolar fluid clearance in ex vivo and guinea pig lungs. J Appl Physiol 90: 10-16, 2001[Abstract/Free Full Text].

32.   Saldias, F, Lecuona E, Comellas A, Ridge K, Rutschman D, and Sznajder J. Beta-adrenergic stimulation restores rat lung ability to clear edema in ventilator-associated lung injury. Am J Respir Crit Care Med 162: 282-287, 2000[Abstract/Free Full Text].

33.   Serda, SM, and Wei ET. Epinephrine-induced pulmonary edema in rats is inhibited by corticotropin-releasing factor. Pharm Res 26: 85-91, 1991.

34.   Simon, RH. Alveolar epithelial cells in pulmonary fibrosis. In: Pulmonary Fibrosis, edited by Phan SH, and Thrall RS.. New York: Dekker, 1995, vol. 80, p. 511-540. (Lung Biol Health Dis Ser)

35.   Simon, RP. Neurogenic pulmonary edema. Neurol Clin 11: 309-323, 1993[ISI][Medline].

36.   Struthers, AD. Mineralocorticoid receptor blockade in congestive heart failure. J Hum Hypertens 9: 443-446, 1995[ISI][Medline].

37.   Uhal, BD. Cell cycle kinetics in the alveolar epithelium. Am J Physiol Lung Cell Mol Physiol 272: L1031-L1045, 1997[Abstract/Free Full Text].

38.   Uhal, BD, Flowers KM, and Rannels DE. Type II pneumocyte proliferation in vitro: problems and future directions. Am J Physiol Suppl (Oct) 261: 110-117, 1991.

39.   Uhal, BD, Gidea C, Bargout R, Bifero A, Ibarra-Sunga O, Papp M, Flynn K, and Filippatos G. Captopril inhibits apoptosis in human lung epithelial cells: a potential antifibrotic mechanism. Am J Physiol Lung Cell Mol Physiol 275: L1013-L1017, 1998[Abstract/Free Full Text].

40.   Uhal, BD, Joshi I, True A, Mundle S, Raza A, Pardo A, and Selman M. Fibroblasts isolated after fibrotic lung injury induce apoptosis of alveolar epithelial cells in vitro. Am J Physiol Lung Cell Mol Physiol 269: L819-L829, 1995[Abstract/Free Full Text].

41.   Uhal, BD, Ramos C, Joshi I, Bifero A, Pardo A, and Selman M. Cell size, cell cycle, and alpha -smooth actin expression by primary human lung fibroblasts. Am J Physiol Lung Cell Mol Physiol 275: L998-L1005, 1998[Abstract/Free Full Text].

42.   Wang, R, Alam G, Zagariya A, Gidea C, Pinillos H, Lalude O, Choudhary G, and Uhal BD. Apoptosis of lung epithelial cells in response to TNF-alpha requires angiotensin II generation de novo. J Cell Physiol 185: 253-259, 2000[ISI][Medline].

43.   Wang, R, Ibarra-Sunga O, Pick R, and Uhal BD. Abrogation of bleomycin-induced epithelial apoptosis and lung fibrosis by captopril or by a caspase inhibitor. Am J Physiol Lung Cell Mol Physiol 279: L143-L151, 2000[Abstract/Free Full Text].

44.   Wang, R, Zagariya A, Ang E, Ibarra-Sunga O, and Uhal BD. Fas-induced apoptosis of alveolar epithelial cells requires angiotensin II generation and receptor interaction. Am J Physiol Lung Cell Mol Physiol 277: L1245-L1250, 1999[Abstract/Free Full Text].

45.   Wang, R, Zagariya A, Ibarra-Sunga O, Gidea C, Ang E, Deshmukh S, Baraboutis J, Filippatos G, and Uhal BD. Angiotensin II induces apoptosis in human and rat alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 276: L885-L889, 1999[Abstract/Free Full Text].

46.   Ward, WF, Molteni A, Ts'ao C, and Hinz J. Captopril reduces collagen and mast cell accumulation in irradiated rat lung. Int J Radiat Oncol Biol Phys 19: 1405-1409, 1990[ISI][Medline].

47.   Ward, WF, Molteni A, Ts'ao C, Kim Y, and Hinz J. Radiation pneumotoxicity in rats: modification by inhibitors of angiotensin converting enzyme. Int J Radiat Oncol Biol Phys 22: 623-625, 1992[ISI][Medline].

48.   Witschi, H. Responses of the lung to toxic injury. Environ Health Perspect 85: 5-13, 1990[ISI][Medline].

49.   Zhang, YQ, Kanzaki M, Mashima M, Mine T, and Kojima I. Norepinephrine reverses the effects of activin-A on DNA synthesis and apoptosis in cultured rat hepatocytes. Hepatology 23: 288-293, 1996[ISI][Medline].


Am J Physiol Lung Cell Mol Physiol 281(3):L624-L630
1040-0605/01 $5.00 Copyright © 2001 the American Physiological Society