Effects of Dual Endothelin Receptor Antagonist on Antiapoptotic Marker Bcl-2 Expression in Streptozotocin-Induced Diabetic Rats

Abstract

Erectile dysfunction (ED) affects approximately 50% of male patients with diabetes mellitus (DM) and is possibly due to the vascular and neuropathic complications of DM. Recently, apoptosis has been regarded as a downstream event in ED. More recently, the importance of alterations in apoptosis-related molecules in the mechanism of DM-induced ED has begun to be appreciated. Endothelin-1 (ET-1) plays a role via ET_A and ET_B receptors in the regulation of cavernosal smooth-muscle tone in penile tissues. We found that the ET-1 level in the penis of rats with DM was higher than that in the penis of control animals. The present study investigated a rat model in which DM was induced by a 3-week regimen of streptozotocin (STZ) to assess the expression of several apoptosis-related molecules in penile tissue and, concomitantly, the effects of ET antagonism on these changes. Male Sprague-Dawley rats (weight [±SD], 450 ± 26 g) received a citrate saline vehicle or STZ (65 mg/kg ip). DM was confirmed by the presence of hyperglycemia. Diabetic animals were further separated into two treatment groups 1 week after onset of disease: one group received ET_A/B dual receptor antagonist (SB209670) by means of osmotic minipump at a dosage of 1 mg/day, and the other group received saline. Rats in both groups were treated for 2 weeks and then sacrificed. Plasma glucose levels (±SD) in rats with DM were significantly higher than those in rats without DM (506 ± 70 vs. 111 ± 11 mg/dl). In the penile tissue of rats with DM, a 35% decrease in the expression of Bcl-2 protein (an important antiapoptotic marker detectable by immunoblotting) was seen, and ET_A/B dual antagonist was observed to significantly counteract this decrease. Real-time polymerase chain reaction revealed that the expression of Bcl-2 mRNA was consistent with Bcl-2 protein expression. Levels of Bax and caspase-3, two important proapoptotic markers, were not significantly altered in the present study. Thus, we conclude that, in the penis of rats with early stage DM, the protection against apoptosis has decreased but can be improved by ET antagonism.

Get full access to this article

View all access options for this article.

References

Jackson G. Sexual dysfunction and diabetes. Int J Clin Pract 58:358–362, 2004.

Mota M, Lichiardopol C, Mota E, Panus C, Panus A. Erectile dysfunction in diabetes mellitus. Rom J Intern Med 41:163–177, 2003.

Hsieh PS, Bochinski DJ, Lin GT, Nunes L, Lin CS, Lue TF. The effect of vascular endothelial growth factor and brain-derived neurotrophic factor on cavernosal nerve regeneration in a nerve-crush rat model. BJU Int 92:470–475, 2003.

Seftel A. Intracavernosal vascular endothelial growth factor (VEGF) injection and adeno-associated virus-mediated VEGF gene therapy and reverse venogenic erectile dysfunction in rats. J Urol 170:681, 2003.

Park K, Ahn KY, Kim MK, Lee SE, Kang TW, Ryu SB. Intracavernosal injection of vascular endothelial growth factor improves erectile function in aged rats. Eur Urol 46:403–407, 2004.

Lee MC, El-Sakka AI, Graziottin TM, Ho HC, Lin CS, Lue TF. The effect of vascular endothelial growth factor on a rat model of traumatic arteriogenic erectile dysfunction. J Urol 167:761–767, 2002.

Byrne RR, Henry GD, Rao DS, Huynh TT, Pippen Am, Annex BH, Hagen PO, Donatucci CF. Vascular endothelial growth factor restores corporeal smooth muscle function in vitro. J Urol 165:1310–1315, 2001.

Kerr JF. Shrinkage necrosis: a distinct mode of cellular death. J Pathol 105:13–20, 1971.

Alici B, Gümüstas MK, Özkara H, Akkus E, Demirel G, Yencilek F, Hattat H. Apoptosis in the erectile tissues of diabetic and healthy rats. BJU International 85:326–329, 2000.

10.

Klein LT, Miller MI, Buttyan R, Raffo AJ, Burchard M, Devris G, Cao YC, Olsson C, Shabsigh R. Apoptosis in the rat penis after penile denervation. J Urol 158:626–630, 1997.

11.

Khan MA, Thompson CS, Sullivan ME, Dashwood MR, Jeremy JY, Morgan RJ, Mikhailidis DP. Endothelin and erectile dysfunction: a target for pharmacological intervention? Expert Opin Investig Drugs 7:1759–1767, 1998.

12.

Jesmin S, Sakuma I, Salah-Eldin A, Nonomura K, Hattori Y, Kitabatake A. Diminished penile expression of vascular endothelial growth factor and its receptors at the insulin-resistant stage of a type II diabetic rat model: a possible cause for erectile dysfunction in diabetes. J Mol Endocrinol 31:401–418, 2003.

13.

Maeda S, Miyauchi T, Iemitsu M, Tanabe T, Yokota T, Goto K, Yamaguchi I, Matsuda M. Effects of exercise training on expression of endothelin-1 mRNA in the aorta of aged rats. Clin Sci 103:S118–S123, 2002.

14.

Yamanaka M, Shirai M, Shiina H, Tanaka Y, Tsujimura A, Matsumiya K, Okuyama A, Dahiya R. Diabetes induced erectile dysfunction and apoptosis in penile crura are recovered by insulin treatment in rats. J Urol 170:291–297, 2003.

15.

Dimmeler S, Zeiher AM. Endothelial cell apoptosis in angiogenesis and vessel regression. Circ Res 87:434–439, 2000.

16.

Kim R. Unknotting the roles of Bcl-2 and Bcl-xL in cell death. Biochem Biophys Res Commun 333:336–343, 2005.

17.

Seftel AD, Vaziri ND, Ni Z, Razmjouei K, Fogarty J, Hampel N, Polak J, Wang RZ, Ferguson K, Block C, Haas C. Advanced glycation end products in human penis: elevation in diabetic tissue, site of deposition, and possible effect through iNOS or eNOS. Urology 50:1016–1026, 1997.

18.

Wang D, Xie H, Wang G. Apoptosis and the expression of Bax and Bcl-2 in the penis of diabetic rats. Zhonghua Nan Ke Xue 10:844–848, 2004.

19.

Takahashi K, Suda K, Lam HC, Ghatei MA, Bloom SR. Endothelin-like immunoreactivity in rat models of diabetes mellitus. J Endocrinol 130:123–127, 1991.

20.

Shin SJ, Lee YJ, Lin SR, Tan MS, Lai YH, Tsai JH. Decrease of renal endothelin 1 content and gene expression in diabetic rats with moderate hyperglycemia. Nephron 70:486–493, 1995.

21.

Hocher B, Lun A, Priem F, Neumayer HH, Raschack M. Renal endothelin system in diabetes: comparison of angiotensin-converting enzyme inhibition and endothelin-A antagonism. J Cardiovasc Pharmacol 31:S492–495, 1998.

22.

Nakamura T, Ebihara I, Fukui M, Tomino Y, Koide H. Effect of a specific endothelin receptor A antagonist on mRNA levels for extracellular matrix components and growth factors in diabetic glomeruli. Diabetes 44:895–899, 1995.

23.

Hopfner RL, Misurski D, Wilson TW, McNeill JR, Gopalakrishnan V. Insulin and vanadate restore decreased plasma endothelin concentrations and exaggerated vascular responses to normal in the streptozotocin diabetic rat. Diabetologia 41:1233–1240, 1998.

24.

Dhein S, Hochreuther S, Aus Dem Spring C, Bollig K, Hufnagel C, Raschack M. Long-term effects of the endothelin(A) receptor antagonist LU 135252 and the angiotensin-converting enzyme inhibitor trandolapril on diabetic angiopathy and nephropathy in a chronic type I diabetes mellitus rat model. J Pharmacol Exp Ther 293:351–359, 2000.

25.

Hamed EA, Meki AR, Gaafar AA, Hamed SA. Role of some vasoactive mediators in patients with erectile dysfunction: their relationship with angiotensin-converting enzyme and growth hormone. Int J Impot Res 15:418–425, 2003.

26.

Benigni A, Colosio V, Brena C, Bruzzi I, Bertani T, Remuzzi G. Unselective inhibition of endothelin receptors reduces renal dysfunction in experimental diabetes. Diabetes 47:450–456, 1998.

27.

Garcia-Reboll L, Mulhall JP, Goldstein I. Drugs for the treatment of impotence. Drugs Aging 11:140–151, 1997.

28.

Andersson KE, Stief CG. Neurotransmission and the contraction and relaxation of penile erectile tissues. World J Urol 15:14–20, 1997.

29.

Mills TM, Pollock DM, Lewis RW, Branam HS, Wingard CJ. Endothelin-1-induced vasoconstriction is inhibited during erection in rats. Am J Physiol Regul Integr Comp Physiol 281:R476–483, 2001.

30.

Dong F, Zhang X, Wold LE, Ren Q, Zhang Z, Ren J. Endothelin-1 enhances oxidative stress, cell proliferation and reduces apoptosis in human umbilical vein endothelial cells: role of ETB receptor, NADPH oxidase and caveolin-1. Br J Pharmacol 145:323–333, 2005.

31.

Tada A, Suzuki I, Im S, Davis MB, Cornelius J, Babcock G, Nordlund JJ, Abdel-Malek ZA. Endothelin-1 is a paracrine growth factor that modulates melanogenesis of human melanocytes and participates in their responses to ultraviolet radiation. Cell Growth Differ 9:575–584, 1998.