Smooth muscle myosin expression, isoform composition, and functional activities in rat corpus cavernosum altered by the streptozotocin-induced type 1 diabetes

Abstract

Zhang X, Kanika ND, Melman A, DiSanto ME. Smooth muscle myosin expression, isoform composition, and functional activities in rat corpus cavernosum altered by the streptozotocin-induced type 1 diabetes. Am J Physiol Endocrinol Metab 302: E32-E42, 2012. First published September 13, 2011; doi:10.1152/ajpendo.00231.2011.-Diabetes mellitus (DM) is a quite common chronic disease, and the prevalence of erectile dysfunction (ED) is three times higher in this large population. Although diabetes-related ED has been studied extensively, the actin-myosin contractile apparatus was not examined. The mRNAs encoding smooth muscle myosin (SMM) heavy chains (MHC) and essential light chains (LC 17) exist as several different alternatively spliced isoforms with distinct contractile properties. Recently, we provided novel data that blebbistatin (BLEB), a specific myosin II inhibitor, potently relaxed corpus cavernosum smooth muscle (CCSM). In this study, we examine whether diabetes alters SMM expression, alternative splicing, and/or functional activities, including sensitivity to BLEB. By using streptozotocin (STZ)-induced 2-mo diabetic rats, functional activities were tested in vivo by intracavernous pressure (ICP) recording during cavernous nerve stimulation and in vitro via organ bath contractility studies. SMM isoform composition was analyzed by competitive RT-PCR and total SMM, myocardin, and embryonic SMM (SMemb) expression by real-time RT-PCR. Results revealed that the blood glucose level of STZ rats was 407.0 vs. 129.5 mg/dl (control). STZ rats exhibited ED confirmed by significantly increased CCSM contractile response to phenylephrine and decreased ICP response. For STZ rats, SM-B, LC 17a and SM2 isoforms, total SMM, and myocardin expression increased, whereas SM-A, LC17b, and SM1 isoforms were decreased, with SMemb unchanged. BLEB was significantly more effective in relaxing STZ CCSM both in vitro and in vivo. Thus we demonstrated a novel diabetes-specific effect on alternative splicing of the SMM heavy chain and essential light chain genes to a SMM isoform composition favoring a heightened contractility and ED. A switch to a more contractile phenotype was supported further by total SMM expression increase. Moreover, the change in CCSM phenotype was associated with an increased sensitivity to BLEB, which may serve as a novel pharmacotherapy for ED.blebbistatin; cross-bridge cycling; erectile dysfunction; smooth muscle relaxation DIABETES MELLITUS (DM) is a common chronic disease affecting 285 million people, corresponding to 6.4% of the world's adult population in 2010 and expected increase to 7.9% by 2030 (40). The prevalence of erectile dysfunction (ED) is three times higher in diabetic men (28 vs. 9.6%) (17), occurs at an earlier age, and increases with disease duration, being ϳ15% at age 30 yr and rising sharply to 55% at 60 yr in diabetics (30, 31). DM may cause ED by affecting one or a combination of the following: psychological function, central nervous system function, androgen secretion, peripheral nerve activity...

Effect of Estrogen on Molecular and Functional Characteristics of the Rodent Vaginal Muscularis

“…On the other hand, MHC isoform expression of the vaginal muscularis was altered by estrogen status in our study, and our findings of a decrease in the %SM1 following ovariectomy (Figures 2 and 3) with no effect on N-terminal MHC isoform expression (SMA, SMB) corroborate the results obtained in studies utilizing smooth muscle from uterus [22,53], aorta [25], and bladder [23]. Alterations in smooth muscle carboxyl-terminal isoform expression have also been reported in animal models of bladder outlet obstruction [54], diabetes [55], atherosclerosis [56], and hypertension [57]. Despite reports of changes in carboxyl-terminal isoform expression in both physiological and pathological conditions, the physiological relevance of the relative expression of SM1/SM2 isoforms is unresolved [16,[26][27][28][29][30][31]58].…”

Characterization of corpus cavernosum smooth muscle cell phenotype in diabetic rats with erectile dysfunction

“…These results suggested that CCSM cells of diabetic ED rats tend to possess the proliferative phenotype. Our proposal contradicts a recent report by Zhang et al, 24 who studied the SM myosin expression, isoform composition and functional activities in rat corpus cavernosum altered by the streptozotocin-induced Type 1 diabetes and concluded that CCSM contractility was increased and switched to a more phasic contractile phenotype in the streptozotocin-induced Type 1 diabetic rats. This discrepancy might be attributed to the use of different isoforms of genes, as well as to the investigation of the different period of phenotype as contractile and proliferative SMCs, which represent the two ends of a spectrum of SMCs with intermediate phenotypes.…”

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