Role of cytochrome P450 metabolites of arachidonic acid in regulation of corporal smooth muscle tone in diabetic and older rats

Association between polyunsaturated fatty acid intake and the prevalence of erectile dysfunction: A cross-sectional analysis of the NHANES 2001-2004

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have demonstrated significant therapeutic potential across a wide range of disease. The aim of this study was to investigate the potential impact of PUFA intake on the prevalence of erectile dysfunction (ED).

METHODS

The study included a total of 3730 participants from the National Health and Nutrition Examination Survey (NHANES) 2001-2004. Univariate analysis, multivariate regression analysis, subgroup analysis and machine learning were utilized to explore the relationship of variables to ED. Dose response curves were constructed to observe the linear or nonlinear relationship between PUFA intake and the prevalence of ED. Propensity score matching (PSM) was used for sensitivity analysis. Finally, the potential mechanistic link between PUFA intake and ED was explored.

RESULTS

Through univariate and multivariate regression analysis results before and after PSM and XGBoost algorithm model results, arachidonic acid (AA) was chosen as the main research object. The consumption of AA was found to be associated with a decreased prevalence of ED under the fully adjusted model [OR = 0.33 (0.20, 0.56), P < 0.001]. The interaction between AA and education was found in the subgroup analysis. Dose-response curves indicated a linear negative correlation between AA intake and the prevalence of ED. The above results were confirmed in the data analysis after 1:1 PSM. In addition, AA intake was associated with a decrease in inflammatory biomarkers and homocysteine.

CONCLUSIONS

The results suggest that AA intake is negatively correlated with the prevalence of ED. Further, anti-inflammatory and anti-endothelial damage may play a role in this.

Coronary Large Conductance Ca2+-Activated K+ Channel Dysfunction in Diabetes Mellitus

Diabetes mellitus (DM) is an independent risk of macrovascular and microvascular complications, while cardiovascular diseases remain a leading cause of death in both men and women with diabetes. Large conductance Ca2+-activated K+ (BK) channels are abundantly expressed in arteries and are the key ionic determinant of vascular tone and organ perfusion. It is well established that the downregulation of vascular BK channel function with reduced BK channel protein expression and altered intrinsic BK channel biophysical properties is associated with diabetic vasculopathy. Recent efforts also showed that diabetes-associated changes in signaling pathways and transcriptional factors contribute to the downregulation of BK channel expression. This manuscript will review our current understandings on the molecular, physiological, and biophysical mechanisms that underlie coronary BK channelopathy in diabetes mellitus.

Targeted analysis of eicosanoids derived from cytochrome P450 pathway by high-resolution multiple-reaction monitoring mass spectrometry

Cytochrome P450 (CYP450) pathway is one of the critical enzymatic via eicosanoid biosynthesis. Nevertheless, their metabolites are far less explored. This pathway plays a crucial role in converting arachidonic acid to hydroxyeicosatetraenoic (HETEs), epoxyeicosatrienoic (EETs), dihydroxyeicosatetraenoic acids (DiHETEs), and dihydroxyeicosatrienoic acids (DiHETrEs), which mediate several physiological and pathological functions. However, CYP450-derived eicosanoids are structurally complex, making those analyses a challenge in lipidomics studies. Herein, a high-resolution multiple-reaction monitoring (MRM^HR ) method has been proposed as a powerful tool for the simultaneous analysis of CYP450-eicosanoids on different biological samples. The developed liquid chromatography (LC)-MRM^HR method was partially validated according to the Food and Drug Administration (FDA) criteria, demonstrating adequate specificity, linearity, precision, and accuracy. Besides, several biological samples were analyzed to guarantee the feasibility of the method. The proposed strategy may improve the understanding of CYP450-derived eicosanoids in biological systems, which could be fundamental to reveal new aspects of those in physiologic and pathologic conditions.

Effects of epoxygenases on the nonadrenergic noncholinergic relaxant responses induced by electrical field stimulation in rabbit corpus cavernosum

We aimed to investigate the effects of epoxygenases on electrical field stimulation (EFS)-mediated nitric oxide (NO)-dependent and NO-independent nonadrenergic noncholinergic (NANC) relaxations in isolated rabbit corpus cavernosum. The tissues of 20 male adult albino rabbits (2.5-3 kg) were suspended in organ baths containing aerated Krebs solution, and isometric contractions were recorded. EFS-mediated NANC relaxations were obtained on phenylephrin (3 × 10^-5  M)-contracted tissues in the presence of guanethidine (10^-6  M) and atropine (10^-6  M). Miconazole (10^-9 -10^-4  M), 17-octadecynoic acid (ODYA) (10^-10 -10^-5  M), 14,15-epoxyeicosatrienoic acid (EET) (10^-11 -10^-8  M), 11,12-EET (10^-12 -3 × 10^-8  M) and 20-hydroxyeicosatetraenoic acid (HETE) (10^-11 -3 × 10^-8  M) were added cumulatively (n = 5-7 for each set of experiments). For NO-independent relaxations, N^ω -nitro-l-arginine methyl ester (l-NAME) (10^-4  M) was added before a group of experiments. Depending on the concentration, miconazole, 17-ODYA, 14,15-EET, 11,12-EET, and 20-HETE significantly enhanced both NO-dependent and NO-independent EFS-mediated relaxations (p < 0.05). Epoxygenases showed similar effect on NO-dependent and NO-independent relaxant responses except 20-HETE which caused significantly more enhanced relaxation on NO-dependent responses (p < 0.05). No drug caused a significant relaxation response on tissues contracted with phenylephrine. Epoxygenases contribute to EFS-mediated NO-dependent and NO-independent NANC relaxations by presynaptic mechanisms, offering a new treatment alternative for erectile dysfunction which needs to be explored in further in vivo, molecular and clinical studies.

Impact of diabetes on male sexual function in streptozotocin-induced diabetic rats: Protective role of soluble epoxide hydrolase inhibitor

Diabetes-induced male sexual dysfunction is associated with endothelial dysfunction. Inhibition of soluble epoxide hydrolase (sEH) is known to improve endothelial function in diabetes. Therefore, we hypothesized that sEH inhibitor (sEHI), [trans-4-{4-[3-(4-trifluoromethoxyphenyl)-ureido]cyclohexyloxy}benzoic acid] / t-TUCB can restore the male sexual function in diabetic rat. After one week of administration of diabetogenic agent STZ (52 mg/kg i.p) injection, diabetic rats were treated with t-TUCB (0.1 and 0.3 mg/kg, p.o) or vehicle for 8 weeks. The sexual behaviour parameters of the animals were evaluated at the end of dosing period. The levels of testosterone and glucose in serum, and sperm were quantified. Effect of treatment on weight of reproductive organs and histopathology of penile tissue was evaluated. Diabetes had a negative effect on male sexual function, weight of sexual organs and production of sperm with a parallel decrease in the level of testosterone. The sEHI, t-TUCB, significantly preserved the sexual function and minimized an increase in the level of blood glucose in diabetic rats. It also prevented a decrease in the level of testosterone and sperm in diabetic rats, in comparison to diabetic control rats. Further, diabetes induced distortion of corpus cavernosum was attenuated by t-TUCB. Based on our findings, sEHI may delay the development of sexual dysfunction in diabetes.

11,12-Epoxyeicosatrienoic acid induces vasodilator response in the rat perfused mesenteric vasculature

Epoxyeicosatrienoic acids (EETs) are endogenous ligands that undergo hydrolysis by soluble epoxide hydrolase (sEH). The responses of 11, 12‐EET in comparison with other vasodilator agonists including carbachol and sodium nitroprusside (SNP) were investigated. The effect of 1‐cyclohexyl‐3‐dodecyl urea (CDU), a sEH, was tested on the vasodilator effect induced by 11, 12‐EET in the perfused mesenteric beds isolated from normo‐glycaemic and type‐1 STZ‐diabetic rats.

In the perfused mesenteric beds of control and diabetic animals, 11, 12‐EET produced vasodilation in a dose‐dependent manner. The vasodilator response induced by 11, 12‐EET was significantly decreased in tissues obtained from diabetic animals, but this was significantly corrected through inhibition of sEH.

The effects of nitric oxide synthase inhibitor, cyclo‐oxygenase inhibitor, specific potassium channel inhibitors, soluble guanylyl cyclase inhibitor and transient receptor potential channel V4 inhibitor, on vasodilator response to 11, 12‐EET were investigated.

In tissues isolated from control animals, vasodilator responses to 11, 12‐EET were not inhibited by acute incubation with l‐NAME, l‐NAME with indomethacin, glibenclamide, iberiotoxin, charybdotoxin, apamin or ODQ.

Incubation with the transient receptor potential channel V4 inhibitor ruthenium red caused significantly reduced vasodilator responses induced by 11, 12‐EET.

In conclusion, results from this study indicate that 11, 12‐EET has a vasodilator effect in the perfused mesenteric bed, partly through activation of vanilloid receptor. A strategy to elevate the levels of EETs may have a significant impact in correcting microvascular abnormality associated with diabetes.

Associations of CYP4A11 gene-gene and gene-smoking interactions with essential hypertension in the male eastern Chinese Han population

OBJECTIVES

The aim of this study was to investigate the impact of CYP4A11 single-nucleotide polymorphisms (SNP), additional gene-gene and gene-environment interactions on essential hypertension (EH) risk.

METHODS

A total of 1648 participants (788 males, 860 females), with a mean age of 56.1 ± 14.1 years old, were selected, including 820 EH patients and 828 normotension subjects. Logistic regression was performed to investigate association of SNPs within CYP4A11 gene with high DBP, high SBP and EH risk, and generalized multifactor dimensionality reduction (GMDR) was used to analyze the gene-gene interaction and gene-smoking interaction.

RESULTS

Logistic regression analysis showed that EH risk was significantly higher in carriers of C allele of the rs1126742 polymorphism than those with TT genotype (TC+CC versus TT, adjusted OR (95%CI) = 1.56 (1.24-1.91). In addition, we also found that EH risk was also significantly higher in carriers of G allele of the rs3890011polymorphism than those with CC genotype (CG+ GG versus CC, adjusted OR (95%CI) = 1.31 (1.15-2.03). GMDR analysis indicated a potential gene-gene interaction between rs1126742 and rs3890011 and a gene-environment interaction between rs1126742 and smoking. We found that subjects with TC or CC of rs1126742 and CG or GG of rs3890011genotype have the highest EH risk, OR (95%CI) was 2.52 (1.28-3.57). Smokers with TC or CC of rs1126742 genotype have the highest EH risk, OR (95%CI) was 2.20 (1.28-3.40).

CONCLUSIONS

Gene-gene interaction between rs1126742 and rs3890011 and gene-environment interaction between rs1126742 and smoking were associated with increased EH risk.

Angiotensin-(1-7) Downregulates Diabetes-Induced cGMP Phosphodiesterase Activation in Rat Corpus Cavernosum

Molecular mechanisms of the beneficial effects of angiotensin-(1-7), Ang-(1-7), in diabetes-related complications, including erectile dysfunction, remain unclear. We examined the effect of diabetes and/or Ang-(1-7) treatment on vascular reactivity and cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE) in corpus cavernosum. Male Wistar rats were grouped as (1) control, (2) diabetic (streptozotocin, STZ, treated), (3) control + Ang-(1-7), and (4) diabetic + Ang-(1-7). Following 3 weeks of Ang-(1-7) treatment subsequent to induction of diabetes, rats were sacrificed. Penile cavernosal tissue was isolated to measure vascular reactivity, PDE gene expression and activity, and levels of p38MAP kinase, nitrites, and cGMP. Carbachol-induced vasorelaxant response after preincubation of corpus cavernosum with PE was significantly attenuated in diabetic rats, and Ang-(1-7) markedly corrected the diabetes-induced impairment. Gene expression and activity of PDE and p38MAP kinase were significantly increased in cavernosal tissue of diabetic rats, and Ang-(1-7) markedly attenuated STZ-induced effects. Ang-(1-7) significantly increased the levels of nitrite and cGMP in cavernosal tissue of control and diabetic rats. Cavernosal tissue of diabetic rats had significantly reduced cGMP levels and Ang-(1-7) markedly prevented the STZ-induced cGMP depletion. This study demonstrates that attenuation of diabetes-induced PDE activity might be one of the key mechanisms in the beneficial effects of Ang-(1-7).

Erectogenic and Aphrodisiac Property of Moringa oleifera: Involvement of Soluble Epoxide Hydrolase Enzyme

Soluble epoxide hydrolase (sEH) inhibitors have been reported to improve penile erection; therefore, sEH could be useful for management of erectile dysfunction. Methanolic and aqueous extracts of 30 Indian medicinal plants were screened for their sEH inhibition potential. Fifteen extracts showed >50% inhibition when screened at 50 µg/mL in sEH inhibition assay. Methanolic extract of Moringa oleifera Lam. (Moringaceae) seeds (MEMO) was most potent with IC50 1.7 ± 0.1 µg/mL and was selected for in vitro studies on isolated rat corpus cavernosum smooth muscle and in vivo sexual behaviour studies on healthy and diabetic rats. Rats were divided into five groups, each containing six animals and treated orally with either water, vehicle (1% Tween-20), MEMO (45 and 90 mg/kg/day for 21 days), and standard drug, sildenafil (5 mg/kg/day for 7 days). An equal number of female rats were used, and the effect of MEMO and sildenafil was compared with that of vehicle. MEMO significantly relaxed isolated rat corpus cavernosum smooth muscle at 0.1-100 µg/mL in vitro and significantly increased (p < 0.05) sexual activity, intracavernous pressure/mean arterial pressure in normal and diabetic rats. The increase in erectile function of rats by MEMO could be because of its sEH inhibitory activity. Copyright © 2016 John Wiley & Sons, Ltd.

L-arginine and tetrahydrobiopterin, but not sodium nitrite partially restored erectile dysfunction in aged rats

Aging is associated with erectile dysfunction (ED), in which nitric oxide synthase (NOS) activity and NO bioavailability are reduced due to deficiencies of NOS cofactor (tetrahydrobiopterin, BH(4)) and substrate (L-arginine). We determined whether the prolonged treatment with sodium nitrite (NaNO(2)) as a storage form of NO ameliorates ED in aged rats. Male Sprague-Dawley rats were divided: younger, aged and NaNO(2)-treated (20 mg/kg per day) aged groups. The erectile (intracavernosal pressure [ICP]/mean arterial pressure [MAP]) and corpus cavernous (CC) responses were evaluated after 12 weeks. The ICP/MAP in aged rats was lower than in young controls, which was not improved by the NaNO(2) treatment. Immunohistochemical (IHC) staining for endothelial NOS and collagen deposition was performed. We assayed NO indirectly by measuring the level of its stable end products, nitrite/nitrate, using the Griess reagent. The relaxations to ACh and EFS in the aged group were considerably less than in the younger group, which were normalized by acute incubations of l-arginine or BH(4) of aged CC. In conclusion, NaNO(2) treatment did not restore erectile response while nitrate levels were enhanced in aged penis. The cofactor or substrate administrations, but not chronic exogenous modulation of NO system may be beneficial in aged men with ED.

Chronic treatment with Ang-(1-7) reverses abnormal reactivity in the corpus cavernosum and normalizes diabetes-induced changes in the protein levels of ACE, ACE2, ROCK1, ROCK2 and omega-hydroxylase in a rat model of type 1 diabetes

Angiotensin-(1-7) [Ang-(1-7)] may have beneficial effects in diabetes mellitus-induced erectile dysfunction (DMIED) but its molecular actions in the diabetic corpus cavernosum (CC) are not known. We characterized the effects of diabetes and/or chronic in vivo administration of Ang-(1-7) on vascular reactivity in the rat corpus cavernosum (CC) and on protein expression levels of potential downstream effectors of the renin-angiotensin-aldosterone system (RAAS) such as angiotensin-converting enzyme (ACE), ACE2, Rho kinases 1 and 2 (ROCK1 and ROCK2), and omega-hydroxylase, the cytochrome-P450 enzyme that metabolizes arachidonic acid to form the vasoconstrictor, 20-hydroxyeicosatetraenoic acid. Streptozotocin-treated rats were chronicically administered Ang-(1-7) with or without A779, a Mas receptor antagonist, during weeks 4 to 6 of diabetes. Ang-(1-7) reversed diabetes-induced abnormal reactivity to vasoactive agents (endothelin-1, phenylepherine, and carbachol) in the CC without correcting hyperglycemia. Six weeks of diabetes led to elevated ACE, ROCK1, ROCK 2, and omega-hydroxylase and a concomitant decrease in ACE2 protein expression levels that were normalized by Ang-(1-7) treatment but not upon coadministration of A779. These data are supportive of the notion that the beneficial effects of Ang-(1-7) in DMIED involve counterregulation of diabetes-induced changes in ACE, ACE2, Rho kinases, and omega-hydroxylase proteins in the diabetic CC via a Mas receptor-dependent mechanism.

Involvement of large-conductance Ca(2+) -activated K(+) channels in both nitric oxide and endothelium-derived hyperpolarization-type relaxation in human penile small arteries

Large-conductance Ca(2+) -activated K(+) channels (BKC a ), located on the vascular smooth muscle, play an important role in regulation of vascular tone. In penile corpus cavernosum tissue, opening of BKC a channels leads to relaxation of corporal smooth muscle, which is essential during erection; however, there is little information on the role of BKC a channels located in penile vascular smooth muscle. This study was designed to investigate the involvement of BKC a channels in endothelium-dependent and endothelium-independent relaxation of human intracavernous penile arteries. In human intracavernous arteries obtained in connection with transsexual operations, change in isometric force was recorded in microvascular myographs, and endothelium-dependent [nitric oxide (NO) and endothelium-derived hyperpolarization (EDH)-type] and endothelium-independent (NO-donor) relaxations were measured in contracted arteries. In penile small arteries contracted with phenylephrine, acetylcholine evoked NO- and EDH-type relaxations, which were sensitive to iberiotoxin (IbTX), a selective blocker of BKC a channels. Iberiotoxin also inhibited relaxations induced by a NO-donor, sodium nitroprusside. NS11021, a selective opener of BKC a channels, evoked pronounced relaxations that were inhibited in the presence of IbTX. NS13558, a BKC a -inactive analogue of NS11021, failed to relax human penile small arteries. Our results show that BKC a channels are involved in both NO- and EDH-type relaxation of intracavernous penile arteries obtained from healthy men. The effect of a selective opener of BKC a channels also suggests that direct activation of the channel may be an advantageous approach for treatment of impaired endothelium-dependent relaxation often associated with erectile dysfunction.

The potent relaxant effect of resveratrol in rat corpus cavernosum and its underlying mechanisms

The aim of this study was to evaluate the relaxant effect of resveratrol (RVT), one of the most commonly employed dietary polyphenols, in rat corpus cavernosum, and to further investigate the contribution of possible underlying mechanisms. Strips of corpus cavernosum were used in organ baths for isometric tension studies. RVT (10(-6)-10(-4) M) produced concentration-dependent relaxation responses in rat corpus cavernosum precontracted by phenylephrine. The relaxant responses to RVT partially, but significantly inhibited by removal of endothelium. Nitric oxide (NO) synthase (NOS) blocker N-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10(-5) M) caused a significant inhibition on relaxation response to RVT, whereas cyclooxygenase inhibitor indomethacin (10(-5) M) did not significantly alter relaxant responses of corpus cavernosum strips to RVT. Corpus cavernosum contractions induced by stepwise addition to Ca2+ to high KCl solution with no Ca2+ were significantly inhibited by RVT incubation. The treatment of corpus cavernosum tissues with non-specific potassium channel inhibitor tetraethylammonium (TEA, 10(-2) M) did also significantly affect the relaxant activity of RVT. Otherwise, the relaxation response of corpus cavernosum induced by the phosphodiesterase-5 inhibitor sildenafil increased significantly in the group pretreated with 10(-5) M RVT. These results demonstrated that RVT has a potent relaxant effect on rat corpus cavernosum via endothelium-dependent and -independent mechanisms. Endothelium-dependent relaxation of corpus cavernosum to RVT is thought to be mediated primarily through NO/cGMP signaling pathway, and possibly an additional mechanism, endothelium-dependent hyperpolarization factor (EDHF). The residual endothelium-independent corpus cavernosum relaxation induced by RVT is uncertain but seems to depend on the interactions of RVT with Ca2+ entry mechanism from the extracellular space and also other undefined direct effects in this tissue.

Screening for Rho-kinase 2 inhibitory potential of Indian medicinal plants used in management of erectile dysfunction

THE AIM OF THE STUDY

Activation of Rho-kinase 2 (ROCK-II) results in contraction of corpus cavernosum smooth muscle and ROCK-II inhibitors relax corpus cavernosum in vitro and in vivo hence, plant extracts capable of inhibiting ROCK-II enzyme may be useful in management of erectile dysfunction (ED). The aim of the study was to screen selected Indian medicinal plants, having similar ethnopharmacological use for ROCK-II inhibition.

MATERIALS AND METHODS

Some Indian medicinal plants reported as aphrodisiacs in Ayurveda and modern scientific literature were collected, authenticated and extracted. Direct methanol and successive aqueous extracts of these plants were screened for ROCK-II inhibitory activity using HTRF(®)KinEASE™ STK S2 Kit (Cisbio Bioassays). Relaxant effect of potent extract was recorded on isolated rat corpus cavernosum.

RESULTS

Methanolic and successive aqueous extracts of 30 plants were screened for ROCK-II inhibition and 15 herbal extracts showed inhibition ranging between 50 and 88% at 50 μg/mL. While IC(50) of Y-27632, a standard ROCK-II inhibitor, was found to be 163.8 ± 1.2 nM. The Methanolic extract of Terminalia chebula (METC) with IC(50) value of 6.09 ± 0.17 μg/mL was found to be most potent and relaxed isolated rat corpus cavernosum significantly (p<0.01). Chebulagic and chebulinic acid of METC were found to inhibit ROCK-II and might be responsible for the inhibitory potential of the extract. The traditional use of plants like Butea frondosa, Syzygium aromaticum, Butea superba, Chlorophytum borivilianum and Mucuna pruriens, as aphrodisiacs and for male sexual disorder (MSD) might be in part due to the ROCK II inhibitory potential of these plants.

CONCLUSION

Some of the Indian medicinal plants have ROCK-II inhibitory potential and those deserve further investigation.

Divergent molecular mechanisms underlay CO- and CORM-2-induced relaxation of corpora cavernosa

INTRODUCTION

Similar to nitric oxide (NO), the principal mediator of penile erection, carbon monoxide (CO) possesses vasodilator capacities. However, whether CO could be a therapeutic target for treating erectile dysfunction (ED) is unexplored. The danger associated with systemic administration of CO has led to the development of CO-releasing molecules (CORMs), releasing CO in a local, safe and controlled way. These CORMs have shown positive outcomes in cardiovascular studies. More knowledge on the (patho)physiological functions of CO in erectile function and the potential therapeutic role of CORMs is required.

AIM

The present study aims the assessment of the effect of CO and CO donor CORM-2 on the corporal tension and the underlying molecular mechanisms.

METHODS

Organ bath studies were performed measuring isometric tension on isolated mice corpora cavernosa (CC) strips. Responses to CO (10-300 µmol/L) and CORM-2 (10-100 µmol/L) were measured in the presence/absence of activators/inhibitors of different molecular pathways.

MAIN OUTCOME MEASURES

CO and CORM-2 relax corporal strips concentration dependently, although the molecular mechanisms behind the corporal relaxation seem to differ completely.

RESULTS

CO induces corporal relaxation by activating soluble guanylyl cyclase (sGC), increasing cyclic guanosine monophosphate (cGMP) concentrations. The molecular mechanism involved in CORM-2-induced corporal relaxation is not related to sGC activation and remains obscure.

CONCLUSIONS

Both CO and CORM-2 induce corporal relaxation, although the underlying molecular mechanisms show no resemblance. That CO induces corporal relaxation through a mechanism similar to that of NO could be of importance as it indirectly offers the possibility that endogenous CO might serve as a backup system for insufficient NO availability in cases of ED. Whether CORM-2 possesses the same capacity remains questionable and requires further research.

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

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, LC(17b), 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.

Eicosanoids, β-cell function, and diabetes

Arachidonic acid (AA) is metabolized by cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) enzymes into eicosanoids, which are involved in diverse diseases, including type 1 and type 2 diabetes. During the last 30 years, evidence has been accumulated that suggests important functions for eicosanoids in the control of pancreatic β-cell function and destruction. AA metabolites of the COX pathway, especially prostaglandin E(2) (PGE(2)), appear to be significant factors to β-cell dysfunction and destruction, participating in the pathogenesis of diabetes and its complications. Several elegant studies have contributed to the sorting out of the importance of 12-LOX eicosanoids in cytokine-mediated inflammation in pancreatic β cells. The role of CYP eicosanoids in diabetes is yet to be explored. A recent publication has demonstrated that stabilizing the levels of epoxyeicosatrienoic acids (EETs), CYP eicosanoids, by inhibiting or deleting soluble epoxide hydrolase (sEH) improves β-cell function and reduces β-cell apoptosis in diabetes. In this review we summarize recent findings implicating these eicosanoid pathways in diabetes and its complications. We also discuss the development of animal models with targeted gene deletion and specific enzymatic inhibitors in each pathway to identify potential targets for the treatment of diabetes and its complications.

Effect of cytochrome P450 polymorphism on arachidonic acid metabolism and their impact on cardiovascular diseases

Cardiovascular diseases (CVDs) remain the leading cause of death in the developed countries. Taking into account the mounting evidence about the role of cytochrome P450 (CYP) enzymes in cardiovascular physiology, CYP polymorphisms can be considered one of the major determinants of individual susceptibility to CVDs. One of the important physiological roles of CYP enzymes is the metabolism of arachidonic acid. CYP epoxygenases such as CYP1A2, CYP2C, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which generally possess vasodilating, anti-inflammatory, anti-apoptotic, anti-thrombotic, natriuretic, and cardioprotective effects. Therefore, genetic polymorphisms causing lower activity of these enzymes are generally associated with an increased risk of several CVDs such as hypertension and coronary artery disease. EETs are further metabolized by soluble epoxide hydrolase (sEH) to the less biologically active dihydroxyeicosatrienoic acids (DHETs). Therefore, sEH polymorphism has also been shown to affect arachidonic acid metabolism and to be associated with CVDs. On the other hand, CYP omega-hydroxylases such as CYP4A11 and CYP4F2 metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) which has both vasoconstricting and natriuretic effects. Genetic polymorphisms causing lower activity of these enzymes are generally associated with higher risk of hypertension. Nevertheless, some studies have denied the association between polymorphisms in the arachidonic acid pathway and CVDs. Therefore, more research is needed to confirm this association and to better understand the pathophysiologic mechanisms behind it.