The role of rho kinase in sex-dependent vascular dysfunction in type 1 diabetes

Successful induction of diabetes in mice demonstrates no gender difference in development of early diabetic retinopathy

Purpose

Female mice have been found to be resistant to streptozotocin (STZ)-induced diabetes, and pre-clinical research related to diabetic complications commonly omits females. The purpose of this study was to develop a method to induce diabetes in female mice, and to determine if retinas of diabetic female mice develop molecular changes and histopathological abnormalities comparable to those which develop in male diabetic mice.

Methods

To induce diabetes, animals of both sexes received daily intraperitoneal (i.p.) injection of STZ for 5 consecutive days at 55 mg/kg BW (a dose that is known to induce diabetes in male mice) or for females, 75 mg/kg BW of STZ. Retinal abnormalities that have been implicated in the development of the retinopathy (superoxide generation and expression of inflammatory proteins, iNOS and ICAM-1) were evaluated at 2 months of diabetes, and retinal capillary degeneration was evaluated at 8 months of diabetes.

Results

Daily i.p. injection of STZ for 5 consecutive days at a concentration of 55 mg/kg BW was sufficient to induce diabetes in 100% of male mice, but only 33% of female mice. However, females did become hyperglycemic when the dose of STZ administered was increased to 75 mg/kg BW. The resulting STZ-induced hyperglycemia in female and male mice was sustained for at least 8 months. After induction of the diabetes, both sexes responded similarly with respect to the oxidative stress, expression of iNOS, and degeneration of retinal capillaries, but differed in the limited population evaluated with respect to expression of ICAM-1.

Conclusions

The resistance of female mice to STZ-induced diabetes can be overcome by increasing the dose of STZ used. Female mice can, and should, be included in pre-clinical studies of diabetes and its complications.

Evaluation of the Rho A/Rho-kinase pathway in the uterus of the rat model of polycystic ovary syndrome

The aim of this study was to investigate the expression of RhoA/Rho-kinase in the uterus and the effect of Rho-kinase inhibitors on uterine contractions of dehydroepiandrosterone (DHEA) induced polycystic ovary syndrome (PCOS) rats. Forty-four female Sprague-Dawley (21 days old) rats divided into three groups: The control group (n = 14, any procedure was not performed), vehicle group (n = 14, 0.2 ml of sesame oil, subcutaneous injection, 20 days) and PCOS group (n = 16, DHEA 6 mg/100 g in 0.2 ml of sesame oil, subcutaneous injection, 20 days). The myometrium thickness and uterine wet weight were assessed. The mRNA and protein expressions of Rho A, the effect of Rho-kinase inhibitors (fasudil and Y-27632) on KCl, carbachol, and PGF2α induced contractions were evaluated in the uterus. In the PCOS group, the myometrium thickness and uterine wet weight significantly increased compared to the control group and vehicle group. The mRNA expression level and the immunoreactive score of Rho A, ROCK 1, ROCK 2 were similar in all groups. In the PCOS group, KCl, carbachol, and PGF2α induced uterine contractions significantly increased compared to the control group and vehicle group. Fasudil and Y-27632 significantly inhibited KCl, carbachol, and PGF2α induced uterine contractions in all groups. In conclusion, the expression of Rho A, ROCK 1, ROCK 2 not changed although myometrium thickness, uterine wet weight and the contractile responses of uterus increased in the PCOS group. The results suggest that the Rho-kinase inhibitors effectively suppressed increased contractions in the PCOS group they might be potential therapeutic agents.

Dietary Fatty Acid Saturation Modulates Sphingosine-1-Phosphate-Mediated Vascular Function

Sphingolipids, modified by dietary fatty acids, are integral components of plasma membrane and caveolae that are also vasoactive compounds. We hypothesized that dietary fatty acid saturation affects vasoconstriction to sphingosine-1-phosphate (S1P) through caveolar regulation of rho kinase. Wild type (WT) and caveolin-1-deficient (cav-1 KO) mice which lack vascular caveolae were fed a low-fat diet (LF), 60% high-saturated fat diet (lard, HF), or 60% fat diet with equal amounts of lard and n-3 polyunsaturated menhaden oil (MO). Weight gain of WT on HF and MO diets was similar while markedly blunted in cav-1 KO. Neither high-fat diet affected the expression of cav-1, rho, or rho kinase in arteries from WT. In cav-1 KO, MO increased the vascular expression of rho but had no effect on rho kinase. HF had no effect on rho or rho kinase expression in cav-1 KO. S1P produced a concentration-dependent constriction of gracilis arteries from WT on LF that was reduced with HF and restored to normal with MO. Constriction to S1P was reduced in cav-1 KO and no longer affected by a high-saturated fat diet. Inhibition of rho kinase which reduced constriction to PE independent of diet in arteries from WT and cav-1 KO only reduced constriction to S1P in arteries from WT fed MO. The data suggest that dietary fatty acids modify vascular responses to S1P by a caveolar-dependent mechanism which is enhanced by dietary n-3 polyunsaturated fats.

Diastolic dysfunction is more apparent in STZ-induced diabetic female mice, despite less pronounced hyperglycemia

Diabetic cardiomyopathy is a distinct pathology characterized by early emergence of diastolic dysfunction. Increased cardiovascular risk associated with diabetes is more marked for women, but an understanding of the role of diastolic dysfunction in female susceptibility to diabetic cardiomyopathy is lacking. To investigate the sex-specific relationship between systemic diabetic status and in vivo occurrence of diastolic dysfunction, diabetes was induced in male and female mice by streptozotocin (5x daily i.p. 55 mg/kg). Echocardiography was performed at 7 weeks post-diabetes induction, cardiac collagen content assessed by picrosirius red staining, and gene expression measured using qPCR. The extent of diabetes-associated hyperglycemia was more marked in males than females (males: 25.8 ± 1.2 vs 9.1 ± 0.4 mM; females: 13.5 ± 1.5 vs 8.4 ± 0.4 mM, p < 0.05) yet in vivo diastolic dysfunction was evident in female (E/E' 54% increase, p < 0.05) but not male diabetic mice. Cardiac structural abnormalities (left ventricular wall thinning, collagen deposition) were similar in male and female diabetic mice. Female-specific gene expression changes in glucose metabolic and autophagy-related genes were evident. This study demonstrates that STZ-induced diabetic female mice exhibit a heightened susceptibility to diastolic dysfunction, despite exhibiting a lower extent of hyperglycemia than male mice. These findings highlight the importance of early echocardiographic screening of asymptomatic prediabetic at-risk patients.

Effect of Long-Term Diabetes on Serotonin-Mediated Contraction in Carotid Arteries from Streptozotocin-Induced Diabetic Male and Female Rats

An accumulating body of evidence suggests that males and females differ in vascular function in arteries under pathophysiological states. In this study, we tested whether there was a sex difference associated with serotonin (5-hydroxytryptamine, 5-HT)-mediated contraction in the carotid arteries of long-term streptozotocin (STZ)-induced diabetic rats [viz. 23 or 24 weeks after STZ (65 mg/kg, intravenously (i.v.)) injection starting at 8 weeks old of rats]. In the control group, the 5-HT- and high-K⁺-induced contractions were greater in females than in males. In both sexes, treatment with STZ led to a decrease of 5-HT-induced contraction in carotid arteries compared to controls. In STZ-induced diabetic rats, the carotid arterial 5-HT-induced contraction was greater in female rats than in diabetic male rats. The high-K⁺-induced contraction was greater in diabetic female rats than in either age-matched female controls or diabetic male rats. Expression of the 5-HT_2A receptor, which is the main receptor for 5-HT-induced contraction in rat carotid arteries, was similar among the four groups. These results suggest that decreased 5-HT-induced carotid arterial contraction is seen in both sexes under long-term STZ-induced diabetic conditions. Further, this reduction seems to be weaker in females than in males. This alteration of 5-HT-induced contraction may be partly associated with increased voltage-dependent Ca²⁺ channel activity.

Blocking 5-HT2 receptor restores cardiovascular disorders in type 1 experimental diabetes

This study aimed to determine whether the serotonergic modulation, through selective 5-HT₂ receptor blockade, restores cardiovascular disturbances in type 1 diabetic rats. Diabetes was induced by alloxan (150 mg/kg, s.c.) and maintained for 4 weeks. 5-HT₂ receptor was blocked by sarpogrelate (30 mg/kg.day; 14 days; p.o.). Systolic blood pressure (SBP), heart rate (HR), glycaemia and body weight (BW) were monitored periodically. Animals were sacrificed at the end of the study and the heart, right kidney and thoracic aorta were removed; plasma samples were also obtained. Left ventricular hypertrophy index (LVH) and renal hypertrophy index (RH) were determined. Vascular function was studied in aorta rings; additionally, superoxide anion (O₂•⁻) production (by lucigenin-enhanced chemiluminescence) and lipid peroxidation (by thiobarbituric acid reactive substances assay) were measured. Neither alloxan nor sarpogrelate treatments altered HR, LVH or endothelium-independent relaxation. SBP, glycaemia, BW, RH, O₂•⁻ production and lipid peroxidation were significantly altered in diabetic animals compared with controls. Sarpogrelate treatment considerably decreased SBP, RH, O₂•⁻ production and lipid peroxidation. Endothelium-dependent relaxation was severely reduced in diabetic animal aortas compared to controls; sarpogrelate treatment markedly improved it. Our outcomes show that selectively blocking 5-HT₂ receptors has beneficial effects on impaired cardiovascular parameters in diabetes.

Multiple activation mechanisms of serotonin-mediated contraction in the carotid arteries obtained from spontaneously hypertensive rats

Serotonin (5-hydroxytryptamine, 5-HT) is an important endogenous substance that regulates the vascular tone, and the abnormal signaling of 5-HT has been observed in the arteries under several pathophysiological conditions such as diabetes and hypertension. However, signaling pathways of 5-HT-mediated vasocontraction in hypertension remain unclear. Therefore, we tested the hypothesis that 5-HT-mediated contraction and contributions of various kinases such as mitogen-activated protein kinases (MAPKs), phosphoinositide 3-kinase (PI3K), Rho kinase (ROCK), and 3-phosphoinositide-dependent kinase 1 (PDK1) to the contraction would be altered in the carotid arteries obtained from spontaneously hypertensive rats (SHR) compared to control Wistar Kyoto (WKY) rats. In the carotid arteries from SHR (vs. those from WKY), (1) the 5-HT-mediated contraction was increased, whereas the norepinephrine-mediated contraction was not; (2) 5-HT-mediated contractions were partly inhibited by each kinase (extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, c-Jun N-terminal kinase (JNK), PI3K, ROCK, and PDK1) inhibitor; and (3) 5-HT-stimulated phosphorylation of ERK1/2, p38 MAPK, JNK, myosin phosphatase target subunit 1 (MYPT1), and PDK1 was increased. The expression of ROCK2 but not ROCK1 was increased in the carotid arteries from SHR compared to WKY. The expression of 5-HT2A receptor, a major receptor of 5-HT-mediated contraction in rat carotid artery, was similar in carotid arteries between the two groups. These results suggest that 5-HT-mediated contraction was utilized multiple signaling pathways such as ERK1/2, p38 MAPK, JNK, PI3K, ROCK, and PDK1. Although 5-HT-mediated contraction was increased in the carotid arteries obtained from SHR, further studies are necessary to clarify how each kinase may integrate in the vascular smooth muscles under hypertension.

Rho Kinases in Health and Disease: From Basic Science to Translational Research

Rho-associated kinases ROCK1 and ROCK2 are key regulators of actin cytoskeleton dynamics downstream of Rho GTPases that participate in the control of important physiologic functions, S including cell contraction, migration, proliferation, adhesion, and inflammation. Several excellent review articles dealing with ROCK function and regulation have been published over the past few years. Although a brief overview of general molecular, biochemical, and functional properties of ROCKs is included, an effort has been made to produce an original work by collecting and synthesizing recent studies aimed at translating basic discoveries from cell and experimental models into knowledge of human physiology, pathophysiological mechanisms, and medical therapeutics. This review points out the specificity and distinct roles of ROCK1 and ROCK2 isoforms highlighted in the last few years. Results obtained from genetically modified mice and genetic analysis in humans are discussed. This review also addresses the involvement of ROCKs in human diseases and the potential use of ROCK activity as a biomarker or a pharmacological target for specific inhibitors.

Sex, sex steroids, and diabetic cardiomyopathy: making the case for experimental focus

More than three decades ago, the Framingham study revealed that cardiovascular risk is elevated for all diabetics and that this jeopardy is substantially accentuated for women in particular. Numerous studies have subsequently documented worsened cardiac outcomes for women. Given that estrogen and insulin exert major regulatory effects through common intracellular signaling pathways prominent in maintenance of cardiomyocyte function, a sex-hormone:diabetic-disease interaction is plausible. Underlying aspects of female cardiovascular pathophysiology that exaggerate cardiovascular diabetic risk may be identified, including increased vulnerability to coronary microvascular disease, age-dependent impairment of insulin-sensitivity, and differential susceptibility to hyperglycemia. Since Framingham, considerable progress has been made in the development of experimental models of diabetic disease states, including a diversity of genetic rodent models. Ample evidence indicates that animal models of both type 1 and 2 diabetes variably recapitulate aspects of diabetic cardiomyopathy including diastolic and systolic dysfunction, and cardiac structural pathology including fibrosis, loss of compliance, and in some instances ventricular hypertrophy. Perplexingly, little of this work has explored the relevance and mechanisms of sexual dimorphism in diabetic cardiomyopathy. Only a small number of experimental studies have addressed this question, yet the prospects for gaining important mechanistic insights from further experimental enquiry are considerable. The case for experimental interrogation of sex differences, and of sex steroid influences in the aetiology of diabetic cardiomyopathy, is particularly compelling-providing incentive for future investigation with ultimate therapeutic potential.

Zinc protects against diabetes-induced pathogenic changes in the aorta: roles of metallothionein and nuclear factor (erythroid-derived 2)-like 2

BACKGROUND

Cardiovascular diseases remain a leading cause of the mortality world-wide, which is related to several risks, including the life style change and the increased diabetes prevalence. The present study was to explore the preventive effect of zinc on the pathogenic changes in the aorta.

METHODS

A genetic type 1 diabetic OVE26 mouse model was used with/without zinc supplementation for 3 months. To determine gender difference either for pathogenic changes in the aorta of diabetic mice or for zinc protective effects on diabetes-induced pathogenic changes, both males and females were investigated in parallel by histopathological and immunohistochemical examinations, in combination of real-time PCR assay.

RESULTS

Diabetes induced significant increases in aortic oxidative damage, inflammation, and remodeling (increased fibrosis and wall thickness) without significant difference between genders. Zinc treatment of these diabetic mice for three months completely prevented the above pathogenic changes in the aorta, and also significantly up-regulated the expression and function of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a pivotal regulator of anti-oxidative mechanism, and the expression of metallothionein (MT), a potent antioxidant. There was gender difference for the protective effect of zinc against diabetes-induced pathogenic changes and the up-regulated levels of Nrf2 and MT in the aorta.

CONCLUSIONS

These results suggest that zinc supplementation provides a significant protection against diabetes-induced pathogenic changes in the aorta without gender difference in the type 1 diabetic mouse model. The aortic protection by zinc against diabetes-induced pathogenic changes is associated with the up-regulation of both MT and Nrf2 expression.

Sex differences in the enhanced responsiveness to acute angiotensin II in growth-restricted rats: role of fasudil, a Rho kinase inhibitor

This study tested the hypothesis that Rho kinase contributes to the enhanced pressor response to acute angiotensin II in intact male growth-restricted and gonadectomized female growth-restricted rats. Mean arterial pressure (MAP) and renal function were determined in conscious animals pretreated with enalapril (250 mg/l in drinking water) for 1 wk to block the endogenous renin-angiotensin system and normalize blood pressure (baseline). Blood pressure and renal hemodynamics did not differ at baseline. Acute Ang II (100 ng·kg(-1)·min(-1)) induced a greater increase in MAP and renal vascular resistance and enhanced reduction in glomerular filtration rate in intact male growth-restricted rats compared with intact male controls (P < 0.05). Cotreatment with the Rho kinase inhibitor fasudil (33 μg·kg(-1)·min(-1)) significantly attenuated these hemodynamic changes (P < 0.05), but it did not abolish the differential increase in blood pressure above baseline, suggesting that the impact of intrauterine growth restriction on blood pressure in intact male growth-restricted rats is independent of Rho kinase. Gonadectomy in conjunction with fasudil returned blood pressure back to baseline in male growth-restricted rats, and yet glomerular filtration rate remained significantly reduced (P < 0.05). Thus, these data suggest a role for enhanced renal sensitivity to acute Ang II in the developmental programming of hypertension in male growth-restricted rats. However, inhibition of Rho kinase had no effect on the basal or enhanced increase in blood pressure induced by acute Ang II in the gonadectomized female growth-restricted rat. Therefore, these studies suggest that Rho kinase inhibition exerts a sex-specific effect on blood pressure sensitivity to acute Ang II in growth-restricted rats.

5HT(2A) and 5HT(2B) receptors contribute to serotonin-induced vascular dysfunction in diabetes

Although 5HT(2A) receptors mediate contractions of normal arteries to serotonin (5HT), in some cardiovascular diseases, other receptor subtypes contribute to the marked increase in serotonin contractions. We hypothesized that enhanced contractions of arteries from diabetics to 5HT are mediated by an increased contribution from multiple 5HT receptor subtypes. We compared responses to selective 5HT receptor agonists and expression of 5HT receptor isoforms (5HT(1B), 5HT(2A), and 5HT(2B)) in aorta from nondiabetic (ND) compared to type 2 diabetic mice (DB, BKS.Cg-Dock7(m)+/+Lepr(db)/J). 5HT, 5HT(2A) (TCB2 and BRL54443), and 5HT(2B) (norfenfluramine and BW723C86) receptor agonists produced concentration-dependent contractions of ND arteries that were markedly increased in DB arteries. Neither ND nor DB arteries contracted to a 5HT(1B) receptor agonist. MDL11939, a 5HT(2A) receptor antagonist, and LY272015, a 5HT(2B) receptor antagonist, reduced contractions of arteries from DB to 5HT more than ND. Expression of 5HT(1B), 5HT(2A), and 5HT(2B) receptor subtypes was similar in ND and DB. Inhibition of rho kinase decreased contractions to 5HT and 5HT(2A) and 5HT(2B) receptor agonists in ND and DB. We conclude that in contrast to other cardiovascular diseases, enhanced contraction of arteries from diabetics to 5HT is not due to a change in expression of multiple 5HT receptor subtypes.

Prevention of diabetes-induced arginase activation and vascular dysfunction by Rho kinase (ROCK) knockout

AIMS

We determined the role of the Rho kinase (ROCK) isoforms in diabetes-induced vascular endothelial dysfunction and enhancement of arginase activity and expression.

METHODS AND RESULTS

Studies were performed in aortic tissues from haplo-insufficient (H-I) ROCK1 and ROCK2 mice and wild-type (WT) mice rendered diabetic with streptozotocin and in bovine aortic endothelial cells (BAECs) treated with high glucose (HG, 25 mM). Protein expression of both ROCK isoforms was substantially elevated in aortas of WT mice after 8 weeks of diabetes and in BAECs after 48 h in HG. Impairment of endothelium-dependent vasorelaxation of aortas was observed in diabetic WT mice. However, there was no impairment in aortas of diabetic ROCK1 H-I mice and less impairment in aortas of diabetic ROCK2 H-I mice, compared with non-diabetic mice. These vascular effects were associated with the prevention of diabetes-induced decrease in nitric oxide (NO) production and a rise in arginase activity/expression. Acute treatment with the arginase inhibitor, BEC, improved endothelium-dependent vasorelaxation of aortas of both diabetic WT and ROCK2, but not of ROCK1 mice.

CONCLUSION

Partial deletion of either ROCK isoform, but to a greater extent ROCK1, attenuates diabetes-induced vascular endothelial dysfunction by preventing increased arginase activity and expression and reduction in NO production in type 1 diabetes. Limiting ROCK and arginase activity improves vascular function in diabetes.

RhoA localization with caveolin-1 regulates vascular contractions to serotonin

Vascular smooth muscle contraction occurs following an initial response to an increase in intracellular calcium concentration and a sustained response following increases in the sensitivity of contractile proteins to calcium (calcium sensitization). This latter process is regulated by the rhoA/rho kinase pathway and activated by serotonin. In multiple cell types, signaling molecules compartmentalize within caveolae to regulate their activation. We hypothesized that serotonin differentially compartmentalizes rhoA within caveolar versus noncaveolar lipid rafts to regulate sustained vascular contractions. To test this hypothesis, we measured aortic contractions in response to serotonin in wild-type (WT) and cav-1-deficient mice (cav-1 KO). RhoA-dependent contractions in response to serotonin were markedly augmented in arteries from cav-1 KO mice despite a modest reduction in rhoA expression compared with WT. We found that under basal conditions, rhoA in WT arteries was primarily localized within high-density sucrose gradient fractions but temporally shifted to low-density fractions in response to serotonin. In contrast, rhoA in cav-1 KO arteries was primarily in low-density fractions and shifted to high-density fractions in a similar timeframe as that seen in WT mice. We conclude that localization of rhoA to caveolar versus noncaveolar lipid rafts differentially regulates its activation and contractions to rhoA-dependent agonists with greater activation associated with its localization to noncaveolar rafts. Disruption of rhoA localization within caveolae may contribute to increased activation and enhanced vascular contractions in cardiovascular disease.