Jessica Faulkner

Deletion of soluble epoxide hydrolase gene improves renal endothelial function and reduces renal inflammation and injury in streptozotocin-induced type 1 diabetes

Studies suggest that soluble epoxide hydrolase (sEH) inhibition reduces end-organ damage in cardiovascular diseases. We hypothesize that sEH gene (Ephx2) knockout (KO) improves endothelial function and reduces renal injury in streptozotocin-induced diabetes. After 6 wk of diabetes, afferent arteriolar relaxation to acetylcholine was impaired in diabetic wild-type (WT) mice, as the maximum relaxation was 72% of baseline diameter in the WT but only 31% in the diabetic mice. Ephx2 KO improved afferent arteriolar relaxation to acetylcholine in diabetes as maximum relaxation was 58%. Urinary monocyte chemoattractant protein-1 (MCP-1) excretion significantly increased in diabetic WT mice compared with control (868 ± 195 vs. 31.5 ± 7 pg/day), and this increase was attenuated in diabetic Ephx2 KO mice (420 ± 98 pg/day). The renal phospho-IKK-to-IKK ratio and nuclear factor-κB were significantly decreased, and hemeoxygenase-1 (HO-1) expression increased in diabetic Ephx2 KO compared with diabetic WT mice. Renal NADPH oxidase and urinary thiobarbituric acid reactive substances excretion were reduced in diabetic Ephx2 KO compared with diabetic WT mice. Albuminuria was also elevated in diabetic WT mice compared with control (170 ± 43 vs. 37 ± 13 μg/day), and Ephx2 KO reduced this elevation (50 ± 15 μg/day). Inhibition of sEH using trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (tAUCB) also reduced renal inflammation and injury in diabetic WT mice. Furthermore, inhibition of HO with stannous mesoporphyrin negated the reno-protective effects of tAUCB or Ephx2 KO during diabetes. These data demonstrate that Ephx2 KO improves endothelial function and reduces renal injury during diabetes. Additionally, our data also suggest that activation of HO-1 contributes to improved renal injury in diabetic Ephx2 KO mice.

Tyrosine kinase inhibitor, genistein, reduces renal inflammation and injury in streptozotocin-induced diabetic mice.

Tyrosine kinase inhibition is known to reduce diabetes-induced end-organ damage but the mechanisms remain elusive. We hypothesized that inhibition of tyrosine kinase reduces renal inflammation and injury in streptozotocin-induced diabetes. Male C57BL/6 mice were given daily injections of streptozotocin (45 mg/kg/day, i.p. for 5 days); control animals received the vehicle (citrate buffer). Thereafter, streptozotocin-treated mice were treated with genistein (10 mg/kg, i.p three times a week for 10 weeks, n=8-10/group) or the vehicle (5% DMSO). The streptozotocin-treated mice displayed significant elevation in blood glucose level and decrease in plasma insulin level compared to their vehicle-treated controls. Treatment with genistein reduced blood glucose level (~15%; p<0.05) without a significant effect on plasma insulin level; however, blood glucose remained significantly higher than the control group. The development of diabetes was associated with significant increases in total protein, albumin, nephrin and collagen excretions compared to their controls. In addition, the diabetic mice displayed increased urinary MCP-1 excretion in association with increased renal ICAM-1 expression and apoptotic cells. Furthermore, renal gp91 expression levels and urinary Thio-Barbituric Acid Reactive Substances (TBARs) excretion, indices of oxidative stress, were also elevated in diabetic mice. These changes were associated with increased renal phospho-tyrosine expression and renal phospho-ERK/ERK ratio. Importantly, treatment with genistein reduced all these parameters towards control values. Collectively, the results suggest that the reno-protective effect of genistein likely relates to reduced renal inflammation, oxidative stress and apoptosis in diabetic mice.

Induction of hemeoxygenase-1 reduces glomerular injury and apoptosis in diabetic spontaneously hypertensive rats

Induction of hemeoxygenase-1 (HO-1) lowers blood pressure and reduces organ damage in hypertensive animal models; however, a potential protective role for HO-1 induction against diabetic-induced glomerular injury remains unclear. We hypothesize that HO-1 induction will protect against diabetes-induced glomerular injury by maintaining glomerular integrity and inhibiting renal apoptosis, inflammation, and oxidative stress. Diabetes was induced with streptozotocin in spontaneously hypertensive rats (SHR) as a model where the coexistence of hypertension and diabetes aggravates the progression of diabetic renal injury. Control and diabetic SHR were randomized to receive vehicle or the HO-1 inducer cobalt protoporphyrin (CoPP). Glomerular albumin permeability was significantly greater in diabetic SHR compared with control, consistent with an increase in apoptosis and decreased glomerular nephrin and α(3)β(1)-integrin protein expression in diabetic SHR. CoPP significantly reduced albumin permeability and apoptosis and restored nephrin and α(3)β(1)-integrin protein expression levels in diabetic SHR. Glomerular injury in diabetic SHR was also associated with increases in NF-κB-induced inflammation and oxidative stress relative to vehicle-treated SHR, and CoPP significantly blunted diabetes-induced increases in glomerular inflammation and oxidative stress in diabetic SHR. These effects were specific to exogenous stimulation of HO-1, since incubation with the HO inhibitor stannous mesoporphyrin alone did not alter glomerular inflammatory markers or oxidative stress yet was able to prevent CoPP-mediated decreases in these parameters. These data suggest that induction of HO-1 reduces diabetic induced-glomerular injury and apoptosis and these effects are associated with decreased NF-κB-induced inflammation and oxidative stress.

Role of haem oxygenase in the renoprotective effects of soluble epoxide hydrolase inhibition in diabetic spontaneously hypertensive rats

We have shown previously that inhibition of sEH (soluble epoxide hydrolase) increased EETs (epoxyeicosatrienoic acids) levels and reduced renal injury in diabetic mice and these changes were associated with induction of HO (haem oxygenase)-1. The present study determines whether the inhibition of HO negates the renoprotective effect of sEH inhibition in diabetic SHR (spontaneously hypertensive rats). After 6 weeks of induction of diabetes with streptozotocin, SHR were divided into the following groups: untreated, treated with the sEH inhibitor t-AUCB {trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid}, treated with the HO inhibitor SnMP (stannous mesoporphyrin), and treated with both inhibitors for 4 more weeks; non-diabetic SHR served as a control group. Induction of diabetes significantly increased renal sEH expression and decreased the renal EETs/DHETEs (dihydroxyeicosatrienoic acid) ratio without affecting HO-1 activity or expression in SHR. Inhibition of sEH with t-AUCB increased the renal EETs/DHETEs ratio and HO-1 activity in diabetic SHR; however, it did not significantly alter systolic blood pressure. Treatment of diabetic SHR with t-AUCB significantly reduced the elevation in urinary albumin and nephrin excretion, whereas co-administration of the HO inhibitor SnMP with t-AUCB prevented these changes. Immunohistochemical analysis revealed elevations in renal fibrosis as indicated by increased renal TGF-β (transforming growth factor β) levels and fibronectin expression in diabetic SHR and these changes were reduced with sEH inhibition. Co-administration of SnMP with t-AUCB prevented its ability to reduce renal fibrosis in diabetic SHR. In addition, SnMP treatment also prevented t-AUCB-induced decreases in renal macrophage infiltration, IL-17 expression and MCP-1 levels in diabetic SHR. These findings suggest that HO-1 induction is involved in the protective effect of sEH inhibition against diabetic renal injury.

Induction of hemeoxygenase-1 attenuates the hypertension and renal inflammation in spontaneously hypertensive rats

The reno-protective mechanisms of hemeoxygenase-1 (HO-1) induction in hypertension remain unclear. We hypothesize that induction of HO-1 will decrease blood pressure and proteinuria with a marked decrease in oxidative stress and inflammation in spontaneously hypertensive rats (SHR). Male Wistar Kyoto (WKY) and SHR were injected with the HO-1 inducer cobalt protoporphyrin (CoPP, 1.5 mg/kgs.c. twice weekly) which resulted in an increase in renal HO-1 expression after 2 weeks. CoPP reduced mean arterial pressure (133±2 mmHg vs. 144±4 mmHg, p<0.05) and proteinuria (14±1 mg/day vs. 24±2 mg/day, p<0.05) in SHR as compared to baseline values, with no effect in WKY. Renal cortical superoxide (O(2)(-)) production and urinary 8-isoprostane excretion were higher in SHR compared to WKY (O(2)(-): 11±1 CPM/μg vs. 6±1 CPM/μg protein, p<0.05; 8-iso: 7±1 ng/day vs. 3±0.8 ng/day, p<0.05) and CoPP attenuated oxidative stress levels only in SHR (O(2)(-): 5±1 CPM/μg, p<0.05; 8-isoprostane: 4±0.7 ng/day) without an overall effect on antioxidant defense enzymes expression and activities. SHR showed a marked elevation in plasma C-reactive protein (CRP) and urinary monocyte chemoattractant protein-1 (MCP-1) excretion compared with WKY and HO-1 induction reduced the CRP and MCP-1 levels in SHR. Cortical COX2 expression and urinary thromboxane B(2) (TXB(2)) excretion were also significantly elevated in SHR compared to WKY and levels were reduced with induction of HO-1. Inhibition of HO with stannous mesoporphyrin further increased blood pressure and proteinuria in SHR and blocked the ability of CoPP to reduce blood pressure and proteinuria in SHR. These data demonstrate that induction of HO-1 slows the progression of hypertension and proteinuria in SHR and these changes were associated with reduced renal oxidative stress and inflammation.

Induction of Hemeoxygenase-1 Reduces Renal Oxidative Stress and Inflammation in Diabetic Spontaneously Hypertensive Rats

The renoprotective mechanisms of hemeoxygenase-1 (HO-1) in diabetic nephropathy remain to be investigated. We hypothesize that HO-1 protects the kidney from diabetic insult via lowering renal oxidative stress and inflammation. We used control and diabetic SHR with or without HO-1 inducer cobalt protoporphyrin (CoPP) treatment for 6 weeks. Urinary albumin excretion levels were significantly elevated in diabetic SHR compared to control and CoPP significantly attenuated albumin excretion. Immuno-histochemical analysis revealed an elevation in TGF-β staining together with increased urinary collagen excretion in diabetic versus control SHR, both of which were reduced with CoPP treatment. Renal oxidative stress markers were greater in diabetic SHR and reduced with CoPP treatment. The increase in renal oxidative stress was associated with an elevation in renal inflammation in diabetic SHR. CoPP treatment also significantly attenuated the markers of renal inflammation in diabetic SHR. In vitro inhibition of HO with stannous mesoporphyrin (SnMP) increased glomerular NADPH oxidase activity and inflammation and blocked the anti-oxidant and anti-inflammatory effects of CoPP. These data suggest that the reduction of renal injury in diabetic SHR upon induction of HO-1 are associated with decreased renal oxidative stress and inflammation, implicating the role of HO-1 induction as a future treatment of diabetic nephropathy.

Inhibition of 12/15-Lipoxygenase Reduces Renal Inflammation and Injury in Streptozotocin-Induced Diabetic Mice

Previous studies suggest that 12/15 lipoxygenase (12/15-LO) is implicated in diabetic vascular complications. We hypothesize that 12/15-LO inhibition attenuates renal inflammation and injury in streptozotocin-induced diabetes. Diabetes was induced in wild-type C57BL/6J (WT) and 12/15-LO deficient mice using streptozotocin. Additionally, four groups of WT mice were also used; control non diabetic, diabetic, diabetic treated with the 12/15-LO inhibitor baicalein for 10 weeks and diabetic treated with baicalein only for the last 4 weeks of the experiment. After 10 weeks of induction of diabetes with streptozotocin, WT diabetic mice exhibited marked elevation in proteinuria together with elevation in the excretion levels of thiobarbituric acid reactive substance (TBARs), a marker of oxidative stress, and monocyte chemoattractant protein-1 (MCP-1), a marker of inflammation and these changes were significantly reduced in 12/15-LO deficient diabetic mice (P<0.05). Similarly, pharmacological inhibition of 12/15-LO with baicalein prevented the elevation in renal 12-HETE production, the major murine metabolic product of 12/15-LO, in diabetic mice, and this effect was associated with decreased proteinuria, TBARs excretion and renal collagen deposition compared to untreated diabetic mice. Interestingly, the protective effects of baicalein were not noticed when only administered in the last 4 weeks of diabetes compared to untreated diabetic mice. WT diabetic mice displayed elevation in renal interleukin-6 (IL-6) levels and these changes were only reduced in diabetic mice treated with baicalein for 10 weeks (P<0.05). The anti-inflammatory effects of baicalein or 12/15-LO deficiency were further confirmed in lipopolysaccharide (LPS)-induced acute renal inflammation as inhibition of 12/15-LO reduced the elevation in renal soluble epoxide hydrolase expression in LPS-injected mice. These results suggest that increased 12/15-LO activity and 12-HETE production contribute to the elevation of renal oxidative stress, inflammation and injury in streptozotocin-induced diabetic mice.

Sex Differences in Mechanisms of Hypertension Associated With Obesity

Obesity is on a fast track to become the most costly and burdensome health epidemic worldwide. Comorbidities associated with obesity include type II diabetes mellitus and cardiovascular disease (CVD), of which hypertension is a highly prevalent and significant risk factor. Rising hypertension rates in both men and women are closely correlated with, and largely attributable to, rising rates of obesity.1,2 Currently, ≤70% of essential hypertension cases are associated with obesity.1 Understanding the mechanisms that lead to obesity-associated hypertension is vital to treat this growing patient population. However, there is a significant deficit of reports examining sex differences in obesity-associated hypertension in the literature to date because research efforts have been overwhelmingly restricted to male animals, and many clinical reports fail to separate results by sex. The National Institutes of Health, American Heart Association, and others have begun to raise awareness of sex discrepancies in research, and as a result, there has been an increase in publications highlighting differences in mechanisms associated with obesity-associated hypertension in females versus males. This review will summarize current knowledge of (1) epidemiological data of sex discrepancies in obesity-associated hypertension, (2) the sex specificity of the effects of obesity on sympathoactivation and its role in hypertension, (3) the potential role of leptin in sex differences in obesity-associated hypertension, (4) the influence of female sex hormones on leptin and obesity-associated hypertension, and (5) sex differences in renin–angiotensin–aldosterone system activation in obesity. Population rates of obesity are not equal between men and women. Data from the NHANES study (National Health and Nutrition Examination Survey),3–5 REGARDS study (Reasons for Geographic and Racial Differences in Stroke),6 and Jackson Heart Study7 demonstrate that women have a higher obesity rate than men. Worldwide, the prevalence of obesity in women is higher than men …

The regulation of aldosterone secretion by leptin: Implications in obesity-related cardiovascular disease

Purpose of review Although it has been known for some time that increases in body mass enhance aldosterone secretion, particularly in women, the origin of this elevation in aldosterone production is not well defined. Adipocyte-derived factors have emerged as potential candidates to increase aldosterone production in obesity. Recent findings Emerging evidence suggests the presence of a mechanistic link in which the adipocyte-derived hormone leptin stimulates aldosterone production in obesity, thereby creating a positive feedback loop for obesity-associated cardiovascular disease. In addition, recent reports give credence to the concept that this leptin–aldosterone stimulation pathway in obesity is an underlying mechanism for sex-discrepancies in obesity-associated cardiovascular disease. Summary Leptin appears as a new direct regulator of adrenal aldosterone production and leptin-mediated aldosterone production is a novel candidate mechanism underlying obesity-associated hypertension, particularly in females.

Continued Investigation Into 17-OHPCNovelty and Significance: Results From the Preclinical RUPP Rat Model of Preeclampsia

Preeclampsia is characterized by elevated TNF-&agr; (tumor necrosis factor-&agr;), antiangiogenic factors, such as sFlt-1 (soluble vascular endothelial growth factor receptor 1), increased uterine artery resistance index, and decreased of NO during pregnancy. Previously we showed that 17-hydroxyprogesterone caproate (17-OHPC) administered into reduced uterine perfusion pressure (RUPP) rats on day 18 of gestation improved hypertension without improving pup weight. We hypothesized that earlier administration of 17-OHPC on day 15 of gestation could improve pathophysiology of preeclampsia and fetal outcomes in response to placental ischemia. Carotid catheters were inserted on day 18, and mean arterial blood pressure and samples were collected on day 19. Mean arterial blood pressure in normal pregnant rats was 102±2, 105±2 in normal pregnant+day 15 of gestation (GD15) 17-OHPC, 127±2 in RUPP and 112±1 mm Hg in RUPP+GD15 17-OHPC, P<0.05. Pup weight and litter size were improved from 1.9±0.05, 10.1±1.4 in RUPP to 2.1±0.07 g and 13.2±0.6 in RUPP+GD15 17-OHPC, P<0.05. Uterine artery resistance index was 0.8±0.03 in RUPP, which was decreased to 0.6±0.04 in RUPP+GD15 17-OHPC, P<0.05. Plasma TNF-&agr; levels were 164±34 in RUPP and blunted to 29±9 pg/mL in RUPP+GD15 17-OHPC, P<0.05. Plasma nitrate–nitrite levels were 10.8±2.3 in RUPP rats and significantly increased to 25.5±5.2 µmol/L in RUPP+GD15 17-OHPC, P<0.05. sFlt-1 levels were 386±141 in RUPP rats, which were reduced to 110.2±11 in RUPP+17-OHPC, P<0.05. These data indicate that GD15 17-OHPC improves pathophysiology in RUPP rats, possibly via improving sFlt-1 reduced NO during pregnancy.