Peter Vavrinec

Vildagliptin restores renal myogenic function and attenuates renal sclerosis independently of effects on blood glucose or proteinuria in Zucker Diabetic Fatty rat

Type 2 diabetes mellitus (T2DM) is associated with risk for chronic kidney disease (CKD), which is associated with a decrease in renal myogenic tone - part of renal autoregulatory mechanisms. Novel class of drugs used for the treatment of T2DM, dipeptidyl peptidase-4 (DPP-4) inhibitors, have protective effects on the cardiovascular system. A Zucker Diabetic Fatty (ZDF) rat is an animal model of T2DM that displays progressive nephropathy in which inflammation leads to initiation of renal fibrosis and CKD. We hypothesized that CKD in the ZDF rat is related to decrease in myogenic constriction (MC) of intrarenal arteries and that treatment with the DPP-4 inhibitor, vildagliptin, prevents such changes. Renal arteries isolated from 25 weeks old lean, ZDF and ZDF treated with vildagliptin (n=7 in each group) were transferred to an arteriograph to assess agonist and pressure induced contractile responses. Furthermore, blood glucose, proteinuria, focal glomerulosclerosis (FGS) and p22phox mRNA expression of renal tissue were measured. Compared to lean controls, ZDF had significantly increased plasma glucose and cholesterol levels, focal glomerulosclerosis and interstitial α-SMA expression, and urinary protein excretion. ZDF rats also had impaired MC of renal arteries and increased renal p22phox expression. Vildagliptin did not affect plasma glucose levels or proteinuria, but effectively decreased glomerulosclerosis and restored MC and p22phox expression to the levels found in lean rats. Based on these data, it can be suggested that vildagliptin treatment protects diabetic rats from the loss of renal vascular reactivity and the development of glomerulosclerosis perhaps secondary to a reduction in oxidative stress.

Losartan protects mesenteric arteries from ROS-associated decrease in myogenic constriction following 5/6 nephrectomy

Background: Chronic renal failure (CRF) is associated with hypertension, proteinuria, loss of myogenic constriction (MC) of mesenteric arteries and increased production of reactive oxygen species (ROS) under experimental conditions. Previous results showed that ACE (angiotensin-converting enzyme activity) inhibitor therapy is effective in slowing down the progression of disease. Therefore, we wanted to study whether the inverse AT1 (angiotensin II type 1) receptor agonist, losartan (LOS) was effective in preventing loss of MC in a rat model of CRF and whether acute ROS scavengers could improve MC. Methods: Rats underwent 5/6 nephrectomy (5/6 Nx) and were treated with vehicle or LOS (20 mg/kg/day; 5/6 Nx + LOS) for 12 weeks. Thereafter, the MC of the mesenteric arteries were measured in the presence and/or absence of tempol and catalase. Systolic blood pressure and proteinuria were measured weekly. Results: Systolic blood pressure and proteinuria in the 5/6 Nx + LOS group were significantly lower than in the 5/6 Nx group. Moreover, the MC of 5/6 Nx + LOS arteries was significantly increased compared with the untreated 5/6 Nx group (maximum MC, 32.3 ± 6.9 vs 8.9 ± 3.8% (p < 0.01)). Tempol + catalase significantly increased the MC in the 5/6 Nx group, but not in the 5/6 Nx + LOS group (increase in MC, 59.7 ± 13.0 (p < 0.05) vs. 17.0 ± 15.1%). Conclusion: These results support the roles of the RAAS (renin—angiotensin—aldosterone system) and ROS in the vascular dysfunction of systemic vessels in CRF.

Epidermal Growth Factor Receptor Inhibitor PKI-166 Governs Cardiovascular Protection without Beneficial Effects on the Kidney in Hypertensive 5/6 Nephrectomized Rats

Transactivation of epidermal growth factor receptor (EGFR) signaling by G protein–coupled receptors has been implicated in several cardiovascular (CV) conditions, including hypertension, heart failure, and cardiac and vascular hypertrophy. However, the therapeutic potential of EGFR inhibition in these conditions is currently unknown. The main objective of the present study was to investigate cardiac, vascular, and renal effects of EGFR inhibition by 4-[4-[[(1R)-1-phenylethyl]amino]-7H-pyrrolo[2,3-d]pyrimidin-6-yl]phenol (PKI-166) in the hypertensive chronic kidney disease model. Rats underwent 5/6 nephrectomy (5/6Nx) and were treated with PKI-166, lisinopril or vehicle from week 6 after disease induction until week 12. Sham animals received either PKI-166 or vehicle. Treatment with PKI-166 did not affect the development of the characteristic renal features in 5/6Nx, including proteinuria, diminished creatinine clearance, and increased glomerulosclerosis, whereas these were attenuated by lisinopril. Despite absence of effects on progressive renal damage, PKI-166 attenuated the progression of hypertension and maintained cardiac function (left ventricle end-diastolic pressure) to a similar extent as lisinopril. Also, PKI-166 attenuated the increase in phosphorylated EGFR in the heart as induced by 5/6Nx. Moreover, PKI-166 and lisinopril restored the impaired contraction of isolated thoracic aortic rings to phenylephrine and angiotensin II and impaired myogenic constriction of small mesenteric arteries in 5/6Nx rats. Blockade of the EGFR displays a CV benefit independent of limiting the progression of renal injury. Our findings extend the evidence on EGFR signaling as a target in CV disorders.

A case of severe chlorite poisoning successfully treated with early administration of methylene blue, renal replacement therapy, and red blood cell transfusion: case report.

AbstractThe case of a 55-year-old man who attempted suicide by ingesting <100 mL of 28% sodium chlorite solution is presented. On arrival in the intensive care unit, the patient appeared cyanotic with lowered consciousness and displayed anuria and chocolate brown serum.Initial laboratory tests revealed 40% of methemoglobin. The formation of methemoglobin was effectively treated with methylene blue (10% after 29 hours).To remove the toxin, and because of the anuric acute renal failure, the patient received renal replacement therapy. Despite these therapeutic measures, the patient developed hemolytic anemia and disseminated intravascular coagulation, which were treated with red blood cell transfusion and intermittent hemodialysis. These interventions led to the improvement of his condition and the patient eventually fully recovered. Patient gave written informed consent.This is the third known case of chlorite poisoning that has been reported. Based upon this case, we suggest the management of sodium chlorite poisoning to comprise the early administration of methylene blue, in addition to renal replacement therapy and transfusion of red blood cells.

Growth differentiation factor 15 impairs aortic contractile and relaxing function through altered caveolar signaling of the endothelium

Growth differentiation factor 15 (GDF15) is an independent predictor of cardiovascular disease, and increased GDF15 levels have been associated with endothelial dysfunction in selected patients. We therefore investigated whether GDF15 modulates endothelial function in aortas of wild-type (WT) and GDF15 knockout (KO) mice. Vascular contractions to phenylephrine and relaxation to ACh were assessed in aortas obtained from healthy WT and GDF15 KO mice. The effects of GDF15 pretreatment and the involvement of ROS or caveolae were determined. Phenylephrine-induced contractions and ACh-mediated relaxations were similar in WT and GDF15 KO mice. Pretreatment with GDF15 inhibited contraction and relaxation in both groups. Inhibition of contraction by GDF15 was absent in denuded vessels or after blockade of nitric oxide (NO) synthase. Relaxation in WT mice was mediated mainly through NO and an unidentified endothelium-derived hyperpolarizin factor (EDHF), whereas GDF15 KO mice mainly used prostaglandins and EDHF. Pretreatment with GDF15 impaired relaxation in WT mice by decreasing NO; in GDF15 KO mice, this was mediated by decreased action of prostaglandins. Disruption of caveolae resulted in a similar inhibition of vascular responses as GDF15. ROS inhibition did not affect vascular function. In cultured endothelial cells, GDF15 pretreatment caused a dissociation between caveolin-1 and endothelial NO synthase. In conclusion, GDF15 impairs aortic contractile and relaxing function through an endothelium-dependent mechanism involving altered caveolar endothelial NO synthase signaling.

Renal myogenic constriction protects the kidney from age-related hypertensive renal damage in the Fawn- Hooded rat

Introduction: Intact myogenic constriction plays a role in renal blood flow autoregulation and protection against pressure-related (renal) injury. However, to what extent alterations in renal artery myogenic constriction are involved in development of renal damage during aging is unknown. Therefore, we studied two strains of fawn-hooded rats, which differ in expression of hypertension and chronic renal failure. Methods: Ten-week-old fawn-hooded hypertensive (FHH) and fawn-hooded low blood pressure (FHL) rats were followed for SBP and proteinuria for 1 year. At 52 weeks of age, the kidney was removed and studied for focal glomerulosclerosis (FGS) and glomerular cross-sectional area, and myogenic constriction of isolated small renal arteries in a vessel perfusion set up. Renal myogenic constriction and FGS were additionally determined in 10-week-old fawn-hooded rats. Results: At young age, fawn-hooded rats did not differ in SBP, FGS, and urinary protein excretion, but renal artery myogenic constriction already was significantly smaller (∼50%) in FHH compared with FHL rats. Aging in fawn-hooded rats was associated with increase in SBP and urinary protein excretion and loss of renal artery myogenic constriction. These changes occurred in both fawn-hooded strains, although that in FHH rats the onset of hypertension occurred earlier and the increase in proteinuria by far exceeded (>4 times) that observed in FHL rats, and came along with 5.5 times increase in FGS and 1.3 times increase in glomerular cross-sectional area and significantly less preserved renal artery myogenic constriction in FHH rats. Conclusion: Better preservation of renal myogenic constriction protects the kidney from age-related hypertensive renal damage in the fawn-hooded rat.

Vascular smooth muscle function of renal glomerular and interlobar arteries predicts renal damage in rats

Previously, it was shown that individuals with good baseline (a priori) endothelial function in isolated (in vitro) renal arteries developed less renal damage after 5/6 nephrectomy (5/6Nx; Gschwend S, Buikema H, Navis G, Henning RH, de Zeeuw D, van Dokkum RP. J Am Soc Nephrol 13: 2909-2915, 2002). In this study, we investigated whether preexisting glomerular vascular integrity predicts subsequent renal damage after 5/6Nx, using in vivo intravital microscopy and in vitro myogenic constriction of small renal arteries. Moreover, we aimed to elucidate the role of renal ANG II type 1 receptor (AT1R) expression in this model. Anesthetized rats underwent intravital microscopy to visualize constriction to ANG II of glomerular afferent and efferent arterioles, with continuous measurement of blood pressure, heart rate, and renal blood flow. Thereafter, 5/6Nx was performed, interlobar arteries were isolated from the extirpated kidney, and myogenic constriction was assessed in a perfused vessel setup. Blood pressure and proteinuria were assessed weekly for 12 wk, and focal glomerulosclerosis (FGS) was determined at the end of study. Relative expression AT1R in the kidney cortex obtained at 5/6Nx was determined by PCR. Infusion of ANG II induced significant constriction of both afferent and efferent glomerular arterioles, which strongly positively correlated with proteinuria and FGS at 12 wk after 5/6Nx. Furthermore, in vitro measured myogenic constriction of small renal arteries negatively correlated with proteinuria 12 wk after 5/6Nx. Moreover, in vivo vascular reactivity negatively correlated with in vitro reactivity. Additionally, relative expression of AT1R positively correlated with responses of glomerular arterioles and with markers of renal damage. Both in vivo afferent and efferent responses to ANG II and in vitro myogenic constriction of small renal arteries in the healthy rat predict the severity of renal damage induced by 5/6Nx. This vascular responsiveness is highly dependent on AT1R expression. Intraorgan vascular integrity may provide a useful tool to guide the prevention and treatment of renal end-organ damage.

Renal endothelial function is associated with the anti-proteinuric effect of ACE inhibition in 5/6 nephrectomized rats

In healthy rats, the physiological variation of baseline endothelial function of intrarenal arteries correlates with the severity of renal damage in response to a subsequent specific renal injury. However, whether such a variation in endothelial function may also condition or predict the variable response to angiotensin-converting enzyme-inhibiting treatment in these individuals has not been addressed before. To study this, 5/6 nephrectomy was performed to induce renal injury and chronic kidney disease in a group of healthy Wistar rats. At the time of nephrectomy, interlobar arteries were obtained from the extirpated right kidney and studied in vitro for endothelium-dependent relaxation to acetylcholine. Six weeks thereafter, treatment with lisinopril was started (n = 11) and continued for 9 wk. Proteinuria (metabolic cages) and systolic blood pressure (SBP; tail cuff) were evaluated weekly, and these were analyzed in relation to renal endothelial function at baseline. 5/6 Nephrectomy induced an increase in SBP and progressive proteinuria. Treatment with lisinopril reduced SBP and slowed proteinuria, albeit to a variable degree among individuals. The acetylcholine-induced renal artery dilation at baseline negatively correlated with lisinopril-induced reduction of proteinuria (r(2) = 0.648, P = 0.003) and with the decrease in SBP (r(2) = 0.592, P = 0.006). Our data suggest that angiotensin-converting enzyme-inhibitor attenuates the progression of renal damage the most in those individuals with decreased basal renal endothelial-mediated vasodilation.

Synthesis and Biological Evaluation of New Combined α/β-Adrenergic Blockers

The synthesis, characterization, and pharmacological evaluation of new aryloxyaminopropanol compounds based on substituted (4‐hydroxyphenyl)ethanone with alterations in the alkoxymethyl side chain in position 2 and with 2‐methoxyphenylpiperazine in the basic part of the molecule are reported. For the in vitro pharmacological evaluation, isolated aorta and atria from normotensive Wistar rats were used. Compared to naftopidil, compounds with ethoxymethyl, propoxymethyl, butoxymethyl, and methoxyethoxymethyl substituent displayed similar α1‐adrenolytic potency. Compounds with methoxymethyl, ethoxymethyl, and propoxymethyl substituent caused a significant decrease in both spontaneous and isoproterenol‐induced beating of isolated rat atria. Naftopidil and the tested substances containing a butoxymethyl and methoxyethoxymethyl substituent had no effect on the spontaneous or isoproterenol‐induced beating. The tested substance that had the most pronounced effect was the compound with a propoxymethyl substituent. Its antihypertensive efficacy was investigated in vivo on spontaneously hypertensive rats (SHRs). The systolic blood pressure was found to be significantly lower in SHRs subjected to the treatment for 2 weeks than in untreated SHRs. Naftopidil had no significant effect.

Local gene therapy with indoleamine 2,3-dioxygenase protects against development of transplant vasculopathy in chronic kidney transplant dysfunction

Chronic transplant dysfunction (CTD) is the primary cause of late allograft loss in kidney transplantation. Indoleamine 2,3-dioxygenase (IDO) is involved in fetomaternal tolerance and IDO gene therapy inhibits acute rejection following kidney transplantation. The aim of this study is to investigate whether gene therapy with IDO is able to attenuate CTD. Transplantation was performed in a rat Dark-Agouti to Wistar-Furth CTD model. Donor kidneys were incubated either with an adenovirus carrying IDO gene, a control adenovirus or saline. During the first 10 days recipients received low-dose cyclosporine. Body weight, blood pressure, serum creatinine and proteinuria were measured every 2 weeks. Rats were killed after 12 weeks. IDO had a striking beneficial effect on transplant vasculopathy at week 12. It also significantly improved body weight gain; it reduced blood pressure and decreased proteinuria during the follow-up. However, it did not affect the kidney function. In addition, IDO therapy significantly decreased the number of graft-infiltrating macrophages at week 12. The messenger RNA levels of forkhead box p3 and transforming grow factor-β were elevated in the IDO treated group at week 12. Here we show for first time a clear beneficial effect of local IDO gene therapy especially on transplant vasculopathy in a rat model of renal CTD.