Anti-LOX-1 therapy in rats with diabetes and dyslipidemia: ablation of renal vascular and epithelial manifestations.

LOX-1 is a multifunctional membrane receptor that binds and internalizes oxidized LDL (oxLDL). We tested the hypothesis that blockade of LOX-1 with an anti-LOX-1 antibody limits nephropathy in male rats with diabetes and dyslipidemia (ZS rats; F(1) hybrid product of Zucker fatty diabetic rats and spontaneous hypertensive heart failure rats). Lean ZS rats were controls, while untreated obese ZS (OM), ZS obese rats injected with nonspecific rabbit IgG (OM-IgG; 2 microg intravenous injection given weekly), and obese ZS rats given anti-LOX-1 rabbit antibody (OM-Ab; 2 microg intravenous injection given weekly) were the experimental groups. The rats were treated from 6 to 21 wk of age. All obese groups had severe dyslipidemia and hyperglycemia. Kidneys of obese rats expressed LOX-1 in capillaries and tubules, were larger, accumulated lipid, had intense oxidative stress, leukocyte infiltration, depressed mitochondrial enzyme level and function, and peritubular fibrosis (all P < 0.05 vs. lean ZS rats). Injections with LOX-1 antibody limited these abnormalities (P < 0.01 vs. data in OM or OM-lgG rats). In vitro, renal epithelial LOX-1 expression was verified in a cultured proximal tubule cell line. Our study indicates that anti-LOX-1 (vascular and epithelial) therapy may effectively reverse critical pathogenic elements of nephropathy in diabetes and dyslipidemia.

Lipotoxic and inflammatory phenotypes in rats with uncontrolled metabolic syndrome and nephropathy.

Anomalous inflammatory responses triggered by the metabolic syndrome cause renal injury. This discovery links renal lipid accumulation with lipotoxicity to inflammation and may explain the insidious fibrosis and cellular decay characteristic of nephropathy in the metabolic syndrome. However, it is not clear whether control of inflammation protects the kidney independently of lipid accumulation, which is a required step for lipotoxicity in hyperglycemia and dyslipidemia. We hypothesized that in rats with the metabolic syndrome, and overt nephropathy, treatment with mycophenolate mofetil (MMF; 10 mg.kg(-1).day(-1) ip for 14 wk) would reduce the abnormal renal lipid depots and limit renal inflammation and injury. We studied groups of lean and obese F1 hybrid Zucker fatty diabetic/spontaneous hypertensive heart failure (ZS) rats. MMF did not affect lean rats. In obese ZS rats, MMF did not change severe hyperglycemia or the higher kidney loads of unutilized lipid and peroxidation products. Nonetheless, MMF dramatically reduced diabetes/obesity-derived systemic and renal inflammation, limited renal size, hyperfiltration, and fibrosis. These data indicate that in rats, anti-inflammatory therapy presumably acting downstream, and independently of lipotoxicity, can effectively limit renal injury and fibrosis.

Gender differences in pulmonary arterial reactivity to dilatory agonists in pulmonary hypertension.

OBJECTIVES: To determine whether impaired reactivity to dilatory agonists could contribute to pulmonary hypertension, and whether there are gender differences in pulmonary vasodilator reactivity. METHODS: Pulmonary arterial rings from monocrotaline (MCT)-induced pulmonary hypertensive and control rats were isolated. At the peaks of submaximal contractions to norepinephrine (NE) or endothelin (ET-1), rings were exposed to 5 x 10(-6) M acetylcholine (ACh) or 9 x 10(-9) M adrenomedullin (ADM) or 1.3 x 10(-8) M calcitonin gene-related peptide (CGRP). RESULTS: Relaxation to ACh, ADM, and CGRP was endothelium-dependent. Hypertensive pulmonary arterial rings relaxed less to ACh and CGRP than controls in both genders. Female pulmonary hypertensive muscle was more rather than less reactive to ADM compared with controls. ADM-induced relaxation of NE contractions was 2.4 times greater in female compared with male control rings and 5.5 times greater in female compared with male hypertensive preparations. Gender differences in relaxation responses were similar for CGRP. MCT-treated female arterial rings relaxed more than did MCT-treated male arterial muscle in response to ACh. No difference in ACh relaxation was found between genders for controls. CONCLUSIONS: Pulmonary arterial relaxation to endothelium-dependent vasodilators is impaired in MCT-induced pulmonary hypertension with the exception of ADM in females. Vasodilators may be more effective in reducing pulmonary hypertension in females than in males.

Dimethyl sulfoxide: does it change the functional properties of the bladder wall?

PURPOSE: Dimethyl sulfoxide (DMSO) is used in a 50% solution to treat interstitial cystitis. Symptomatic relief occurs in about two-thirds of cases. The mechanism of action and effects of DMSO on bladder tissue function are poorly understood. Therefore, the effect of DMSO on bladder muscle compliance and contractility was evaluated. MATERIALS AND METHODS: Contractility and compliance were evaluated in rat bladder strips exposed to various concentrations of DMSO for 7 minutes, followed by 7 to 60-minute washout periods. The effect of DMSO at concentrations of 25%, 30%, 35%, 40% and 50% on electrical field stimulation induced contractions was assessed. Acetylcholine and high KCl (Sigma Chemical Co.) induced contractions were measured after exposure to 30% DMSO. Compliance was evaluated after exposure to 30% and 50% DMSO. RESULTS: Exposure to 40% DMSO completely abolished electrical field stimulation contractions, while 30% DMSO decreased the electrical field stimulation contraction to 40% +/- 6% of the initial force but there was almost complete recovery within 30 minutes. Contractile force was unaltered by 25% DMSO. Acetylcholine and KCl stimulation after exposure to 30% DMSO produced contractile forces of 78% +/- 6% and 39% +/- 6% of pre-DMSO control contractions, respectively. Compliance decreased by 2.4 and 4.6-fold following 30% and 50% DMSO exposure, respectively. CONCLUSIONS: DMSO completely and irreversibly abolishes contractions at a 40% concentration. Compliance is altered at even lower concentrations (30%). These findings bring into question the current practice of treating patients who have IC with 50% DMSO. Lower concentrations (25%) of DMSO may serve as a safe, effective analgesic and anti-inflammatory treatment for IC and other bladder pathologies.

Gender dichotomy in reactivity to the vasoactive oxidant hydrogen peroxide in spontaneously hypertensive rats.

OBJECTIVES: To determine: 1) whether ovariectomy increases low-density lipoprotein (LDL) cholesterol; 2) if increased LDL cholesterol correlates with increased blood pressure; and 3) whether arterial muscle reactivity to the vasoactive oxidant hydrogen peroxide (H2O2) is gender-dependent in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). METHODS: SHR and WKY females were ovariectomized at four weeks of age. Blood pressures were monitored weekly. Blood was collected at the time of sacrifice at 16-18 weeks, and caudal arteries were excised. LDL cholesterol was measured. Caudal arterial muscle was contracted with high-calcium egtazic acid (EGTA)/ionomycin (calcium ionophore) and relaxed with zero-calcium EGTA/ionomycin. H2O2-induced contractions were elicited in zero calcium. H2O2 reactivity was compared for SHR and WKY, male and female arterial muscle. RESULTS: Ovariectomy increased LDL cholesterol in both SHR and WKY but blood pressure increased only in SHR. Male SHR and WKY arterial muscle was more reactive to H2O2 compared with female preparations. CONCLUSION: Gender dichotomy in the development of hypertension does not appear to be due directly to the LDL-lowering effects of estrogen but is likely due, at least in part, to lower arterial reactivity to vasoactive oxidants, such as H2O2, with a consequent reduction of oxidant-induced vasoconstriction in female SHR.