Folic acid supplementation inhibits NADPH oxidase-mediated superoxide anion production in the kidney

Hyperhomocysteinemia decreases intestinal motility leading to constipation

Elevated levels of plasma homocysteine (Hcy) called hyperhomocysteinemia (HHcy) have been implicated in inflammation and remodeling in intestinal vasculature, and HHcy is also known to aggravate the pathogenesis of inflammatory bowel disease (IBD). Interestingly, colon is the pivotal site that regulates Hcy levels in the plasma. We hypothesize that HHcy decreases intestinal motility through matrix metalloproteinase-9 (MMP-9)-induced intestinal remodeling leading to constipation. To verify this hypothesis, we used C57BL/6J or wild-type (WT), cystathionine β-synthase (CBS(+/-)), MMP-9(-/-), and MMP-9(-/-) + Hcy mice. Intestinal motility was assessed by barium meal studies and daily feces output. Plasma Hcy levels were measured by HPLC. Expression of ICAM-1, inducible nitric oxide synthase, MMP-9, and tissue inhibitors of MMPs was studied by Western blot and immunohistochemistry. Reactive oxygen species (ROS) including super oxide were measured by the Invitrogen molecular probe method. Tissue nitric oxide levels were assessed by a commercially available kit. Plasma Hcy levels in the treated MMP-9 group mice were comparable to CBS(+/-) mice. Barium meal studies suggest that intestinal motility is significantly decreased in CBS(+/-) mice compared with other groups. Fecal output-to-body weight ratio was significantly reduced in CBS(+/-) mice compared with other groups. There was significant upregulation of MMP-9, iNOS, and ICAM-1 expression in the colon from CBS(+/-) mice compared with WT mice. Levels of ROS, superoxide, and inducible nitric oxide were elevated in the CBS(+/-) mice compared with other groups. Results suggest that HHcy decreases intestinal motility due to MMP-9-induced intestinal remodeling leading to constipation.

Interference in mevalonate pathway ameliorates homocysteine-induced endothelium-dysfunction

Homocysteine is a risk factor for atherosclerosis and hypertension and induces endothelium-dysfunction. Accumulation of cholesterol and reactive oxygen species plays a key role in the endothelium-dysfunction. This study investigated the hypothesis of an involvement of mevalonate pathway and oxidative pathway in homocysteine-induced endothelial damage. Homocysteine induced impairment of the endothelium-dependent vasorelaxation of rat aortic rings by isometric tension, while it also reduced the nitric oxide level and the nitric oxide synthase activity in human umbilical vein endothelial cells, followed by accumulation of superoxide anion and cholesterol. However, the level of asymmetric dimethylarginine remained unaffected by homocysteine. The adverse effect of homocysteine on endothelial function was found to be partially enhanced either by squalestatin-reducing cholesterol or by superoxide dismutase-reducing superoxide anion. Moreover, this effect of homocysteine could be completely ameliorated by simvastatin, very similar to that of cotreatment of squalestatin and superoxide dismutase. Respectively, mevalonolactone partly or squalene fully attenuated the effect of simvastatin or squalestatin on homocysteine-induced endothelial dysfunction. In conclusion, our results suggested that the mevalonate pathway mediates homocysteine-induced endothelium dysfunction besides the oxidative pathway. Interference in the mevalonate pathway and oxidative pathway provides effective protection of endothelial function.

Selenium or selenium plus folic acid-supplemented diets ameliorate renal oxidation in ethanol-exposed pups

BACKGROUND

Ethanol (EtOH) exposure during gestation and lactation induces an oxidative stress in offspring. In kidney, the oxidative damage is the primary pathway to alcohol-induced injury. In this study, we have demonstrated that a diet supplemented with selenium (Se) (0.5 ppm) or with Se (0.5 ppm) + folic acid (8 ppm) administered to EtOH-exposed (20% v/v) dams during gestation and lactation prevents the oxidative EtOH-provoked effects in their offspring's kidneys.

METHODS

All the studies were performed on 21-day-old pups. Serum, urine, and kidney Se levels were assessed by graphite-furnace atomic absorption spectrometry. Se and creatinine clearance, antioxidant enzyme activities, and lipid and protein peroxidation were determined by a spectrophotometric method in kidney.

RESULTS

Dietary supplementation treatments used could not improve the glomerular filtration function altered by EtOH exposure during gestation and lactation; however, they did improve renal Se deposits, renal development, and renal protein content while decreasing lipid and protein oxidation and modifying antioxidant enzymes' activity.

CONCLUSIONS

Se or Se + folic acid supplementations improve renal development and protein content and modify antioxidant enzymes' activity, decreasing lipid and protein oxidation after EtOH exposure. In this context, a double-supplemented diet appears to reduce protein peroxidation more efficiently than the Se-only-supplemented one, probably via superoxide dismutase and catalase.

Folic acid supplementation attenuates high fat diet induced hepatic oxidative stress via regulation of NADPH oxidase

Diets high in saturated fat and cholesterol facilitate weight gain, a predisposing factor that contributes to the onset of obesity and metabolic disorders. Hepatic oxidative stress is commonly reported in various animal models of obesity and has been associated with enhanced expression of NADPH oxidase. We have previously reported several antioxidant mechanisms through which folic acid confers protection during hyperhomocysteinemia-induced oxidative stress. The objective of the present study was to investigate whether folic acid supplementation ameliorates high-fat diet induced oxidative stress in the liver, and to identify the underlying mechanisms. Male C57BL/6J mice were fed a control diet, a high-fat diet, or a high-fat diet supplemented with folic acid for 12 weeks. A high-fat diet led to increased body mass, hepatic lipid peroxidation, and liver injury. There was a significant increase in hepatic NADPH oxidase activity, which was associated with enhanced expression of several NADPH-oxidase subunits. Folic acid supplementation had a protective effect against high-fat diet induced hepatic oxidative stress and liver injury. Further analysis revealed that the antioxidant effect of folic acid was attributed, in part, to transcriptional regulation of NADPH oxidase. These results suggested that folic acid supplementation may be hepatoprotective from liver injury associated with a high-fat diet.

Acid sphingomyelinase gene deficiency ameliorates the hyperhomocysteinemia-induced glomerular injury in mice

Hyperhomocysteinemia (hHcys) enhances ceramide production, leading to the activation of NADPH oxidase and consequent glomerular oxidative stress and sclerosis. The present study was performed to determine whether acid sphingomyelinase (Asm), a ceramide-producing enzyme, is implicated in the development of hHcys-induced glomerular oxidative stress and injury. Uninephrectomized Asm-knockout (Asm(-/-)) and wild-type (Asm(+/+)) mice, with or without Asm short hairpin RNA (shRNA) transfection, were fed a folate-free (FF) diet for 8 weeks, which significantly elevated the plasma Hcys level compared with mice fed normal chow. By using in vivo molecular imaging, we found that transfected shRNAs were expressed in the renal cortex starting on day 3 and continued for 24 days. The FF diet significantly increased renal ceramide production, Asm mRNA and activity, urinary total protein and albumin excretion, glomerular damage index, and NADPH-dependent superoxide production in the renal cortex from Asm(+/+) mice compared with that from Asm(-/-) or Asm shRNA-transfected wild-type mice. Immunofluorescence analysis showed that the FF diet decreased the expression of podocin but increased desmin and ceramide levels in glomeruli from Asm(+/+) mice but not in those from Asm(-/-) and Asm shRNA-transfected wild-type mice. In conclusion, our observations reveal that Asm plays a pivotal role in mediating podocyte injury and glomerular sclerosis associated with NADPH oxidase-associated local oxidative stress during hHcys.

Reversal by growth hormone of homocysteine-induced epithelial-to-mesenchymal transition through membrane raft-redox signaling in podocytes

Epithelial-to-Mesenchymal Transition (EMT) is an important pathogenic mechanism mediating glomerular injury or sclerosis in a variety of renal and systemic diseases such as hyperhomocysteinemia (hHcys). The present study was designed to test whether Hcys-induced EMT in podocytes is reversed by growth hormone (GH), a hormone regulating cell differentiation and growth and to explore the cellular and molecular mechanism mediating its action. It was found that Hcys induced significant EMT in podocytes, as shown by marked decreases in slit diaphragm-associated protein P-cadherin and zonula occludens-1 as epithelial markers and by dramatic increases in the expression of mesenchymal markers, fibroblast specific protein-1 and α-smooth muscle actin, which were detected by all examinations via immunocytochemistry, real time RT-PCR and Western blot analysis. When podocytes were treated with GH at 25 ng/mL, however, Hcys failed to induce podocyte EMT. Using electromagnetic spin resonance spectrometry, Hcys-induced superoxide (O(2).(-)) production via NADPH oxidase was found to be significantly inhibited by GH (66%). Functionally, GH was shown to substantially inhibit Hcys-induced increases in the permeability of podocyte monolayers and to block the decrease in podocin expression in these cells. In addition, NADPH oxidase subunit, gp91(phox) and GH receptors aggregated in membrane raft clusters, which produced O(2).(-) in response to Hcys and could be blocked by GH, membrane raft disruptors filipin and MCD or NADPH oxidase inhibitor, apocynin. It is concluded that Hcys-induced podocyte EMT is associated with transmembrane membrane raft-redox signaling and that GH reverses this Hcys-induced EMT protecting podocytes from functional disturbance.