Role of Transient Receptor Potential Vanilloid 4 Channel in Skin Physiology and Pathology.

Transient receptor potential vanilloid 4 (TRPV4) channel responds to temperature, as well as various mechanical and chemical stimuli. This non-selective cation channel is expressed in several organs, including the blood vessels, kidneys, oesophagus and skin. In the skin, TRPV4 channel is present in various cell types such as keratinocytes, melanocytes and sensory neurons, as well as immune and inflammatory cells, and engages in several physiological actions, from skin homeostasis to sensation. In addition, there is substantial evidence implicating dysfunctional TRPV4 channel-in the form of either deficient or excessive channel activity-in pathological cutaneous conditions such as skin barrier compromise, pruritus, pain, skin inflammation and carcinogenesis. These varied functions, combined with the fact that TRPV4 channel owns pharmacologically-accessible sites, make this channel an attractive therapeutic target for skin disorders. In this review, we summarize the different physiological and pathophysiological effects of TRPV4 in the skin.

New model for adenine-induced chronic renal failure in mice, and the effect of gum acacia treatment thereon: comparison with rats.

INTRODUCTION: This study aimed at comparing the effects of feeding mice and rats with adenine to induce a state of chronic renal failure (CRF), and to assess the effect of treatment with gum acacia (GA) thereon. METHODS: We compared the outcome, in mice, of feeding adenine at three different doses (0.75%, 0.3%, and 0.2%, w/w). Biochemical and histopathological studies were conducted in plasma, urine and renal homogenates from both species. RESULTS: When mice and rats were fed adenine (0.75%, w/w), all treated rats survived the treatment, but all treated mice died within 1-2 days. The dosage in mice was reduced to 0.3%, w/w, for 4 weeks, but again all treated mice died within 3-4 days. A further reduction in the dosage in mice to 0.2%, w/w, for 4 weeks resulted in no mortality, and produced alterations similar to those observed in rats fed adenine at a dose of 0.75%,w/w, for 4 weeks. Plasma creatinine, urea and urinary protein were significantly increased (P<0.001) in adenine-treated mice and rats, and this action was incompletely, but significantly (P<0.05), reversed by GA. Adenine significantly (P<0.001) reduced superoxide dismutase (SOD) activity and reduced glutathione (GSH) concentration in renal homogenates from both species, and these reductions were significantly (P<0.05) ameliorated by GA. DISCUSSION: Our data suggest that mice are more sensitive to adenine than rats, and that a dose of adenine of 0.2%, w/w, for 4 weeks in mice is suggested as a model for CRF. In both models, GA (15%, w/v, in the drinking water for 4 weeks) given concomitantly with adenine ameliorated the severity of CRF to a similar extent.

Abrogation of cisplatin-induced nephrotoxicity by emodin in rats.

Nephrotoxicity of the anticancer drug cisplatin (CP) involves the generation of reactive oxygen species in renal cortex, and emodin (a rhubarb anthraquinone) has strong antioxidant and anticancer actions. Therefore, we tested here the possible ameliorative effect of emodin on CP nephrotoxicity in rats. Emodin was given orally (10 mg/kg/day for nine consecutive days), and on day 4, some of the treated rats were also injected intraperitoneally with either saline or CP (6 mg/kg). Five days after CP treatment, rats were killed, and blood and urine samples, and kidneys were collected for the assessment of histopathological renal damage and apoptosis, and for biochemical estimation of creatinine and urea concentrations in plasma and urine, several cytosolic antioxidant enzyme activities in kidneys, and urinalyses. CP significantly increased the concentrations of urea and creatinine, and decreased creatinine clearance. It also significantly reduced cortical glutathione concentration and the activity of superoxide dismutase. CP treatment significantly increased urine volume and N-acetyl-ß-D-glucosaminidase activity and significantly decreased osmolarity and protein concentrations. Emodin treatment markedly and significantly mitigated all these effects. Sections from saline- and emodin-treated rats showed apparently normal proximal tubules. However, kidneys of CP-treated rats had a moderate degree of necrosis. This was markedly lessened when CP was given simultaneously with emodin. The concentration of CP in the cortical tissues was not significantly altered by emodin treatment. The results suggested that emodin had ameliorated CP nephrotoxicity in rats. Pending further pharmacological and toxicological studies emodin may be considered a potentially useful nephroprotective agent.

Protective effects of emodin against cisplatin-induced oxidative stress in cultured human kidney (HEK 293) cells.

Emodin (a rhubarb anthraquinone) has strong antioxidant and anticancer actions, and recent studies indicated that it reduces cellular oxidative stress induced by various insults and drugs. Cisplatin is an anticancer drug that is associated with nephrotoxicity and induces oxidative stress in cultured human kidney (HEK 293) cells. This study aimed to assess the in-vitro antioxidant properties of the emodin against cisplatin-induced oxidative stress in HEK 293 cells. Our study revealed that emodin acted as a potent free radical scavenger and provided nephroprotection against cisplatin-induced oxidative stress. Emodin as low as 0.5 µm did not decrease cell viability and restored the cisplatin-induced glutathione depletion and total antioxidant capacity in a dose-dependent manner. Emodin augmented the cisplatin-induced inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and superoxide dismutase). These results suggest that emodin has the potential to be used as an adjunct therapeutic agent in patients receiving cisplatin treatment.