Negative correlation between serum uric acid and kidney URAT1 mRNA expression caused by resveratrol in rats.

SCOPE: This study established a hyperuricemic rat model to elucidate the effect of resveratrol on the transport of UA in the kidney. METHODS AND RESULTS: Hyperuricemia was induced in rats through daily oral gavage of a potassium oxonate and UA mixture over 3 weeks. Our results revealed that resveratrol significantly reduced the serum UA levels but not creatinine, c-creative protein, alanine aminotransferase, or aspartate aminotransferase levels in these rats. Furthermore, renal URAT1 and OAT1 mRNA expression were significantly higher in the rats treated with allopurinol than in those with no treatment. Therefore, allopurinol not only inhibited UA production but also mediated renal URAT1 and OAT1 expression. The correlation analysis revealed that UA levels correlated negatively with renal IL-6 mRNA expression in rats treated with allopurinol. Moreover, URAT1 showed strong immunoreactivity in the distal convoluted tubule of rats treated with allopurinol or resveratrol and in hyperuricemic treated with allopurinol. Finally, in the rats treated with resveratrol, UA levels correlated negatively with renal URAT1 mRNA expression; thus, resveratrol reduced URAT1 mRNA expression under high UA levels, thereby reducing UA reabsorption in renal cells. CONCLUSION: Resveratrol contributes to URAT1 expression, which is potentially useful in therapeutic strategies aimed at treating hyperuricemia.

Lipoic Acid Exerts Antioxidant and Anti-inflammatory Effects in Response to Heat Shock in C2C12 Myotubes.

This study explored that lipoic acid treatment for 24 h significantly upregulated and promoted heat shock-induced catalase expression and downregulated GPx1 messenger RNA (mRNA) expression, indicating that lipoic acid exhibits antioxidant activity in the decomposition of hydrogen peroxide by upregulating catalase expression. Moreover, lipoic acid treatment for 3 h increased and promoted heat shock-induced interleukin (IL)-6 mRNA and protein levels and that for 24 h downregulated IL-6 mRNA expression, suggesting a dual effect of lipoic acid on IL-6 regulation. Lipoic acid alone failed to increase or reduce tumor necrosis factor (TNF)-α mRNA and protein levels, whereas heat shock alone downregulated TNF-α mRNA and protein expression. These data suggest that lipoic acid does not have a proinflammatory role and that heat shock acts as an anti-inflammatory agent by downregulating TNF-α expression in C2C12 myotubes. Moreover, lipoic acid or heat shock alone upregulated the IL-6 receptor (IL-6R-α) and glycoprotein 130 (gp130) mRNA expression followed by IL-6 expression; these data indicate that the regulation of lipoic acid or heat shock is mediated by IL-6R signaling, thus suggesting that C2C12 myotubes possesses a mechanism for regulating IL-6R and gp130 expression following lipoic acid treatment or heat shock.

Unusual ferromagnetism in CoSi nanowires from internal and interfacial defects.

The diamagnetic semimetal CoSi presents unanticipated ferromagnetism as CoSi/SiO2 nanowires (NWs). Using first-principles calculations, we offer physical insights into the origins of this unusual magnetism. Due to the distorted and dangling bonds near the NW surface with different bond lengths, the transition metal (Co) d-orbital electron spin up and spin down populations become asymmetric from the exchange interactions, providing the mechanism for some of the measured magnetization. However, the distorted and dangling bonds are clearly not the only factor contributing to the magnetization of the NWs. The transmission electron microscopy selected area electron diffraction analysis of the CoSi region suggested a superlattice structure existed in the cubic CoSi, and defects existing as ordered vacancies in the CoSi were present. The simulation's results for the Co moment in the CoSi NWs without these ordered vacancies, but incorporating the surface and internal spin moments, is only 0.1638 µ(B)/atom Co, which is a ∼80% shortfall compared to the experimental value of 0.8400 µ(B)/atom Co. When the effects of ordered vacancies are incorporated into the simulation, 0.7886 µ(B) per surface Co atom, a much better match with the experimental value (within ∼6%), indicating that the internal ordered vacancies in the CoSi NWs are the dominant mechanism of ferromagnetism.

Tumor necrosis factor suppresses NR5A2 activity and intestinal glucocorticoid synthesis to sustain chronic colitis.

Intestinal crypt epithelial cells synthesize glucocorticoids, steroid hormones that protect against inflammatory bowel disease. To investigate how intestinal glucocorticoids are regulated during chronic inflammation, we induced chronic colitis in mice by exposing them to the chemical dextran sulfate sodium (DSS). We found that intestinal glucocorticoid secretion and expression of the genes Cyp11a1 and Cyp11b1 (which encode enzymes that synthesize glucocorticoids) were initially stimulated, but declined during the chronic phase, whereas tumor necrosis factor (TNF) and inflammatory cytokines secreted by T helper type 1 (TH1) and TH17 cells continuously increased in abundance in the inflamed colon. This suggested that inadequate intestinal glucocorticoid synthesis is a feature of chronic intestinal inflammation. We screened for cytokines that regulated intestinal glucocorticoid synthesis and found that TNF suppressed corticosterone secretion and Cyp11a1 and Cyp11b1 expression in an intestinal crypt epithelial cell line. TNF suppressed steroidogenesis by activating the transcription factors c-Jun and nuclear factor κB (NF-κB), which both interacted with the transcription factor NR5A2 and repressed Cyp11a1 reporter activity. This repression was relieved by expression of a dominant-negative form of c-Jun amino-terminal kinase 1 (JNK1), inhibitor of NF-κB, or by a JNK inhibitor. Furthermore, the dominant-negative TNF inhibitor XPro1595 inhibited c-Jun and NF-κB activation in mice, restored intestinal Cyp11a1 and Cyp11b1 expression, reduced colonic cell death, and rescued chronic colitis caused by DSS. Thus, during chronic colitis, TNF suppresses intestinal steroidogenic gene expression by inhibiting the activity of NR5A2, thus decreasing glucocorticoid synthesis and sustaining chronic inflammation.