Osteoarthritis (OA) is the most common cause of musculoskeletal pain and disability. The importance of chondrocytes in the pathogenesis of OA is unequivocal. 17β-estradiol (E2) has a potential protective effect against OA. However, the mechanism of E2 in OA chondrocytes remains unclear. In this study, we investigated the regulative effect of E2 on cell growth and the relationship between E2 and the PI3K/Akt pathway in rat OA model chondrocytes (pretreated with interleukin-1β). We found that E2 induced chondrocyte proliferation, and increased the expression level of Akt simultaneously, especially the expression level of P-Akt. Furthermore, the inhibition of P-Akt could block chondrocyte proliferation induced by E2. These results suggest that PI3K/Akt activation induced by E2 may be an important factor in the mechanism of E2 in cell proliferation in rat OA model chondrocytes, and help further understanding the role of E2 in OA progression.

It has been reported previously that diabetic cardiomyopathy can be inhibited or reverted with chronic zinc supplementation. In the current study, we hypothesized that total cardiac calcium and zinc content is altered in early onset diabetes mellitus characterized in part as hyperglycemia (HG) and that exposure of zinc ion (Zn2+) to isolated cardiomyocytes would enhance contraction-relaxation function in HG more so than in nonHG controls. To better control for differential cardiac myosin isoform expression as occurs in rodents after β-islet cell necrosis, hypothyroidism was induced in 16 rats resulting in 100% β-myosin heavy chain expression in the heart. β-Islet cell necrosis was induced in half of the rats by streptozocin administration. After 6 wks of HG, both HG and nonHG controls rats demonstrated similar myofilament performance measured as thin filament calcium sensitivity, native thin filament velocity in the myosin motility assay and contractile velocity and power. Extracellular Zn2+ reduced cardiomyocyte contractile function in both groups, but enhanced relaxation function significantly in the HG group compared to controls. Most notably, a reduction in diastolic sarcomere length with increasing pacing frequencies, i.e., incomplete relaxation, was more pronounced in the HG compared to controls, but was normalized with extracellular Zn2+ application. This is a novel finding implicating that the detrimental effect of HG on cardiomyocyte Ca2+ regulation can be amelioration by Zn2+. Among the many post-translational modifications examined, only phosphorylation of ryanodine receptor (RyR) at S-2808 was significantly higher in HG compared to nonHG. We did not find in our hypothyroid rats any differentiating effects of HG on myofibrillar protein phosphorylation, lysine acetylation, O-linked N-acetylglucosamine and advanced glycated end-products, which are often implicated as complicating factors in cardiac performance due to HG. Our results suggest that the relaxing effects of Zn2+ on cardiomyocyte function are more pronounced in the HG state due an insulin-dependent effect of enhancing removal of cytosolic Ca2+ via SERCA2a or NCX or by reducing Ca2+ influx via L-type channel or Ca2+ leak through the RyR. Investigations into the effects of Zn2+ on these mechanisms are now underway.

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Initial clinical studies indicate a potential beneficial effect of erythropoietin (EPO) in patients with anemia and heart failure. Here, we investigate the direct contractile effects of erythropoietin on myocardial tissue. Treatment with EPO (50 U/ml) using excitable murine and human left ventricular muscle preparations resulted in a 37% and 62% increase in twitch tension, respectively (P<0.05). Isolated murine cardiomyocytes exposed to EPO demonstrated a 41% increase in peak sarcomere shortening (P=0.012). Using compounds that specifically stimulate a non-erythropoietic EPO receptor yielded similar increases in contractile dynamics. Cardiomyocyte Ca2+ dynamics showed an 18% increase in peak calcium in EPO treated cardiomyocytes over controls (P=0.03). Studies in muscle strips skinned after EPO treatment demonstrated a phosphorylation dependant increase in the viscous modulus as well as an increase in oscillatory work. The EPO mediated increase in peak sarcomere shortening was abrogated by PI3-K blockade via wortmannin and by non-isozyme specific PKC blockade by chelerythrine. Finally, EPO treatment resulted in an increase in PKCε in the particulate cellular fraction, indicating activation of this isoform. EPO exhibits direct positive inotropic and lusitropic effects in cardiomyocytes and ventricular muscle preparation. These effects are mediated through PI3-K and PKCε isoform signaling to directly affect both calcium release dynamics and myofilament function.

Blood lipid profile is changed in gout patients. Gout patients who suffer from lipid metabolism disorder and vascular diseases might be associated with hyperuricemia, which leading to endothelial cell damage and vascular smooth muscle cell proliferation. CysC might be as a marker of the renal function damage and inflammation. Hyperuricemia is the risk factor of renal disorder in gout patients.