No abstract

Close physical association of Ca1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling (ECC) in skeletal muscle. However, the molecular mechanism underlying the JM targeting of LTCCs is unexplored. Junctophilin 1 (JP1) and JP2 stabilize the JM by bridging the sarcolemmal and SR membranes. Here, we examined the roles of JPs in localization and function of LTCCs. Knockdown of JP1 or JP2 in cultured myotubes inhibited LTCC clustering at the JM and suppressed evoked Ca transients without disrupting JM structure. Coimmunoprecipitation and GST pull-down assays demonstrated that JPs physically interacted with 12-aa residues in the proximal C terminus of the Ca1.1. A JP1 mutant lacking the C terminus including the transmembrane domain (JP1ΔCT) interacted with the sarcolemmal/T-tubule membrane but not the SR membrane. Expression of this mutant in adult mouse muscles in vivo exerted a dominant-negative effect on endogenous JPs, impairing LTCC-RyR coupling at triads without disrupting JM morphology, and substantially reducing Ca transients without affecting SR Ca content. Moreover, the contractile force of the JP1ΔCT-expressed muscle was dramatically reduced compared with the control. Taken together, JPs recruit LTCCs to the JM through physical interaction and ensure robust ECC at triads in skeletal muscle.

Following the discovery of a new series of benzimidazole derivatives bearing a diarylmethyl group as inhibitors of hepatitis C virus NS5B RNA-dependent RNA polymerase (HCV NS5B RdRp),1,2 we extended the structure-activity relationship (SAR) study to analogues bearing a substituted biphenyl group and succeeded in a significant advancement of activity. Starting from compound 1, optimization of the A, B, and C rings afforded potent inhibitors with low nanomolar potency against genotype 1b NS5B. The compounds, which have a substituent with a carbonyl function at the 4-position of the B-ring, efficiently blocked subgenomic viral RNA replication in the replicon cell assay at low submicromolar concentrations. Among the new compounds, compound 10n (JTK-109) exhibited favorable pharmacokinetic profiles, high selectivity for NS5B, and good safety profiles, suggesting the potential for a clinical candidate in the treatment of hepatitis C.

Background: Evidence suggests hemodialysis (HD) patients with resistance to erythropoiesis-stimulating agents (ESA) have a higher mortality rate. We investigated the association between ESA responsiveness and mortality in our HD population. Methods: A prospective cohort study of chronic HD patients was conducted at Jyoban Hospital in Fukushima, Japan. We collected data on patient demographic factors, comorbidities, dialysis vintage, body weight, ESA dose and hemoglobin concentration, as well as data on known risk factors for ESA hyporesponsiveness. The erythropoietin resistance index (ERI) was calculated by dividing the weekly body-weight-adjusted epoetin dose by the hemoglobin concentration. The association between ESA hyporesponsiveness estimated by the highest tertile of ERI and mortality was investigated by using the Cox proportional hazards model with adjustments for demographic factors, comorbidities, dialysis adequacy and serum biochemical data. Results: A total of 248 patients were included as subjects in the cohort, and their overall 2-year mortality rate was 13.3%. According to the results of the Kaplan-Meier analysis, patients with an ERI in the highest tertile had significantly higher mortality than patients with an ERI in the lower two tertiles (p = 0.0121). The highest ERI tertile was associated with higher all-cause mortality in both the unadjusted hazards model (hazard ratio, HR: 4.429; 95% CI: 1.249-15.704) and the adjusted hazards model (HR: 4.204; 95% CI: 1.173-15.065). Conclusions: A higher degree of resistance to ESA in chronic HD patients is associated with increased mortality.

Free radical scavenging activity of the extracts of petals (bud, early stage, full blooming and ending stage), leaf, stem, root and seeds of Mogami-benibana (safflower, Carthamus tinctorius Linne), the contents of the major active components of carthamin and polyphenols, and neuroprotective effect of the petal extracts and carthamin in the brain of mice and rats were examined. Water extracts of Mogami-benibana petals scavenged superoxide, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and singlet oxygen. The scavenging activities of the extract of safflower petals with various colors showed the order of orange, yellow and white from high to low. This order is consistent with the contents of carthamin, which is a pigment of orange color and is found highest in orange petals and lowest in white petals. There was also a relationship between DPPH radical scavenging activity and carthamin content in the petal extracts of safflower. The neuroprotective effects were examined in cellular and animal models. Mogami-benibana petal extract inhibited glutamate-induced C6 glia cell death, significantly decreased the formation of malondialdehyde in mouse cerebrum, and inhibited the increase in thiobarbituric acid reactive substances and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the cerebral cortex of rats subjected to an injection of FeCl(3) solution into the sensory motor cortex. Carthamin showed similar effects in inhibiting 8-OHdG by the petal extract in rats. These results suggest that the petal extract of Mogami-benibana has free radical scavenging activity and neuroprotective effect and carthamin is one of the major active components.