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Background Sarcopenia and osteoporosis frequently co‐occur in the elderly and have common pathophysiological determinants. Slit guidance ligand 3 (SLIT3) has been recently discovered as a novel therapeutic factor against osteoporosis, and a SLIT3 fragment containing the second leucine‐rich repeat domain (LRRD2) had a therapeutic efficacy against osteoporosis. However, a role of SLIT3 in the skeletal muscle is unknown. Methods Skeletal muscle mass, strength, and/or physical activity were evaluated in Slit3−/−, ovariectomized, and aged mice, based on the measurements of muscle weight and grip strength, Kondziella's inverted hanging test, and/or wheel‐running test. Skeletal muscles were also histologically evaluated by haematoxylin and eosin staining and/or immunofluorescence. The ovariectomized and aged mice were intravenously injected with recombinant SLIT3 LRRD2 for 4 weeks. C2C12 cells were used to know cellular effects of SLIT3, such as in vitro myogenesis, fusion, cell viability, and proliferation, and also used to evaluate its molecular mechanisms by immunocytochemistry, immunoprecipitation, western blotting, real‐time PCR, siRNA transfection, and receptor‐ligand binding ELISA. Results Slit3‐deficient mice exhibited decreased skeletal muscle mass, muscle strength, and physical activity. The relative masses of gastrocnemius and soleus were lower in the Slit3−/− mice (0.580 ± 0.039% and 0.033 ± 0.003%, respectively) than those in the WT littermates (0.622 ± 0.043% and 0.038 ± 0.003%, respectively) (all, P < 0.05). Gastrocnemius of Slit3−/− mice showed the reduced number of Type I and Type IIa fibres (all, P < 0.05), but not of Type IIb and Type IIx fibres. SLIT3 activated β‐catenin signalling by promoting its release from M‐cadherin, thereby increasing myogenin expression to stimulate myoblast differentiation. In vitro experiments involving ROBO2 expression, knockdown, and interaction with SLIT3 indicated that ROBO2 functions as a SLIT3 receptor to aid myoblast differentiation. SLIT3 LRRD2 dissociated M‐cadherin‐bound β‐catenin and up‐regulated myogenin expression to increase myoblast differentiation, in a manner similar to full‐length SLIT3. Systemic treatment with SLIT3 LRRD2 increased skeletal muscle mass in both ovariectomized and aged mice (all, P < 0.05). The relative masses of gastrocnemius and soleus were higher in the treated aged mice (0.548 ± 0.045% and 0.033 ± 0.005%, respectively) than in the untreated aged mice (0.508 ± 0.016% and 0.028 ± 0.003%, respectively) (all, P < 0.05). SLIT3 LRRD2 treatment increased the hanging duration of the aged mice by approximately 1.7‐fold (P < 0.05). Conclusions SLIT3 plays a sarcoprotective role by activating β‐catenin signalling. SLIT3 LRRD2 can potentially be used as a therapeutic agent against muscle loss.

Sphingomyelinase catalyzes the hydrolysis of sphingomyelin to generate ceramide, an important molecule involved in the regulation of various cellular responses. In this study, we partially purified the neutral sphingomyelinase2 (nSMase2) and identified the inhibitors, D-lyxophytosphingosine and D-arabino-phytosphingosine, which have an inhibitory effect on nSMase2 in a concentration-dependent manner. A Dixon plot of each phytosphingosines revealed their probable inhibitory pattern, i.e., apparent competitive inhibition. These compounds did not inhibit the Mg(2+)-independent neutral SMase activity, although the known nSMase2 inhibitor, GW4869, showed inhibitory effects on Mg(2+)-independent neutral SMase activity. Further, the two phytosphingosines specifically inhibited the ceramide generation regulated by nSMase2.

In the present study, we examined the mechanisms underlying the effect of DA-9801 on neurite outgrowth. We found that DA-9801 elicits its effects via the mitogen-activated protein kinase ( Peripheral neuropathy is a common disease in diabetes patients. According to recent estimates, more than half of all diabetes patients develop diverse neuropathic symptoms.

J. Neurochem. (2010) 112, 1088–1097. Abstract Ceramide is produced by sphingomyelinase (SMase) and it plays a key role in cellular responses such as apoptosis. In this study, we report the purification and characterization of neutral SMase2 (nSMase2) from bovine brain tissue. Triton X‐100 extracts of bovine brain membranes were purified in nine steps, including sequential chromatography. The specific activity of purified nSMase increased 8183‐fold over the brain membrane fraction. Purified nSMase showed similarities to nSMase2, which had been purified and cloned previously. Interestingly, purified nSMase2 was Ca2+‐dependent and could be activated by micromolar concentrations of Ca2+ under Mg2+‐free conditions. Ceramide generation was dependent upon the calcium ionophore A23187 and was observed in nSMase2‐over‐expressing COS‐7 cells. This generation was suppressed by GW4869, an nSMase2 inhibitor, but not to fumonisin B1, an inhibitor of the de novo ceramide synthesis pathway. The present study demonstrates the Ca2+‐dependent activation of nSMase2.

Aging is associated with immune dysfunction and conditions such as inflamm-aging and immunosuppression. Arsenic, an environmental contaminant distributed worldwide, affects the immune system. This study tested the hypothesis that arsenic has distinct effects on T cell proliferation and the production of cytokines by activated T cells. Murine splenocytes from young (2 months) and aged (24-26 months) C57BL/6 mice were exposed to arsenite (As(3+)), the most toxic form of inorganic arsenic, and stimulated with concanavalin A (Con A) or anti-CD3 antibody. T cell proliferation decreased significantly in response to Con A and anti-CD3 at subtoxic doses of arsenite in splenocytes from both young and aged mice. Arsenite, added concurrently with Con A or anti-CD3, significantly inhibited the production of interleukin-2 (IL-2), interferon-γ (IFN-γ), and interleukin-4 (IL-4) by splenocytes from young mice and significantly reduced the production of IL-10 by splenocytes from aged mice. In contrast, the production of IL-2 and IL-4 by splenocytes from aged mice was only slightly affected by arsenite. The results show that arsenic exposure reduces the immune response in splenocytes. Moreover, this effect may be influenced by aging.

Sepsis, a systemic inflammatory response syndrome, remains a potentially lethal condition. (S)-1-α-Naphthylmethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (CKD712) is noted as a drug candidate for sepsis. Many studies have demonstrated its significant anti-inflammatory effects. Here we first examined whether CKD712 inhibits lipopolysaccharide (LPS)-induced arachidonic acid (AA) release in the RAW 264.7 mouse monocyte cell line, and subsequently, its inhibitory mechanisms. CKD712 reversed LPS-associated morphological changes in the RAW 264.7 cells, and inhibited LPS-induced release of AA in a concentrationdependent manner. The inhibition was apparently due to the diminished expression of a cytosolic form of phospholipase A 2 (cPLA 2 ) by CKD712, resulting from reduced NF-κB activation. Furthermore, CKD712 inhibited the activation of ERK1/2 and SAP/JNK, but not of p38 MAPK. CKD712 had no effect on the activity or phosphorylation of cPLA 2 and on calcium influx. Our results collectively suggest that CKD712 inhibits LPS-induced AA release through the inhibition of a MAPKs/NF-κB pathway leading to reduced cPLA 2 expression in RAW 264.7 cells.