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Ceramide 1-phosphate (C1P) is a novel bioactive sphingolipid formed by ceramide kinase (CERK)-catalyzed phosphorylation of ceramide. It has been implicated in the regulation of such vital pathophysiological functions as phagocytosis and inflammation, but there have been no reports ascribing a biological function to CERK in vascular disorders. Here the potential role of CERK/C1P in neointimal formation was investigated using rat aortic vascular smooth muscle cells (VSMCs) in primary culture and a rat carotid injury model. Exogenous C8-C1P stimulated cell proliferation, DNA synthesis, and cell cycle progression of rat aortic VSMCs in primary culture. In addition, wild-type CERK-transfected rat aortic VSMCs induced a marked increase in rat aortic VSMC proliferation and [(3)H]-thymidine incorporation when compared to empty vector transfectant. C8-C1P markedly activated extracellular signal-regulated kinase 1 and 2 (ERK1/2) within 5min, and the activation could be prevented by U0126, a MEK inhibitor. Also, K1, a CERK inhibitor, decreased the ERK1/2 phosphorylation and cell proliferation on platelet-derived growth factor (PDGF)-stimulated rat aortic VSMCs. CERK expression and C1P levels were found to be potently increased during neointimal formation using a rat carotid injury model. However, ceramide levels decreased during the neointimal formation process. These findings suggest that C1P can induce neointimal formation via cell proliferation through the regulation of the ERK1/2 protein in rat aortic VSMCs and that CERK/C1P may regulate VSMC proliferation as an important pathogenic marker in the development of cardiovascular disorders.

Most living organisms exhibit circadian rhythms in physiology and behavior. These oscillations are generated by an endogenous circadian clock and control many biological processes. Ceramide has attracted attention as a signal mediator in diverse cell processes including cell death and differentiation. The relationships between ceramide expression levels and the circadian clock have not previously been investigated. To determine if there are circadian variations in the content of ceramide, we measured ceramide concentrations in the livers of wild-type (WT) and mPer1/mPer2 double knockout (DKO) mice. The ceramide concentration in WT mice was dramatically increased at Zeitgeber Time 9 (ZT9; 9 h after lights-on time) and ZT21 but no rhythmicity in ceramide expression was seen in DKO mice. Because ceramide can be generated by the hydrolysis of sphingomyelin via sphingomyelinase (SMase), or by ceramide synthase (CerS)-mediated synthesis, we assayed the expression patterns of ceramide-related genes using real-time PCR. CerS2 expression levels showed a biphasic pattern of expression in WT mice but no rhythmicity in DKO mice. While the neutral SMase (nSMase) and acidic SMase (aSMase) mRNA in WT mice were expressed in a circadian manner, the correlation between the expression levels of these SMases with times of day was weak in DKO mice. Collectively, our findings suggest that both SMases and CerS2 mRNA expression are regulated by the presence of mPer1/mPer2 circadian clock genes in vivo, and imply that ceramide may play a vital role in circadian rhythms and physiology.

Muscle disorders, such as muscular dystrophy, are associated with an increase in oxidative stress. Proposed treatments for muscular dystrophy, some in clinical trials, include gene therapy and muscle cell transplantation. In this study, we investigated the effects of idesolide, isolated from the fruits of Idesia polycarpa, on changes that occur in muscle disuse atrophy. We noted protective effects on oxidative stress response and HSP70 regulation. Pre-treatment with idesolide for 24 h maintained cell viability and decreased apoptosis in H(2)O(2)-treated C(2)C(12) muscle cells. The idesolide pretreatment also increased intracellular HSP70 protein. Our results suggest that idesolide inhibits cell death through induction of HSP70 in C(2)C(12) muscle cells. This work is the first to report that idesolide can regulate the decrease in HSP70 that occurs during skeletal muscle atrophy.