Alport syndrome (AS) is a progressive hereditary renal disease that is characterized by sensorineural hearing loss and ocular abnormalities. It is divided into three modes of inheritance, namely, X-linked Alport syndrome (XLAS), autosomal recessive AS (ARAS), and autosomal dominant AS (ADAS). XLAS is caused by pathogenic variants in COL4A5, while ADAS and ARAS are caused by those in COL4A3/COL4A4. Diagnosis is conventionally made pathologically, but recent advances in comprehensive genetic analysis have enabled genetic testing to be performed for the diagnosis of AS as first-line diagnosis. Because of these advances, substantial information about the genetics of AS has been obtained and the genetic background of this disease has been revealed, including genotype-phenotype correlations and mechanisms of onset in some male XLAS cases that lead to milder phenotypes of late-onset end-stage renal disease (ESRD). There is currently no radical therapy for AS and treatment is only performed to delay progression to ESRD using nephron-protective drugs. Angiotensin-converting enzyme inhibitors can remarkably delay the development of ESRD. Recently, some new drugs for this disease have entered clinical trials or been developed in laboratories. In this article, we review the diagnostic strategy, genotype-phenotype correlation, mechanisms of onset of milder phenotypes, and treatment of AS, among others.

Abstract-Although recent investigations have suggested that a Rho-kinase-mediated Ca 2ϩ sensitization of vascular smooth muscle contraction plays a critical role in the pathogenesis of cerebral and coronary vasospasm, the upstream of this signal transduction has not been elucidated. In addition, the involvement of protein kinase C (PKC) may also be related to cerebral vasospasm. We recently reported that sphingosylphosphorylcholine (SPC), a sphingolipid, induces Rho-kinase-mediated Ca 2ϩ sensitization in pig coronary arteries. The purpose of this present study was to examine the possible mediation of SPC in Ca 2ϩ sensitization of the bovine middle cerebral artery (MCA) and the relation to signal transduction pathways mediated by Rho-kinase and PKC. In intact MCA, SPC induced a concentration-dependent (EC 50 ϭ3.0 mol/L) contraction, without [Ca 2ϩ ] i elevation. In membrane-permeabilized MCA, SPC induced Ca 2ϩ sensitization even in the absence of added GTP, which is required for activation of G-proteins coupled to membrane receptors. The SPC-induced Ca 2ϩ sensitization was blocked by a Rho-kinase inhibitor (Y-27632) and a dominantnegative Rho-kinase, but not by a pseudosubstrate peptide for conventional PKC, which abolished the Ca 2ϩ -independent contraction induced by phorbol ester. In contrast, phorbol ester-induced Ca 2ϩ sensitization was resistant to a Rho-kinase inhibitor and a dominant-negative Rho-kinase. In primary cultured vascular smooth muscle cells, SPC induced the translocation of cytosolic Rho-kinase to the cell membrane. We propose that SPC is a novel messenger for Rho-kinase-mediated Ca 2ϩ sensitization of cerebral arterial smooth muscle and, therefore, may play a pivotal role in the pathogenesis of abnormal contraction of the cerebral artery such as vasospasm. The SPC/Rho-kinase pathway functions independently of the PKC pathway.

Abstract-We recently reported that sphingosylphosphorylcholine (SPC) is a novel messenger for Rho-kinase-mediated Ca 2ϩ sensitization of vascular smooth muscle (VSM) contraction. Subcellular localization and kinase activity of Src family protein kinases (SrcPTKs), except for c-Src, is controlled by a reversible S-palmitoylation, an event inhibited by eicosapentaenoic acid (EPA). We examined the possible involvement of SrcPTKs in SPC-induced Ca 2ϩ sensitization and effects of EPA. We used porcine coronary VSM and rat aortic VSM cells (VSMCs) in primary culture. An SrcPTKs inhibitor, PP1, and EPA inhibited SPC-induced contraction, concentration-dependently, without affecting [Ca 2ϩ ] i levels and the Ca 2ϩ -dependent contraction induced by high K ϩ depolarization. A digitized immunocytochemical analysis in VSMCs revealed that SPC induced translocation of Fyn, but not of c-Src, from the cytosol to the cell membrane, an event abolished by EPA. Translocation of Rho-kinase from the cytosol to the cell membrane by SPC was also inhibited by EPA and PP1. The SPC-induced activation of SrcPTKs was blocked by EPA and PP1, but not by Y27632, an Rho-kinase inhibitor. Rho-kinase-dependent phosphorylation of myosin phosphatase induced by SPC was inhibited by EPA, PP1, and Y27632. Translocation and activation of SrcPTKs, including Fyn, play an important role in Ca