Cyclosporine A-induced hypertension involves synapsin in renal sensory nerve endings

The calcineurin inhibitor cyclosporine A (CsA) has emerged as a major cause of secondary hypertension in humans, but the underlying pathogenetic mechanisms have remained enigmatic. Synapsins are a family of synaptic vesicle phosphoproteins that are essential for normal regulation of neurotransmitter release at synapses. In addition to synaptic vesicles, synapsins and other vesicle proteins are found on microvesicles in sensory nerve endings in peripheral tissues. However, the functions of the sensory microvesicles in general, and of synapsins in particular, are unknown. We now demonstrate in a mouse model that CsA raises blood pressure by stimulating renal sensory nerve endings that contain synapsin-positive microvesicles. In knockout mice lacking synapsin I and II, sensory nerve endings are normally developed but not stimulated by CsA whereas a control stimulus, capsaicin, is fully active. The reflex activation of efferent sympathetic nerve activity and the increase in blood pressure by CsA seen in control are greatly attenuated in synapsin-deficient mice. These results provide a mechanistic explanation for CsA-induced acute hypertension and suggest that synapsins could serve as a drug target in this refractory condition. Furthermore, these data establish evidence that synapsin-containing sensory microvesicles perform an essential role in sensory transduction and suggest a role for synapsin phosphorylation in this process.

Phenytoin and cyclosporin A suppress the expression of MMP-1, TIMP-1, and cathepsin L, but not cathepsin B in cultured gingival fibroblasts

BACKGROUND

Fibroblasts are known not only to synthesize and secrete extracellular matrix proteins, but also to degrade them for connective tissue remodeling. Drug-induced gingival overgrowth is characterized by a massive accumulation of extracellular matrix components in gingival connective tissues. Although some previous reports suggested that causative drugs stimulated the fibroblast proliferation, the results are not conclusive yet. In this study, we hypothesized that drug-induced gingival overgrowth could be a consequence of impaired ability of matrix degradation rather than an enhanced proliferation of gingival fibroblasts induced by these drugs.

METHODS

Normal human gingival fibroblasts were cultured with or without either 20 microg/ml of phenytoin or 200 ng/ml of cyclosporin A. Total RNA and cellular proteins were collected every day for RT-PCR analyses and for measuring lysosomal enzyme activity. In addition, an immunohistochemical study was performed to detect lysosomal enzymes in cells from enlarged gingiva of the patients with phenytoin-induced gingival overgrowth.

RESULTS

RT-PCR analyses revealed that these drugs suppressed the expression of MMP-1, TIMP-1, and cathepsin L, but not that of cathepsin B in a time-dependent manner. Then, we measured the activity of lysosomal enzymes and cathepsin B and L. The results indicated that although cathepsin B activity was not observed to be impaired, regardless of the drugs used in these cells, both total and active forms of combined activity of cathepsins B and L were suppressed in a time-dependent manner.

CONCLUSIONS

The results indicate that, besides suggested effects of these drugs on gingival fibroblasts and/or on accumulated cells in the gingival tissues, extracellular matrix-degrading ability, particularly that by cathepsin L, is also suppressed by cyclosporin A and phenytoin in gingival fibroblasts, and that lysosomal enzyme plays an important role in the pathogenesis of drug-induced gingival hyperplasia.

Identification of morc (microrchidia), a mutation that results in arrest of spermatogenesis at an early meiotic stage in the mouse

The microrchidia, or morc, autosomal recessive mutation results in the arrest of spermatogenesis early in prophase I of meiosis. The morc mutation arose spontaneously during the development of a mouse strain transgenic for a tyrosinase cDNA construct. Morc -/- males are infertile and have grossly reduced testicular mass, whereas -/- females are normal, indicating that the Morc gene acts specifically during male gametogenesis. Immunofluorescence to synaptonemal complex antigens demonstrated that -/- male germ cells enter meiosis but fail to progress beyond zygotene or leptotene stage. An apoptosis assay revealed massive numbers of cells undergoing apoptosis in testes of -/- mice. No other abnormal phenotype was observed in mutant animals, with the exception of eye pigmentation caused by transgene expression in the retina. Spermatogenesis is normal in +/- males, despite significant transgene expression in germ cells. Genomic analysis of -/- animals indicates the presence of a deletion adjacent to the transgene. Identification of the gene inactivated by the transgene insertion may define a novel biochemical pathway involved in mammalian germ cell development and meiosis.

Pluripotential rabbit embryonic stem (ES) cells are capable of forming overt coat color chimeras following injection into blastocysts

The isolation of pluripotent embryonic stem (ES) cell lines from preimplantation rabbit embryos and their in vitro properties have been previously described. In the present investigation, these ES cell lines were further characterized and their capacity to contribute to formation of adult, fertile animals upon injection into recipient New Zealand White blastocysts demonstrated. The efficiency of chimera formation was low (5% of live born), but the degree of chimerism, as assessed by coat color contribution from the Dutch belted strain, was high (10-50%). Thus a significant step is taken toward the development of gene-targeting technology in the rabbit, an animal whose physiology and size lend itself to unique applications in biomedical research.

Analysis of idiotypic and anti-idiotypic antibodies as models of receptor and ligand

Antibodies to small bioactive ligands and peptides may mimic the binding characteristics of the natural receptor; in turn, the anti-idiotypic antibodies generated against the binding sites of such anti-ligand antibodies may mimic some aspects of small bioactive ligands and peptides. Among the several levels of investigation of such antibody-receptor networks are (a) the quantitative structure-activity relationships of ligand binding to antibody as compared with natural receptor; (b) the molecular modeling of antibody-receptor binding sites and the genomic basis for such structures; and (c) the characteristics of the molecular mimicry exhibited by "mimetopes" on anti-idiotypic antibodies. To illustrate the analysis encountered at each of these levels, we discuss here antibody and anti-idiotypic systems that are directed to small neuroactive ligands and their receptors.

Analysis of idiotypic and anti-idiotypic antibodies as models of receptor and ligand

Antibodies to small bioactive ligands and peptides may mimic the binding characteristics of the natural receptor; in turn, the anti-idiotypic antibodies generated against the binding sites of such anti-ligand antibodies may mimic some aspects of small bioactive ligands and peptides. Among the several levels of investigation of such antibody-receptor networks are (a) the quantitative structure-activity relationships of ligand binding to antibody as compared with natural receptor; (b) the molecular modeling of antibody-receptor binding sites and the genomic basis for such structures; and (c) the characteristics of the molecular mimicry exhibited by "mimetopes" on anti-idiotypic antibodies. To illustrate the analysis encountered at each of these levels, we discuss here antibody and anti-idiotypic systems that are directed to small neuroactive ligands and their receptors.