The mitochondrial permeability transition pore and nitric oxide synthase mediate early mitochondrial depolarization in astrocytes during oxygen-glucose deprivation.

Recent studies suggest that the degree of mitochondrial dysfunction in cerebral ischemia may be an important determinant of the final extent of tissue injury. Although loss of mitochondrial membrane potential (psi(m)), one index of mitochondrial dysfunction, has been documented in neurons exposed to ischemic conditions, it is not yet known whether astrocytes, which are relatively resistant to ischemic injury, experience changes in psi(m) under similar conditions. To address this, we exposed cortical astrocytes cultured alone or with neurons to oxygen-glucose deprivation (OGD) and monitored psi(m) using tetramethylrhodamine ethyl ester. Both neurons and astrocytes exhibited profound loss of psi(m) after 45-60 min of OGD. However, although this exposure is lethal to nearly all neurons, it is hours less than that needed to kill astrocytes. Astrocyte psi(m) was rescued during OGD by cyclosporin A, a permeability transition pore blocker, and (G)N-nitro-arginine, a nitric oxide synthase inhibitor. Loss of mitochondrial membrane potential in astrocytes was not accompanied by depolarization of the plasma membrane. Recovery of astrocyte psi(m) after reintroduction of O(2) and glucose occurred over a surprisingly long period (>1 hr), suggesting that OGD caused specific, reversible changes in astrocyte mitochondrial physiology beyond the simple lack of O(2) and glucose. Decreased psi(m) was associated with a cyclosporin A-sensitive loss of cytochrome c but not with activation of caspase-3 or caspase-9. Our data suggest that astrocyte mitochondrial depolarization could be a previously unrecognized event early in ischemia and that strategies that target the mitochondrial component of ischemic injury may benefit astrocytes as well as neurons.

Cyclooxygenase-2 is upregulated in inflamed gingival tissues.

BACKGROUND: Increased release of prostaglandins (PG) within periodontal tissues is considered to play a pathogenetic role during periodontal disease progression. The rate-limiting step in the formation of PG from arachidonic acid is catalyzed by cyclooxygenase (COX). Currently there are 2 known isoforms of the enzyme. COX-1 is constitutively expressed in various tissues whereas COX-2 is an inducible enzyme believed to be responsible for PG synthesis at sites of inflammation. The purpose of this study was to compare COX-2 expression in inflamed and healthy human gingiva and further explore some of the pathogenetic mechanisms which may lead to elevated COX-2 expression in vivo. METHODS: Thirty-two gingival biopsies were obtained during routine oral surgical procedures and were processed histologically using hematoxylin and eosin to determine the degree of inflammation. Of these biopsies, 7 with low and 7 with high histological levels of inflammation were further processed immunohistochemically in order to assess the levels of COX-2 expression in situ. To explore some potential mechanisms of COX-2 upregulation, gingival connective tissue primary cell cultures were established and challenged with periodontal bacteria or proinflammatory cytokines in vitro. The levels of COX-2 expression were analyzed by Western blot of cell lysates. COX-2 activity was assessed by quantifying prostaglandin E2 (PGE2) levels in culture supernatants by competitive EIA. RESULTS: We have shown by immunohistochemistry that COX-2 expression was significantly higher (P < 0.01) in tissues with higher levels of inflammatory infiltrates. Expression of COX-2 was detected in gingival epithelium, endothelial cells as well as cells with fibroblast morphology. In vitro studies indicated that gingival fibroblasts (GF) did not express COX-2 constitutively. However, when these cells were challenged with interleukin (IL)-1 beta or bacterial cells (A. actinomycetemcomitans JP2 or B. forsythus ATCC 43037), COX-2 expression as well as COX-2 activity were upregulated. COX-2 expression was upregulated as early as 2 hours post IL-1 beta challenge and was accompanied by a sustained PGE2 release in the culture supernatants. Cyclosporin A (CsA) did not inhibit COX-2 expression induced by bacterial challenge. In contrast, NS-398, a selective inhibitor of COX-2 activity, almost completely abolished PGE2 synthesis by these cells in response to bacterial or cytokine challenge. CONCLUSIONS: We conclude that COX-2 expression is significantly upregulated in inflamed periodontal tissues. Both inflammatory cytokines such as IL-1 beta and bacterial constituents may be responsible for the enhanced COX-2 expression and PGE2 synthesis in vivo.

Neural actions of immunophilin ligands.

Immunophilins, protein receptors for immunosuppressant drugs such as cyclosporin A and FK506, are enriched far more in the brain than in the immune system. Drug-immunophilin complexes bind to calcineurin, inhibiting its phosphatase activity and leading to immunosuppressant effects. The immunophilin FKBP-12 (FK506 binding protein, 12 kDa) forms a complex with the ryanodine and inositol (1,4,5) trisphosphate (IP3) receptors to regulate their physiological release of intracellular Ca2+. Here, Solomon Snyder and colleagues describe how non-immunosuppressant as well as immunosuppressant immunophilin ligands are neurotrophic for numerous classes of damaged neurones, both in culture systems and intact animals. Their ability to stimulate functional regrowth of damaged sciatic, cortical cholinergic, dopamine and 5-HT neurones may have therapeutic relevance.

Osteomyelitis due to Mycobacterium haemophilum in a cardiac transplant patient: case report and analysis of interactions among clarithromycin, rifampin, and cyclosporine.

We describe a case of osteomyelitis due to Mycobacterium haemophilum in a cardiac transplant recipient and review the two other reported cases of M. haemophilum infection in cardiac transplant patients. Our patient had an excellent response to a prolonged course of therapy with clarithromycin and rifampin. We examine in detail the interactions between these two antibiotics and cyclosporine, including the apparently offsetting effects of clarithromycin/rifampin combination therapy on blood levels of cyclosporine.

Efeitos da ciclosporina A sobre a síntese de proteínas de matriz extracelular de fibroblastos de gengiva normal e de portadores de fibromatose gengival hereditária / The effect of cyclosporin on the synthesis of extracelular matrix proteins in fibroblasts of patients with hereditary gingival fibromatosis

A fibromatose gengival pode ser hereditária ou induzida por drogas. O padräo da doença sugere que os fibroblastos gengivais podem produzir grandes volumes de substância extracelular. Um dos efeitos colaterais da ciclosporina A (CsA) é a induçäo de fibromatose gengival. Os efeitos de 3 diferentes concentraçöes de CsA sobre a morfologia, síntese de colagenase, de fibronectina e atividade colagenolítica, foram estudados "in vitro" em 6 linhagens de fibroblastos, 3 de gengivas normais e 3 de fibromatose gengival hereditária. Os fibroblastos foram cultivados com meio contendo concentraçöes de 250, 500 e 1.000 ng/ml de CsA, por 24, 48 e 78h. O meio foi coletado e submetido a ensaios enzimográficos e de atividade colagenolítica. A síntese de fibronectina foi avaliada através de "dot blot" e de proteína total pela análise eletroforética do sobrenadante.