Experimental T‐cell‐mediated hepatitis induced by concanavalin A (Con A) involves the production of proinflammatory cytokines. Because interleukin (IL)‐10 is a potent anti‐inflammatory cytokine derived from macrophages and T cells and is produced within the liver, we investigated the role of IL‐10 in modulating the hepatotoxicity and the secretion of cytokines following in vivo injection of Con A. IL‐10 is produced early in the serum after Con A challenge. Neutralization of endogenous IL‐10 by monoclonal antibodies (mAbs) increases the secretion of tumor necrosis factor α (TNF‐α) (+111%), interferon gamma (IFN‐γ) (+92%), and IL‐12 (+730%) 8 hours after Con A injection, and increases the hepatotoxicity, assessed by serum alanine transaminase (ALT) (+174%) measurement and by histology, 24 hours after induction of hepatitis. Conversely, preadministration of recombinant IL‐10 reduces the production of these proinflammatory cytokines (‐47%, ‐80%, and ‐47% for TNF‐α, IL‐12, and IFN‐γ, respectively), and decreases neutrophil infiltration and ALT serum concentration (‐74%) 8 hours after Con A challenge. We conclude that IL‐10, either endogenously produced or exogenously added, has a hepatoprotective role in Con A‐induced hepatitis, through its suppressive property on proinflammatory cytokine production, and that it might be of therapeutic relevance in human liver diseases involving activated T cells.

Background: Previous studies have described apoptosis in the stratum granulosum and in the stratum corneum, but not in the germinative compartment in normal skin. In psoriasis, an increased epidermal apoptosis has been observed in the differentiated compartment, suggesting that apoptosis has a key role in the pathogenesis of psoriasis, as a counteracting factor to the overproduction of cells. Little is known on apoptosis in the germinative compartment. Methods: Apoptosis was studied on biopsies of normal skin, established lesions of psoriasis and PUVA-treated psoriasis using the transferase-mediated uridine nick end labelling method, which detects fragmented DNA, and electron microscopy. Counting of apoptotic cells was restricted to the germinative compartment as defined by Mib1 staining to evaluate the impact of cell loss on cell production and tissue architecture. Results: The apoptotic index was 0.12% in normal epidermis, 0.035% in established psoriasis and 0.31% in regressive psoriasis. Conclusion: These results have three implications: (1) they show the physiological presence of apoptosis in the germinative compartment in normal epidermis; (2) they suggest that induction of apoptosis is involved in the regression of psoriatic hyperplasia after PUVA therapy; (3) the decrease of physiological apoptosis in the psoriatic lesion suggests that this phenomenon could play a role in the induction of psoriatic hyperplasia.

The P2Y 4 receptor is responsive to UTP in human and to ATP and UTP in rodents. With the aim of identifying its pharmacotherapeutic interest, we generated P2Y 4 -null mice by a classic gene targeting method. The proportion of genotypes was consistent with X-linked Mendelian transmission. Gene inactivation was checked by the complete disappearance of P2Y 4 receptor mRNA from liver, stomach, and intestine. The P2Y 4 -null mice had a grossly normal behavior, growth, and reproduction. Chloride secretion by the jejunal epithelium was assessed in Ussing chambers by the measurement of the short circuit current in the presence of phlorizin. We show here that the UTP-and ATPinduced chloride secretory responses observed in wild-type mice are abolished in P2Y 4 -null mice. This is the first clearcut demonstration of a biological role of the P2Y 4 receptor.

HL-60 and MCF-7 cells were treated with 0.15 microM camptothecin (CPT) or with the solvent dimethylsulfoxide (DMSO) for the controls, for 2, 3 and 4 h or for 24, 48 and 72 h, respectively. The apoptotic index (AI) was then evaluated in parallel by the following flow cytometric methods: (1) double staining of unfixed cells with fluoresceinated annexin V and propidium iodide (PI), this after detachment by trypsinization in the case of MCF-7 cultures; (2) prefixation in 70% ethanol, extraction of degraded, low molecular weight DNA with 0.2 M phosphatecitrate buffer and analysis of the DNA content stained with PI; (3) TUNEL, i.e. labelling of DNA strand breaks with biotin-dUTP, followed by staining with streptavidin-fluorescein and counterstaining with PI. In HL-60 cells, the three methods gave similar results for the AI (3-4% in the controls and at 2 h of CPT treatment, and 35-43% at 3 and 4 h after CPT). This indicates that CPT-induced membrane alteration and DNA fragmentation occurred concomitantly in those cells. For MCF-7 cells, CPT-induced apoptosis developed more slowly, the AI, whether based on annexin V or on DNA content, remained unchanged at 24 h, then was increasing to 8% at 48 h and to 25% at 72 h of treatment. In these cells, the TUNEL index did not increase prior to 72 h, and the increase was minor (up to 9% vs. 2-3% in the controls) at 72 h of the treatment. This indicates that in MCF-7 cells DNA strand breaks cannot be effectively labelled, which may be due to inaccessibility of 3'-OH ends in the breaks to exogenous terminal deoxynucleotidyl transferase. The mechanism of endonucleolytic DNA fragmentation thus may be different, depending on the cell type.

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