Cadmium induces caspase-independent apoptosis in liver Hep3B cells: role for calcium in signaling oxidative stress-related impairment of mitochondria and relocation of endonuclease G and apoptosis-inducing factor

Cadmium-induced cellular toxicity has been related to necrosis and/or caspase-dependent apoptosis. In the present study, we show that, on cadmium exposure, the human hepatocarcinoma Hep3B cells undergo caspase-independent apoptosis associated with nuclear translocation of endonuclease G and apoptosis-inducing factor, two mitochondrial apoptogenic proteins. Release of these proteins is likely related to calcium-induced alteration of mitochondrial homeostasis. Indeed, it was first preceded by a rapid and sustained increase in cytoplasmic calcium and then by a coincident loss in mitochondrial membrane potential and production of reactive oxygen species. Bapta-AM (acetoxymethyl ester of 5, 5′-dimethyl-bis (o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid), a calcium chelator, blocked all these events and prevented cadmium-induced apoptosis. Production of reactive oxygen species was inhibited by ruthenium red and rotenone, two mitochondrial inhibitors, and by diphenyleneiodonium, a flavoprotein inhibitor, which also prevented both loss in mitochondrial membrane potential and apoptosis. In addition, Bapta-AM and diphenyleneiodonium were found to almost totally block decreased expression of the mitochondrial anti-apoptotic nuclear factor-κB-regulated bcl-x_L protein in cadmium-treated cells. Taken together, our results show that cadmium induces Hep3B cells apoptosis mainly by calcium- and oxidative stress-related impairment of mitochondria, which probably favors release of apoptosis-inducing factor and endonuclease G.     

Interleukin-7 regulates adipose tissue mass and insulin sensitivity in high-fat diet-fed mice through lymphocyte-dependent and independent mechanisms

Although interleukin (IL)-7 is mostly known as a key regulator of lymphocyte homeostasis, we recently demonstrated that it also contributes to body weight regulation through a hypothalamic control. Previous studies have shown that IL-7 is produced by the human obese white adipose tissue (WAT) yet its potential role on WAT development and function in obesity remains unknown. Here, we first show that transgenic mice overexpressing IL-7 have reduced adipose tissue mass associated with glucose and insulin resistance. Moreover, in the high-fat diet (HFD)-induced obesity model, a single administration of IL-7 to C57BL/6 mice is sufficient to prevent HFD-induced WAT mass increase and glucose intolerance. This metabolic protective effect is accompanied by a significant decreased inflammation in WAT. In lymphocyte-deficient HFD-fed SCID mice, IL-7 injection still protects from WAT mass gain. However, IL-7-triggered resistance against WAT inflammation and glucose intolerance is lost in SCID mice. These results suggest that IL-7 regulates adipose tissue mass through a lymphocyte-independent mechanism while its protective role on glucose homeostasis would be relayed by immune cells that participate to WAT inflammation. Our observations establish a key role for IL-7 in the complex mechanisms by which immune mediators modulate metabolic functions.     

Thiadiazoles as new inhibitors of diacylglycerol acyltransferase type 1

A novel class of DGAT1 inhibitors containing a thiadiazole core has been discovered. Chemical optimization lead to inhibitors of human DGAT1 with an appropriate ADME profile and that show in vivo activity in target tissues.     

Mitochondrial activity,hemocyte parameters and lipid composition modulation by dietary conditioning in the Pacific oyster Crassostrea gigas

Several parameters can affect membrane lipid composition in bivalves, including diet. Although two fatty acids (FA) 22:6n-3 and 20:5n-3 are essential membrane components, they are sparingly synthesized by bivalves and must be obtained from their diet. Here, effects of dietary modifications of membrane lipid composition were studied at both cellular and subcellular levels in the oyster Crassostrea gigas. To this end, we compared oysters fed two monoalgal diets that differed markedly in their FA composition and a mix of both. As expected, algae impacted phospholipids, in particular 22:6n-3 and 20:5n-3, reflecting differences of dietary microalgae FA composition. Meantime, total saturated FA, total monounsaturated FA, total polyunsaturated FA and total non-methylene-interrupted FA varied little and phospholipid class composition was only slightly affected by diets. Measures made in hemocytes indicated that only mitochondrial membrane potential was affected by diets. Total ROS production as well as mitochondrial superoxide production did not differ with diet. There was no difference in phosphorylating (state 3) and non-phosphorylating (state 4) rates of oxygen consumption rates or in cytochrome c oxidase activity of mitochondria isolated from gills between the three diets. Similarly, neither cytochromes a, b, c or c ₁ content nor citrate synthase activities were changed, suggesting that number and morphology of mitochondria were not affected by dietary treatment. These results suggest that oysters could possess high homeostatic capabilities, at both cellular and subcellular levels, to minimize the effect of dietary FA and related membrane lipid FA modifications on mitochondrial functions. These capabilities could be a means to face variations in diet composition in their natural environment and to preserve important oyster physiological functions such as growth and reproduction.     

Kallikrein activates bradykinin B2 receptors in absence of kininogen

Kallikreins cleave plasma kininogens to release the bioactive peptides bradykinin (BK) or kallidin (Lys-BK). These peptides then activate widely disseminated B2 receptors with consequences that may be either noxious or beneficial. We used cultured cells to show that kallikrein can bypass kinin release to activate BK B2 receptors directly. To exclude intermediate kinin release or kininogen uptake from the cultured medium, we cultured and maintained cells in medium entirely free of animal proteins. We compared the responses of stably transfected Chinese hamster ovary (CHO) cells that express human B2 receptors (CHO B2) and cells that coexpress angiotensin I-converting enzyme (ACE) as well (CHO AB). We found that BK (1 nM or more) and tissue kallikrein (1-10 nM) both significantly increased release of arachidonic acid beyond unstimulated baseline level. An enzyme-linked immunoassay for kinin established that kallikrein did not release a kinin from CHO cells. We confirmed the absence of kininogen mRNA with RT-PCR to rule out kininogen synthesis by CHO cells. We next tested an ACE inhibitor for enhanced BK receptor activation in the absence of kinin release and synthesized an ACE-resistant BK analog as a control for these experiments. Enalaprilat (1 microM) potentiated kallikrein (100 nM) in CHO AB cells but was ineffective in CHO B2 cells that do not bear ACE. We concluded that kallikrein activated B2 receptors without releasing a kinin. Furthermore, inhibition of ACE enhanced the receptor activation by kallikrein, an action that may contribute to the manifold therapeutic effects of ACE inhibitors.     

Investigations of new structures with pharmacological activity,II : Anticonvulsant properties of benzocyclobutenols and benzocyclenones

Anticonvulsant properties of two new series of benzocyclobutenols and benzocyclenones have been demonstrated against electroshock and chemically (pentylene-tetrazol, picrotoxin, and isoniazid) induced seizures. The activities were compared to those of diphenylhydantoin and sodium valproate. Two kinds of effects were observed. One type acts preferentially against electroshock seizure, teh other agianst chemically induced seizures.     

Non-additive phenotypic and transcriptomic inheritance in a citrus allotetraploid somatic hybrid between <Emphasis Type="Italic">C. reticulata</Emphasis> and <Emphasis Type="Italic">C. limon</Emphasis>: the case of pulp carotenoid biosynthesis pathway

Allopolyploidy is known to induce novel patterns of gene expression and often gives rise to new phenotypes. Here we report on the first attempt to relate phenotypic inheritance in an allotetraploid somatic hybrid with gene expression. Carotenoid compounds in the fruit pulp of the two parental species and the hybrid were evaluated quantitatively by HPLC. Only very low levels of β-carotene and β-cryptoxanthin were observed in Citrus limon, while β-cryptoxanthin was a major component of C. reticulata, which also displayed high levels of phytoene, phytofluene, β-carotene, lutein, zeaxantin and violaxanthin. Total carotenoid content in mandarin juice sacs was 60 times greater than that in lemon. The allotetraploid hybrid produced all the same compounds as mandarin but at very low levels. Transgressive concentration of abscisic acid (ABA) was observed in the somatic hybrid. Real-time RT-PCR of total RNA from juice sacs was used to study expression of seven genes (CitDxs, CitPsy, CitPds, CitZds, CitLcy-b, CitChx-b, and CitZep) of the carotenoid biosynthetic pathway and two genes (CitNced1 and CitNced2) involved in abscisic acid synthesis from carotenoid. Gene expression was significantly higher for mandarin than lemon for seven of the nine genes analyzed. Lemon under expression was partially dominant in the somatic hybrid for three upstream steps of the biosynthetic pathway, particularly for CitDxs. Transgressive over expression was observed for the two CitNced genes. A limitation of the upstream steps of the pathway and a downstream higher consumption of carotenoids may explain the phenotype of the somatic hybrid.