Activités antimicrobiennes des huiles essentielles de Eucalyptus citriodora Hook et Eucalyptus houseana W.Fitzg. ex Maiden

Les huiles essentielles de Eucalyptus citriodora et Eucalyptus houseana récoltées à N’Débougou (Mali) ont été testées sur les bactéries Escherichia coli, Staphylococcus aureus et le champignon Candida albicans. Nous avons utilisé la méthode de diffusion en Agar pour de la détermination des activités antibactériennes. La plus grande activité a été notée avec l’huile essentielle de Eucalyptus houseana sur Staphylococcus aureus. L’activité antifongique a été déterminée par chromatographie sur couche mince (CCM). Les deux huiles essentielles ont été actives sur Candida albicans.Mots clés: Antibactérienne, antifongique, Escherichia coli, Staphylococcus aureus, Candida albicans

A subcytotoxic dose of subtilase cytotoxin prevents lipopolysaccharide-induced inflammatory responses, depending on its capacity to induce the unfolded protein response

Subtilase cytotoxin (SubAB) is the prototype of a newly identified family of AB5 cytotoxins produced by Shiga toxigenic Escherichia coli. SubAB specifically cleaves the essential endoplasmic reticulum (ER) chaperone BiP (GRP78), resulting in the activation of ER stress-induced unfolded protein response (UPR). We have recently shown that the UPR following ER stress can suppress cellular responses to inflammatory stimuli during the later phase, in association with inhibition of NF-B activation. These findings prompted us to hypothesize that SubAB, as a selective UPR inducer, might have beneficial effects on inflammation-associated pathology via a UPR-dependent inhibition of NF-B activation. The pretreatment of a mouse macrophage cell line, RAW264.7, with a subcytotoxic dose of SubAB-triggered UPR and inhibited LPS-induced MCP-1 and TNF- production associated with inhibition of NF-B activation. SubAA272B, a SubAB active site mutant that cannot induce UPR, did not show such effects. In addition, pretreatment with a sublethal dose of SubAB, but not SubAA272B, protected the mice from LPS-induced endotoxic lethality associated with reduced serum MCP-1 and TNF- levels and also prevented the development of experimental arthritis induced by LPS in mice. Collectively, although SubAB has been identified originally as a toxin associated with the pathogenesis of hemolytic uremic syndrome, the unique ability of SubAB to selectively induce the UPR may have the potential to prevent LPS-associated inflammatory pathology under subcytotoxic conditions. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.Daisuke Harama, Kensuke Koyama, Mai Mukai, Naomi Shimokawa, Masanori Miyata, Yuki Nakamura, Yuko Ohnuma, Hideoki Ogawa, Shuji Matsuoka, Adrienne W. Paton, James C. Paton, Masanori Kitamura, and Atsuhito Naka

Resistance to type 2 diabetes mellitus: a matter of hormesis?

Type 2 diabetes mellitus is characterized by subclinical systemic inflammation and impaired regulation of blood glucose levels. Interestingly, impairment of glycemic control occurs despite substantial insulin secretion early in the course of this disease. Dysfunction of several organs (including pancreatic islets, liver, skeletal muscle, adipose tissue, gut, hypothalamus and the immune system) has been implicated in the pathogenesis of type 2 diabetes mellitus. However, diabetes-promoting lifestyle factors do not inevitably cause disease in all persons exposed. Hence, defense mechanisms must exist that can keep the detrimental influence of these risk factors at bay. Hormesis describes the phenomenon that exposure to a mild stressor confers resistance to subsequent, otherwise harmful, conditions of increased stress. This Review discusses the emerging concept that the effectiveness of an adaptive (hormetic) response to detrimental lifestyle factors determines the extent of protection from progression to type 2 diabetes mellitus. Further analysis of these protective hormetic responses at the molecular level should help to identify novel targets for preventive or therapeutic intervention in patients at risk of developing type 2 diabetes mellitus or those with overt disease.Journal ArticleResearch Support, Non-U.S. Gov'tReviewSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Bacteria, the endoplasmic reticulum and the unfolded protein response: friends or foes?

The unfolded protein response (UPR) is a cytoprotective response that is aimed at restoring cellular homeostasis following physiological stress exerted on the endoplasmic reticulum (ER), which also invokes innate immune signalling in response to invading microorganisms. Although it has been known for some time that the UPR is modulated by various viruses, recent evidence indicates that it also has multiple roles during bacterial infections. In this Review, we describe how bacteria interact with the ER, including how bacteria induce the UPR, how subversion of the UPR promotes bacterial proliferation and how the UPR contributes to innate immune responses against invading bacteria