Similarities and differences between the responses induced in human phagocytes through activation of the medium chain fatty acid receptor GPR84 and the short chain fatty acid receptor FFA2R

GPR84 is a recently de-orphanized member of the G-protein coupled receptor (GPCR) family recognizing medium chain fatty acids, and has been suggested to play important roles in inflammation. Due to the lack of potent and selective GPR84 ligands, the basic knowledge related to GPR84 functions is very limited. In this study, we have characterized the GPR84 activation profile and regulation mechanism in human phagocytes, using two recently developed small molecules that specifically target GPR84 agonistically (ZQ16) and antagonistically (GLPG1205), respectively. Compared to our earlier characterization of the short chain fatty acid receptor FFA2R which is functionally expressed in neutrophils but not in monocytes, GPR84 is expressed in both cell types and in monocyte-derived macrophages. In neutrophils, the GPR84 agonist had an activation profile very similar to that of FFA2R. The GPR84-mediated superoxide release was low in naïve cells, but the response could be significantly primed by TNFα and by the actin cytoskeleton disrupting agent Latrunculin A. Similar to that of FFA2R, a desensitization mechanism bypassing the actin cytoskeleton was utilized by GPR84. All ZQ16-mediated cellular responses were sensitive to GLPG1205, confirming the GPR84-dependency. Finally, our data of in vivo transmigrated tissue neutrophils indicate that both GPR84 and FFA2R are involved in neutrophil recruitment processes in vivo.In summary, we show functional similarities but also some important differences between GPR84 and FFA2R in human phagocytes, thus providing some mechanistic insights into GPR84 regulation in blood neutrophils and cells recruited to an aseptic inflammatory site in vivo.     

Molecular Paths Linking Metabolic Diseases,Gut Microbiota Dysbiosis and Enterobacteria Infections

Alterations of both ecology and functions of gut microbiota are conspicuous traits of several inflammatory pathologies, notably metabolic diseases such as obesity and type 2 diabetes. Moreover, the proliferation of enterobacteria, subdominant members of the intestinal microbial ecosystem, has been shown to be favored by Western diet, the strongest inducer of both metabolic diseases and gut microbiota dysbiosis. The inner interdependence between the host and the gut microbiota is based on a plethora of molecular mechanisms by which host and intestinal microbes modify each other. Among these mechanisms are as follows: (i) the well-known metabolic impact of short chain fatty acids, produced by microbial fermentation of complex carbohydrates from plants; (ii) a mutual modulation of miRNAs expression, both on the eukaryotic (host) and prokaryotic (gut microbes) side; (iii) the production by enterobacteria of virulence factors such as the genotoxin colibactin, shown to alter the integrity of host genome and induce a senescence-like phenotype in vitro; (iv) the microbial excretion of outer-membrane vesicles, which, in addition to other functions, may act as a carrier for multiple molecules such as toxins to be delivered to target cells. In this review, I describe the major molecular mechanisms by which gut microbes exert their metabolic impact at a multi-organ level (the gut barrier being in the front line) and support the emerging triad of metabolic diseases, gut microbiota dysbiosis and enterobacteria infections.     

Differences in faecal bacteria populations and faecal bacteria metabolism in healthy adults and celiac disease patients

Differences in the intestinal microbiota between children and adults with celiac disease (CD) have been reported; however, differences between healthy adults and adults with CD have not been clearly demonstrated. The aim of this study was to evaluate the differences in the intestinal microbiota between adults with CD and healthy individuals. Microbial communities in faecal samples were evaluated by PCR-denaturing gradient gel electrophoresis (DGGE) and gas-liquid chromatography of short chain fatty acids (SCFAs). The study group included 10 untreated CD patients, 11 treated CD patients and 11 healthy adults (in normal gluten diet and in GFD). UPGMA clustered the dominant microbial communities of healthy individuals together and separated them from the dominant microbial communities of the untreated CD patients. Most of the dominant microbial communities of the treated CD patients clustered together with those of healthy adults. The treated CD patients showed a reduction in the diversity of Lactobacillus and Bifidobacterium species. The presence of Bifidobacterium bifidum was significantly higher in untreated CD patients than healthy adults. There was a significant difference between untreated CD patients and healthy adults, as well as between treated CD patients and healthy adults, regarding acetic acid, propionic acid, butyric acid, and total SCFAs. In conclusion: healthy adults have a different faecal microbiota from that of untreated CD patients. A portion of the treated CD patients displayed a restored "normal" microbiota. The treated CD patients significantly reduce the Lactobacillus and Bifidobacterium diversity. Healthy adults have a different faecal SCFAs content from that of CD patients.     

乳杆菌在Caco-2细胞模型中对肠吸收短链脂肪酸的促进作用

[背景]短链脂肪酸(Short-Chain Fatty Acids,SCFAs)具有提供能量、调节营养物质代谢、抑制内源性胆固醇合成等广泛的生理活性和生物学效应.[目的]利用建立的Caco-2细胞吸收SCFAs模型研究乳杆菌对肠吸收SCFAs的影响.[方法]通过跨膜电阻值(Transepithelial Electri...     

取代短链脂肪酸对秀丽隐杆线虫的抗氧化作用

短链脂肪酸(short chain fatty acids, SCFAs)是碳原子数为1～6的有机脂肪酸,不但可以作为生物体内能源物质,而且还具有抗炎、影响肠道菌群代谢和预防早发1型糖尿病等重要作用。然而,目前多数是对传统短链脂肪酸的生物学作用进行研究,对取代短链脂肪酸(short branched-chain fatty acids, SBCFAs)的相关研究甚少。本研究以秀丽隐杆线虫为模式动物,系统探究SBCFAs的抗氧化生物活性作用。采用胡桃醌氧化应激模型,在体内评价SBCFAs对秀丽隐杆线虫生存能力的影响,并通过体外抗氧化及H_2DCFDA荧光染色实验,进一步评价SBCFAs清除活性氧自由基(reactive oxygen species,ROS)的能力。本研究证实,在氧化应激研究中,传统脂肪酸不能延长秀丽隐杆线虫的存活时间,而2′-甲基取代短链脂肪酸(n=4-6)具有显著的抗氧化作用。体外抗氧化实验表明,2′-甲基取代短链脂肪酸(n=4-6)不具有体外直接清除ROS的能力,但是H_2DCFDA荧光染色实验显示2′-甲基丁酸能够显著降低线虫体内的ROS水平,表明2′-甲基丁酸通过降低体内ROS水平,从而增强秀丽隐杆线虫的抗氧化应激能力。本研究提示,传统短链脂肪酸不具有抗氧化作用;2′-甲基取代短链脂肪酸(n=4-6)能显著增强秀丽隐杆线虫的抗氧化能力;甲基取代位置和取代烷基长度对短支链脂肪酸的抗氧化作用至关重要,其作用机制需进一步研究。     

Entamoeba histolytica: cyst-like structures in vitro induction

The cyst of Entamoeba histolytica is responsible for amebiasis infection. However, no axenic in vitro system exists that promotes mass encystation for studying this process of this human-infecting parasite. Cyst-like structures of E. histolytica obtained in this work were induced using TYI-S-33 media in combination with enterobacterias Escherichia coli and Enterococcus faecalis conditioned media, high CO2 tension and histamine. Cyst-like structures showed the same characteristics of a typical E. histolytica cyst: aggregation, resistance to 0.15% sarcosyl for 10 min, high signal of fluorescence under UV light when stained with 10% calcofluor M2r and the surface topology showed a wrinkled wall. In addition these structures are multinucleated with condensed chromatin attached to nuclear membrane, contain big vacuoles and ribonucleoproteic helices in the cytoplasm and also present a thin cell wall. Last all characteristics are all the same as a typical of E. histolytica cyst.     

Subacute ruminal acidosis suppressed the expression of MCT1 in rumen of cows

Subacute ruminal acidosis (SARA) is characterized by the depression of ruminal pH and an increase in the concentrations of short-chain fatty acids (SCFAs) and lipopolysaccharide (LPS) in the rumen of cows. The onset of SARA was linked to the accumulation of SCFAs. However, the mechanism of SCFAs transport is unknown. The proton-linked monocarboxylate transporter (MCT1) plays a vital role in the transportation of SCFAs. The goal of this study was to elucidate the distribution of MCT1 along the gastrointestinal tract of calves and adult cows; the expression change of MCT1 in SARA cows and the effect of ruminal pH, SCFAs, and LPS on MCT1 expression in rumen epithelial cells in vitro. The results indicated the presence of MCT1 along the gastrointestinal tract of calves and adult cows, most abundantly expressed in the rumen. Importantly, the expression of MCT1 was decreased in the rumen epithelium of SARA cows, and the expression of MCT1 was restored in the SARA treatment group. In vitro, LPS, low rumen fluid pH, high concentrations of SCFAs (90 mM acetate, 40 mM propionate, and 30 mM butyrate), and high concentrations of acetate, propionate, and butyrate, respectively, inhibited the expression of MCT1 in rumen epithelial cells. Taken together, these results indicated that LPS, low ruminal pH, and high concentrations of SCFAs decreased the expression of MCT1, further aggravating the accumulation of SCFAs in the rumen by decreasing the absorption of SCFAs.