SH479, a Betulinic Acid Derivative, Ameliorates Experimental Autoimmune Encephalomyelitis by Regulating the T Helper 17/Regulatory T Cell Balance.

CD4+ T helper cells, especially T helper 17 (TH17) cells, combined with immune regulatory network dysfunction, play key roles in autoimmune diseases including multiple sclerosis (MS). Betulinic acid (BA), a natural pentacyclic triterpenoid, has been reported to be involved in anti-inflammation, in particular having an inhibitory effect on proinflammatory cytokine interleukin 17 (IL-17) and interferon-γ (IFN-γ) production. In this study, we screened BA derivatives and found a BA derivative, SH479, that had a greater inhibitory effect on TH17 differentiation. Our further analysis showed that SH479 had a greater inhibitory effect on TH17 and TH1, and a more stimulatory effect on regulatory T (Treg) cells. To evaluate the effects of SH479 on autoimmune diseases in vivo, we employed the extensively used MS mouse model experimental autoimmune encephalomyelitis (EAE). Our results showed that SH479 ameliorated clinical and histologic signs of EAE in both prevention and therapeutic protocols by regulating the TH17/Treg balance. SH479 dose-dependently reduced splenic lymphocyte proinflammatory factors and increased anti-inflammatory factors. Moreover, SH479 specifically inhibited splenic lymphocyte viability from EAE mice but not normal splenic lymphocyte viability. At the molecular level, SH479 inhibited TH17 differentiation by regulating signal transducer and activator of transcription-3 (STAT3) phosphorylation, DNA binding activity, and recruitment to the Il-17a promoter in CD4+ T cells. Furthermore, SH479 promoted the STAT5 signaling pathway and inhibited the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Together, our data demonstrated that SH479 ameliorated EAE by regulating the TH17/Treg balance through inhibiting the STAT3 and NF-κB pathways while activating the STAT5 pathway, suggesting that SH479 is a potential novel drug candidate for autoimmune diseases including MS.

The G2A Receptor Deficiency Aggravates Atherosclerosis in Rats by Regulating Macrophages and Lipid Metabolism.

The orphan G protein-coupled receptor G2A has been linked to atherosclerosis development. However, available data from mouse models are controversial. Rat G2A receptor bears more similarities with its human homolog. We proposed that the atherosclerosis model established from Ldlr -/- rat, which has been reported to share more similar phenotypes with the human disease, may help to further understand this lipid receptor. G2A deletion was found markedly aggravated in the lipid disorder in the rat model, which has not been reported in mouse studies. Examination of aortas revealed exacerbated atherosclerotic plaques in G2A deficient rats, together with increased oxidative stress and macrophage accumulation. In addition, consistently promoted migration and apoptosis were noticed in G2A deficient macrophages, even in macrophages from G2A single knockout rats. Further analysis found significantly declined phosphorylation of PI3 kinase (PI3K) and AKT, together with reduced downstream genes Bcl2 and Bcl-xl, suggesting possible involvement of PI3K/AKT pathway in G2A regulation to macrophage apoptosis. These data indicate that G2A modulates atherosclerosis by regulating lipid metabolism and macrophage migration and apoptosis. Our study provides a new understanding of the role of G2A in atherosclerosis, supporting it as a potential therapeutic target.

Hyperlipidemia induces typical atherosclerosis development in Ldlr and Apoe deficient rats.

BACKGROUND AND AIMS: Low-density lipoprotein receptor (Ldlr) and apolipoprotein E (Apoe) knockout (KO) mice have been widely used as animal models of atherosclerosis. However, data suggested that it is difficult to develop typical atherosclerosis in rats. To this end, Ldlr and Apoe KO rats were generated and the potential to develop novel atherosclerosis models was evaluated. METHODS: We established Apoe/Ldlr single and double KO (DKO) rats via the CRISPR/Cas9 system in the same background. Phenotypes of dyslipidemia and atherosclerosis in these KO rats were systematically characterized. RESULTS: Knockout of either gene led to severe dyslipidemia and liver steatosis. Significant atherosclerotic plaques were observed in the abdominal aorta of all mutant rats fed a normal diet for 48 weeks. Western diet greatly aggravated atherosclerosis and fatty liver. In addition, we found mononuclear cell infiltration in early lesions. Increased expression of inflammatory cytokines, as well as macrophage accumulation in lesions of mutants, was observed, indicating that mononuclear cell trafficking and endothelial inflammation affected atherogenesis. Moreover, mutant rats displayed a sex difference profile more similar to humans in which males had heavier plaque burdens than females. CONCLUSIONS: Deficiency of either Ldlr or Apoe genes induced hyperlipidemia, which promoted endothelial inflammation and led to typical atherosclerosis in rats on normal or Western diets. These models display certain advantages, which will benefit future investigations of atherosclerotic pathology and antiatherosclerotic therapeutics.

GPR54 deficiency reduces the Treg population and aggravates experimental autoimmune encephalomyelitis in mice.

GPR54 is highly expressed in the central nervous system and plays a crucial role in pubertal development. However, GRP54 is also expressed in the immune system, implying possible immunoregulatory functions. Here we investigated the role of GPR54 in T cell and immune tolerance. GPR54 deficiency led to an enlarged thymus, an increased number of thymocytes, and altered thymic micro-architecture starting around puberty, indicating GPR54 function in T-cell development through its regulatory effect on the gonadal system. However, flow cytometry revealed a significant reduction in the peripheral regulatory T cell population and a moderate decrease in CD4 single-positive thymocytes in prepubertal Gpr54-/- mice. These phenotypes were confirmed in chimeric mice with GPR54 deficient bone marrow-derived cells. In addition, we found elevated T cell activation in peripheral and thymic T cells in Gpr54-/- mice. When intact mice were immunized with myelin oligodendrocyte glycoprotein, a more severe experimental autoimmune encephalomyelitis (EAE) developed in the Gpr54-/- mice. Interestingly, aggravated EAE disease was also manifested in castrated and bone marrow chimeric Gpr54-/- mice compared to the respective wild-type control, suggesting a defect in self-tolerance resulting from GPR54 deletion through a mechanism that bypassed sex hormones. These findings demonstrate a novel role for GPR54 in regulating self-tolerant immunity in a sex hormone independent manner.

Kisspeptin Receptor GPR54 Promotes Adipocyte Differentiation and Fat Accumulation in Mice.

GPR54, Kisspeptin-1 receptor (KISS1R), a member of rhodopsin family, plays a critical role in puberty development and has been proposed to be involved in regulation of energy metabolism. This study aims to explore the function of GPR54 in adipogenesis, lipid metabolism, and obesity in addition to its effect through hormones. Results showed that when fed a high-fat diet, the weight growth of castrated or ovariectomized Gpr54-/- mice was significantly slower than that of WT control, together with a lower triglyceride concentration. The ratio of white adipose tissue was lower, and average size of adipocytes was smaller in Gpr54-/- mice. Meanwhile, there were less adipose tissue macrophages (ATMs), especially pro-inflammatory macrophages. Expression of inflammatory related genes also indicated that inflammatory response caused by obesity was not as drastic in Gpr54-/- mice as in WT mice. Liver triglyceride in Gpr54-/- mice was reduced, especially in female mice. On the other hand, oil drop formation was accelerated when hepatocytes were stimulated by kisspeptin-10 (Kp-10). Primary mesenchymal stem cells (MSCs) of Gpr54-/- mice were less likely to differentiate into adipocytes. When stimulated by Kp-10, 3T3-L1 cell differentiation into adipocytes was accelerated and triglyceride synthesis was significantly promoted. These data indicated that GPR54 could affect obesity development by promoting adipocyte differentiation and triglyceride accumulation. To further elucidate the mechanism, genes related to lipid metabolism were analyzed. The expression of genes involved in lipid synthesis including PPARγ, ACC1, ADIPO, and FAS was significantly changed in Gpr54-/- mice. Among them PPARγ which also participate in adipocyte differentiation displayed a marked reduction. Moreover, phosphorylation of ERK, which involved in GPR54 signaling, was significantly decreased in Gpr54-/- mice, suggesting that GPR54 may promote lipid synthesis and obesity development by activating MAP kinase pathway. Therefore, in addition to the involvement in hormone regulation, our study demonstrated that GPR54 directly participates in obesity development by promoting adipocyte differentiation and fat accumulation. This provided evidence of involvement of GPR54 in lipid metabolism, and revealed new potentials for the identification and development of novel drug targets for metabolic diseases.

Effects of Melanocortin 3 and 4 Receptor Deficiency on Energy Homeostasis in Rats.

Melanocortin-3 and 4 receptors (MC3R and MC4R) can regulate energy homeostasis, but their respective roles especially the functions of MC3R need more exploration. Here Mc3r and Mc4r single and double knockout (DKO) rats were generated using CRISPR-Cas9 system. Metabolic phenotypes were examined and data were compared systematically. Mc3r KO rats displayed hypophagia and decreased body weight, while Mc4r KO and DKO exhibited hyperphagia and increased body weight. All three mutants showed increased white adipose tissue mass and adipocyte size. Interestingly, although Mc3r KO did not show a significant elevation in lipids as seen in Mc4r KO, DKO displayed even higher lipid levels than Mc4r KO. DKO also showed more severe glucose intolerance and hyperglycaemia than Mc4r KO. These data demonstrated MC3R deficiency caused a reduction of food intake and body weight, whereas at the same time exhibited additive effects on top of MC4R deficiency on lipid and glucose metabolism. This is the first phenotypic analysis and systematic comparison of Mc3r KO, Mc4r KO and DKO rats on a homogenous genetic background. These mutant rats will be important in defining the complicated signalling pathways of MC3R and MC4R. Both Mc4r KO and DKO are good models for obesity and diabetes research.