The splicing-factor oncoprotein SF2/ASF activates mTORC1

The splicing factor SF2/ASF is an oncoprotein that is up-regulated in many cancers and can transform immortal rodent fibroblasts when slightly overexpressed. The mTOR signaling pathway is activated in many cancers, and pharmacological blockers of this pathway are in clinical trials as anticancer drugs. We examined the activity of the mTOR pathway in cells transformed by SF2/ASF and found that this splicing factor activates the mTORC1 branch of the pathway, as measured by S6K and eIF4EBP1 phosphorylation. This activation is specific to mTORC1 because no activation of Akt, an mTORC2 substrate, was detected. mTORC1 activation by SF2/ASF bypasses upstream PI3K/Akt signaling and is essential for SF2/ASF-mediated transformation, as inhibition of mTOR by rapamycin blocked transformation by SF2/ASF in vitro and in vivo. Moreover, shRNA-mediated knockdown of mTOR, or of the specific mTORC1 and mTORC2 components Raptor and Rictor, abolished the tumorigenic potential of cells overexpressing SF2/ASF. These results suggest that clinical tumors with SF2/ASF up-regulation could be especially sensitive to mTOR inhibitors.     

虎杖苷对慢性阻塞性肺疾病大鼠PI3K/AKT/mTOR通路以及气道炎症的影响

目的 构建慢性阻塞性肺疾病（COPD）大鼠模型,探讨虎杖苷对COPD大鼠PI3K/AKT/mTOR通路以及气道炎症的影响。方法 100只Wistar大鼠随机分为对照组、模型组、地塞米松（0.2 mg/kg,阳性药）组和虎杖苷低、高剂量（30、60 mg/kg）组,每组20只。除对照组外,其他组熏香烟加气管注射内毒素法制备COPD模型,COPD造模前1 d开始ig给药,每天1次,持续30 d。ELISA法检测支气管肺泡灌洗液（BALF）中肿瘤坏死因子（TNF）-α和白细胞介素（IL）-6水平;RSE3020肺功能检测仪测定用力肺活量（FVC）、第1秒用力呼气容积（FEV₁）、呼气峰流速（PEF）;取肺组织4%甲醛固定后制作切片,HE染色,并进行肺组织损伤病理评分;Western blotting检测肺组织PI3K、AKT、mTOR蛋白表达。结果 虎杖苷高、低剂量组大鼠BALF中TNF-α和IL-6表达水平、肺组织损伤病理评分以及PI3K、AKT和mTOR蛋白表达均显著低于模型组（P<0.01）;虎杖苷高、低剂量组大鼠FVC、FEV1、PEF肺功能指标显著高于模型组（P<0.01）。结论 虎杖苷可以抑制COPD大鼠PI3K/AKT/mTOR通路,抑制气道炎症,发挥肺损伤保护作用。     

AMPK: A metabolic switch for CD8+ T‐cell memory

Adenosine monophosphate‐activated protein kinase (AMPK) is a serine/threonine kinase and is crucial for cellular energy homeostasis. The exact role of AMPK during memory CD8⁺ T‐cell differentiation, a process that changes from the metabolically active state of effector T cells to one of quiescence in memory cells is not well understood; however, a report by Cantrell and colleagues [Eur. J. Immunol. 2013. 43: 889‐896] in this issue of the European Journal of Immunology shows that AMPK, by sensing glucose stress, is an important upstream molecule of mammalian target of rapamycin (mTOR) complex 1 for memory CD8⁺ T‐cell differentiation. This study provides new insights into how AMPK monitors energy stress to control effector and memory CD8⁺ T‐cell formation as discussed in this Commentary.     

Induced regulatory T cells suppress Tc1 cells through TGF-β signaling to ameliorate STZ-induced type 1 diabetes mellitus

Type 1 diabetes mellitus (T1D) is a chronic autoimmune condition in which the immune system destroys insulin-producing pancreatic β cells. In addition to well-established pathogenic effector T cells, regulatory T cells (Tregs) have also been shown to be defective in T1D. Thus, an increasing number of therapeutic approaches are being developed to target Tregs. However, the role and mechanisms of TGF-β-induced Tregs (iTregs) in T1D remain poorly understood. Here, using a streptozotocin (STZ)-induced preclinical T1D mouse model, we found that iTregs could ameliorate the development of T1D and preserve β cell function. The preventive effect was associated with the inhibition of type 1 cytotoxic T (Tc1) cell function and rebalancing the Treg/Tc1 cell ratio in recipients. Furthermore, we showed that the underlying mechanisms were due to the TGF-β-mediated combinatorial actions of mTOR and TCF1. In addition to the preventive role, the therapeutic effects of iTregs on the established STZ-T1D and nonobese diabetic (NOD) mouse models were tested, which revealed improved β cell function. Our findings therefore provide key new insights into the basic mechanisms involved in the therapeutic role of iTregs in T1D.     

Rebamipide potentially mitigates methotrexate-induced nephrotoxicity via inhibition of oxidative stress and inflammation: A molecular and histochemical study

Methotrexate (MTX) is a widely used chemotherapeutic agent; nevertheless, the nephrotoxicity associated with its use has limited its clinical use. Rebamipide (REB) is a gastro-protective agent with diverse promising biological activities. Here, we investigated the renoprotective effects of REB against MTX-induced nephrotoxicity in rats. Male Wistar rats were allocated into four groups: the normal control group, the REB group (100 mg kg⁻¹ day⁻¹, PO, for 12 days), the MTX group (which received a single injection of 20 mg/kg, ip), and the REB + MTX group (which received 100 mg kg⁻¹ day⁻¹ REB for 7 days before and 5 days after being injected with 20 mg/kg MTX). Interestingly, MTX triggered kidney injury, characterized by renal dysfunction along with histopathological alterations. Moreover, increased reactive oxygen species level and inflammatory response were detected in the kidney of MTX-treated rats. However, REB prevented MTX-induced oxidative kidney injury and boosted an antioxidant balance. Mechanistically, REB markedly activated the NRF-2 protein and upregulated the expression of both SIRT-1 and FOXO-3 genes. Additionally, REB administration strongly inhibited the inflammatory response by downregulating both NF-κB-p65 and TLR-4. Finally, the coadministration of REB and MTX activated the mTOR/PI3K/AKT signaling pathway. Simultaneously, REB treatment attenuated the reduction in glomerular size, the widening of the capsular spaces, and the tubular cell damage due to MTX administration. Taken together, these results indicate the potential of REB as adjuvant therapy to prevent nephrotoxicity in patients receiving MTX treatment.     

Rapamycin ameliorates the CTLA4‐Ig–mediated defect in CD8+ T cell immunity during gammaherpesvirus infection

Latent viral infections are a major concern among immunosuppressed transplant patients. During clinical trials with belatacept, a CTLA4‐Ig fusion protein, patients showed an increased risk of Epstein–Barr virus‐associated posttransplant lymphoproliferative disorder, thought to be due to a deficient primary CD8⁺ T cell response to the virus. Using a murine model of latent viral infection, we observed that rapamycin treatment alone led to a significant increase in virus‐specific CD8⁺ T cells, as well as increased functionality of these cells, including the ability to make multiple cytokines, while CTLA4‐Ig treatment alone significantly dampened the response and inhibited the generation of polyfunctional antigen‐specific CD8⁺ T cells. However, the addition of rapamycin to the CTLA4‐Ig regimen was able to quantitatively and qualitatively restore the antigen‐specific CD8⁺ T cell response to the virus. This improvement was physiologically relevant, in that CTLA4‐Ig treated animals exhibited a greater viral burden following infection that was reduced to levels observed in untreated immunocompetent animals by the addition of rapamycin. These results reveal that modulation of T cell differentiation though inhibition of mTOR signaling can restore virus‐specific immune competence even in the absence of CD28 costimulation, and have implications for improving protective immunity in transplant recipients.