Analysis of phosphoinositide 3-kinase inhibitors by bottom-up electron-transfer dissociation hydrogen/deuterium exchange mass spectrometry.

Until recently, one of the major limitations of hydrogen/deuterium exchange mass spectrometry (HDX-MS) was the peptide-level resolution afforded by proteolytic digestion. This limitation can be selectively overcome through the use of electron-transfer dissociation to fragment peptides in a manner that allows the retention of the deuterium signal to produce hydrogen/deuterium exchange tandem mass spectrometry (HDX-MS/MS). Here, we describe the application of HDX-MS/MS to structurally screen inhibitors of the oncogene phosphoinositide 3-kinase catalytic p110α subunit. HDX-MS/MS analysis is able to discern a conserved mechanism of inhibition common to a range of inhibitors. Owing to the relatively minor amounts of protein required, this technique may be utilised in pharmaceutical development for screening potential therapeutics.

Prevention of antipsychotic-induced hyperglycaemia by vitamin D: a data mining prediction followed by experimental exploration of the molecular mechanism.

Atypical antipsychotics are associated with an increased risk of hyperglycaemia, thus limiting their clinical use. This study focused on finding the molecular mechanism underlying antipsychotic-induced hyperglycaemia. First, we searched for drug combinations in the FDA Adverse Event Reporting System (FAERS) database wherein a coexisting drug reduced the hyperglycaemia risk of atypical antipsychotics, and found that a combination with vitamin D analogues significantly decreased the occurrence of quetiapine-induced adverse events relating diabetes mellitus in FAERS. Experimental validation using mice revealed that quetiapine acutely caused insulin resistance, which was mitigated by dietary supplementation with cholecalciferol. Further database analysis of the relevant signalling pathway and gene expression predicted quetiapine-induced downregulation of Pik3r1, a critical gene acting downstream of insulin receptor. Focusing on the phosphatidylinositol 3-kinase (PI3K) signalling pathway, we found that the reduced expression of Pik3r1 mRNA was reversed by cholecalciferol supplementation in skeletal muscle, and that insulin-stimulated glucose uptake into C2C12 myotube was inhibited in the presence of quetiapine, which was reversed by concomitant calcitriol in a PI3K-dependent manner. Taken together, these results suggest that vitamin D coadministration prevents antipsychotic-induced hyperglycaemia and insulin resistance by upregulation of PI3K function.

ETP-46321, a dual p110α/δ class IA phosphoinositide 3-kinase inhibitor modulates T lymphocyte activation and collagen-induced arthritis.

Class IA phosphoinositide 3-kinases (PI3Ks) are essential to function of normal and tumor cells, and to modulate immune responses. T lymphocytes express high levels of p110α and p110δ class IA PI3K. Whereas the functioning of PI3K p110δ in immune and autoimmune reactions is well established, the role of p110α is less well understood. Here, a novel dual p110α/δ inhibitor (ETP-46321) and highly specific p110α (A66) or p110δ (IC87114) inhibitors have been compared concerning T cell activation in vitro, as well as the effect on responses to protein antigen and collagen-induced arthritis in vivo. In vitro activation of naive CD4(+) T lymphocytes by anti-CD3 and anti-CD28 was inhibited more effectively by the p110δ inhibitor than by the p110α inhibitor as measured by cytokine secretion (IL-2, IL-10, and IFN-γ), T-bet expression and NFAT activation. In activated CD4(+) T cells re-stimulated through CD3 and ICOS, IC87114 inhibited Akt and Erk activation, and the secretion of IL-2, IL-4, IL-17A, and IFN-γ better than A66. The p110α/δ inhibitor ETP-46321, or p110α plus p110δ inhibitors also inhibited IL-21 secretion by differentiated CD4(+) T follicular (Tfh) or IL-17-producing (Th17) helper cells. In vivo, therapeutic administration of ETP-46321 significantly inhibited responses to protein antigen as well as collagen-induced arthritis, as measured by antigen-specific antibody responses, secretion of IL-10, IL-17A or IFN-γ, or clinical symptoms. Hence, p110α as well as p110δ Class IA PI3Ks are important to immune regulation; inhibition of both subunits may be an effective therapeutic approach in inflammatory autoimmune diseases like rheumatoid arthritis.

Leptin rapidly improves glucose homeostasis in obese mice by increasing hypothalamic insulin sensitivity.

Obesity is associated with resistance to the actions of both leptin and insulin via mechanisms that remain incompletely understood. To investigate whether leptin resistance per se contributes to insulin resistance and impaired glucose homeostasis, we investigated the effect of acute leptin administration on glucose homeostasis in normal as well as leptin- or leptin receptor-deficient mice. In hyperglycemic, leptin-deficient Lep(ob/ob) mice, leptin acutely and potently improved glucose metabolism, before any change of body fat mass, via a mechanism involving the p110α and ß isoforms of phosphatidylinositol-3-kinase (PI3K). Unlike insulin, however, the anti-diabetic effect of leptin occurred independently of phospho-AKT, a major downstream target of PI3K, and instead involved enhanced sensitivity of the hypothalamus to insulin action upstream of PI3K, through modulation of IRS1 (insulin receptor substrate 1) phosphorylation. These data suggest that leptin resistance, as occurs in obesity, reduces the hypothalamic response to insulin and thereby impairs peripheral glucose homeostasis, contributing to the development of type 2 diabetes.

[Effect of Shenqi compound on PTEN/PI3K signal transduction in GK rats with diabetes mellitus macroangiopathy].

OBJECTIVE: To research the effects and mechanism of Shenqi compound (SQC) on PTEN/ PI3K signal transducing path and angiogenesis in Goto-Kakizaki (GK) rats with diabetes mellitus type 2 (DM2) caused macroangiopathy. METHOD: GK rats with blood sugar > or = 11.1 mmol/L were divided into 4 groups, the GK group, the model group, the Western medicine (WM) group treated by atorvastatin 1.5 mg/(kg x d) and the Chinese medicine (CM) group treated with SQC 1.44 g/(kg x d). All were fed 35 days with high fatty diet, but to the latter three groups, N omega-nitriyl-L-arginine methyl ester 0.1 mg/mL was added into their drinking water for macroangiopathy model establishing. Besides, a group of normal Wistar rats fed with ordinary forage was set for control. Rat's blood glucose and lipids were measured, morphology of abdominal aorta wall tissue was observed with HE staining, and mRNA expressions of PTEN and PI3Kp85 in aortic wall were detected by Real-time PCR. RESULTS: General condition, gluco-lipid metabolism and aortic morphology in the CM group were significantly better than those in the model group. PTEN mRNA expression in the CM group (1.10 +/- 0.48) was significantly higher than that in the GK group (0.63 +/- 0.16) and the model group (0.17 +/- 0.07, both P < 0.01), but near to that in the WM group (1.11 +/- 0.46), while the PI3Kp85 mRNA expression in the TCM group (0.19 +/- 0.05) was lower than that in the GK group (1.38 +/- 0.43, P < 0.01), but near to that in the model group (0.33 +/- 0.09) and the WM group (0.11 +/- 0.06, both P > 0.05). CONCLUSION: SQC could increase the PTEN mRNA expression and restrain the PI3Kp85 mRNA expression in aorta, which is possibly the partial mechanisms of action of the remedy in inhibiting angiogenesis and preventing diabetic macroangiopathy.

[PI3K p85alpha gene silencing by RNA interference promotes 5-fluorouracil-induced apoptosis of colorectal cancer LoVo cells].

OBJECTIVE: To explore the effect of PI3K p85alpha gene silencing on the 5-fluorouracil (5-FU)-induced apoptosis of colorectal cancer cells. METHODS: The PI3K p85alpha/RNAi transfected cells (PI3K p85alpha/RNAi-LoVo) were cultured in RPMI 1640 supplemented with 10% fetal calf serum and 500 microg/ml G418. The 50% inhibitory concentration (IC50) values of 5-FU (0.000625, 0.00125, 0.005, 0.01, 0.02, 0.04, 0.08, 0.16, 0.32 micromol/ml) were evaluated by MTT assay. Mitochondrial membrane potential was detected by JC-1 fluorescence, and Western blotting was used to analyze the expression of apoptotic proteins Bcl-6 and Bim. RESULTS: Compared with the untransfected LoVo cells, PI3K p85alpha/RNAi-LoVo showed obviously decreased IC(50) of 5-FU (P=0.000). The mitochondrial membrane potential of PI3K p85alpha/RNAi-LoVo cells was significantly lower than that of LoVo cells, suggesting that silencing PI3K p85alpha expression increased the sensitivity of LoVo cells to 5-FU. The expression of apoptotic protein Bcl-6 and Bim were significantly higher in PI3K p85alpha/RNAi-LoVo cells treated with 5-FU than LoVo cells (P=0.000). CONCLUSION: PI3Kp85alpha gene silencing can significantly promote 5-FU-induced apoptosis of colorectal LoVo cells.