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Articles by X Cai
Total Records ( 4 ) for X Cai
  L Ji , F Fu , L Zhang , W Liu , X Cai , Q Zheng , H Zhang and F. Gao

It is well known that insulin possesses a cardioprotective effect and that insulin resistance is closely related to cardiovascular diseases. Peroxynitrite (ONOO) formation may trigger oxidative/nitrative stress and represent a major cytotoxic effect in heart diseases. This study was designed to investigate whether insulin attenuates ONOO generation and oxidative/nitrative stress in acute myocardial ischemia/reperfusion (MI/R). Adult male rats were subjected to 30 min of myocardial ischemia and 3 h of reperfusion. Rats randomly received vehicle, insulin, or insulin plus wortmannin. Arterial blood pressure and left ventricular pressure were monitored throughout the experiment. Insulin significantly improved cardiac functions and reduced myocardial infarction, apoptotic cell death, and blood creatine kinase/lactate dehydrogenase levels following MI/R. Myocardial ONOO formation was significantly attenuated after insulin treatment. Moreover, insulin resulted in a significant increase in Akt and endothelial nitric oxide (NO) synthase (eNOS) phosphorylation, NO production, and antioxidant capacity in ischemic/reperfused myocardial tissue. On the other hand, insulin markedly reduced MI/R-induced inducible NOS (iNOS) and gp91phox expression in cardiac tissue. Inhibition of insulin signaling with wortmannin not only blocked the cardioprotection of insulin but also markedly attenuated insulin-induced antioxidative/antinitrative effect. Furthermore, the suppression on ONOO formation by either insulin or an ONOO scavenger uric acid reduced myocardial infarct size in rats subjected to MI/R. We concluded that insulin exerts a cardioprotective effect against MI/R injury by blocking ONOO formation. Increased physiological NO production (via eNOS phosphorylation) and superoxide anion reduction contribute to the antioxidative/antinitrative effect of insulin, which can be reversed by inhibiting phosphatidylinositol 3'-kinase. These results provide important novel information on the mechanisms of cardiovascular actions of insulin.

  R Bao , C. J Lai , H Qu , D Wang , L Yin , B Zifcak , R Atoyan , J Wang , M Samson , J Forrester , S DellaRocca , G. X Xu , X Tao , H. X Zhai , X Cai and C. Qian

Purpose: We designed and synthesized CUDC-305, an HSP90 inhibitor of the novel imidazopyridine class. Here, we report its unique pharmacologic properties and antitumor activities in a variety of tumor types.

Experimental Design: The potency of the compound was analyzed by fluorescence polarization competition binding assay. Its antiproliferative activities were assessed in 40 human cancer cell lines. Its pharmacologic properties and antitumor activities were evaluated in a variety of tumor xenograft models.

Results: CUDC-305 shows high affinity for HSP90/β (IC50, ~100 nmol/L) and HSP90 complex derived from cancer cells (IC50, 48.8 nmol/L). It displays potent antiproliferative activity against a broad range of cancer cell lines (mean IC50, 220 nmol/L). CUDC-305 exhibits high oral bioavailability (96.0%) and selective retention in tumor (half-life, 20.4 hours) compared with normal tissues. Furthermore, CUDC-305 can cross blood-brain barrier and reach therapeutic levels in brain tissue. CUDC-305 exhibits dose-dependent antitumor activity in an s.c. xenograft model of U87MG glioblastoma and significantly prolongs animal survival in U87MG orthotopic model. CUDC-305 also displays potent antitumor activity in animal models of erlotinib-resistant non–small cell lung cancer and induces tumor regression in animal models of MDA-MB-468 breast cancer and MV4-11 acute myelogenous leukemia. Correlating with its efficacy in these various tumor models, CUDC-305 robustly inhibits multiple signaling pathways, including PI3K/AKT and RAF/MEK/ERK, and induces apoptosis. In combination studies, CUDC-305 enhances the antitumor activity of standard-of-care agents in breast and colorectal tumor models.

Conclusion: CUDC-305 is a promising drug candidate for the treatment of a variety of cancers, including brain malignancies.

  Z Ni , Z Bikadi , X Cai , M. F Rosenberg and Q. Mao

The human breast cancer resistance protein (BCRP/ABCG2) mediates efflux of drugs and xenobiotics. In this study, we investigated the role of polar residues within or near the predicted transmembrane -helices 1 and 6 of BCRP in drug transport. We substituted Asn387, Gln398, Asn629, and Thr642 with Ala, Thr402 with Ala and Arg, and Tyr645 with Phe, and the mutants were stably expressed in human embryonic kidney-293 or Flp-In-293 cells. Immunoblotting and confocal microscopy analysis revealed that all of the mutants were well expressed and predominantly targeted to the plasma membrane. While T402A and T402R showed a significant global reduction in the efflux of mitoxantrone, Hoechst 33342, and BODIPY-prazosin, N629A exhibited significantly increased efflux activities for all of the substrates. N387A and Q398A displayed significantly impaired efflux for mitoxantrone and Hoechst 33342, but not for BODIPY-prazosin. In contrast, T642A and Y645F showed a moderate reduction in Hoechst 33342 efflux only. Drug resistance profiles of human embryonic kidney-293 cells expressing the mutants generally correlated with the efflux data. Furthermore, N629A was associated with a marked increase, and N387A and T402A with a significant reduction, in BCRP ATPase activity. Mutations of some of the polar residues may cause conformational changes, as manifested by the altered binding of the 5D3 antibody to BCRP in the presence of prazosin. The inward-facing homology model of BCRP indicated that Thr402 within transmembrane 1 may be important for helical interactions, and Asn629 may be involved in BCRP-substrate interaction. In conclusion, we have demonstrated the functional importance of some of these polar residues in BCRP activity.

  E Brailoiu , D Churamani , X Cai , M. G Schrlau , G. C Brailoiu , X Gao , R Hooper , M. J Boulware , N. J Dun , J. S Marchant and S. Patel

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a widespread and potent calcium-mobilizing messenger that is highly unusual in activating calcium channels located on acidic stores. However, the molecular identity of the target protein is unclear. In this study, we show that the previously uncharacterized human two-pore channels (TPC1 and TPC2) are endolysosomal proteins, that NAADP-mediated calcium signals are enhanced by overexpression of TPC1 and attenuated after knockdown of TPC1, and that mutation of a single highly conserved residue within a putative pore region abrogated calcium release by NAADP. Thus, TPC1 is critical for NAADP action and is likely the long sought after target channel for NAADP.

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