Effects of rottlerin on in vitro proliferation of and expressions of interleukin-17C, CCL20 and nuclear factor-κB in a human keratinocyte cell line HaCaT / 中华皮肤科杂志

Objective To investigate the effects of rottlerin on in vitro proliferation of and expressions of interleukin (IL)-17C,CCL20 chemokine,and nuclear factor (NF)-κB in cultured human HaCaT keratinocytes.Methods Some HaCaT cells were divided into several test groups treated with rottlerin at concentrations of 0.5,1.0,2.0 and 4.0 μmol/L,a solvent group treated with RPMI 1640 culture solution containing the same volume of dimethyl sulfoxide (DMSO) as that of 4.0 μmol/L rottlerin,and a control group treated with RPMI 1640 culture solution.Cell counting kit-8 (CCK8) assay was conducted to estimate the proliferative activity of HaCaT cells after 24-,48-and 72-hour culture,RT-PCR to determine the mRNA expressions of IL-17C and CCL20 after 48-hour culture,and Western blot to measure the protein expressions of IL-17C,CCL20 and NF-κB after 48-hour culture.Statistical analysis was carried out by using repeated-measures analysis of variance,one-way analysis of variance and Pearson correlation analysis with the SPSS16.0 software.Results Rottlerin showed an inhibitory effect on the proliferation of HaCaT cells,and the inhibitory effect increased over time (F =126.936,P ＜ 0.05) and with the increase of rottlerin concentrations (F =838.308,P ＜ 0.05),with a significant interaction effect between rottlerin concentrations and treatment duration (F =15.961,P ＜ 0.05).After 48-hour treatment,a significant decrease was observed in the mRNA and protein expressions of IL-17C (F =206.041,233.887,respectively,both P ＜ 0.05) and CCL20 (F =143.883,162.431,respectively,both P ＜ 0.05),as well as in the protein expression of NF-κB (F =577.915,P ＜ 0.05) in the test groups with the increase in rottlerin concentrations.Conclusions Rottlerin can inhibit the proliferation of HaCaT cells in vitro,and decrease the mRNA and protein expressions of IL-17C and CCL20 likely by downregulating the protein expression of NF-κB.

Rottlerin enhances IL-1beta-induced COX-2 expression through sustained p38 MAPK activation in MDA-MB-231 human breast cancer cells

Cyclooxygenase-2 (COX-2) is an important enzyme in inflammation. In this study, we investigated the underlying molecular mechanism of the synergistic effect of rottlerin on interleukin1beta (IL-1beta)-induced COX-2 expression in MDA-MB-231 human breast cancer cell line. Treatment with rottlerin enhanced IL-1beta-induced COX-2 expression at both the protein and mRNA levels. Combined treatment with rottlerin and IL-1beta significantly induced COX-2 expression, at least in part, through the enhancement of COX-2 mRNA stability. In addition, rottlerin and IL-1beta treatment drove sustained activation of p38 Mitogen-activated protein kinase (MAPK), which is involved in induced COX-2 expression. Also, a pharmacological inhibitor of p38 MAPK (SB 203580) and transient transfection with inactive p38 MAPK inhibited rottlerin and IL-1beta-induced COX-2 upregulation. However, suppression of protein kinase C delta (PKC delta) expression by siRNA or overexpression of dominant-negative PKC delta (DN-PKC-delta) did not abrogate the rottlerin plus IL-1beta-induced COX-2 expression. Furthermore, rottlerin also enhanced tumor necrosis factor-alpha (TNF-alpha), phorbol myristate acetate (PMA), and lipopolysaccharide (LPS)-induced COX-2 expression. Taken together, our results suggest that rottlerin causes IL-1beta-induced COX-2 upregulation through sustained p38 MAPK activation in MDA-MB-231 human breast cancer cells.

PKC-delta inhibitors sustain self-renewal of mouse embryonic stem cells under hypoxia in vitro

Under hypoxia, mouse embryonic stem cells (mESCs) lose their self-renewal activity and display an early differentiated morphology mediated by the hypoxia-inducible factor-1alpha (HIF-1alpha). Previous studies have demonstrated that PKC-delta is activated by hypoxia and increases the protein stability and transcriptional activity of HIF-1alpha in human cancer cells. Furthermore, activation of PKC-delta mediates cardiac differentiation of ESCs and hematopoietic stem cells. However, the role of PKC-delta in hypoxia-induced early differentiation of mESCs remains largely unknown. Here, we show the inhibition of PKC-delta activity prevents the early differentiation of mESCs under hypoxia using PKC-delta inhibitors, GF 109203X and rottlerin. Reduction of PKC-delta activity under hypoxia effectively decreased HIF-1alpha protein levels and substantially recovered the expression of LIF-specific receptor (LIFR) and phosphorylated-STAT3 in mESCs. Furthermore, PKC-delta inhibitors aid to sustain the expression of self-renewal markers and suppress the expression of early differentiation markers in mESCs under hypoxia. Taken together, these results suggest that PKC-delta inhibitors block the early differentiation of mESCs via destabilization of HIF-1alpha under hypoxia.

Prevention of TNF-induced necrotic cell death by rottlerin through a Nox1 NADPH oxidase

Previous studies have demonstrated that rottlerin, a specific PKCdelta inhibitor, potentiates death receptor- mediated apoptosis through a cytochrome c-dependent or -independent pathway. However, its ability to regulate necrotic cell death, as well as the underlying mechanism, remains unknown. We found that in murine fibrosarcoma L929 cells, treatment with rottlerin protected the cells against TNF-induced necrosis, whereas it sensitized the cells to apoptosis induced by co-treatment with Hsp90 inhibitor geldanamycin and TNF, in a manner independent of its ability to inhibit PKC-delta. TNF treatment induced rapid accumulation of mitochondrial superoxide (O2") through the Nox1 NADPH oxidase when cells undergo necrosis. Moreover, pretreatment with rottlerin failed to induce the GTP-bound form of small GTPase Rac1 by TNF treatment, and subsequently suppressed mitochondrial O2(-) production and poly(ADP-ribose) polymerase activation, thus inhibiting necrotic cell death. Therefore, our study suggests that Nox1 NADPH oxidase is a new molecular target for anti-necrotic activity of rottlerin upon death-receptor ligation.