Dimethyl Cardamonin Exhibits Anti-inflammatory Effects via Interfering with the PI3K-PDK1-PKCalpha Signaling Pathway

Consumption of herbal tea [flower buds of Cleistocalyx operculatus (Roxb.) Merr. et Perry (Myrtaceae)] is associated with health beneficial effects against multiple diseases including diabetes, asthma, and inflammatory bowel disease. Emerging evidences have reported that High mobility group box 1 (HMGB1) is considered as a key "late" proinflammatory factor by its unique secretion pattern in aforementioned diseases. Dimethyl cardamonin (2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone, DMC) is a major ingredient of C. operculatus flower buds. In this study, the anti-inflammatory effects of DMC and its underlying molecular mechanisms were investigated on lipopolysaccharide (LPS)-induced macrophages. DMC notably suppressed the mRNA expressions of TNF-alpha, IL-1beta, IL-6, and HMGB1, and also markedly decreased their productions in a time- and dose-dependent manner. Intriguingly, DMC could notably reduce LPS-stimulated HMGB1 secretion and its nucleo-cytoplasmic translocation. Furthermore, DMC dose-dependently inhibited the activation of phosphatidylinositol 3-kinase (PI3K), phosphoinositide-dependent kinase 1 (PDK1), and protein kinase C alpha (PKCalpha). All these data demonstrated that DMC had anti-inflammatory effects through reducing both early (TNF-alpha, IL-1beta, and IL-6) and late (HMGB1) cytokines expressions via interfering with the PI3K-PDK1-PKCalpha signaling pathway.

Der f 2 activates phospholipase D in human T lymphocytes from Dermatophagoides farinae specific allergic individuals: Involvement of protein kinase C-alpha

The major house-dust mite allergen, Der f 2, stimulates the phospholipase D (PLD) in T lymphocytes from Dermatophagoides farinae specific allergic individuals. PLD activity increased more than two-fold in T cells from allergic patients compared with those cells from normal controls with maximal responses within 30 min after exposure of Der f 2. A well-known PLD activator PKC-alpha was found to be translocated to membrane from cytosol in Der f 2-treated T cells from Dermatophagoides farinae specific allergic individuals. Down-regulation of PKC-alpha with phorbol myristate acetate pretreatment for 24 h abolished Der f 2-induced PLD activation. Ro 320432, PKC inhibitor also reduced the effects of Der f 2-induced PLD activation suggesting that PKC-alpha acts as upstream activator of PLD in Der f 2-treated T cells. Taken together, the present data suggest that Der f 2 can stimulate PLD activity through the PKC-alpha activation in T cells from Dermatophagoides farinae allergic individuals

Effects of Sense and Antisense Expression of Protein Kinase Calpha on the Proliferation and Radiosensitization of U-87 Human Glioblastoma Cells

OBJECTIVE: It has been suggested that protein kinase C(PKC) may be one of a number of important regulatory enzymes influencing the tumor cell proliferation and intracellular sensitivity to irradiation. In this study, authors investigate the role of PKC in the growth and radiosensitization of glial brain tumors. METHODS: Human glioblastoma cell line U-87 was stably transfected with sense and antisense complementary deoxyribonucleic acid(cDNA) encoding PKCalpha. The effect of sense and antisense PKCalpha cDNA transfection on PKCalpha expression, PKC activity, cell proliferation, and radiosensitivity of tumor cells was determined. RESULTS: There was no significant difference in cell proliferation between control cells and cDNA(sense and antisense) transfected cells on thiazolyl blue(microculture tetrazolium, MTT) assay. PKC activity was increased by 68% in cells transfected with the sense PKCalpha cDNA(U-87/sPKCalpha), and was reduced by 32% in cells transfected with the antisense PKCalpha cDNA(U-87/aPKCalpha) compared to control cells(p<0.05). Western blotting with a polyclonal antibody against PKCalpha and scanning densitometric analysis of autoradiograms revealed that PKCalpha expression was enhanced by about 5 times of that of control cells in U-87/sPKCalpha cells and was suppressed by more than 30% of that of control cells in U-87/aPKCalpha cells. After exposure to 6 Gy irradiation, cell viability on MTT assay was increased by 43.7% in U-87/sPKCalpha cells and was reduced by 24.3% in U-87/aPKCalpha cells compared to control cells(p<0.001). CONCLUSION: The results of this study demonstrate that PKCalpha overexpression confers a relative radior-esistance and PKCalpha suppression enhances a radiosensitivity on U-87 cells. These observations suggest that PKCalpha plays an important role in regulating cell response to irradiation and a specific modulation of PKCalpha expression in malignant gliomas may influence the radiosensitivity of them.