Protective effect of protein kinase C inhibitor on rat renal vascular endothelial injury induced by lipopolysaccharide / 中华危重病急救医学

OBJECTIVE@#To investigate the protective effect of protein kinase C (PKC) inhibitor rottlerin on rat renal vascular endothelial injury induced by lipopolysaccharide (LPS).@*METHODS@#Rat renal microvascular endothelial cells cultured for 3-6 generations were divided into three groups according to random number table: blank control group in which cells were not challenged, LPS group in which cells were only stimulated by LPS 10 mg/L for 24 hours, and PKC inhibitor group in which cells were treated with PKC inhibitor rottlerin 2 μmol/L 30 minutes before LPS stimulation. The levels of tumor necrosis factor-α (TNF-α) and interleukins (IL-1β, IL-8) were determined by enzyme-linked immunosorbent assay (ELISA). Monolayer permeability was determined by Transwell assay. The expressions of PKC, RhoA and vascular endothelial-cadherin (VE-cadherin) were detected by Western Blot. The morphological characteristic and distribution of F-actin was measured by laser confocal fluorescence microscope.@*RESULTS@#Compared with blank control group, the levels of inflammatory cytokines at 24 hours after 10 mg/L LPS stimulation were significantly increased in LPS group [TNF-α (ng/L): 397.3±25.4 vs. 46.8±8.9, IL-1β (ng/L): 76.7±11.2 vs. 12.6±3.2, IL-8 (ng/L): 574.5±31.4 vs. 73.2±9.6, all P < 0.05], the permeability of endothelial cells was significantly increased (A value: 1.32±0.03 vs. 0.36±0.02, P < 0.05), while the expressions of PKC and RhoA were significantly up-regulated (PKC/β-actin: 0.88±0.02 vs. 0.61±0.03, RhoA/β-actin: 0.96±0.01 vs. 0.49±0.03, both P < 0.05), VE-cadherin expression was significantly down-regulated (VE-cadherin/β-actin: 0.51±0.01 vs. 0.72±0.04, P < 0.05), and the F-actin distribution disorder had obvious stress fiber formation. Compared with LPS group, the levels of inflammatory cytokines were significantly lowered in PKC inhibitor group [TNF-α (ng/L): 127.4±14.6 vs. 397.3±25.4, IL-1β(ng/L): 43.2±7.8 vs. 76.7±11.2, IL-8 (ng/L): 212.7±18.2 vs. 574.5±31.4, all P < 0.05], the permeability of endothelial cells was significantly decreased (A value: 0.81±0.02 vs. 1.32±0.03, P < 0.05), the expressions of PKC and RhoA were significantly down-regulated (PKC/β-actin: 0.44±0.03 vs. 0.88±0.02, RhoA/β-actin: 0.63±0.05 vs. 0.96±0.01, both P < 0.05), the VE-cadherin expression was significantly up-regulated (VE-cadherin/β-actin: 0.69±0.03 vs. 0.51±0.01, P < 0.05), and the F-actin remodeling and stress fiber formation were significantly reduced.@*CONCLUSIONS@#PKC inhibitor could significantly attenuate the damage of vascular endothelial barrier induced by LPS, and plays an important role in endothelial cell barrier.

Inhibition of PKC-dependent extracellular Ca2+ entry contributes to the depression of contractile activity in long-term pressure-overloaded endothelium-denuded rat aortas

We examined the contractile responsiveness of rat thoracic aortas under pressure overload after long-term suprarenal abdominal aortic coarctation (lt-Srac). Endothelium-dependent angiotensin II (ANG II) type 2 receptor (AT2R)-mediated depression of contractions to ANG II has been reported in short-term (1 week) pressure-overloaded rat aortas. Contractility was evaluated in the aortic rings of rats subjected to lt-Srac or sham surgery (Sham) for 8 weeks. ANG I and II levels and AT2R protein expression in the aortas of lt-Srac and Sham rats were also evaluated. lt-Srac attenuated the contractions of ANG II and phenylephrine in the aortas in an endothelium-independent manner. However, lt-Srac did not influence the transient contractions induced in endothelium-denuded aortic rings by ANG II, phenylephrine, or caffeine in Ca2+-free medium or the subsequent tonic constrictions induced by the addition of Ca2+ in the absence of agonists. Thus, the contractions induced by Ca2+ release from intracellular stores and Ca2+ influx through stored-operated channels were not inhibited in the aortas of lt-Srac rats. Potassium-elicited contractions in endothelium-denuded aortic rings of lt-Srac rats remained unaltered compared with control tissues. Consequently, the contractile depression observed in aortic tissues of lt-Srac rats cannot be explained by direct inhibition of voltage-operated Ca2+ channels. Interestingly, 12-O-tetradecanoylphorbol-13-acetate-induced contractions in endothelium-denuded aortic rings of lt-Srac rats were depressed in the presence but not in the absence of extracellular Ca2+. Neither levels of angiotensins nor of AT2R were modified in the aortas after lt-Srac. The results suggest that, in rat thoracic aortas, lt-Srac selectively inhibited protein kinase C-mediated activation of contraction that is dependent on extracellular Ca2+ entry.

Morphine Postconditioning Attenuates ICAM-1 Expression on Endothelial Cells

The purpose of this study is to determine 1) whether morphine postconditiong (MPostC) can attenuate the intercellular adhesion molecules-1 (ICAM-1) expression after reoxygenation injury and 2) the subtype(s) of the opioid receptors (ORs) that are involved with MPostC. Human umbilical vein endothelial cells (HUVECs) were subjected to 6 hr anoxia followed by 12 hr reoxygenation. Three morphine concentrations (0.3, 3, 30 microM) were used to evaluate the protective effect of MPostC. We also investigated blockading the OR subtypes' effects on MPostC by using three antagonists (a micro-OR antagonist naloxone, a kappa-OR antagonist nor-binaltorphimine, and a delta-OR antagonist naltrindole) and the inhibitor of protein kinase C (PKC) chelerythrine. As results, the ICAM-1 expression was significantly reduced in the MPostC (3, 30 microM) groups compared to the control group at 1, 6, 9, and 12 hours reoxygenation time. As a consequence, neutrophil adhesion was also decreased after MPostC. These effects were abolished by coadministering chelerythrine, nor-binaltorphimine or naltrindole, but not with naloxone. In conclusion, it is assumed that MPostC could attenuate the expression of ICAM-1 on endothelial cells during reoxygenation via the kappa and delta-OR (opioid receptor)-specific pathway, and this also involves a PKC-dependent pathway.

Protein kinase C micron plays an essential role in hypertonicity-induced heat shock protein 70 expression

Heat shock protein 70 (HSP70), which evidences important functions as a molecular chaperone and anti-apoptotic molecule, is substantially induced in cells exposed to a variety of stresses, including hypertonic stress, heavy metals, heat shock, and oxidative stress, and prevents cellular damage under these conditions. However, the molecular mechanism underlying the induction of HSP70 in response to hypertonicity has been characterized to a far lesser extent. In this study, we have investigated the cellular signaling pathway of HSP70 induction under hypertonic conditions. Initially, we applied a variety of kinase inhibitors to NIH3T3 cells that had been exposed to hypertonicity. The induction of HSP70 was suppressed specifically by treatment with protein kinase C (PKC) inhibitors (Go6976 and GF109203X). As hypertonicity dramatically increased the phosphorylation of PKC micron, we then evaluated the role of PKC micron in hypertonicity-induced HSP70 expression and cell viability. The depletion of PKC micron with siRNA or the inhibition of PKC micron activity with inhibitors resulted in a reduction in HSP70 induction and cell viability. Tonicity-responsive enhancer binding protein (TonEBP), a transcription factor for hypertonicity-induced HSP70 expression, was translocated rapidly into the nucleus and was modified gradually in the nucleus under hypertonic conditions. When we administered treatment with PKC inhibitors, the mobility shift of TonEBP was affected in the nucleus. However, PKC micron evidenced no subcellular co-localization with TonEBP during hypertonic exposure. From our results, we have concluded that PKC micron performs a critical function in hypertonicity-induced HSP70 induction, and finally cellular protection, via the indirect regulation of TonEBP modification.

Role of interleukin-3 and signaling pathways on beta-thalassemia/HbE erythroid progenitor cell in culture.

In order to study the role of the cytokine interleukin-3 (IL-3) and its signaling pathways in erythropoiesis of beta-thalassemia/HbE erythroid progenitor cells, CD34 positive cells were isolated from peripheral blood of patients and healthy subjects. After culturing the cells in the presence or absence of IL-3, cell viability was measured by trypan blue staining and apoptotic cells were analyzed by flow cytometry. After 7 days of culture the highest percent erythroid progenitor cell viability was obtained with cells from healthy subjects, while the lowest percentage was found in those from splenectomized beta-thalassemia/HbE. Viability of beta-thalassemia/HbE erythroid progenitor cells in the presence of IL-3 was higher than that of nonsupplemented cells. In addition, specific inhibitors of protein kinase C (Ro-318220), phospholipase C (U-73122) and Janus kinase 2 (AG-490) were used to investigate the involvement of signaling pathways in erythropoiesis. Percent apoptosis of erythroid progenitor cells from splenectomized beta-thalassemia/HbE subjects treated with RO-318220 was higher than those of nonsplenectomized beta-thalassemia/HbE and healthy subjects. Treatment with U-73122 resulted in enhanced percent apoptotic cells from normal and beta-thalassemia/HbE subjects. All these effects were independent of IL-3 treatment.

Activation of macrophages with N-formyl-methionyl-leucyl-phenylalanine: involvement of protein kinase C and tyrosine kinase.

N-formyl-methionyl-leucyl-phenylalanine (fMLP) a potent chemotactic peptide stimulates immune responses by activating macrophages and other cells of the immune system. The present study reports inhibition of fMLP-induced activation of murine peritoneal and P388D-1 macrophage cell line by protein kinase C (PKC) inhibitors, H-7 and chelerythrine chloride. Similarly, tumoricidal activity was also downregulated by protein tyrosine kinase (PTK) inhibitors genestein and lavendustin A. Further, fMLP increased tyrosine phosphorylation of several proteins in murine macrophages, which were inhibited in presence of genestein and lavendustin A. These findings suggest the involvement of PKC and PTK in the activation of murine macrophages with fMLP.

Phospholipase D activity is elevated in hepatitis C virus core protein-transformed NIH3T3 mouse fibroblast cells

Hepatitis C Virus (HCV) is associated with a severe liver disease and increased frequency in the development of hepatocellular carcinoma. Overexpression of HCV core protein is known to transform fibroblast cells. Phospholipase D (PLD) activity is commonly elevated in response to mitogenic signals, and has also been overexpressed and hyperactivated in some human cancer cells. The aim of this study was to understand how PLD was regulated in the HCV core protein-transformed NIH3T3 mouse fibroblast cells. We observed that PLD activity was elevated in the NIH3T3 cells overexpressing HCV core protein over the vector alone-transfected control cells, however, expression levels of PLD protein and protein kinase C (PKC) in the HCV core protein-transformed cells was similar to the control cells. Phorbol 12-myristate 13-acetate (PMA), which is known to activate PKC, stimulated PLD activity significantly more in the core protein-transformed cells, in comparison with that of the control cells. PLD activity assay using PKC isozyme-specific inhibitor and PKC translocation experiment showed that PKC-delta was mainly involved in the PMA- induced PLD activation in the core-transformed cells. Moreover, in cells overexpressing HCV core protein, PMA also stimulated p38 kinase more potently than that of the control cells, and an inhibitor of p38 kinase abolished PMA-induced PLD activation in cells overexpressing HCV core protein. Taken together, these results suggest that PLD might be implicated in core protein-induced transformation.

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

Interleukin-1beta stimulates matrix metalloproteinase-2 expression via a prostaglandin E2-dependent mechanism in human chondrocytes

IL-1beta is known promote cyclooxygenase-2 (COX- 2) and matrix metalloproteinase-2 (MMP-2) expression. This study focuses on the characterization of the signaling cascade associated with IL-1beta-induced matrix metalloproteinase-2 (MMP- 2) regulation in human chondrocytes. The decrease in collagen levels in the conditioned media was prevented by a broad spectrum MMP inhibitor, suggesting that IL-1beta promotes the proteolytic process leading to MMP-2 activation. IL-1beta-related MMP-2 expression was found to be dependent on prostaglandin E2 (PGE2) production. In addition, the induction of COX-2 and MMP-2 was inhibited by the pretreatment of chondrocytes with a SB203580 or Ro 31-8220, indicating the involvement of protein kinase C (PKC) or p38 mitogen-activated protein kinase (MAPK). However, there is no cross-talk between PKC and p38 MAPK in the IL-1beta-induced MMP-2 activation. Taken together, these results demonstrated that IL-1beta induces MMP-2 expression through the PGE2-dependent mechanism in human chondrocytes.

Phosphorylation of glycogen synthase kinase-3beta at serine-9 by phospholipase Cgamma1 through protein kinase C in rat 3Y1 fibroblasts

Phospholipase Cgamma1 (PLCgamma1) plays an important role in controlling cellular proliferation and differentiation. PLCgamma1 is overexpressed in some tumors, and its overexpression induces solid tumors in nude mice. However, the regulatory mechanisms underlying PLCgamma1-induced cell proliferation are not fully understood. Here we show that overexpression of PLCgamma1 highly phosphorylated glycogen synthase kinase-3beta (GSK-3beta) at serine-9 in 3Y1 fibroblasts. Inhibition of protein kinase C (PKC)s with GF109203X abrogated GSK-3beta phosphorylation by PLCgamma1. We also found that steady-state level of cyclin D1 protein, but not cyclin D1 mRNA, was highly elevated in response to serum stimulation in PLCgamma1-transfected cells as compared with vector-transfected cells. Since GSK-3beta is involved in cyclin D1 proteolysis in response to mitogenic stimulation, PLCgamma1-mediated GSK-3beta phosphorylation may function as a regulation of cyclin D1 accumulation in PLCgamma1-overexpressing cells.

Deoxyhypusine synthase is phosphorylated by protein kinase C in vivo as well as in vitro

Deoxyhypusine synthase catalyzes the first step in the posttranslational synthesis of an unusual amino acid, hypusine, in the eukaryotic translation initiation factor 5A (eIF-5A) precursor protein. We earlier observed that yeast recombinant deoxyhypusine synthase was phosphorylated by protein kinase C (PKC) in vitro (Kang and Chung, 1999) and the phosphorylation rate was synergistically increased to a 3.5-fold following treatment with phosphatidylserine (P.Ser)/diacylglycerol (DAG)/ Ca2+, suggesting a possible involvement of PKC. We have extended study on the phosphorylation of deoxyhypusine synthase in vivo in different cell lines in order to define its role on the regulation of eIF5A in the cell. Deoxyhypusine synthase was found to be phosphorylated by endogenous kinases in CHO, NIH3T3, and chicken embryonic cells. The highest degree of phosphorylation was found in CHO cells. Moreover, phosphorylation of deoxyhypusine synthase in intact CHO cells was revealed and the expression of phosphorylated deoxyhypusine synthase was significantly diminished by diacyl ethylene glycol (DAEG), a PKC inhibitor, and enhanced by phorbol 12-myristate 13-acetate (PMA) or Ca2+/DAG. Endogenous PKC in CHO cell and cell lysate was able to phosphorylate deoxyhypusine synthase and this modification is enhanced by PMA or Ca2+ plus DAG. Close association of PKC with deoxyhypusine synthase in the CHO cells was evident in the immune coprecipitation and was PMA-, and Ca2+/phospholipiddependent. These results suggest that phosphorylation of deoxyhypusine synthase was PKC-dependent cellular event and open a path for possible regulation in the interaction with eIF5A precursor for hypusine synthesis.

ATP-induced focal adhesion kinase activity is negatively modulated by phospholipase D2 in PC12 cells

Extracellular ATP has been known to modulate various cellular responses including mitogenesis, secretion and morphogenic activity in neuronal cells. In the ATP-induced morphogenic activity, focal adhesion kinase(s) such as Fak have been suggested to play a critical role. Binding of ATP to its specific cell surface receptor in PC12 cells induces phospholipase D (PLD) activity. However, the role of PLD on ATP-induced Fak activation in PC12 cells remains unclear. In this study, we investigated the role of PLD on the ATP-induced Fak activation and paxillin phosphorylation using two established cell lines: wild type PLD2- and lipase-inactive mutant PLD2-inducible PC12 cells. Stimulation of cells with ATP caused PLD2 activation via classical protein kinase C activation. ATP also induced Fak activation, and paxillin phosphorylation, and were dramatically reduced by wild type PLD2 overexpression but not by lipase-inactive mutant PLD2 overexpression. When the PC12 cells were pretreated with propranolol, a specific inhibitor for phosphatidic acid phosphohydrolase resulting in the accumulation of PA, ATP-induced Fak activation and paxillin phosphorylation were also reduced. We found that inhibition of tyrosine phosphatases by pervanadate completely blocked PLD2-dependent Fak and paxillin dephosphorylation. Taken together, we suggest that PLD2 activity might play a negative role in ATP-induced Fak and paxillin phosphorylation possibly through tyrosine phosphatases.

Protein kinase C modulates telomerase activity in human cervical cancer cells

Telomerase, a ribonucleoprotein reverse transcriptase that extends telomeres of eukaryotic chromosomes is repressed in normal somatic cells but is activated during development and neoplasia. The regulation mechanism of telomerase activity in cancer cells is not clearly known. In this report, a possible affect of PKC on telomerase activity was examined using HeLa and CUMC-6 cervical cancer cell lines. Exposure of cells to PKC inhibitor, bisindolylmaleimide I and Go6976, and high levels of PKC activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA) resulted in the inhibition of PKC activity in both cells. Telomerase activities were also inhibited by bisindolyl-maleimide I and Go6976, respectively, in a time-dependent manner. As PKC activity changes in TPA-treated cervical cancer cells, telomerase activities were increased at low dose of TPA and decreased at high dose. The expression levels of human telomerase subunits, human telomerase RNA (hTR) were not influenced by PKC modulating drugs. In contrast, the expression of full-length human telomerase reverse transcriptase (hTERT) was decreased after exposure to bisindolylmaleimide I and Go6976 in a time-dependent manner. hTERT expression was not affected by low dose of TPA. In contrast, high dose of TPA inhibited hTERT expression level. But the expression patterns of beta-deletion transcript of hTERT after 72 h of treatment with PKC inhibitors or high dose of TPA exposure were not discernable as compared with those of full-length hTERT transcripts to PKC modulating drugs. These results suggest that PKC-modulating drugs altered telomerase activities by affecting full-length hTERT expression profile in human cervical cancers.

Hypericum perforatum: nature's mood stabilizer.

Hypericum perforatum (HP), better known as St. John's Wort, has been used clinically for centuries. Modern usage is still quite diverse and includes kidney and lung ailments, insomnia and depression. Standardised extracts of HP are widely used in the treatment of psychovegetative disorders and especially for mild forms of depression. Several bioactive constituents of this plant may play important role in its well-known antidepressant activity, which are discussed in the present article. Furthermore, emphasis is also given on its botany, chemistry, pharmacology and clinical efficacy.

Changes of phospholipase D activity in TNF-alpha and anti-Fas/Apo1 monoclonal antibody induced apoptosis in HL-60 and A20 cells

The changes of phospholipase D (PLD) activity were investigated during the courses of apoptotic process induced by tumor necrosis factor (TNF)-alpha or anti-Fas/Apo1 antibody in human premyelocyte HL-60 and murine B cell lymphoma A20 cells. The treatment of recombinant TNF-alpha to HL-60 cells resulted in the increased PLD activity as determined by the phosphatidylethanol formation in the presence of 1% ethanol. The enhancement of PLD activity was also observed in the anti-Fas/Apo1 monoclonal antibody-treated A20 cells. However, the activity of PLD was maximized when HL-60 and A20 cells were treated with either TNF-alpha or anti-Fas/Apo1 monoclonal antibody for 6 h. Both TNF-alpha and anti-Fas/Apo1 monoclonal antibody increased PLD activity in a dose-dependent manner up to 200 U/ml and 200 ng/ml, respectively. When the intracellular activity of protein kinase C (PKC) was interrupted by treatment of calphostin-C, both the PLD activation and the apoptosis induced by TNF-alpha and anti-Fas/Apo1 monoclonal antibody appeared to be inhibited. Since PKC is reported to activate PLD, the results indicate that the intracellular signaling cascade via PLD may play a role in the induction of apoptosis induced by TNF-alpha and anti-Fas/Apo1 monoclonal antibody.

Cell-mediated immunosuppression in mice by street rabies virus not restored by calcium ionophore or PMA.

It is known that rabies virus can suppress the host immune system. In this study we demonstrate a depression of cell-mediated immunity in mice, peripherally infected with Thai street rabies virus. The cell-mediated cytolysis of spleen cells from mice increased transiently on day 5 after infection and declined rapidly thereafter until death. The proliferation of spleen cells stimulated with a T-cell mitogen such as phytohemagglutinin or concanavalin A, was significantly suppressed during the course of infection. There was also a marked suppression of IL-2 secretion in parallel with a decrease of the T-cell proliferative response to mitogen. The suppression of T-cell proliferation was not restored by treatment with a calcium ionophore (A 23187) or phorbol 12-myristate-13 acetate (PMA).

Effect of adenylate cyclase inhibitor and protein kinase C inhibitor on GnRH-induced LH release and LH beta subunit biosynthesis in rat anterior pituitary cells

According to our previous studies together with others, GnRH, a hypothalamic decapeptide, has been known to be a major regulator for LH release and its subunit biosynthesis in anterior pituitary gonadotropes. But the precise mechanisms by which GnRH exerts stimulatory effects on LH release and its subunit biosynthesis have not been clearly understood. In the present study we examined the effect of GnRH on protein kinase C (PKC) activity and intracellular cAMP content in cultured anterior pituitary cells of rat to clarify whether PKC or cAMP are involved in GnRH action. Moreover, we examined the effects of staurosporine (ST), a PKC inhibitor and 2',3'-dideoxyadenosine (2',3'-DDA), an adenylate cyclase inhibitor, on LH release and steady state LH beta subunit mRNA levels in cultured anterior pituitary cells of rat. PKC activity was rapidly increased within 30 min after GnRH treatment whereas intracellular cAMP level was elevated 18 h after GnRH treatment. ST significantly inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner, showing an half maximal response at 50 nM ST. 2',3'-DDA inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner in pituitary cells. From these results, it is suggested that GnRH stimulates LH beta subunit mRNA level as well as LH release in anterior pituitary cells and this GnRH action might be mediated by PKC activation and cAMP stimulation.