PKCalpha Protein Research Articles

Bone-edge electroacupuncture relieves pain by regulating expression of GRK5, β-arrestin 2 and PKCα proteins in locus coeruleus in bone cancer pain rats with morphine tolerance

To observe the effect of bone-edge electroacupuncture (EA) intervention on mechanical pain threshold (PT) and expression of G protein-coupled receptor kinase (GRK5), β-arrestin 2, total and phosphorylated PKC alpha (p-PKCα) proteins in the locus coeruleus (LC) of rats with bone cancer pain induced morphine tolerance, so as to reveal its partial central mechanisms underlying pain relief. Forty SD rats were randomly divided into 5 groups, namely sham bone cancer, bone cancer pain, morphine tolerance, bone-edge EA, and sham EA (n＝ 8 rats in each group). The bone cancer with morphine tolerance model was established by intramedullary injection of MRMT-1 cells into the tibial cavity, and then intraperitoneal injection of morphine hydrochloride injection. After successful establishment of morphine tolerance model, the bone-edge EA (2 Hz/100 Hz，0.5－1.5 mA) was applied to bilateral "Zusanli" (ST36) and "Kunlun" (BL60) for 30 min, once a day for 7 days, after inserting the needle-tip to the tibial bone surface. The ipsilateral mechanical paw withdrawal thresholds (PWTs) were detected dynamically. The expression levels of GRK5, β-arrestin 2, PKCα and p-PKCα in the LC area were measured by Western blot. The PWTs of bone cancer pain rats were decreased on day 10 after inoculation of cancer cells (P<0.01). After i．p. of morphine for 11 days, no analgesic effect and pain tolerance appeared (P>0.05). The PWTs were significantly increased in the bone-edge EA intervention group (P<0.01), not in the sham EA group (P>0.05). In comparison with the sham bone cancer group, the expression of GRK5 protein in morphine tolerance group was significantly decreased (P<0.01); compared with morphine tolerance group, the expression of GRK5 protein in bone-edge EA group was increased(P<0.01). In comparison with the sham bone cancer group, the expression of β-arrestin 2 and p-PKCα in bone cancer group significantly increased (P<0.01). After the intervention, the increased β-arrestin 2 and p-PKCα expressions were reversed in the bone-edge EA group (P<0.01); compared with morphine tolerance group and sham EA group, the expression of PKCα protein was decreased(P<0.01). Bone-edge EA can effectively relieve morphine tolerance in bone cancer pain rats, which may be related to its functions in up-regulating GRK5 protein and down-regulating β-arrestin 2, PKCα and p-PKCα proteins in LC. .

Markers of MEK inhibitor resistance in low-grade serous ovarian cancer: EGFR is a potential therapeutic target

BackgroundAlthough low-grade serous ovarian cancer (LGSC) is rare, case-fatality rates are high as most patients present with advanced disease and current cytotoxic therapies are not overly effective. Recognizing that these cancers may be driven by MAPK pathway activation, MEK inhibitors (MEKi) are being tested in clinical trials. LGSC respond to MEKi only in a subgroup of patients, so predictive biomarkers and better therapies will be needed.MethodsWe evaluated a number of patient-derived LGSC cell lines, previously classified according to their MEKi sensitivity. Two cell lines were genomically compared against their matching tumors samples. MEKi-sensitive and MEKi-resistant lines were compared using whole exome sequencing and reverse phase protein array. Two treatment combinations targeting MEKi resistance markers were also evaluated using cell proliferation, cell viability, cell signaling, and drug synergism assays.ResultsLow-grade serous ovarian cancer cell lines recapitulated the genomic aberrations from their matching tumor samples. We identified three potential predictive biomarkers that distinguish MEKi sensitive and resistant lines: KRAS mutation status, and EGFR and PKC-alpha protein expression. The biomarkers were validated in three newly developed LGSC cell lines. Sub-lethal combination of MEK and EGFR inhibition showed drug synergy and caused complete cell death in two of four MEKi-resistant cell lines tested.ConclusionsKRAS mutations and the protein expression of EGFR and PKC-alpha should be evaluated as predictive biomarkers in patients with LGSC treated with MEKi. Combination therapy using a MEKi with EGFR inhibition may represent a promising new therapy for patients with MEKi-resistant LGSC.

P5-06-08: Mesenchymal Stem Cells and Carcinoma-Associated Fibroblasts Sensitize Breast Cancer Cells in 3D Cultures to Kinase Inhibitors.

Abstract Background: Bone-derived mesenchymal stem cells (MSCs) are attracted to cancer lesions and may differentiate to CAFs. By interacting with cancer cells, MSCs and CAFs may promote cancer progression and modulate drug sensitivity. Material and Methods: To analyze ability of MSCs and CAFs to modulate drug response, we generated spheroids of MCF-7 or MDA-MB-231 breast cancer cells in the absence or presence of human (h) MSCs or hCAFs and tested the susceptibility of the breast cancer cells to three different kinase inhibitors (TKI258, RAD001 and RAF265) as used in cancer therapy. Results: While MSCs and CAFs did not affect the response of either breast cancer cell line to PDGFR/FGFR/VEGFR inhibitor TKI258, they sensitized breast cancer cells to the mTOR inhibitor RAD001. In MCF-7 cells, this was accompanied by increased apoptosis. hMSCs and to a lesser extent hCAFs also enhanced the cytotoxic effect of RAF inhibitor RAF265 on MDA-MB-231 cells. Searching for the mechanism that underlies the effect of stromal cells on RAF265 response we found that stromal cells inhibited RAF265-induced increase in ERK1/2 phosphorylation, supported RAF265-dependent downregulation of PKCalpha (protein kinase Calpha) and prevented RAF265-induced conversion of LC3B, a marker of autophagy. To mimic the changes in ERK1/2 phosphorylation and PKCalpha expression in response to the stromal cells, we treated cells with MEK1 inhibitor U0126 or PKCalpha inhibitor Gö6976, respectively. U0126, but not Gö6976, was as effective as hMSCs in sensitizing MDA-MB-231 cells to RAF265. Discussion: Our data suggest that hMSCs and hCAFs increased the cytotoxic effect of RAF265 on MDA-MB-231 cells by downregulating ERK1/2 phosphorylation. In summary, this study shows that hMSCs are able to render breast cancer cells more susceptible to kinase inhibitors and that, to the most part, hCAFs to which hMSCs can differentiate are able to mimic the drug-sensitizing effects of hMSCs. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-06-08.

12‐O‐tetradecanoylphorbol‐13‐acetate‐induced invasion/migration of glioblastoma cells through activating PKCα/ERK/NF‐κB‐dependent MMP‐9 expression

An increase in MMP-9 gene expression and enzyme activity with stimulating the migration of GBM8401 glioma cells via wound healing assay by 12-O-tetradecanoylphorbol-13-acetate (TPA) was detected in glioblastoma cells GBM8401. TPA-induced translocation of protein kinase C (PKC)alpha from the cytosol to membranes, and migration of GBM8401 elicited by TPA was suppressed by adding the PKCalpha inhibitors, GF109203X and H7. Activation of extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) by TPA was identified, and TPA-induced migration and MMP-9 activity was significantly blocked by ERK inhibitor PD98059 and U0126, but not JNK inhibitor SP600125. Activation of NF-kappaB protein p65 nuclear translocation and IkappaBalpha protein phosphorylation with increased NF-kappaB-directed luciferase activity by TPA were observed, and these were blocked by the PD98059 and IkB inhibitor BAY117082 accompanied by reducing migration and MMP-9 activity induced by TPA in GBM8401 cells. Transfection of GBM8401 cells with PKCalpha siRNA specifically reduced PKCalpha protein expression with blocking TPA-induced MMP-9 activation and migration. Additionally, suppression of TPA-induced PKCalpha/ERK/NK-kappaB activation, migration, and MMP-9 activation by flavonoids including kaempferol (Kae; 3,5,7,4'-tetrahydroxyflavone), luteolin (Lut; 5,7,3'4'-tetrahydroxyflavone), and wogonin (Wog; 5,7-dihydroxy-8-methoxyflavone) was demonstrated, and structure-activity relationship (SAR) studies showed that hydroxyl (OH) groups at C4' and C8 are critical for flavonoids' action against MMP-9 enzyme activation and migration/invasion of glioblastoma cells elicited by TPA. Application of flavonoids to prevent the migration/invasion of glioblastoma cells through blocking PKCalpha/ERK/NF-kappaB activation is first demonstrated herein.

Podocytic PKC-Alpha Is Regulated in Murine and Human Diabetes and Mediates Nephrin Endocytosis

BackgroundMicroalbuminuria is an early lesion during the development of diabetic nephropathy. The loss of high molecular weight proteins in the urine is usually associated with decreased expression of slit diaphragm proteins. Nephrin, is the major component of the glomerular slit diaphragm and loss of nephrin has been well described in rodent models of experimental diabetes as well as in human diabetic nephropathy.Methodology/Principal FindingsIn this manuscript we analyzed the role of PKC-alpha (PKCα) on endocytosis of nephrin in podocytes. We found that treatment of diabetic mice with a PKCα-inhibitor (GÖ6976) leads to preserved nephrin expression and reduced proteinuria. In vitro, we found that high glucose stimulation would induce PKCα protein expression in murine and human podocytes. We can demonstrate that PKCα mediates nephrin endocytosis in podocytes and that overexpression of PKCα leads to an augmented endocytosis response. After PKC-activation, we demonstrate an inducible association of PKCα, PICK1 and nephrin in podocytes. Moreover, we can demonstrate a strong induction of PKCα in podocytes of patients with diabetic nephropathy.Conclusions/SignificanceWe therefore conclude that activation of PKCα is a pathomechanistic key event during the development of diabetic nephropathy. PKCα is involved in reduction of nephrin surface expression and therefore PKCα inhibition might be a novel target molecule for anti-proteinuric therapy.

Changes of protein kinase Cα and cyclin D1 expressions in pulmonary arteries from smokers with and without chronic obstructive pulmonary disease

The purpose of this study was to investigate the changes of protein kinase Calpha (PKCalpha) and cyclin D1 expressions in pulmonary arteries from smokers with normal lung function and smokers with mild to moderate chronic obstructive pulmonary disease (COPD). The peripheral lung tissues were obtained from 10 non-smokers with normal lung function (non-smoker group), 14 smokers with normal lung function (smoker group), 11 smokers with mild to moderate COPD (COPD group). The morphological changes of pulmonary arteries were observed by HE-staining. The expressions of alpha-smooth muscle actin (alpha-SMA), proliferating cell nuclear antigen (PCNA), PKCalpha and cyclin D1 proteins in pulmonary artery smooth muscle cells (PASMCs) were immunohistochemically determined. The percentages of PCNA-positive cells were taken as the smooth muscle cells proliferation index (PI). The mRNA expressions of PKCalpha and cyclin D1 in PASMCs were evaluated by real-time fluorescence PCR. Morphometrical analysis showed that the ratio of pulmonary artery wall area to total area (WA%) in smoker group and COPD group was significantly greater than that in non-smoker group (P<0.01). The PASMCs proliferation index in smoker group and COPD group was significantly higher than that in nonsmoker group (P<0.01). The protein levels of PKCalpha and cyclin D1 in PASMCs were significantly increased in smoker group and COPD group as compared with non-smoker group (P<0.01). The mRNA expressions of PKCalpha and cyclin D1 in PASMCs were significantly elevated in smoker group and COPD group as compared with non-smoker group (P<0.01). Significant correlations were found between PKCalpha protein and WA% or PI (P<0.01). Correlations between cyclin D1 protein and WA% or PI also existed (P<0.01). The expression of PKCalpha was positively correlated with the expression of cyclin D1 at both protein and mRNA levels (P<0.01). In conclusion, increased expressions of PKCalpha and cyclin D1 might be involved in the pathogenesis of abnormal proliferation of PASMCs in smokers with normal lung function and smokers with mild to moderate COPD.

Protein kinase C mRNA and protein expressions in hypobaric hypoxia‐induced cardiac hypertrophy in rats

Protein kinase C (PKC), cloned as a serine/threonine kinase, plays key roles in diverse intracellular signalling processes and in cardiovascular remodelling during pressure overload or volume overload. We looked for correlations between changes in PKC isoforms (levels and/or subcellular distributions) and cardiac remodelling during experimental hypobaric hypoxic environment (HHE)-induced pulmonary hypertension. To study the PKC system in the heart during HHE, 148 male Wistar rats were housed for up to 21 days in a chamber at the equivalent of 5500 m altitude level (10% O(2)). At 14 or more days of exposure to HHE, pulmonary arterial pressure (PAP) was significantly increased. In the right ventricle (RV): (1) the expression of PKC-alpha protein in the cytosolic and membrane fractions was increased at 3-14 days and at 5-7 days of exposure respectively; (ii) the cytosolic expression of PKC-delta protein was increased at 1-5, 14 and 21 days of exposure; (3) the membrane expressions of the proteins were decreased at 14-21 (PKC-betaII), 14-21 (PKC-gamma), and 0.5-5 and 21 (PKC-epsilon) days of exposure; (4) the expression of the active form of PKC-alpha protein on the plasma membrane was increased at 3 days of exposure (based on semiquantitative analysis of the immunohistochemistry). In the left ventricle, the expressions of the PKC mRNAs, and of their cytosolic and membrane proteins, were almost unchanged. The above changes in PKC-alpha, which were strongly evident in the RV, occurred alongside the increase in PAP. PKC-alpha may help to modulate the right ventricular hypertrophy caused by pulmonary hypertension in HHE.

Protein kinase C alpha-dependent signaling mediates endometrial cancer cell growth and tumorigenesis.

Endometrial cancer is the most common invasive gynecologic malignancy, yet molecular mechanisms and signaling pathways underlying its etiology and pathophysiology remain poorly characterized. We sought to define a functional role for the protein kinase C (PKC) isoform, PKCalpha, in an established cell model of endometrial adenocarcinoma. Ishikawa cells depleted of PKCalpha protein grew slower, formed fewer colonies in anchorage-independent growth assays and exhibited impaired xenograft tumor formation in nude mice. Consistent with impaired growth, PKCalpha knockdown increased levels of the cyclin-dependent kinase (CDK) inhibitors p21(Cip1/WAF1) (p21) and p27(Kip1) (p27). Despite the absence of functional phosphatase and tensin homolog (PTEN) protein in Ishikawa cells, PKCalpha knockdown reduced Akt phosphorylation at serine 473 and concomitantly inhibited phosphorylation of the Akt target, glycogen synthase kinase-3beta (GSK-3beta). PKCalpha knockdown also resulted in decreased basal ERK phosphorylation and attenuated ERK activation following EGF stimulation. p21 and p27 expression was not increased by treatment of Ishikawa cells with ERK and Akt inhibitors, suggesting that PKCalpha regulates CDK expression independently of Akt and ERK. Immunohistochemical analysis of Grade 1 endometrioid adenocarcinoma revealed aberrant PKCalpha expression, with foci of elevated PKCalpha staining, not observed in normal endometrium. These studies demonstrate a critical role for PKCalpha signaling in endometrial tumorigenesis by regulating expression of CDK inhibitors p21 and p27 and activation of Akt and ERK-dependent proliferative pathways. Thus, targeting PKCalpha may provide novel therapeutic options in endometrial tumors.

Akt Demoted in Glioblastoma

In glioblastomas, an Akt-independent, PTEN (phosphatase and tensin homolog deleted on chromosome ten)-regulated signaling pathway links EGFR (epidermal growth factor receptor) to the phosphorylation of TOR (target of rapamycin) and of the ribosomal protein S6 and to the control of cell replication. Although PKCalpha (protein kinase Calpha) has been identified as an essential component, the detailed wiring of this previously unexplored noncanonical pathway remains to be worked out.

Protein kinase C alpha (PKCα) regulates growth and invasion of endometrial cancer cells

The etiology of endometrial cancers remains poorly understood, particularly with respect to signal transduction pathways underlying the development and progression of the more aggressive, type II steroid-independent tumors. Protein kinase C alpha (PKCalpha) regulates cellular processes critical to malignancy and has been implicated in the pathogenesis of endometrial cancers. The objective of these studies was to determine the functional role of PKCalpha in endometrial cancer cell proliferation, anchorage-independent growth, and invasion. PKCalpha expression in endometrial cancer cell lines was examined by Western blotting. PKCalpha levels were increased in type II HEC-50, HEC-1-A and HEC-1-B cell lines relative to the type I Ishikawa and RL-95-2 lines. Retroviral constructs were used to either overexpress PKCalpha or selectively knockdown levels by shRNA in Ishikawa and HEC 50 cells, respectively. Knockdown of PKCalpha expression in HEC-50 cells resulted in a diminished growth rate and attenuation of anchorage-independent growth. Correspondingly, Ishikawa cells overexpressing PKCalpha protein exhibited increased proliferation, resistance to growth factor deprivation and enhanced anchorage-independent growth. Consistent with the observed changes in cell proliferation, PKCalpha also modulated cyclin D1 promoter activity in both cell lines. A reduction in PKCalpha levels rendered HEC-50 cells significantly less invasive, whereas PKCalpha overexpression enhanced invasion of Ishikawa cells. These data indicate that PKCalpha promotes growth and invasion of endometrial cancer cells, suggesting that PKCalpha dependent signaling pathways could provide novel prognostic indicators or therapeutic targets, particularly in clinically aggressive type II endometrial tumors.

Antisense expression of PKCalpha improved sensitivity of SGC7901/VCR cells to doxorubicin

To explore whether antisense blocking of protein kinase C alpha (PKCalpha) would reverse multi-drug resistance (MDR) in the vincristine (VCR)-resistant human gastric cancer cell line SGC7901/VCR. SGC7901/VCR cells expressing antisense PKCalpha, SGC7901/VCR/aPKC, were established by transfection with a recombinant plasmid reversely inserted with PKCalpha cDNA. Empty vector (PCI-neo)-transfected cell clones, SGC7901/VCR/neo, served as the control. Western blot method was used to detect PKCalpha content in SGC7901, SGC7901/VCR, SGC7901/VCR/neo and SGC7901/VCR/aPKC cells, using PKCalpha-specific antibody. The sensitivity of SGC7901, SGC7901/VCR, SGC7901/VCR/neo and SGC7901/VCR/aPKC cells to doxorubicin (DOX) in vitro was determined by MTT assay. The uptake of DOX in these cells was detected with fluorescence spectrophotometer. Western blot analysis showed that the PKCalpha protein level was about 8.7-fold higher in SGC7901/VCR cells than that in SGC7901 cells, whereas the protein expression of PKCalpha was reduced by 78% in SGC7901/VCR/aPKC cells when compared with the SGC7901/VCR cells. SGC7901/VCR/aPKC cells had a 4.2-fold increase in DOX cytotoxicity, accompanied by a 1.7-fold increase of DOX accumulation in comparison with SGC7901/VCR cells. PKCalpha positively regulates MDR in SGC7901 cells, and inhibition of PKCalpha can partially attenuate MDR in human gastric cancer cells.

PKC alpha protein but not kinase activity is critical for glioma cell proliferation and survival

Protein kinase C alpha (PKCalpha) has been implicated in tumor development with high levels of PKCalpha expression being associated with various malignancies including glioblastomas and tumors of the breast and prostate. To account for its upregulation in these cancers, studies have suggested that PKCalpha plays a role in promoting cell survival. Here we show by siRNA depletion in U87MG glioma cells that a critical threshold level of PKCalpha protein expression is essential for their growth in the presence of serum and for their survival following serum deprivation. Derivation of PKCalpha wt and KO mouse embryo fibroblast cell lines confirms a role for PKCalpha in protecting cells from apoptosis induced by serum deprivation. Notably, PKCalpha was found to mediate chemo-protection in these fibroblastic cell lines. In U87MG cells PKCalpha does not confer chemoprotection though this likely reflects growth arrest associated with its depletion. To determine the requirements for catalytic function, comparison was made between distinct classes of PKC inhibitors. In contrast to loss of PKCalpha protein, inhibition of PKC kinase activity in glioma cell lines does not significantly inhibit growth or survival. Conversely, inhibition with calphostin C, which targets the regulatory domain of PKC, potently inhibits proliferation and induces apoptosis. Evidence is presented that it is the fully phosphorylated, folded form of PKCalpha that confers this activity-independent behaviour. These results indicate an essential pro-proliferative and pro-survival role for PKCalpha in glioma but question the use of ATP competitive inhibitors as therapeutics, either alone, or in combination with chemotoxic agents.

Preclinical studies of molecular-targeting diagnostic and therapeutic strategies against breast cancer

We have investigated protein kinase C (PKC) signaling, a putative differentiation-related and metastasis suppressor gene Cap43/NDRG1/Drg-1, and Y-box binding protein-1 (YB-1) to identify new molecular targeting for breast cancer. PKC is a family of serine/threonine kinases that is involved in the regulation of cell growth. We have demonstrated that PKC caused G(1) arrest in a breast cancer cell line through a mechanism involving a PKC-ERK MAPK-JNK-Rb protein signaling pathway. We have also characterized a novel mechanism through which all-trans retinoic acid (ATRA) and antineoplaston, anticancer drug, caused cell growth inhibition in breast cancer cells through effects on intracellular pathways. ATRA decreased the expression of PKCalpha, as well as reduced ERK MAPK phosphorylation, and consequently caused G(1) arrest. Antineoplaston caused the down-regulation of PKCalpha protein expression, resulting in inhibition of ERK MAPK phosphorylation, with resultant inhibition of Rb phosphorylation leading to G(1) arrest. PKC signaling represents a promising target for development of novel therapeutic agents. Cap43 is known as N-myc downstream-regulated gene 1 (NDRG1). Treatment with estradiol (E(2)) significantly decreased the expression of Cap43 in ER-alpha-positive breast cancer cell lines. Co-administration of tamoxifen abrogated the E(2)-induced downregulation of Cap43 in ER-alpha-positive cell lines. These results suggested that Cap43 may hold the potential of being a molecular marker to determine the therapeutic efficacy of anti-estrogenic anticancer agents in breast cancer. YB-1 is a member of the cold shock domain protein family. The expression of nuclear YB-1 was correlated with HER2 positively in clinical specimens of human breast cancer. Immunostaining studies showed that nuclear YB-1 expression was an independent prognostic factor of overall survival. Expression of nuclear YB-1 played an essential role in acquirement of malignant characteristics through HER2-dependent pathways in breast cancer patients. PKC, Cap43 and YB-1 may be useful in new molecular-targeting diagnosis and therapeutics in breast cancer.

Effect of cigarette smoke extract on proliferation of rat pulmonary artery smooth muscle cells and the relevant roles of protein kinase C

Increased proliferation of pulmonary vascular cells and muscularisation of pulmonary vessels are frequently observed in human smokers and in animals exposed to cigarette smoke. To elucidate the molecular mechanisms leading to these changes, we studied the in vitro effect of cigarette smoke extract (CSE) on proliferation of pulmonary artery smooth muscle cells (PASMCs) and activation of protein kinase C (PKC), an important kinase implicated in cell proliferation. PASMCs cultured from 12 normal Wistar rats were studied in the following conditions: (1) PASMCs were exposed to different concentrations of CSE for 24 hours, then MTT colorimetric assay was used for detection of cell proliferation. Cell viability was assessed by trypan blue exclusion. (2) PASMCs were pre-incubated with phorbol 12-myristate 13-acetate (PMA) for 24 hours or Ro31-8220 for 30 minutes before exposure to 5% CSE for 24 hours. Cell proliferation was examined by MTT colorimetric assay, cell cycle analysis and proliferating cell nuclear antigen (PCNA) immunocytochemical staining. (3) PASMCs were exposed to 5% CSE for 24 hours. Then PKC-alpha mRNA expression was detected by reverse transcription-polymerase chain reaction (RT-PCR) and protein expression by Western blotting, while PKC-alpha translocation was observed by immunofluorescence staining and confocal microscopy. (4) PASMCs were transfected with specific antisense oligodeoxynucleotides against PKC-alpha 6 hours before exposure to 5% CSE for 24 hours. PKC-alpha protein expression and cell proliferation were detected by methods described previously. (1) Low concentration of CSE (5%) increased proliferation of PASMCs, whereas high concentrations (20%, 30%) were inhibitory as a result of cytotoxicity. (2) The value of absorbance (Value A), proliferation index (PI), S-phase cell fraction (SPF) and average optical density of PCNA staining in PASMCs from 5% CSE exposure group (0.306 +/- 0.033, 0.339 +/- 0.033, 0.175 +/- 0.021, 0.315 +/- 0.038, respectively) were significantly increased compared with those of control group (0.249 +/- 0.018, 0.177 +/- 0.055, 0.092 +/- 0.023, 0.187 +/- 0.022, respectively) (P < 0.05). PKC down-regulation by PMA pretreatment or PKC inhibition by Ro31-8220 pre-incubation abolished the effect of 5% CSE on PASMCs proliferation. (3) After exposure to 5% CSE for 24 hours, PKC-alpha mRNA and protein expression in PASMCs (1.054 +/- 0.078, 1.185 +/- 0.041, respectively) were much higher than in untreated cells (0.573 +/- 0.054, 0.671 +/- 0.055, respectively) (P < 0.01). Moreover, 5% CSE induced a translocation of PKC-alpha from cytoplasm toward the perinuclear area and into the nucleus. (4) Specific antisense oligodeoxynucleotides against PKC-alpha reduced 5% CSE-induced expression of PKC-alpha protein (0.713 +/- 0.047 vs 1.180 +/- 0.056), also abolished the effect of 5% CSE on PASMCs proliferation significantly. CSE can be cytotoxic at high concentrations. But at low concentrations, it makes a mitogenic effect on cultured PASMCs. PKC, especially its alpha isozyme, seems to play an important role in CSE-induced proliferation of PASMC.

Phytosterol Pygeum africanum regulates prostate cancer in vitro and in vivo

Prostate cancer is an important public health problem. It is an excellent candidate disease for chemoprevention because prostate cancer is typically slow growing and is usually diagnosed in elderly males. Pygeum africanum (Prunus africana or Rosaceae) is an African prune (plum) tree found in tropical Africa. An extract from the bark of Pygeum africanum has been used in Europe as a prevention and treatment of prostate disorders including benign prostatic hypertrophy (BPH). More recently in the USA, the phytotherapeutic preparations of Pygeum africanum and Saw palmetto have been marketed for prostate health including prostate cancer prevention and treatment. The anti-cancer potential of Pygeum africanum has been tested both in vitro (PC-3 and LNCaP cells) and in vivo (TRAMP mouse model). In tissue culture, ethanolic extracts (30%) of Pygeum africanum inhibited the growth of PC-3 and LNCaP cells; induced apoptosis and altered cell kinetics; down regulated ERalpha and PKC-alpha protein, and demonstrated good binding ability to both mouse uterine estrogen receptors and LNCaP human androgen receptors. TRAMP mice fed Pygeum africanum showed a significant reduction (P = 0.034) in prostate cancer incidence (35%) compared to casein fed mice (62.5%). Pygeum africanum, which is widely used in Europe and USA for treatment of BPH, has a significant role in regulation of prostate cancer both in vitro and in vivo and therefore may be a useful supplement for people at high risk for developing prostate cancer.

High‐fat diet‐induced hepatic steatosis reduces glucagon receptor content in rat hepatocytes: potential interaction with acute exercise

Studies have revealed that high-fat (HF) diets promote hyperglycaemia, whole-body insulin resistance and non-alcoholic fatty liver disease (NAFLD). Recently, hepatic glucagon resistance has been shown to occur in rats fed a HF diet. More precisely, diet-induced obesity (DIO) reduces the number of hepatic plasma membrane glucagon receptors (GR), which results in a diminished response to glucagon during a hyperglucagonaemic clamp. The present study was undertaken to test the hypothesis that a HF-DIO is associated with a desensitization and destruction of the hepatic GR. We also hypothesized that a single bout of endurance exercise would modify the GR cellular distribution under our DIO model. Male rats were either fed a standard (SD) or a HF diet for two weeks. Each group was subdivided into a non-exercised (Rest) and an acute exercised (EX) group. The HF diet resulted in a reduction of total hepatic GR (55%) and hepatic plasma membrane GR protein content (20%). These changes were accompanied by a significant increase in endosomal and lysosomal GR content with the feeding of a HF diet. The reduction of GR plasma membrane as well as the increase in endosomal GR was strongly correlated with an increase of PKC-alpha, suggesting a role of PKC-alpha in GR desensitization. EX increased significantly PKC-alpha protein content in both diets, suggesting a role of PKC-alpha in EX-induced GR desensitization. The present results suggest that liver lipid infiltration plays a role in reducing glucagon action in the liver through a reduction in total cellular and plasma membrane GR content. Furthermore, the GR desensitization observed in our in vivo model of HF diet-induced hepatic steatosis and in EX individuals may be regulated by PKC-alpha.

Study on sensitivity to chemotherapy by combination therapy with tumor necrosis factor-alpha and bromocriptine in the multidrug resistant subcell line of HepG2

To investigate the change of chemosensitivity of hepatocarcinoma cell line (HepG(2)/ADM) after treated by bromocriptine (BCT) combination with human tumor necrosis factor-alpha (TNF-alpha). Firstly, TNF-alpha gene was transfected into HepG(2)/ADM cell line by liposome to establish a cell model expressing the TNF-alpha protein stably. All experiments were divided into four groups and named blank control group (group A), drug resistant group HepG(2)/ADM (group B), TNF-alpha gene group HepG(2)/ADM/TNF (group C) and BCT group (group D) respectively. And group D came from group C treated with BCT simultaneously. MTT assay was tested to detect the sensitivity to ADM of each group and Rhodamine 123 (Rh123) was applied to test the function of P-gp by flow cytometric analysis (FCM). MDR associated genes and proteins and PKC-alpha protein were detected by immunohistochemistry (IHC), Western blot and reverse transcriptase polymerase chain reaction (RT-PCR) methods, respectively. The expression and the apoptosis rate of Bcl-2 in the hepatocarcinoma cells were detected by FCM. There was significant difference between group C and D in the rate of reversing resistance and the intracellular Rho123 accumulation (P < 0.01). MDR1 mRNA and P-gp protein expression in group C and D were low similar to that in group A, but no difference could be found among them (P > 0.05). As we found that PKC-alpha protein expression was downregulated in group D but Bcl-2 protein expression was downregulated in group C, and there was significant difference compared to other groups. The apoptosis rate of hepatocarcinoma cells was much higher in group D than that in group C (P < 0.01) with FCM, but similar to group A (P > 0.05). Synergistic effect of BCT and TNF-alpha on reversing hepatocellular carcinoma multidrug resistance could enhance the susceptibility of HepG(2)/ADM cells to cytotoxic drugs.

Protein kinase C (PKC) regulates contractility of myometrium from pregnant women

PREGNANT WOMEN VICTOR FOMIN, ANDRIS KRONBERGS, MATTHEW HOFFMAN, University of Delaware, Biological Sciences, Newark, Delaware, Christiana Hospital, Newark, Delaware OBJECTIVE: Prematurity is one of the most significant problems of human pregnancy. According to the March of Dimes, the rate of premature birth increased between 1981 and 2003 by 30% (from 9.4 to 12.3%). A detailed knowledge of the mechanisms of uterine contraction can help to improve clinical control of abnormal uterine function and reverse this trend. Important regulator of smooth muscle contraction is protein kinase C (PKC). However, the role of PKC in uterine (myometrial) contraction remains unclear. This study was designed to investigate an effect of PKC on contraction and intracellular Ca concentration ([Ca]i) in myometrium from term pregnant women. STUDY DESIGN: The myometrial samples were obtained at the time of cesarean section surgery according to the protocol approved by Christiana Hospital and University of Delaware IRB Committees. The isometric contraction (tension) and [Ca]i were measured simultaneously in fura-2 loaded myometrial strips. RESULTS: The PKC activation with phorbol 12,13-dibutyrate (PDBu) increased tonic contraction time and dosedependently reaching maximum after 2hrs at 10 -6M with no effect on [Ca]i. PDBu first potentiated KCl(50mM) contractile responses followed by their inhibition after 1 hr incubation with no effect on the amplitude of the [Ca]i response. PKCalpha inhibitor Go6976 decreased the PDBu effect on the tonic contraction. The depletion of PKCalpha protein with the specific antisense oligonucleotide decreased the KCl-induced contractile and [Ca]i responses. CONCLUSION: It is suggested that PKC regulates uterine contraction through different signaling pathways. First, PKC (possibly PKCalpha) stimulates KCl-induced contractile responses followed by their inhibition due to yet to be determined mechanisms. PKC also induces myometrial tonic contraction without changes in [Ca]i. (Supported by NIH R55 HD45802).

How brain-dead state affects the hepatic morphology and function of Ba-Ma mini pigs and its mechanism

To investigate the impact of brain death (BD) on the morphology and function of liver. Fifteen Ba-ma minipigs were randomly divided into 3 equal groups: brain death group (Group B) made into BD models by increasing the intracranial pressure; breviscapine pretreatment group (Group P), with breviscapine 2.5 mg x kg(-1) given intravenous drip 1-2 hours after the successful establishment of BD model; and control group (Group C) undergoing operation similar to that in Group B but without increasing the intracranial pressure. 3, 6, 12, 18, and 24 hours after the initial confirmation of BD blood samples were collected from the superior vena cava to detect the serum alanine transaminase (ALT), aspartate transaminase (AST), tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6, and a piece of liver tissues were collected to undergo light microscopy and electron microscopy, and immunohistochemistry to examine the expression of protein kinase (PKC)-alpha by RT-PCR. The levels of serum ALT and AST of Group B began to increase since 12 h after BD, and were both significantly higher than those of Group C 18 and 24 hours after BD (both P < 0.05). The levels of serum ALT and AST of Group P began to increase since 12 h after BD, and were both significantly lower than those of Group B (both P < 0.05). The levels of serum TNF-alpha, IL-1beta, and IL-6 of Group B and Group P began to increase gradually since 3 h after BD, however, those of Group B were all significantly higher than those of group P (all P < 0.05). PKC-alpha was only expressed in the plasma of a few normal liver cells. The PKC-alpha mRNA and protein levels of Groups B and P began to increase since 6 h after BD, however, those of Group B were all significantly higher than those of Group P (all P < 0.05). Light and electron microscopy showed that only mild edema of liver cells was seen in Group P, and since 12 h after BD swelling of mitochondria, edema of liver cells, etc. were seen in Group B, and the morphologic damages were more severe in Group B. Brain death evokes hepatic functional and morphological injuries. PKC-alpha may involve in the mechanism. Breviscapine inhibits the activation of PKC-alpha, thus reducing the damage in liver.

Overexpression of PKC is required to impart estradiol inhibition and tamoxifen-resistance in a T47D human breast cancer tumor model

We previously reported that stable overexpression of protein kinase C alpha (PKCalpha) in hormone responsive T47D:A18 breast cancer cells produces a hormone-independent/tamoxifen (TAM)-resistant and 17beta-estradiol (E2)-inhibitory phenotype in vivo. Furthermore, overexpression of PKCalpha in T47D:A18 cells also results in cross-upregulation of PKCs beta and delta. In this study, we further characterized the contribution of PKC isozymes alpha, beta and delta to this complex phenotype. To determine whether downregulation of PKCalpha is sufficient to restore the hormone-dependent phenotype in T47D:A18/PKCalpha cells, PKCalpha was selectively knocked down using short hairpin RNA (shRNA). To determine the contribution of PKCbeta or delta to the hormone-independent/TAM-resistant and E2-inhibitory phenotype, stable T47D:A18/PKCbeta and T47D:A18/PKCdelta clones were established. Downregulation of PKCalpha by shRNA in T47D:A18/PKCalpha20 cells also resulted in reduced PKCbeta protein expression in vitro. Tumors established from a T47D:A18/PKCalpha/shRNA stable clone exhibit 50% reduction of PKCalpha protein without concomitant reduction in PKCbeta, and exhibit partial reversal of the TAM-resistant and E2-inhibitory phenotype in vivo. Furthermore, stable overexpression of neither PKCbeta nor PKCdelta in T47D:A18 cells are sufficient to produce hormone-independent growth in vitro or in vivo, nor TAM-resistant and E2-inhibited growth in vivo. Taken together, these results suggest that PKCalpha is required to impart the TAM-resistant and E2-inhibitory phenotype in vivo.