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

AIM: 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. METHODS: 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. RESULTS: 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. CONCLUSION: PKCalpha positively regulates MDR in SGC7901 cells, and inhibition of PKCalpha can partially attenuate MDR in human gastric cancer cells.

Dynamic changes in myocardial matrix metalloproteinase activity in mice with viral myocarditis.

BACKGROUND: Matrix metalloproteinases (MMPs) are the major regulators of collagen degradation involved in the pathogenesis of several diseases of the heart. The purpose of this study was to investigate the dynamic changes in myocardial MMP activity in mice with viral myocarditis (VM), the relationship between MMP activity and both cardiac function and the quantity of myocardial collagen, and the role MMPs playing in the pathological lesions of VM. METHODS: Sixty-five six-week-old male DBA/2 mice were divided into two groups. Mice in the infected group (n = 50) were inoculated intraperitoneally with 0.14 ml of Coxsackievirus B3 (CVB3, Nancy strain). Control mice (n = 15) were inoculated intraperitoneally with 0.14 ml of Eagle's medium. Eight infected mice and three control mice were sacrificed on each of days 3, 7, 10, 21 and 30 after inoculation. MMP activity was measured on an SDS-PAGE substrate gel embedded with type I gelatin (zymography). Echocardiographic studies were performed under anesthesia with 3% chloralhydrate administered intraperitoneally (0.01 ml/g - 0.015 ml/g). Cardiac systolic function indices, such as peak velocity of the aorta (Vp), flow velocity integral of the aorta (Vi), ejection fraction (EF), and fractional shortening (FS) were determined by echocardiography. Histological cross sections of the hearts were stained with hematoxylin-eosin and myocardial histopathological scores were determined under an optical microscope. The amount of myocardial collagen was measured by means of hydroxyproline quantification. RESULTS: In virus-infected mice, both MMP-2 and MMP-9 activities were significantly higher than in control mice, reaching a peak on day 10 (P < 0.01). On day 10, cardiac systolic function indices (EF, FS, Vp, and Vi) were all significantly lower compared both to other stages following viral inoculation and to the control group (P < 0.05). In the acute stage, the amount of myocardial collagen in mice with VM was not significantly different from normal control mice (P > 0.05). However, the amount of myocardial collagen in infected mice at the recovery stage (on days 21 and 30) was significantly greater than those of the control mice. MMP-2 and MMP-9 activities positively correlated with myocardial histopathological scores (r = 0.801, 0.821, P < 0.01) and negatively correlated with Vp (r = -0.649, -0.683, P < 0.01) and Vi (r = -0.711, -0.755, P < 0.01). However, Vp negatively correlated with myocardial histopathological scores (r = -0.756, P < 0.01). CONCLUSIONS: In mice with VM, the activities of myocardial MMP-2 and MMP-9 increase significantly during the acute stage, and the total quantity of myocardial collagen increases by the time of recovery. These changes are associated with myocardial interstition remodeling and cardiac dysfunction. MMP activity is an important reference marker for myocardial pathological lesions and can be used to evaluate the severity of myocardial interstitial damage and cardiac dysfunction.