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Biomedical subjects

A K Ghosh

Publications and source records attributed to A K Ghosh.

At least 73 records · Page 4Linked to original sources
PubMed2000

Hepatitis C virus NS5A protein protects against TNF-alpha mediated apoptotic cell death.

Hepatitis C virus (HCV) often causes a prolonged and persistent infection which may lead to hepatocellular carcinoma. We have previously reported that the nonstructural 5A (NS5A) protein of HCV promotes cell growth [Ghosh, A.K., Steele, R., Meyer, K., Ray, R., Ray, R.B., 1999. Hepatitis C virus NS5A protein modulates cell cycle regulatory genes and promotes cell growth. J. Gen. Virol. 80, 1179-1183]. In this study, we investigated the role of HCV NS5A (genotype 1a, strain H) in TNF-alpha induced apoptotic cell death. HepG2 cells expressing NS5A exhibited an inhibitory role in relation to TNF-alpha mediated apoptotic cell death. The NS5A protein blocked the activation of caspase-3 and inhibited proteolytic cleavage of the death substrate poly (ADP-ribose) polymerase in TNF-alpha induced cells. Together, these results suggest that HCV NS5A protein protects against TNF-alpha mediated apoptotic cell death.

Blotting, Western↗
PubMed2000

Protection of apoptotic cell death by protein A.

The word "Apoptosis" or pragrammed cell death is described as the ultimate end of multiple cellular events converging from numerous initiating events to the ultimate death of a cell or organism. Several processes, such as initiation of death signals at the plasma membrane, expression of pro-apoptotic oncoproteins, activation of death proteases, endonucleases etc., that ultimately coalesce to a common irreversible execution phase, lead to cell demise. Counteracting the death signals are cell survival factors. A balance between the cell death and cell survival factors plays a major role in the decision making process as to whether a cell should die or must live. It is, therefore, hypothesized that if the balance can be shifted in favor of cell survival, one might be able to arrest the aging process, save the injured cells or else if the balance is shifted toward cell-kill it might help destroy tumors and other undesirable cells. Protein A (PA) of Staphylococcus aureus has been found to have multifarious biological response modifying properties. It has been shown to possess anti-tumor, antitoxic, anti-parasitic and antifungal activities. It also acts as a potent immunostimulator. PA can protect bone marrow progenitor cells from zidovudin(AZT)-induced apoptosis and can stimulate immunocyte proliferation, thereby helping to replenish/restore the depleted hematopoietic cell pool. Such ability to replenish hematopoietic cells is a common property of PA observed against a number of toxic drugs/chemicals, such as cyclophosphamide, benzene, aflatoxin, salmonella endotoxin, etc. Interestingly, it was further demonstrated in our laboratory that PA can selectively kill tumor cells without affecting normal cells of the host. A search for the mechanisms of PA action revealed that this bacterial protein could shift the balance between pro- and anti-apoptotic proteins in favor of survival in normal cells, but in favor of cell death in tumor cells at a particular dose level. This unique property of PA suggests that controlled use of such type of Biological Response Modifier might help in controlling both cell growth and death phenomena.

Animals↗
PubMed2000

Cyclooxygenase-2-mediated angiogenesis in carrageenin-induced granulation tissue in rats.

The possible participation of cyclooxygenase (COX)-2 in angiogenesis in granulation tissue was analyzed using an air pouch-type carrageenin-induced inflammation model in rats. Injection of carrageenin solution into an air pouch induced gradual increases in the pouch fluid volume and granulation tissue weight as well as angiogenesis in granulation tissue. NS-398 (10-100 microg) inhibited all of these parameters in a dose-dependent manner. NS-398 (100 microg), indomethacin (100 microg), and dexamethasone (10 microg) markedly reduced prostaglandin (PG) E(2) levels in the pouch fluid at day 6. NS-398 and indomethacin did not affect protein levels of COX-1 and COX-2 but dexamethasone significantly reduced the level of COX-2 in granulation tissue at day 6. Protein levels of vascular endothelial growth factor (VEGF) in granulation tissue and in the pouch fluid were higher at day 6 than at day 3, and the levels were decreased by treatment with NS-398 (10-100 microg) in a dose-dependent manner. The inhibitory effects of NS-398 (100 microg) were almost the same as those of indomethacin (100 microg). Dexamethasone (10 microg) also reduced VEGF protein levels in granulation tissue at day 6. To clarify the role of PGE(2) in VEGF production, minced granulation tissue obtained 3 days after carrageenin injection from the indomethacin-treated rats was incubated in the presence of various concentrations of PGE(2). It was shown that VEGF mRNA and protein levels in the minced granulation tissue were increased by PGE(2) in a concentration-dependent manner. These findings suggest that COX-2-derived PGE(2) plays a significant role in angiogenesis in the carrageenin-induced granulation tissue through VEGF formation.

Animals↗
PubMed2000

Correlation and modulation of Ehrlich ascites tumor growth with tumor-plasma IgA.

Plasma IgA level of Ehrlich ascites tumor bearing mice showed correlation with progress of tumor growth. In PAGE analysis total plasma IgA separated into 3 major bands corresponding to mol. wt. > or = 669,000 daltons, identical to 443,000 daltons and between 443,000 and 150,000 daltons. All the three bands increased gradually with progress of tumor growth upto day 14 and then declined on day 16. Total plasma IgA isolated by anti-IgA affinity chromatography when adoptively transferred to mice inhibited tumor growth. Affinity-purified plasma IgA separated into three major peak fractions after Sephadex G-200 column chromatography which corresponded with the bands of IgA on PAGE analysis. Three Sephadex G-200 IgA fractions when adoptively transferred to tumor-bearing mice showed effect different from total IgA. High mol. wt. IgA fraction (> or = 669,000 daltons) inhibited tumor growth whereas medium mol. wt. fraction (identical to 443,000 daltons) enhanced tumor growth. The low mol. wt. IgA fraction (< 443,000 and > 150,000 daltons) had no significant effect on tumor growth. The high mol. wt. IgA fraction enhanced tumor killing ability of peripheral blood lymphocytes (PBL) and peritoneal macrophages of tumor bearer in vitro. Medium mol. wt. IgA fraction inhibited tumor-killing ability of PBL in vitro but had no significant effect on peritoneal macrophages. The low mol. wt. IgA fraction showed a mild enhancing effect on tumor-killing ability of PBL but had no significant effect on peritoneal macrophages. The results established importance of IgA in tumor growth regulation and its therapeutic potentiality. The results indicated that tumor growth modulation by tumor plasma IgA is also mediated by its effect on cellular anti-tumor immune factors of the host.

Adoptive Transfer↗
PubMed2000

Diverse manifestation of arrhythmogenic right ventricular dysplasia in a family.

Arrhythmogenic right ventricular dysplasia (ARVD) is a cardiomyopathy of unknown cause associated with life-threatening arrhythmias. The purpose of this case report is two-fold: (i) To highlight the utility of a definite set of diagnostic criteria encompassing structural, histologic, electrocardiographic, arrhythmic and genetic factors in establishing diagnosis of ARVD in institutions like ours which are handicapped by lack of magnetic resonance imaging (MRI) and endomyocardial biopsy facilities, (ii) to present diverse arrhythmic manifestations in a single family.

Adolescent↗
PubMed2000

Characterization of cypovirus isolates from tropical and temperate Indian saturniidae silkworms.

Cytoplasmic polyhedrosis virus (cypovirus, CPV) isolates from larvae of saturniidae silkworms Antheraea mylitta, Antheraea proylei, and Antheraea assamensis were obtained and characterized. Scanning electron microscopic (SEM) studies revealed the presence of hexahedral (rhombic dodecahedron) polyhedral bodies of various size (1-4 microns) in individual hosts while transmission electron microscopic (TEM) studies of isolated virions showed their uniform (icosahedral) shape and size (approximately 55 nm). Genomes of these isolates were obtained from purified polyhedral bodies and analyzed by agarose and polyacrylamide gel electrophoresis. Eleven bands ranging from about 350 bp to 3.9 kb (total of 25.35 kb) were detected. These bands were completely degraded after treatment of the genome preparations with RNase A at low salt but not at high salt concentration. The banding pattern of the genomes remained unaffected by treatment of the respective preparations with DNase I, indicating that the genomes were composed of 11 double-stranded (ds) RNA segments. The RNA banding patterns of the CPV isolates from the saturniidae silkworms were similar to each other. These characteristics were similar to that of Antheraea mylitta cypovirus 4 (AmCPV-4) but different from that of Bombyx mori cypovirus 1 (BmCPV-1). In comparison to AmCPV-4 the isolates contained an additional, eleventh RNA segment and the size of the RNA segments was also different. Dot blot hybridization showed hybridization of the cloned 9th and 10th segment cDNAs from the A. mylitta CPV (AmCPV) isolate with RNAs from the A. proylei and A. assamensis CPV (ApCPV, AaCPV) isolates but not with RNA from BmCPV-1. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) of polyhedral proteins from the AmCPV isolate showed the presence of 3 major and 5 minor bands of M(r) from 29.4 K to 163 K, but BmCPV-1 polyhedral bodies showed different protein banding pattern. Two heterologous cell lines infected with the AmCPV isolate showed very slow virus growth with the accumulation of polyhedral bodies in the cytoplasm of infected cells indicating a restricted host range of this CPV isolate.

Animals↗
PubMed1999

Counterions of BINAP-Pt(II) and -Pd(II) complexes: novel catalysts for highly enantioselective Diels-Alder reaction.

[formula: see text] Platinum and palladium chiral bisphosphine complexes and their counterion effects in asymmetric Diels-Alder reactions have been investigated. The reaction of cyclopentadiene and various bidentate dienophiles in the presence of a catalytic amount of Pt(II)- or Pd(II)-BINAP complex proceeds with excellent endo/exo selectivity as well as endo enantioselectivity (up to 99% ee).

Catalysis↗
PubMed1999

Protection by protein A of apoptotic cell death caused by anti-AIDS drug zidovudine.

Zidovudine, the anti-AIDS drug, caused inhibition of mitogen-induced proliferation and perturbation of cell-cycle progression of cultured bone marrow cells of mice. There was significant hypoploidy observed in flow cytometric analysis of AZT-treated bone marrow cells. In apo-direct analysis, cells showed apoptosis in G0/G1 phase. In DNA gel analysis, characteristic laddering of apoptosis was observed in AZT-treated bone marrow cells. We demonstrated that, when the animals were pretreated with protein A (PA) of Staphylococcus aureus, the apoptotic changes could be prevented in bone marrow cells of AZT-treated animals. There is a significant (p < 0.05) increase in proliferation of bone marrow cells subjected to mitogen treatment in PA+AZT-treated animals, compared to only AZT-treated animals. However, cell-cycle phase distribution was not hampered and no laddering in DNA gel analysis was also observed in this group. In apo-direct analysis, PA treatment showed significant (p < 0.001) inhibition of AZT-induced apoptosis. These observations indicate that by using a suitable agent such as protein A the toxic side effects of AZT could be minimized.

Animals↗
PubMed1999

PTEN transcriptionally modulates c-myc gene expression in human breast carcinoma cells and is involved in cell growth regulation.

A novel tumor suppressor gene, PTEN, has recently been identified at chromosome 10q23, which is inactivated in a number of different tumor types including breast cancer. An investigation of the functional role suggested that PTEN transcriptionally represses both exogenous and endogenous c-myc expressions in human breast carcinoma cells. PTEN, when ectopically expressed in human breast carcinoma cells, exhibited an inhibition of phosphorylation of both activating residues of protein kinase B (PKB)/AKT at Ser-473 and Thr-308 without any significant alteration of AKT expression. Furthermore, introduction of PTEN into human breast carcinoma cells induced apoptotic cell death and inhibited cell growth and tumor formation in nude mice. Taken together, our data suggest that PTEN acts as a transcriptional repressor, inhibits the AKT-mediated cell survival signaling pathway, and negatively regulates human breast carcinoma cell growth. These results further emphasize the potential of PTEN as a gene therapeutic agent.

Animals↗
PubMed1999

MBP-1 physically associates with histone deacetylase for transcriptional repression.

MBP-1, a c-myc promoter binding protein, is a mammalian transcription factor with intriguing properties including transcriptional repression of cellular genes. Recently, we have identified and characterized two different repressor domains of MBP-1. In this report, we have demonstrated that MBP-1 physically associates with histone deacetylase (HDAC), thus promoting formation of neucleosomes that inhibit transcription. Trichostatin A, an inhibitor of histone deacetylase, significantly reduces MBP-1-mediated transcriptional repression. However, MBP-1-mediated repression on c-myc promoter is resistant to histone deacetylase activity. Our results suggest that MBP-1 represses transcription by recruiting histone deacetylase as one of the mechanisms, whereas the other mechanism is resistant to HDAC activity and probably related to direct binding of promoter sequences or interaction through yet unidentified factor.

3T3 Cells↗
PubMed1999

Protein A of Staphylococcus aureus evokes Th1 type response in mice.

Protein A (PA) of Staphylococcus aureus is known to elicit several cytokines such as IFN gamma, TNF alpha and IL1. However, it has not been delineated yet as to which differentiation pathway lymphocytes follow after stimulation by PA. In this report, we attempted to collect such evidences. Cytokines, such as IFN gamma, IL2, IL4, IL6, IL10, TNF alpha, IL1alpha and IL1beta were measured in serum by ELISA. Our results show that 1 microg dose of PA stimulates the production of IFN gamma (115 +/- 5 pg/ml), TNF alpha (250 +/- 8 pg/ml) and IL1alpha (100 +/- 5 pg/ml) as compared to control levels of, 22 +/- 2, 20 +/- 2 and 35 +/- 3 pg/ml respectively whereas IL2 and IL1beta secretion were less (beyond the lower detection limit of the kit and 25 +/- 1 pg/ml, respectively) as compared to control (28 +/- 2 and 52 +/- 4 pg/ml, respectively). Larger dose of PA (10 microg) increases the expression of IL2 (75 +/- 3 pg/ml), TNF alpha (1380 +/- 120 pg/ml), IL1alpha (495 +/- 10 pg/ml) and IL1beta (110 +/- 7 pg/ml) as compared to controls described above. We also observed that 1 microg dose of PA decreases IL4, IL6 and IL10 secretion to 9 +/- 1, 10 +/- 1 and 10 +/- 2 pg/ml, respectively, whereas 10 microg dose also decreased them to 11 +/- 1, 12 +/- 2 and 30 +/- 4 pg/ml, respectively as compared to the background controls, i.e. 50 +/- 5, 50 +/- 2 and 215 +/- 9 pg/ml respectively. The ratio of IFN gamma to IL4 increased and the peak value at 4 h, came to 13 +/- 1 and 9.6 +/- 0.5 with 1 microg and 10 microg PA, respectively, which is an established parameter indicating a Th1 type response. Flow cytometry analysis of CD4+/CD8+ cells, and c-myc protein expression by splenocytes indicate that 1 microg dose of PA causes 2-fold increase of CD4+ cells with no change in CD8+ cells, and 10-fold increase in c-myc protein, whereas 10 microg dose increases CD4+ cells 4-fold, CD8+ cells 3-fold and c-myc protein 100-fold. The cell cycle data shows an induction of apoptosis in thymocytes and splenocytes with the large dose (10 microg), whereas the 1 microg dose does not show any apoptosis. This report indicates that a Th1 response is induced in mice, after PA inoculation at a dose of 1 microg animal. Thus, cytokine mediated therapeutic strategies should consider the fact that an induction of large concentration of some cytokines might become detrimental to the host.

Animals↗
PubMed1999

S. aureus superantigen protein A expands CD4(+)/CD8(+)/CD19(+)/CD34(+) cells in mice: a potential immunorestorer.

Protein A (PA) of Staphylococcus aureus is known for its immunostimulatory, anti-cancer, and anti-toxic properties. The present study revealed that PA stimulates specific immunocytes to act as a potential immunorestorer. It has also been shown that the percentage of various cell types bearing different clusters of differentiation markers, e.g., CD4(+), CD8(+), CD19(+), increases considerably after inoculation with PA. It has also been observed that CD34(+) progenitor cells of bone marrow also increased significantly (P < 0.05) upon PA treatment. PA significantly elevated Th-1 cytokines, e.g., IFN-gamma, TNF-alpha, and IL-1alpha. The increased percentages of CD4(+), CD8(+), CD19(+), CD34(+) cells and elevated cytokine levels in PA treated animals may contribute to the reported anti-tumor, anti-fungal, anti-parasitic, and anti-toxic properties of PA. Since in various diseased conditions and during toxic drug therapy lymphocytes bearing such differentiation markers get suppressed, this type of approach could help in immunorestoration of the host. These findings might help in designing therapeutic approaches toward various diseases which cause immunosuppression.

Animals↗