Human telomerase enzyme activity in human hepatoma cell line [HEPG2] and its interaction with the heme oxygenase gene

Objective: to examine the contribution of telomerase and HO-1 in the adaptive cellular response to survive exposure to oxidative stresses in human hepatoma cell line [HepG2]

Materials and Methods: induction and activities of HO and telomerase enzymes were assessed in HepG2 cells in response to oxidative stress [represented by treatment with heme, SnC12 and H202] and in the presence of the HO inhibitor stannic mesoporphyrin [SnMP]. Induction of HO and telomerase mRNA were assessed using RT-PCR and western blotting techniques, while HO and telomerase enzyme activities were assessed spectrophotometrically Cytoprotection against oxidative stress was measured by assessing cell viability using a novel colorimetric method

Results: upregulation of HO-1 provided cytoprotection against oxidative stress while its downregulation increased oxidative stress mediated cell injury without altering telomerase activity. Telomerase was active in hepatocellular carcinoma cell line [HepG2] and human telomerase enzyme catalytic subunit [hTERT] was expressed in telomerase positive cancer cells. However, telomerase activity was not affected by oxidants, heme and H[2]O[2] or downregulation of HO gene activity by SnMP, similarly. hTERT, which is considered as the major regulator of telomerase activity, was not affected by oxidants, inducers or inhibitors of HO activity. On the other hand, HO-1 gene induction stimulated cell proliferation and accelerates cell cycle in HepC2 cells, while inhibition of HO activity augmented the damaging effects of oxidants

Conclusion: Induction of HO-1 gene mediates protection against oxidants and increases cell survival by a mechanism independent of telomerase enzyme activity

Differential Mast Cell Response to Different Bacteria

Mast cells (MCs) are highly specialized for the synthesis and secretion of pharmacologically active products. Although implicated in various inflammatory diseases such as asthma, allergy, multiple sclerosis, and Crohn's disease, MCs have also an important physiologic role in immunosurveillance and modulation of host's innate immune responses following bacterial infection. Here, we present that MCs show varying capability of recognizing and responding to different bacteria. Whereas MCs were readily degranulated and released neutrophil chemoattractants in response to E. coli or S. aureus infections, they failed to degranulate during S. typhimurium infections. Consequently, E. coli infections were associated with a vigorous neutrophil response and early bacterial clearance whereas S. typhimurium infections were associated limited neutrophil influx and bacterial multiplication at sites of infection. Interestingly, injection of compound 48/80, a MC specific activator, at sites of S. typhimurium infection triggered MC mediated neutrophil influx and bacterial clearance.

Differential Mast Cell Response to Different Bacteria

Mast cells (MCs) are highly specialized for the synthesis and secretion of pharmacologically active products. Although implicated in various inflammatory diseases such as asthma, allergy, multiple sclerosis, and Crohn's disease, MCs have also an important physiologic role in immunosurveillance and modulation of host's innate immune responses following bacterial infection. Here, we present that MCs show varying capability of recognizing and responding to different bacteria. Whereas MCs were readily degranulated and released neutrophil chemoattractants in response to E. coli or S. aureus infections, they failed to degranulate during S. typhimurium infections. Consequently, E. coli infections were associated with a vigorous neutrophil response and early bacterial clearance whereas S. typhimurium infections were associated limited neutrophil influx and bacterial multiplication at sites of infection. Interestingly, injection of compound 48/80, a MC specific activator, at sites of S. typhimurium infection triggered MC mediated neutrophil influx and bacterial clearance.