Evaluation of telomerase activity in nasal polyps

Background: The objective of this study was to assess if nasal polyps express telomerase activity and whether a difference could be found between the polyp and the surrounding mucosa of the middle meatus and between different portions of the polyp itself. Methods: Nine patients affected by nasal polyposis were included in this study; four of these patients had recurring polyposis. Telomerase activity was measured by telomeric repeat amplification protocol assay. In six patients, the telomeric repeat amplification protocol assay was performed on the polyp and on the mucosa from the ipsilateral middle meatus. In a polyp, we were able to investigate telomerase activity of its different portions, corresponding to pedicle and fundus. Results: Telomerase activity observed in nasal polyps was higher than that observed in samples from the ipsilateral middle meatus mucosa. High or intermediate telomerase activity was found to be related to predominant recurring polyposis. Conclusions: Therefore, it could be postulated that telomerase activity could be related with the tendency of polyps to recur

Interferon-induced changes in the susceptibility of murine and human lymphoma cells to natural cytotoxic lymphocytes

Mouse YAC-1 and human K562 leukemic cells were treated in vitro with fibroblast interferon (IF) and tested for their susceptibility to NK effector lymphocytes. In both cases a decrease in target susceptibility was induced by the IF treatment. "Cold" competition experiments confirmed that loss or masking of NK target structures occurred in IF-pretreated cells. In fact, when radio-labeled untreated cells were used as targets, IF-pretreated leukemias produced inhibitory effects lower than those mediated by intact cells. However when IF-pretreated targets were used, cold cells either intact or preincubated with IF gave similar competitive effects. These data suggest that IF modulates differentially distinct subsets of NK target structures

IL-2 reverses the inhibition of cytotoxic T-cell responses induced by 5-(3,3' dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) in vitro

One of the major limitations in the use of triazene compounds for inducing increased immunogenicity of tumor cells in vivo (i.e. chemical xenogenization) is the profound immunodepressive activity of these drugs. The present study analysed the inhibitory effects of DTIC on various T-dependent immune responses in mice in an attempt to determine the mechanism of action and appropriate treatments for reverting the immune damage produced by the agent. Results obtained show that treatment with DTIC in vivo produced: (a) inhibition of spleen cell proliferation; (b) reduced IL-2 production in response to allogeneic stimuli; (c) reduction of the generation of IL-2R + CD8 + cells in allogeneic MLC; (d) inhibition of allo-CTL generation. The addition of IL-2 to MLC on day 2 of the co-culture restored full allogeneic CTL responses. These data suggest that exogenous IL-2 could be used to counteract DTIC-induced depression of T-cell reactivity, which is presumably involved in hosts' responses against autochthonous xenogenized tumor cells

Beneficial and Detrimental Effects of Antiretroviral Therapy on HIV-Associated Immunosenescence

Since the introduction of highly active antiretroviral therapy more than 2 decades ago, HIV-related deaths have dramatically decreased and HIV infection has become a chronic disease. Due to the inability of antiretroviral drugs to eradicate the virus, treatment of HIV infection requires a systemic lifelong therapy. However, even when successfully treated, HIV patients still show increased incidence of age-associated co-morbidities compared with uninfected individuals. Virus- induced immunosenescence, a process characterized by a progressive decline of immune system function, contributes to the premature ageing observed in HIV patients. Although antiretroviral therapy has significantly improved both the quality and length of patient lives, the life expectancy of treated patients is still shorter compared with that of uninfected individuals. In particular, while antiretroviral therapy can contrast some features of HIV-associated immunosenescence, several anti-HIV agents may themselves contribute to other aspects of immune ageing. Moreover, older HIV patients tend to have a worse immunological response to the antiviral therapy. In this review we will examine the available evidence on the role of antiretroviral therapy in the control of the main features regulating immunosenescence

In vitro inactivation of human O6-alkylguanine DNA alkyltransferase by antitumor triazene compounds

The cytotoxic and mutagenic properties of antitumor triazene compounds (TZC) have been mainly attributed to their ability to form DNA adducts at the O6 position of guanine. Repair of these lesions is mediated by O6-alkylguanine DNA alkyltransferase (OGAT) in an autoinactivating reaction. Therefore when lesion repair has occurred, cells are depleted of OGAT until synthesis of new enzyme molecules takes place. In this study, we have evaluated the ability of DNA alkylated by different TZC to deplete OGAT activity. Moreover, we have also investigated whether these compounds might inactivate the OGAT enzyme by a direct reaction with the protein. Human OGAT protein was partially purified from insect cells infected with a recombinant baculovirus containing the human OGAT coding sequences. Thereafter human OGAT protein was exposed directly to TZC or to TZC-alkylated DNA. Among the TZC tested, p-(3-methyl-1-triazeno)benzoic acid was the most effective OGAT inactivator by direct interaction with the protein. Moreover DNA substrates treated with methylating TZC, such as temozolomide or p-(3-methyl-1-triazeno)benzoic acid, were more effective in depleting the repair enzyme, compared to DNA pretreated with the chloroethylating TZC mitozolomide. In conclusion, our results show that TZC inactivate in vitro OGAT activity by either direct or indirect mechanisms. Therefore TZC are good candidates for 1) increasing their own cytotoxicity, if used according to appropriate dose and treatment schedules and 2) reversing tumor cell resistance to O6-guanine alkylating agents

Effect of hydrocortisone on human natural killer activity and its modulation by beta interferon

It is well known that glucocorticoids depress the natural killer (NK) activity of human peripheral blood lymphocytes when used both in vivo and in vitro. Since interferons enhance natural cytotoxicity, potential interaction between beta-interferon and hydrocortisone hemisuccinate has been investigated using mononuclear cells of peripheral blood obtained from 17 healthy donors. At the end of in vitro treatment mononuclear cells were tested for NK activity against K562 cells in a 4 h 51Cr-release assay. The results suggest that beta-interferon at the optimal treatment schedule (i.e. before and after exposure to hydrocortisone) is capable of abrogating the hydrocortisone-mediated impairment of NK function. These findings provide valuable suggestions for optimal treatment schedules with beta-interferon (i.e. beta-interferon treatment before and after exposure of effector cells to hydrocortisone) for overriding the suppressive effects of glucocorticoid therapy on natural immunity