The antiviral drug amantadine has a direct inhibitory effect on T-lymphocytes

Inflammation in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease that is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Inflammatory responses manifested by glial reactions, T cell infiltration, and increased expression of inflammatory cytokines, as well as other toxic mediators derived from activated glial cells, are currently recognized as prominent features of PD. The consistent findings obtained by various animal models of PD suggest that neuroinflammation is an important contributor to the pathogenesis of the disease and may further propel the progressive loss of nigral dopaminergic neurons. Furthermore, although it may not be the primary cause of PD, additional epidemiological, genetic, pharmacological, and imaging evidence support the proposal that inflammatory processes in this specific brain region are crucial for disease progression. Recent in vitro studies, however, have suggested that activation of microglia and subsequently astrocytes via mediators released by injured dopaminergic neurons is involved. However, additional in vivo experiments are needed for a deeper understanding of the mechanisms involved in PD pathogenesis. Further insight on the mechanisms of inflammation in PD will help to further develop alternative therapeutic strategies that will specifically and temporally target inflammatory processes without abrogating the potential benefits derived by neuroinflammation, such as tissue restoration.

Effect of co-administration of fluoxetine and amantadine on immunoendocrine parameters in rats subjected to a forced swimming test

Considerable attention has been paid to a possible role of immunological dysregulation in the pathogenesis of depression. It has been reported that combined administration of antidepressant drugs and the non-competitive NMDA receptor antagonist amantadine reduces immobility time in the forced swimming test (FST). Moreover, preliminary clinical data show that such a combination of drugs has a beneficial effect on treatment-resistant depressed patients. Since immune activation and a pro-inflammatory response are clearly evident in treatment-resistant depression, the aim of the present study was to examine the effect of a combination of the antidepressant fluoxetine and amantadine on immunoendocrine parameters in rats subjected to the forced swimming test. The obtained results revealed synergistic antidepressant effects of the combined administration of fluoxetine (10 mg/kg) and amantadine (10 mg/kg) - drugs otherwise ineffective when given separately in the above doses. Antidepressant activity was accompanied with a significant decrease in the capacity of splenocytes to proliferate in response to concanavalin A. Moerover, fluoxetine and the combination of amantadine and fluoxetine reduced relative spleen weight in rats subjected to the FST, compared to rats treated with the vehicle. The combination of amantadine and fluoxetine enhanced the production of the negative immunoregulator interleukin-10 (but not interferon-gamma) in rats subjected to the FST. The exposure to the FST produced an increase in plasma corticosterone levels, which was significantly attenuated by pretreatment with fluoxetine and amantadine. In summary, the antidepressive efficacy of a combination of fluoxetine and amantadine given in suboptimal doses may be related to the negative immunoendocrine effects of these drugs.

Amantadine in Parkinson's disease: lymphocyte subsets and IL-2 secreting T cell precursor frequencies

The antiviral drug amantadine, that is effective in idiopathic Parkinson's disease (PD), may affect the composition and function of peripheral blood lymphocytes. In an explorative study, we therefore compared lymphocyte subpopulations and IL-2 secreting T cell precursors frequencies (HTLp-frequencies) in 15 PD patients without amantadine and six patients on long-term treatment. Five patients were investigated before and three months after the start of treatment. Group comparisons for long-term amantadine treatment showed no differences in subpopulations of B-, T-, and NK cells, and HTLp-frequencies. However, three months after initiation of treatment we noted in all five patients an increase of CD3+CD4+ and decrease of CD3+CD8+ cells, associated with an increase of the CD3+CD4+/CD3+CD8+ ratio. These changes had no effect on the HTLp-frequencies. Thus, at least for a short period of time, amantadine improves the T cell mediated immune system in PD patients.

Inhibition of lymphocyte proliferation by amantadine and its isomer, 2-aminoadamantane; impact on Lyt-2+ T cells while sparing L3T4+ T cells

The present in vitro investigations on amantadine (AmTd) and its isomer 2-aminoadamantane (2-NH2-Adam), and the corresponding analogs, 1-nitroadamantane (1-NO2-Adam) and 2-nitroadamantane (2-NO2-Adam), were undertaken to gain information about molecular features that might have a dominant role in inhibiting T lymphocyte proliferation and to determine whether all, or a subpopulation of thymic-dependent (T) lymphocytes might be impacted by these drugs. Studies were done using lymphocytes from untreated normal mice as well as cloned murine cytotoxic T lymphocytes, CTLL cells. T lymphocytes were defined by their proliferative response to concanavalin A (Con A), and thymic-independent (B) lymphocytes by their proliferative response lipopolysaccharide (LPS). Proliferation of CTLL cells was induced by supplementing the culture medium with lymphokine-containing medium or by adding recombinant interleukin (IL)-2. Proliferation was assessed by quantifying cellular incorporation of tritiated thymidine. The data show that the aminoadamantanes, AmTd and 2-NH2-Adam, impacted on Lyt-2+ T lymphocytes while sparing L3T4+ T lymphocytes. In addition, the data show that the location of the substituent group on the adamantane ring altered the molecule's capacity to modulate lymphocyte activity. And finally, results of studies comparing the inhibitory activity of AmTd and 1-NO2-Adam suggest a non-lysosomal mechanism of action. Possible implications of these findings are discussed.