Adaptative mechanism of the equilibrative nucleoside transporter 1 (ENT-1) and blood adenosine levels in elite freedivers.

PURPOSE: Long static or intense dynamic apnoea-like high-altitude exposure is inducing hypoxia. Adenosine is known to participate to the adaptive response to hypoxia leading to the control of heart rate, blood pressure and vasodilation. Extracellular adenosine level is controlled through the equilibrative nucleoside transporter 1 (ENT-1) and the enzyme adenosine deaminase (ADA). The aim of this study was to determine the control of adenosine blood level (ABL) via ENT-1 and ADA during apnoea-induced hypoxia in elite freedivers was similar to high-altitude adaptation. METHODS: Ten freediver champions and ten controls were studied. Biological (e.g. ENT-1, ADA, ABL, PaO2, PaCO2 and pH) and cardiovascular (e.g. heart rate, arterial pressure) parameters were measured at rest and after a submaximal dry static apnoea. RESULTS: In freedivers, ABL was higher than in control participants in basal condition and increased more in response to apnoea. Also, freedivers showed an ADA increased in response to apnoea. Finally, ENT-1 level and function were reduced for the free divers. CONCLUSION: Our results suggest in freedivers the presence of an adaptive mechanism similar to the one observed in human exposed to chronic hypoxia induced by high-altitude environment.

HIV infection en route to endogenization: two cases.

The long-term spontaneous evolution of humans and the human immunodeficiency virus (HIV) is not well characterized; many vertebrate species, including humans, exhibit remnants of other retroviruses in their genomes that question such possible endogenization of HIV. We investigated two HIV-infected patients with no HIV-related disease and no detection with routine tests of plasma HIV RNA or cell-associated HIV DNA. We used Sanger and deep sequencing to retrieve HIV DNA sequences integrated in the human genome and tested the host humoral and cellular immune responses. We noticed that viruses from both patients were inactivated by the high prevalence of the transformation of tryptophan codons into stop codons (25% overall (3-100% per gene) and 24% overall (0-50% per gene)). In contrast, the humoral and/or cellular responses were strong for one patient and moderate for the other, indicating that a productive infection occurred at one stage of the infection. We speculate that the stimulation of APOBEC, the enzyme group that exchanges G for A in viral nucleic acids and is usually inhibited by the HIV protein Vif, has been amplified and made effective from the initial stage of the infection. Furthermore, we propose that a cure for HIV may occur through HIV endogenization in humans, as observed for many other retroviruses in mammals, rather than clearance of all traces of HIV from human cells, which defines viral eradication.

Erlotinib in combination with capecitabine (5'dFUR) in resistant pancreatic cancer cell lines.

The combination of capecitabine and the tyrosine kinase inhibitor erlotinib has recently been tested in patients with gemcitabine-refractory pancreatic tumors, with limited success. To understand this lack of efficacy, we studied the molecular effects of these agents in Capan-1 and Capan-2 human pancreatic resistant cancer cells. Erlotinib up-regulated thymidine phosphorylase (+50%) and downregulated dihydropyrimidine dehydrogenase (+55%) in a cell-dependent manner, thus suggesting that the combination should result in synergism. However, only mild additivity was achieved at best when combining both drugs, and several sequences tested even led to strong antagonism. Further experiments were performed to understand this lack of efficacy. We found that the fluoropyrimidine down-regulated EGFR expression by 30%, an unexpected finding resulting in a possible reduction in efficacy when cells were subsequently exposed to erlotinib. We also observed marked drug-induced over-expression of both cytosolic and extracellular vascular endothelial growth factor (VEGF) secretion, thus possibly triggering proliferation. These preliminary findings strongly suggest that these observations could be new mechanisms in the development of acquired drug resistance in pancreatic cancer cells.