B. Veyret

Mouse Strain Susceptibility to Trypanosome Infection: An Arginase-Dependent Effect

We previously reported that macrophage arginase inhibits NO-dependent trypanosome killing in vitro and in vivo. BALB/c and C57BL/6 mice are known to be susceptible and resistant to trypanosome infection, respectively. Hence, we assessed the expression and the role of inducible NO synthase (iNOS) and arginase in these two mouse strains infected with Trypanosoma brucei brucei. Arginase I and arginase II mRNA expression was higher in macrophages from infected BALB/c compared with those from C57BL/6 mice, whereas iNOS mRNA was up-regulated at the same level in both phenotypes. Similarly, arginase activity was more important in macrophages from infected BALB/c vs infected C57BL/6 mice. Moreover, increase of arginase I and arginase II mRNA levels and of macrophage arginase activity was directly induced by trypanosomes, with a higher level in BALB/c compared with C57BL/6 mice. Neither iNOS expression nor NO production was stimulated by trypanosomes in vitro. The high level of arginase activity in T. brucei brucei-infected BALB/c macrophages strongly inhibited macrophage NO production, which in turn resulted in less trypanosome killing compared with C57BL/6 macrophages. NO generation and parasite killing were restored to the same level in BALB/c and C57BL/6 macrophages when arginase was specifically inhibited with Nω-hydroxy-nor-l-arginine. In conclusion, host arginase represents a marker of resistance/susceptibility to trypanosome infections.

A Confirmation Study of Russian and Ukrainian Data on Effects of 2450 MHz Microwave Exposure on Immunological Processes and Teratology in Rats

Abstract In a series of Russian and Ukrainian papers published from 1974–1986, it was reported that 30-day whole-body exposures to continuous-wave (CW) radiofrequency (RF) radiation at 2375 MHz and 5 W/m2 disrupted the antigenic structure of rat brain tissue. The authors suggested that this action caused an autoimmune response in exposed animals. Moreover, these studies reported that blood serum from exposed rats injected into intact nonexposed female rats on the 10th day of pregnancy led to increased postimplantation embryo mortality and decreased fetus size and body weight. Because the results of these studies served in part as the basis for setting exposure limits in the former USSR, it was deemed necessary to perform confirmation studies, using modern dosimetric and biological methods. In our study, a new system was constructed to expose free-moving rats under far-field conditions. Whole-body and brain-averaged specific absorption rates (SARs) were calculated. All results, using ELISA and classic teratology end points, were negative in our laboratory. On the basis of this investigation, we conclude that, under these exposure conditions (2450 MHz, CW, 7 h/day, 30 days, 0.16 W/kg whole-body SAR), RF-radiation exposure had no influence on several immune and degenerative parameters or on prenatal development.

Detection of nitrosylated epitopes in Trypanosoma brucei gambiense by polyclonal and monoclonal anti-conjugated-NO-cysteine antibodies

Activated macrophages with the Calmette/Guérin bacillus (BCG) have a cytotoxic/cytostatic effect on the extracellular parasite, Trypanosoma brucei gambiense. This effect was inhibited when the NO-synthase inhibitor NG-monomethyl-L-arginine (NMMA; 0.5 mM) was added to the culture media. Using an immunocytochemical method with rabbit polyclonal or mouse monoclonal antibodies directed against conjugated nitroso-epitopes (anti-conjugated-NO-cysteine), nitrosylated antigens were visualized in fixed trypanosomes. These results suggest that NO was synthesized by the activated macrophages and that it reacted with some parasitic proteins containing cysteine. The release of NO bound to parasitic proteins may cause the killing of trypanosomes. The immunoreactivity was positive when the trypanosomes were obtained from the supernatant of the BCG-activated macrophages that contains BSA (4 mg/mL). In contrast, the parasites cocultured with non-activated macrophages remained completely viable, and, the immunoreactivity was completely negative.

Circulating antibodies to cysteinyl catecholamines in amyotrophic lateral sclerosis and Parkinson's disease patients

Amyotrophic lateral sclerosis (ALS) is a degenerative disease of unknown aetiology, affecting motor neurons. Many radical species, such as O2− NO, and ONOO−, and lipoperoxidative products are involved, but not all processes have yet been identified. It is known that the oxidation of catecholamines leads to quinone formation. These orthoquinones react with the sulphhydril group of cysteine to produce neurotoxic cysteinyl catecholamine (Cyst‐CA) neo‐compounds. We synthesised Cyst‐CA in order to mimic their endogenous formation. Using the ELISA method, circulating antibodies to Cyst‐CA were found in sporadic ALS sera. First, the antibody titres were compared to those of controls and patients with other neurodegenerative diseases. Significant antibody levels were found for Cyst‐CA. The G and A isotypes were found but not the M isotype. A second series of experiments showed that A and G titres were elevated, depending on the type of Cyst‐CA and the onset of the disease. IgG to Cyst‐3,4‐dihydroxyphenylalanine (L‐DOPA) were present in cases of bulbar and upper limb onsets. IgA to Cyst‐homovanillic acid (HVA), Cyst‐adrenaline (A), and Cyst‐dopamine (DA) were found in lower limb onset. These results indirectly show that: 1) the oxidation of CA and the formation of Cyst‐CA may be involved in ALS; 2) these radical processes have different targets depending on the onset of the disease.