Oxidative stress and immune system analysis after cycle ergometer use in critical patients

OBJECTIVE: The passive cycle ergometer aims to prevent hypotrophy and improve muscle strength, with a consequent reduction in hospitalization time in the intensive care unit and functional improvement. However, its effects on oxidative stress and immune system parameters remain unknown. The aim of this study is to analyze the effects of a passive cycle ergometer on the immune system and oxidative stress in critical patients. METHODS: This paper describes a randomized controlled trial in a sample of 19 patients of both genders who were on mechanical ventilation and hospitalized in the intensive care unit of the Hospital Agamenom Magalhães. The patients were divided into two groups: one group underwent cycle ergometer passive exercise for 30 cycles/min on the lower limbs for 20 minutes; the other group did not undergo any therapeutic intervention during the study and served as the control group. A total of 20 ml of blood was analysed, in which nitric oxide levels and some specific inflammatory cytokines (tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ) and interleukins 6 (IL-6) and 10 (IL-10)) were evaluated before and after the study protocol. RESULTS: Regarding the demographic and clinical variables, the groups were homogeneous in the early phases of the study. The nitric oxide analysis revealed a reduction in nitric oxide variation in stimulated cells (p=0.0021) and those stimulated (p=0.0076) after passive cycle ergometer use compared to the control group. No differences in the evaluated inflammatory cytokines were observed between the two groups. CONCLUSION: We can conclude that the passive cycle ergometer promoted reduced levels of nitric oxide, showing beneficial effects on oxidative stress reduction. As assessed by inflammatory cytokines, the treatment was not associated with changes in the immune system. However, further research in a larger population is necessary for more conclusive results.

Protective immunity induced by porin against Salmonella infection in mice.

Porin, a major outer membrane protein was purified from Salmonella typhimurium and its immune potential was studied in mice. Active immunization with porin induced about 45 per cent protection to an intravenous challenge with 10LD50 of S. typhimurium. Further, in porin immunized mice significant level of anti-porin antibodies and DTH reaction were detected. Attempts were also made to improve the immune potential of porin. Freund's complete adjuvant when mixed with immunogenic doses of porin enhanced the anti-porin antibody titre. However, it could not improve the protective ability of porin. On the other hand, porin when injected along with lipopolysaccharide (LPS) induced a higher level (55% survival with 50LD50) of protection than porin or LPS alone. This finding was also substantiated by the significantly reduced in vivo growth of challenge organisms in mice immunized with porin plus LPS. These results indicate that porin is a protective antigen and LPS significantly enhances the protective ability of porin.