Effect of microcystin on leukocyte viability and function.

Microcystin (MC) has been found in several areas of the world. In addition to its hepatotoxicity, microcystin may have an immunomodulatory effect. Considering that patients receiving hemodialysis may be chronically exposed to variable concentrations of MC, and that they present important changes in this immune response, we have assessed the effect of MC on the function of leukocytes. Polymorphonuclear leukocytes isolated from healthy volunteers (HV) and patients receiving hemodialysis (HD) were incubated with microcystin (10 microg/L) for 24h and evaluated for reactive oxygen species production (ROS), phagocytosis and apoptosis. Monocytes incubated with and without LPS (100 ng/mL) and microcystin for 24h were assessed for TNFalpha and IL-10 production. Leukocytes of HV presented an increase in apoptosis rates and leukocytes from HD exhibited a lower production of oxygen-reactive species, both spontaneously and after stimulus with S. aureus, when compared with leukocytes incubated without toxin. Monocytes presented an increase in cytokine production after stimulation by LPS in both groups, but there was no difference between the groups with and without MC that were incubated with or without LPS. Low concentrations of microcystin can induce mild changes in leukocyte function of HV and HDP, particularly in the ability to produce ROS.

Efeito da microcistina na apoptose e função de leucócitos / Effect of microcystin in leukocyte apoptosis and function

Introdução: Microcistina (MC), que é uma cianotoxina, tem sido identificada na água de várias regiões do Brasil e do mundo. Vários estudos têm identificado além da hepatotoxicidade um papel imunomodulatório desta toxina. Considerando-se que pacientes com insuficiência renal crônica em hemodiálise (HD) possam estar cronicamente expostos a variáveis concentrações de MC, e que apresentam alterações importantes na resposta imune, avaliamos o efeito da MC em concentrações que podem ser encontradas na água para diálise, na função de leucócitos. Métodos: Leucócitos polimorfonucleares (PMN) e monócitos foram isolados de sangue periférico de voluntários saudáveis (VS) e de pacientes em HD (PHD). Leucócitos de VS (n=6) foram incubados com MC (0,1g/L, 1g/L e 10g/L) 24h e então avaliados quanto ao metabolismo oxidativo, fagocitose e apoptose (citometria de fluxo) para determinação de uma curva dose-resposta. Leucócitos de PHD (n=10) e de VS (n=l0) foram incubados com MC 1Og/L 24h e avaliados da mesma forma. Monócitos foram incubados com e sem LPS (100ng/ml) e MC (1Og/L) 24h e avaliados quanto à produção de TNF- e IL-10. Resultados: Não houve diferenças na viabilidade ou função de leucócitos com diferentes concentrações de MC. PMN de todos os grupos apresentaram maior produção de espécies reativas de oxigênio ao serem estimulados com PMA ou S. aureus. Ao serem incubados com MC (10gg/L), leucócitos de VS (n=10) apresentaram aumento nas taxas de apoptose. Leucócitos de PHD incubados com MC apresentaram menor produção de espécies reativas de oxigênio basal e estimulada com S. aureus do que células do mesmo grupo sem toxina. Monócitos apresentaram aumento da produção de citocinas após estímulo pelo LPS em ambos os grupos, mas não houve diferença entre os grupos com e sem MC no basal ou com LPS

[Elevated cyclosporine A trough levels in HCV positive kidney transplant recipients]. / Níveis de vale de ciclosporina elevados em transplantados renais anti-HCV positivos.

OBJECTIVE: Compare the CsA trough levels of HCV+ kidney transplant recipients to a control group METHODS: All anti-HCV positive patients that received a renal allograft between January 1992 and April 1996 were initially included as cases. Patients with diabetes mellitus, HBsAg+, who were taking medication that could modify CsA pharmacokinetics and those with elevated aminotransferases were excluded. For each anti-HCV positive index case the following transplanted anti-HCV negative patient was included as a control. Third generation ELISA was used for determination of the anti-HCV status and CsA dosages were performed by polarized fluorometry with polyclonal antibodies. RESULTS: No differences in the demographic variables were found. The average CsA through levels in the first month were higher (551 +/- 280 ng/ml) in the 23 cases as compared to the 31 controls (418 +/- 228 ng/ml; p< 0.05). The differences became apparent at the end of the first week (528 +/- 275 versus 344 +/- 283 ng/ml; p<0.01) and persisted at discharge (582 +/-284 versus 457 +/- 229; p=0,08). CONCLUSION: We concluded that anti-HCV positive patients have higher blood levels of CsA for a particular dosage, than anti-HCV negative controls. Prospective studies with a more appropriate pharmacokinetic approach are needed to confirm the present findings.

The role of growth factors on renal tubular cells submitted to hypoxia and deprived of glucose.

BACKGROUND: In acute renal failure (ARF) renal tubular cell death and detachment can be induced by necrotic and apoptotic mechanisms. Several studies have demonstrated some benefits of the use of growth factors in experimental models of ARF. METHODS: MDCK cells were cultured in a glucose-free medium for 24h and were submitted to hypoxia (PO2 around 35 mmHg) for additional 24 h. To evaluate the possible protective role of growth factors, EGF, IGF-I or HGF were added to the medium (20 ng mL). LDH release, viability (acridine orange and ethidium bromide dyes) and quantification of apoptotic cells (Hoechst 33342 dye fluorescence) were determined. RESULTS: In the injury group, an increase on LDH release (60% vs. 3%) and on number of apoptotic cells (22% vs. 0.2%) which was associated with a reduced cell viability (61% vs. 94%) when compared with controls. Only HGF, not EGF or IGF-I, was able to protect cells from injury. HGF caused a significant reduction on LDH release (30%) and on number of apoptotic cells (5%), with an increase on viability cellular (79%). CONCLUSIONS: HGF decreases cell death on MDCK cells after hypoxic-induced injury, probably acting in both necrotic and apoptotic mechanisms.

Níveis de vale de ciclosporina elevados em transplantados renais anti-HCV positivos / Elevated cyclosporine A trough levels in HCV positive kidney transplant recipients

OBJETIVO: Comparar os níveis de vale de CsA de transplantados renais anti-HCV+ com um grupo controle. MÉTODOS: Incluímos como casos todos os pacientes anti-HCV+ transplantados entre janeiro de 1992 e abril de 1996, e os anti-HCV- transplantados a seguir do caso como controles. Excluímos pacientes diabéticos, HbsAg+, os que recebiam fármacos com interaçäo com a CsA e aqueles com transaminases elevadas. A sorologia para HCV foi testada pelo método ELISA de 3ª geraçäo, e as dosagens de ciclosporina através de fluorimetria polarizada com anticorpo policlonal. RESULTADOS: As principais variáveis demográficas näo diferiram entre os grupos. O nível de vale médio de CsA do primeiro mês pós-transplante foi maior nos 23 pacientes anti-HCV+ (551 ± 280 ng/ml) do que nos 31 controles (418 ± 228 ng/ml, p<0,05). As diferenças tornaram-se aparentes ao final da primeira semana (528 ± 275 versus 344 ± 283 ng/ml; p<0,01) e persistiam no momento da alta (582 ± 284 ng/ml versus 457 ± 229 ng/ml; p=0,08). CONCLUSÄO: Os pacientes anti-HCV+ apresentam níveis de vale de CsA elevados em relaçäo à populaçäo controle, o que indica a realizaçäo de estudo farmacocinético da droga neste prevalente grupo de transplantados renais