Changes in concentrations of type IV collagen and tissue inhibitor of metalloproteinase-1 in patients with paraquat poisoning

Mechanism of cytotoxicity of paraquat

Acute paraquat poisoning seems to be very complex because many possible mechanisms of paraquat cytotoxicity have been reported. Some may not be the cause of paraquat poisoning but the result or an accompanying phenomenon of paraquat action. The mechanism critical for cell damage is still unknown. Paraquat poisoning is probably a combination of several paraquat actions. Arguing which mechanism is more critical may not be important, and these clarified mechanisms should be connected and utilized in the development of treatment for paraquat poisoning. Many people still die of pulmonary fibrosis after paraquat exposure. The next target of study will be to verify the mechanism of pulmonary fibrosis by paraquat on the basis of the outcome of studies such as this review.

Paraquat poisonings: mechanisms of lung toxicity, clinical features, and treatment

Paraquat dichloride (methyl viologen; PQ) is an effective and widely used herbicide that has a proven safety record when appropriately applied to eliminate weeds. However, over the last decades, there have been numerous fatalities, mainly caused by accidental or voluntary ingestion. PQ poisoning is an extremely frustrating condition to manage clinically, due to the elevated morbidity and mortality observed so far and due to the lack of effective treatments to be used in humans. PQ mainly accumulates in the lung (pulmonary concentrations can be 6 to 10 times higher than those in the plasma), where it is retained even when blood levels start to decrease. The pulmonary effects can be explained by the participation of the polyamine transport system abundantly expressed in the membrane of alveolar cells type I, II, and Clara cells. Further downstream at the toxicodynamic level, the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. With this review we aimed to collect and describe the most pertinent and significant findings published in established scientific publications since the discovery of PQ, focusing on the most recent developments related to PQ lung toxicity and their relevance to the treatment of human poisonings. Considerable space is also dedicated to techniques for prognosis prediction, since these could allow development of rigorous clinical protocols that may produce comparable data for the evaluation of proposed therapies.

Effect of polymyxin B-immobilized fiber on blood metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 levels in acute respiratory distress syndrome patients

BACKGROUND/AIMS

Metalloproteinase (MMP)-9 plays a role in the pathogenesis of acute respiratory distress syndrome (ARDS). Polymyxin B-immobilized fiber (PMX-F) treatment improves circulatory disturbance and oxygenation in ARDS patients. We aimed to assess whether PMX-F treatment alters the blood MMP-9 and tissue inhibitor of MMP (TIMP)-1 levels in ARDS patients.

METHODS

Twelve ARDS patients who received PMX-F treatment and 20 healthy control volunteers were included in this study. PMX-F was carried out twice at a rate of 100 ml/min for 2 h with a time interval of 24 h. Blood MMP-9 and TIMP-1 levels were measured before and after PMX-F treatment. We monitored blood pressure and the PaO2/FiO2 (PF) ratio before and after PMX-F treatment.

RESULTS

The mortality of ARDS patients after PMX-F treatment was 16.7%. Chest X-ray abnormalities were ameliorated in surviving patients after PMX-F treatment. Systolic and diastolic blood pressure increased significantly after PMX-F treatment (p < 0.01). The PF ratio also increased significantly after PMX-F treatment (p < 0.01). Blood MMP-9 and TIMP-1 levels in ARDS patients (126.4 +/- 36.4 and 326.5 +/- 52.5 ng/ml) were significantly higher than in controls (34.5 +/- 12.5 and 160.5 +/- 24.5 ng/ml; p < 0.01). PMX-F treatment reduced these levels significantly (the first treatment: MMP-9 85.4 +/- 28.6 ng/ml, p < 0.05, TIMP-1 265.8 +/- 36.6 ng/ml, p < 0.05; the second treatment: MMP-9 56.5 +/- 18.8 ng/ml, p < 0.01, TIMP-1 220.6 +/- 30.5 ng/ml, p < 0.01).

CONCLUSION

These data suggest that MMP-9 and TIMP-1 may play a role in the pathogenesis of ARDS and that PMX-F treatment ameliorated increased MMP-9 and TIMP-1 levels in ARDS patients.