The effect of 3-methylindole on the quantity and functional quality of lung surfactant

Impact of ventilation-induced lung injury on the structure and function of lamellar bodies

Alterations to the pulmonary surfactant system have been observed consistently in ventilation-induced lung injury (VILI) including composition changes and impairments in the surface tension reducing ability of the isolated extracellular surfactant. However, there is limited information about the effects of VILI on the intracellular form of surfactant, the lamellar body. It is hypothesized that VILI leads to alterations of lamellar body numbers and function. To test this hypothesis, rats were randomized to one of three groups, nonventilated controls, control ventilation, and high tidal volume ventilation (VILI). Following physiological assessment to confirm lung injury, isolated lamellar bodies were tested for surfactant function on a constrained sessile drop surfactometer. A separate cohort of animals was used to fix the lungs followed by examination of lamellar body numbers and morphology using transmission electron microscopy. The results showed an impaired ability of reducing surface tension for the lamellar bodies isolated from the VILI group as compared with the two other groups. The morphological assessment revealed that the number, and the relative area covered by, lamellar bodies were significantly decreased in animals with VILI animals as compared with the other groups. It is concluded that VILI causes significant alterations to lamellar bodies. It is speculated that increased secretion causes a depletion of lamellar bodies that cannot be compensated by de novo synthesis of surfactant in these injured lungs.

Pulmonary manifestations of the eosinophilia-myalgia syndrome associated with tryptophan ingestion

Pulmonary manifestations are not infrequent in the L-tryptophan-induced eosinophilia-myalgia syndrome (EMS). However, previous reports have not described the results of longitudinal pulmonary function, exercise testing, high-resolution computerized tomographic (HRCT) scanning of the chest, or detailed bronchoalveolar lavage (BAL) analysis. We report six patients with EMS who had dyspnea. The diffusing capacity for carbon monoxide was decreased in five patients tested. Exercise testing with arterial blood gas sampling in three patients was consistent with pulmonary vascular or parenchymal disease. Serial exercise testing in two of these patients demonstrated marked improvement temporally associated with corticosteroid treatment. In four patients, HRCT scanning of the chest was abnormal. One of these patients showed no abnormality on routine chest roentgenogram. Two patients undergoing BAL exhibited increased eosinophils in the lavage fluid; a third had elevated lymphocytes. Serial measurements of fibroblast proliferation-stimulating-activity in samples of BAL fluid obtained from serial examinations in two patients exhibited heightened pretreatment activity that returned to the normal range following corticosteroid therapy. In these two patients, increased proportions of T-suppressor/cytolytic (CD8+) cells were observed in the BAL fluid. Despite aggressive immunosuppressive therapy, one of the patients died of respiratory failure. Another remains markedly dyspneic with pulmonary hypertension. Of the remaining four patients, two exhibited resolution of pulmonary symptoms after systemic corticosteroid therapy, and two experienced partial improvement.

The metabolic basis of 3-methylindole-induced pneumotoxicity

3-Methylindole (3MI), an abnormal metabolite of tryptophan, causes acute pulmonary edema and emphysema. 3MI toxicity is species-, tissue- and cell-specific and is an excellent model for understanding the processes of chemically-induced lung injury. Experimental evidence showed that 3MI is metabolically activated by both microsomal cytochrome P-450-dependent mixed function oxidase (MFO) and prostaglandin H synthase (PHS) systems in the lung. Formation of a free radical intermediate during 3MI metabolism is the initial chemical event which is responsible for the pneumotoxicity. 3MI free radicals bind covalently to microsomal protein and induce lipid peroxidation. Microsomal enzymes which regulate the glycogen and phospholipid biosynthesis in the lung are altered during the cellular repair processes after 3MI-induced lung injury. Inhibition of cellular differentiation from Type II to Type I cells and impaired surfactant function may be crucial to the disease process.

Impaired surfactant function in 3-methylindole-induced lung injury in goats

1. This study was designed to monitor the changes in surfactant quantity and function in the 72 hr following 3-methylindole (3MI) infusion in goats. 2. 3MI, at 35 mg/kg body wt, caused an increase in surfactant phospholipid isolated from lamellar bodies and lavage fluid. 3. The function of surfactant isolated from lavage fluid was tested using the pulsating bubble surfactometer. The results indicated a serious impairment in the ability to lower surface tension in vitro. 4. Results suggested 3MI caused an impaired surfactant function rather than surfactant synthesis in response to epithelial damage.