Distribution of NOS in normoxic vs. hypoxic rat lung: upregulation of NOS by chronic hypoxia.

Expression and localization of nitric oxide synthase (NOS) in the lungs of chronically hypoxic and normoxic rats were studied using both immunohistochemistry and NADPH diaphorase (NADPH-d) staining techniques. In the normoxic and in the hypoxic rat, NOS was detected by both methods in the endothelium of large pulmonary vessels and in the epithelium of bronchi and bronchioli. NOS expression was not detected in the endothelium of normoxic pulmonary resistance vessels but was prominently expressed in the endothelium of these vessels after 2-4 wk of chronic hypoxia. In contrast to small pulmonary vessels, the endothelium of small bronchial vessels exhibited NOS immunostaining in both normoxic and hypoxic lungs. Hypoxia was also found to induce de novo NOS expression in the smooth muscle of large and small pulmonary vessels and in bronchial smooth muscle. NOS enzyme activity in lung homogenates was assessed by [3H]arginine to [3H]citrulline conversion. The activity of soluble NOS, but not particulate NOS, was increased in the hypoxic lungs. These results demonstrate chronic hypoxia-induced upregulation of NOS protein expression and activity in the rat lung, suggesting a potentially important role of nitric oxide in adaptation of the pulmonary circulation to chronic hypoxia. The lack of immunostaining in small pulmonary resistance vessels is also consistent with physiological studies suggesting that NO may not be involved in the mechanism for maintaining the normally low pulmonary vascular resistance.

Purging of small cell lung cancer cells from human bone marrow using ethiofos (WR-2721) and light-activated merocyanine 540 phototreatment.

One limitation of autologous bone marrow transplantation for patients with cancer has been the presence of tumor cells in the bone marrow. Methods to eliminate tumor cells while preserving hematopoietic stem cells have been sought. The present study was performed to analyze the in vitro effectiveness of light-activated merocyanine 540 phototreatment (LAMP) and an aminothiol (ethiofos) as a marrow-purging regimen for small cell lung cancer (SCLC). Two human SCLC cell lines (ATCC HTB-119 and HTB-120) were treated with LAMP and exposed to light for varying periods of time up to 120 min. LAMP reduced SCLC cell proliferation and colony formation in a light exposure-dependent manner; colony formation was not totally inhibited until light exposure of 120 min was used. At this light exposure interval, multipotential hematopoietic progenitors, colony-forming units-granulocyte, erythroid, macrophage, megakaryocyte (CFU-GEMM), were substantially reduced. In an attempt to diminish hematopoietic toxicity, SCLC cells were incubated with ethiofos (formerly WR-2721) for 1 hour before LAMP. SCLC colony formation was eliminated at light exposure intervals (90 min or less) which had no inhibitory effect on CFU-GEMM. Ethiofos did not protect CFU-GEMM from LAMP inhibition at 120 min. Ethiofos alone had no effect on the SCLC or hematopoietic cells. When normal bone marrow was contaminated with 1 or 5% SCLC cells, ethiofos plus 60 min of LAMP eliminated SCLC cells but had no effect on CFU-GEMM. The results suggest that ethiofos sensitized SCLC cells to LAMP; thus ethiofos-enhanced LAMP may be an effective method for removing metastatic SCLC cells from bone marrow used for autologous marrow transplantation after high dose chemotherapy.