Nicotine effects on proliferation and the bombesin-like peptide autocrine system in human small cell lung carcinoma SHP77 cells in culture

OBJECTIVES

To determine whether nicotine affects the proliferation and expression of the bombesin-like peptide autocrine system in human small cell lung carcinoma (SCLC) SHP77 cells compared with nonmalignant human bronchial epithelial BEAS 2B cells as non-neuroendocrine controls.

METHODS

Human lung cells were cultured in defined serum-free medium with various concentrations of nicotine added for various times. Proliferation was measured by cell counts and colorimetric assay, bombesin-like peptide receptor expression was assayed by specific binding assays and quantitative competitive PCR, and bombesin-like peptides determined by ELISA.

RESULTS

Nicotine significantly stimulated the growth of human SCLC SHP77 and NCI-H865 cells, but not BEAS 2B cells. Bombesin-like peptide receptor specific binding and mRNA expression were not affected by nicotine exposure in SHP77 cells or BEAS 2B cells. An increase in SHP77 cellular bombesin-like peptide content was observed.

CONCLUSIONS

Human SCLC SHP77 cells express the components of the bombesin-like peptide autocrine system. Increased proliferation in the presence of nicotine may be due in part to increased levels of bombesin-like peptides in SHP77 cultured in nicotine. Nicotine effects on nonmalignant pulmonary neuroendocrine cells may provide additional insight into how nicotine itself may promote lung carcinogenesis.

Nonconstitutive expression of the gastrin-releasing peptide autocrine growth system in human small cell lung carcinoma NCI-H345 cells

Constitutive, unregulated autocrine growth is thought to be an important mechanism whereby cancer cells gain a proliferative advantage over nonmalignant cells. The question addressed here was whether the autocrine growth system for gastrin-releasing peptide (GRP) in human small cell lung carcinoma cells is, in fact, always expressed in a constitutive, unregulated fashion. Lag, rapid, and plateau growth states were defined for small cell lung carcinoma NCI-H345 cells based on periods during which they expressed different growth rates after plating as single cell suspensions. Immunoreactive GRP in the conditioned medium and in NCI-H345 cells harvested during each of these growth states, as well as cell DNA content, GRP mRNA expression, specific 125I-GRP uptake, specific 125I-GRP binding to solubilized membranes, and GRP and neuromedin B receptor mRNA expression by reverse transcription-PCR were analyzed. Maximal levels of GRP expression were observed during the lag growth state, with the highest concentration of immunoreactive GRP in the conditioned medium during the rapid growth state. Specific 125I-GRP uptake and binding were also highest during the lag growth state; however, GRP receptor mRNA did not significantly change. In contrast to prevailing concepts, these studies support the conclusion that the expression of the GRP autocrine growth system in NCI-H345 cells is indeed regulated. Furthermore, the components are maximally expressed before rapid growth begins, suggesting that other mechanisms are activated to support the actual proliferation.

Bombesin-like peptide receptors in human bronchial epithelial cells

Northern blot and RNAse protection assays previously failed to detect bombesin-like peptide (BLP) receptors in normal human lung tissue, but by RT/PCR cultured human bronchial epithelial (HBE) cells expressed all three BLP receptor subtypes, predominantly neuromedin B (NMB) receptor. By RT/PCR, we found expression of all three BLP receptor subtypes by human lung tissue and confirmed NMB receptor expression in six out of six HBE samples. However, transformed HBE BEAS B2B cells expressed only gastrin-releasing peptide (GRP) receptors; saturable, high-affinity (Kd = 3.5 nM) specific [125I]GRP binding confirmed functional GRP receptor, with M(r) = 75 kDa and immunologic cross-reactivity with GRP receptor from human small-cell lung carcinoma (SCLC) NCI-H345 cells. Altered regulation of BLP receptors may accompany transformation of normal lung cells to cancer.

Serum melatonin levels in melanoma patients after repeated oral administration

The goal of this study was to determine the effect of oral melatonin in divided doses on plasma melatonin levels in patients with metastatic melanoma. Hourly blood samples were obtained from five patients for 24 h prior to melatonin administration and for 24 h during oral administration of melatonin, 50 mg every 4 h. In two of the five patients, the expected nocturnal plasma melatonin peak was observed. Oral melatonin was well absorbed. Plasma melatonin levels exhibited six peaks and troughs, were two to four-fold higher during peaks than troughs, and remained more than 25 times higher than peak pretreatment melatonin levels, even during troughs. Divided oral doses of melatonin were well tolerated and maintained plasma melatonin levels 25-80 times higher than endogenous peak values.

Novel soluble, high-affinity gastrin-releasing peptide binding proteins in Swiss 3T3 fibroblasts

Swiss 3T3 cells contained substantial amounts of soluble and specific [125I]GRP binders. Like the membrane-associated GRP receptor, they were of high affinity, saturable, bound to GRP(14-27) affinity gels, and exhibited specificity for GRP(14-27) binding. They differed in that acid or freezing destroyed specific binding, specific binding exhibited different time and temperature effects, no detergent was required for their solubilization, ammonium sulfate fractionation yielded different profiles, the M(rs) were lower, GRP(1-16) also blocked binding, and a polyclonal anti-GRP receptor antiserum did not bind on Western blots. The isolated, soluble GRP binding protein(s) rapidly degraded [125I]GRP. These soluble GRP binding proteins may play a role in the regulation of the mitogenic effects of GRP on these cells.

Isolation of an antibacterial peptide from human lung lavage fluid

The contribution of extracellular secretions to the antibacterial defenses of the lungs remains poorly defined. Recent studies have demonstrated that mouse and rabbit bronchoalveolar washings contain a low-molecular-weight peptide that has antibacterial activity against Escherichia coli. In this study we investigated whether a similar peptide could be identified in human secretions. Bronchoalveolar lavage fluid was obtained from normal volunteers and patients with interstitial lung disease or pulmonary alveolar proteinosis. Cellular material and surfactant lipids were removed from the fluid by sequential centrifugations, and the supernatant was fractionated by exclusion filtration to isolate peptides with a molecular weight less than 10,000. Gel filtration chromatography separated the ultrafiltrate into several peaks, the first of which had antibacterial activity against E. coli. This material was further separated into several hydrophilic peaks by reverse-phase high-pressure liquid chromatography (RPHPLC). All samples had similar RPHPLC graphs. Material from the third RPHPLC peak produced an antibacterial effect similar to that produced by the rabbit and mouse peptide.

Immune stimulation of lung bactericidal activity: evidence for both cellular and humoral participation after immunization with Serratia marcescens

Mice were immunized by aerosol or by a parenteral route with Serratia marcescens, and subsequently challenged by aerosol with both Staphylococcus aureus and S. marcescens. After a single aerosol immunization, intrapulmonary bactericidal activity was initially enhanced against both organisms. Repetitive aerosol immunization caused the same initial response; however, after antistaphylococcal activity returned to normal, enhanced antiserratia activity was still demonstrable. Parenteral immunization was associated with increased in situ bactericidal activity against both organisms with more pronounced antiserratia activity. Intracellular bactericidal activity against S. aureus of lung phagocytes harvested from mice after aerosol immunization with serratia paralleled the above findings. Aerosol immunization also resulted in recruitment of polymorphonuclear leukocytes. These data suggested that macrophage activation, leukocyte recruitment, and local antibody are important contributing factors to heightened lung antibacterial activity after aerosol immunization with S. marcescens.