Regulation of catecholamine release and tyrosine hydroxylase in human adrenal chromaffin cells by interleukin-1beta: role of neuropeptide Y and nitric oxide.

Adrenal chromaffin cells synthesize and secrete catecholamines and neuropeptides that may regulate hormonal and paracrine signaling in stress and also during inflammation. The aim of our work was to study the role of the cytokine interleukin-1beta (IL-1beta) on catecholamine release and synthesis from primary cell cultures of human adrenal chromaffin cells. The effect of IL-1beta on neuropeptide Y (NPY) release and the intracellular pathways involved in catecholamine release evoked by IL-1beta and NPY were also investigated. We observed that IL-1beta increases the release of NPY, norepinephrine (NE), and epinephrine (EP) from human chromaffin cells. Moreover, the immunoneutralization of released NPY inhibits catecholamine release evoked by IL-1beta. Moreover, IL-1beta regulates catecholamine synthesis as the inhibition of tyrosine hydroxylase decreases IL-1beta-evoked catecholamine release and the cytokine induces tyrosine hydroxylase Ser40 phosphorylation. Moreover, IL-1beta induces catecholamine release by a mitogen-activated protein kinase (MAPK)-dependent mechanism, and by nitric oxide synthase activation. Furthermore, MAPK, protein kinase C (PKC), protein kinase A (PKA), and nitric oxide (NO) production are involved in catecholamine release evoked by NPY. Using human chromaffin cells, our data suggest that IL-1beta, NPY, and nitric oxide (NO) may contribute to a regulatory loop between the immune and the adrenal systems, and this is relevant in pathological conditions such as infection, trauma, stress, or in hypertension.

Ventilation, Oxidative Stress, and Nitric Oxide in Hypobaric versus Normobaric Hypoxia.

PURPOSE: Slight differences in physiological responses and nitric oxide (NO) have been reported at rest between hypobaric hypoxia (HH) and normobaric hypoxia (NH) during short exposure.Our study reports NO and oxidative stress at rest and physiological responses during moderate exercise in HH versus NH. METHODS: Ten subjects were randomly exposed for 24 h to HH (3000 m; FIO2, 20.9%; BP, 530 ± 6 mm Hg) or to NH (FIO2, 14.7%; BP, 720 ± 1 mm Hg). Before and every 8 h during the hypoxic exposures, pulse oxygen saturation (SpO2), HR, and gas exchanges were measured during a 6-min submaximal cycling exercise. At rest, the partial pressure of exhaled NO, blood nitrate and nitrite (NOx), plasma levels of oxidative stress, and pH levels were additionally measured. RESULTS: During exercise, minute ventilation was lower in HH compared with NH (-13% after 8 h, P < 0.05). End-tidal CO2 pressure was lower (P < 0.01) than PRE both in HH and NH but decreased less in HH than that in NH (-25% vs -37%, P < 0.05).At rest, exhaled NO and NOx decreased in HH (-46% and -36% after 24 h, respectively, P < 0.05) whereas stable in NH. By contrast, oxidative stress was higher in HH than that in NH after 24 h (P < 0.05). The plasma pH level was stable in HH but increased in NH (P < 0.01). When compared with prenormoxic values, SpO2, HR, oxygen consumption, breathing frequency, and end-tidal O2 pressure showed similar changes in HH and NH. CONCLUSION: Lower ventilatory responses to a similar hypoxic stimulus during rest and exercise in HH versus NH were sustained for 24 h and associated with lower plasma pH level, exaggerated oxidative stress, and impaired NO bioavailability.

Interplay between connexin40 and nitric oxide signaling during hypertension.

Connexins (Cxs) and endothelial nitric oxide synthase (eNOS) contribute to the adaptation of endothelial and smooth muscle cells to hemodynamic changes. To decipher the in vivo interplay between these proteins, we studied Cx40-null mice, a model of renin-dependent hypertension which displays an altered endothelium-dependent relaxation of the aorta because of reduced eNOS levels. These mice, which were either untreated or subjected to the 1-kidney, 1-clip (1K1C) procedure, a model of volume-dependent hypertension, were compared with control mice submitted to either the 1K1C or the 2-kidney, 1-clip (2K1C) procedure, a model of renin-dependent hypertension. All operated mice became hypertensive and featured hypertrophy and altered Cx expression of the aorta. The combination of volume- and renin-dependent hypertension in Cx40-/- 1K1C mice raised blood pressure and cardiac weight index. Under these conditions, all aortas showed increased levels of Cx40 in endothelial cells and of both Cx37 and Cx45 in smooth muscle cells. In the wild-type 1K1C mice, the interactions between Cx40 and Cx37 with eNOS were enhanced, resulting in increased NO release. The Cx40-eNOS interaction could not be observed in mice lacking Cx40, which also featured decreased levels of eNOS. In these animals, the volume overload caused by the 1K1C procedure resulted in increased phosphorylation of eNOS and in a higher NO release. The findings provide evidence that Cx40 and Cx37 play an in vivo role in the regulation of eNOS.

L-tyrosine and nitric oxide synergize to prevent cytotoxic effects of superoxide.

We found previously that the nitric oxide donor DEA/NO enhanced lipid peroxidation, DNA fragmentation, and cytotoxicity in human bronchial epithelial cells (BEAS-2B) when they were cultured in LHC-8 medium containing the superoxide-generating system hypoxanthine/xanthine oxidase (HX/XO). We have now discovered that DEA/NO's prooxidant action can be reversed by raising the L-tyrosine concentration from 30 to 400 microM. DEA/NO also protected the cells when they were cultured in Dulbecco's Modified Eagle's Medium (DMEM), whose standard concentration of L-tyrosine is 400 microM. Similar trends were seen with the colon adenoma cell line CaCo-2. Since HPLC analysis of cell-free DMEM or LHC-8 containing 400 microM L-tyrosine, DEA/NO, and HX/XO revealed no evidence of L-tyrosine nitration, our data suggest the existence of an as-yet uncharacterized mechanism by which L-tyrosine can influence the biochemical and toxicological effects of reactive nitrogen species.