Cigarette smoke and its formaldehyde component inhibit bradykinin-induced calcium increase in pig aortic endothelial cells

Formaldehyde impairs transepithelial sodium transport

Unsaturated oxidative formaldehyde is a noxious aldehyde in cigarette smoke that causes edematous acute lung injury. However, the mechanistic effects of formaldehyde on lung fluid transport are still poorly understood. We examined how formaldehyde regulates human epithelial sodium channels (ENaC) in H441 and expressed in Xenopus oocytes and exposed mice in vivo. Our results showed that formaldehyde reduced mouse transalveolar fluid clearance in vivo. Formaldehyde caused a dose-dependent inhibition of amiloride-sensitive short-circuit Na+ currents in H441 monolayers and of αβγ-ENaC channel activity in oocytes. α-ENaC protein was reduced, whereas phosphorylation of the extracellular regulated protein kinases 1 and 2 (ERK1/2) increased significantly post exposure. Moreover, both α- and γ-ENaC transcripts were down-regulated. Reactive oxygen species (ROS) was elevated significantly by formaldehyde in addition to markedly augmented membrane permeability of oocytes. These data suggest that formaldehyde contributes to edematous acute lung injury by reducing transalveolar Na+ transport, through decreased ENaC activity and enhanced membrane depolarization, and by elevating ROS production over long-term exposure.

Cigarette smoke elicits relaxation of renal arteries

BACKGROUND

Epidemiological studies suggest that cigarette smoking - probably by eliciting hyperperfusion - increases glomerular filtration rate; thus, we hypothesized that cigarette smoke affects the vasomotor tone of renal arteries.

MATERIALS AND METHODS

Acute changes in the resistance index of a segmental renal artery were measured in healthy individuals during smoking. In addition, the effects of water-soluble components of cigarette smoke on the isometric tension of isolated rat renal arteries were investigated in various conditions.

RESULTS

In humans, cigarette smoking transiently reduced the resistance index of the renal artery segments (83·25 ± 5·67% of the baseline, P < 0·05). In the experimental model, water-soluble components of cigarette smoke (wCS) - either nicotinic or nicotine-free - elicited dose-dependent relaxations of rat isolated renal arteries (1% solution of nicotinic wCS: 41·18 ± 14·86% relaxation, 5% nicotinic wCS: 79·28 ± 8·91% relaxation, 10% nicotinic wCS 90·3 ± 6·1% relaxation, P < 0·05), which were not affected by removal of the endothelium, or by the soluble guanylate cyclase inhibitor oxadiazolo-quinoxalin-1, or the non specific potassium channel blocker tetraethylammonium, or the K(ATP) channel blocker glibenclamide. However, relaxations were reduced by catalase (1000 U mL⁻¹ catalase + 5% nicotinic wCS: 49·71 ± 18·4%, P < 0·05) and enhanced by superoxide dismutase (200 U mL⁻¹ SOD + 5% nicotinic wCS: 95·7 ± 2·3%, P < 0·05).

CONCLUSIONS

On the basis of these findings, we propose that cigarette smoking could contribute to the increased glomerular filtration rate observed in healthy smokers. In addition, cigarette smoke via hydrogen peroxide mediation reduces vasomotor tone of renal arteries, which could lead to hyperperfusion of kidneys.

Cigarette smoke-induced alterations in endothelial nitric oxide synthase phosphorylation: role of protein kinase C

Endothelial nitric oxide synthase (eNOS) is regulated by phosphorylation of Ser(1177) and Thr(495), which affects NO bioavailability. Cigarette smoke disturbs the eNOS-cGMP-NO pathway and causes decreased NO production. Here the authors investigated the acute effects of cigarette smoke on eNOS phosphorylation, focusing on protein kinases (PKs). Endothelial cell culture was concentration- and time-dependently treated first with cigarette smoke buffer (CSB), then with reduced glutathione (GSH) or various PK inhibitors (H-89, LY-294002, Ro-318425, and ruboxistaurin). eNOS, phospho-Ser(1177)-eNOS, phospho-Thr(495)-eNOS, Akt(PKB), and phospho-Akt protein levels were determined by Western blot. CSB increased the phosphorylation of eNOS at Ser(1177) and more at Thr(495) in a concentration- and time-dependent manner (p < .01, p < .05 versus control, respectively) and resulted in the dissociation of the active dimeric form of eNOS (p < .05). GSH decreased the phosphorylation of eNOS at both sites (p < .05 versus CSB without GSH) and prevented the decrease of dimer eNOS level. CSB treatment also decreased the level of phospho-Ser(473)-Akt (p < .05 versus control). Inhibition of PKA by H-89 did not affect CSB-induced phosphorylation, whereas the PKB inhibitor LY-294002 enhanced it at Ser(1117). The PKC blockers Ro-318425 and ruboxistaurin augmented the CSB-induced phosphorylation at Ser(1177) but decreased phosphorylation at Thr(495) (p < .05 versus CSB). Cigarette smoke causes a disruption of the enzymatically active eNOS dimers and shifts the eNOS phosphorylation to an inhibitory state. Both effects might lead to reduced NO bioavailability. The shift of the eNOS phosphorylation pattern to an inhibitory state seems to be independent of the PKA and phosphoinositol 3-kinase (PI3-K)/Akt pathways, whereas PKC appears to play a key role.