The role of γδ T cells in airway epithelial injury and bronchial responsiveness after chlorine gas exposure in mice

BACKGROUND: Acute exposure to chlorine (Cl(2)) gas causes epithelial injury and airway dysfunction. γδ T cells are present in the mucosal surface of the airways and may contribute to the injury/repair response of the epithelium. METHODS: C57Bl/6J (wild type) and TCR-δ(-/- )mice exposed to Cl(2 )(400 ppm) for 5 minutes underwent measurements of airway responses to i.v. methacholine (MCh) at 1, 3, and 5 days after exposure. Bronchoalveolar lavage was performed to determine epithelial and leukocyte counts, and protein content. Tissue repair was assessed by proliferating cell nuclear antigen (PCNA) immunoreactivity and by expression of keratinocyte growth factor (KGF) mRNA by real-time PCR. RESULTS: Wild type mice developed a greater degree of airway hyperresponsiveness to MCh at 1 day post exposure to Cl(2 )compared with TCR-δ(-/- )mice. Epithelial cell counts in BAL after Cl(2 )exposure were greater in TCR-δ(-/- )mice, but macrophages showed a later peak and granulocyte numbers were lower in TCR-δ(-/- )than in wild type mice. Both groups had increased levels of total protein content in BAL after Cl(2 )exposure that resolved after 3 and 5 days, respectively. Epithelial proliferating cell nuclear antigen staining was increased at 1 and 3 days post exposure and was similar in the two groups. KGF mRNA was constitutively expressed in both groups and did not increase significantly after Cl(2 )but expression was lower in TCR-δ(-/- )mice. CONCLUSION: The severity of airway epithelial injury after Cl(2 )is greater in TCR-δ(-/- )mice but the inflammatory response and the change in airway responsiveness to methacholine are reduced. The rates of epithelial regeneration are comparable in both groups

Dissociation of natriuresis and diuresis by oxytocin molecular forms in rats.

In the rat, oxytocin (OT) produces dose-dependent diuretic and natriuretic responses. Post-translational enzymatic conversion of the OT biosynthetic precursor forms both mature and C-terminally extended peptides. The plasma concentrations of these C-terminally extended peptides (OT-G; OT-GK and OT-GKR) are elevated in newborns and pregnant rats. Intravenous injection of OT-GKR to rats inhibits diuresis, whereas injection of amidated OT stimulates diuresis. Since OT and OT-GKR show different effects on the urine flow, we investigated whether OT-GKR modulates renal action by inhibition of the arginine-vasopressin (AVP) receptor V2 (V2R), the receptor involved in renal water reabsorption. Experiments were carried out in the 8-week-old Wistar rats receiving intravenous (iv) injections of vehicle, OT, OT-GKR or OT+OT-GKR combination. OT (10 μmol/kg) increased urine outflow by 40% (P<0.01) and sodium excretion by 47% (P<0.01). Treatment with OT-GKR (10 μmol/kg) decreased diuresis by 50% (P<0.001), decreased sodium excretion by 50% (P<0.05) and lowered potassium by 42% (P<0.05). OT antagonist (OTA) reduced diuresis and natriuresis exerted by OT, whereas the anti-diuretic effect of OT-GKR was unaffected by OTA. The treatment with V2R antagonist (V2A) in the presence and absence of OT induced diuresis, sodium and potassium outflow. V2A in the presence of OT-GKR only partially increased diuresis and natriuresis. Autoradiography and molecular docking analysis showed potent binding of OT-GKR to V2R. Finally, the release of cAMP from CHO cells overexpressing V2 receptor was induced by low concentration of AVP (EC50:4.2e-011), at higher concentrations of OT (EC50:3.2e-010) and by the highest concentrations of OT-GKR (EC50:1.1e-006). OT-GKR potentiated cAMP release when combined with AVP, but blocked cAMP release when combined with OT. These results suggest that OT-GKR by competing for the OT renal receptor (OTR) and binding to V2R in the kidney, induces anti-diuretic, anti-natriuretic, and anti-kaliuretic effects