Upregulation of airway smooth muscle calcium-sensing receptor by low-molecular-weight hyaluronan.

We investigated the mechanisms involved in the development of airway hyperresponsiveness (AHR) following exposure of mice to halogens. Male mice (C57BL/6; 20-25 g) exposed to either bromine (Br2) or Cl2 (600 or 400 ppm, respectively, for 30 min) developed AHR 24 h after exposure. Nifedipine (5 mg/kg body wt; an L-type calcium channel blocker), administered subcutaneously after Br2 or Cl2 exposure, produced higher AHR compared with Br2 or Cl2 alone. In contrast, diltiazem (5 mg/kg body wt; a nondihydropyridine L-type calcium channel blocker) decreased AHR to control (air) values. Exposure of immortalized human airway smooth muscle cells (hASMC) to Br2 resulted in membrane potential depolarization (Vm Air: 62 ± 3 mV; 3 h post Br2:-45 ± 5 mV; means ± 1 SE; P < 0.001), increased intracellular [Ca2+]i, and increased expression of the calcium-sensing receptor (Ca-SR) protein. Treatment of hASMC with a siRNA against Ca-SR significantly inhibited the Br2 and nifedipine-induced Vm depolarization and [Ca2+]i increase. Intranasal administration of an antagonist to Ca-SR in mice postexposure to Br2 reversed the effects of Br2 and nifedipine on AHR. Incubation of hASMC with low-molecular-weight hyaluronan (LMW-HA), generated by exposing high-molecular-weight hyaluronan (HMW-HA) to Br2, caused Vm depolarization, [Ca2+]i increase, and Ca-SR expression to a similar extent as exposure to Br2 and Cl2. The addition of HMW-HA to cells or mice exposed to Br2, Cl2, or LMW-HA reversed these effects in vitro and improved AHR in vivo. We conclude that detrimental effects of halogen exposure on AHR are mediated via activation of the Ca-SR by LMW-HA.

Effects of granulocyte colony-stimulating factor (G-CSF) and neutrophil elastase inhibitor (ONO-5046) on acid-induced lung injury in rats.

It has been suggested that neutrophils play an important role in acid-aspirated lung injury. We examined the effects of the high dose of granulocyte-colony stimulating factor (G-CSF), which is capable of increasing peripheral neutrophils, and a specific neutrophil elastase inhibitor (ONO-5046) on acid lung injury in rats. Animals were anesthetized and normal saline (NS, 2 mL kg(-1)) or hydrochloric acid (HCl, 0.1 N 2 mL kg(-1)) was then instilled into trachea. Thirty minutes before HCl instillation, G-CSF (150 microg kg(-1)) was injected subcutaneously or ONO-5046 (10 mg kg(-1) h(-1)) was infused continuously into the right jugular vein. Animals were ventilated during the experiments. Five hours after HCl or NS instillation, bronchoalveolar lavage fluid (BALF) and lung tissue samples were obtained. Total nuclear cell count, absorbance, albumin, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, cytokine-induced neutrophil chemoattractant (CINC), neutrophil elastase in BALF, wet-to-dry (W/D) ratio were measured. HCl aspiration markedly increased these values in BALF and W/D ratio. Both ONO-5046 and G-CSF attenuated the parameters increased by acid-induced lung injury in rats. The data suggests that neutrophils play an important role in acid-induced lung injury. However, high-dose G-CSF does not exacerbate acid-aspirated lung injury in rats, although this agent causes an increase in peripheral neutrophils.