Ginger attenuates acetylcholine-induced contraction and Ca2+ signalling in murine airway smooth muscle cells

Asthma is a chronic disease characterized by inflammation and hypersensitivity of airway smooth muscle cells (ASMCs) to different spasmogens. The past decade has seen increased use of herbal treatments for many chronic illnesses. Ginger (Zingiber officinale) is a common food plant that has been used for centuries in treating respiratory illnesses. In this study, we report the effect of its 70% aqueous methanolic crude extract (Zo.Cr) on acetylcholine (ACh)-induced airway contraction and Ca(2+) signalling in ASMCs using mouse lung slices. Airway contraction and Ca(2+) signalling, recorded via confocal microscopy, were induced with ACh, either alone or after pretreatment of slices with Zo.Cr and (or) verapamil, a standard Ca(2+) channel blocker. ACh (10 micromol/L) stimulated airway contraction, seen as decreased airway diameter, and also stimulated Ca(2+) transients (sharp rise in [Ca(2+)]i) and oscillations in ASMCs, seen as increased fluo-4-induced fluorescence intensity. When Zo.Cr (0.3-1.0 mg/mL) was given 30 min before ACh administration, the ACh-induced airway contraction and Ca(2+) signalling were significantly reduced. Similarly, verapamil (1 micromol/L) also inhibited agonist-induced airway contraction and Ca(2+) signalling, indicating a similarity in the modes of action. When Zo.Cr (0.3 mg/mL) and verapamil (1 micromol/L) were given together before ACh, the degree of inhibition was the same as that observed when each of these blockers was given alone, indicating absence of any additional inhibitory mechanism in the extract. In Ca(2+) -free solution, both Zo.Cr and verapamil, when given separately, inhibited Ca(2+) (10 mmol/L)-induced increase in fluorescence and airway contraction. This shows that ginger inhibits airway contraction and associated Ca(2+) signalling, possibly via blockade of plasma membrane Ca(2+) channels, thus reiterating the effectiveness of this age-old herb in treating respiratory illnesses.