GPR68 and asthma: Indeed, extracellular acidification to around pH 6.3 increased the production of IL-6 and connective tissue growth factor (CTGF), both of which are thought to be involved in the exacerbation of asthma and remodeling of airways, and induced Ca2+ mobilization and cell contraction through OGR1 in human airway smooth muscle cells in vitro [14-16].