DA-6034 Induces [Ca(2+)]i Increase in Epithelial Cells

Conjunctival Fluid Secretion Impairment via CaCC-CFTR Dysfunction Is the Key Mechanism in Environmental Dry Eye

Dry eye disease (DED) is a multifactorial disease with an incidence of approximately 50% worldwide. DED seriously affects quality of life and work. The prevalence of environmental DED (eDED) ranges from 35 to 48%. Conjunctival fluid secretion dysfunction may be one of the major causes of DED. Notably, the Cl^- flux corresponds to the conjunctival fluid secretion and could be affected by ATP. Both the cystic fibrosis transmembrane conductance regulator (CFTR) and the Ca²⁺-activated Cl^- channel (CaCC) are Cl^- channels involved in epithelial fluid secretion. Conjunctival fluid secretion could be increased by activating P2Y₂R (an ATP receptor) in DED. However, the role of the CaCC and CFTR channels regulated by P2Y₂R in eDED remains unclear. In this study, we established a rabbit eDED model using a controlled drying system. A Ussing chamber was used to perform a conjunctival short-circuit current induced by ATP to evaluate the reactivity of the ion channels to the ATP. Our results revealed that eDED accompanied by conjunctival fluid secretion impairment was caused by a P2Y₂R dysfunction, which is related to CaCC-CFTR signaling in the conjunctiva epithelium. Notably, the coupling effect of the ATP-induced CaCC-CFTR activation and intracellular Ca²⁺ may represent a promising therapeutic target for treating eDED.

A phase I study to evaluate the safety, tolerability, pharmacodynamic and pharmacokinetic profiles of ocular GLH8NDE in healthy male adults

GLH8NDE, a derivative of eupatilin, is currently under development to treat dry eye disease. We conducted a randomized, double-masked, placebo-controlled, single- and multiple-day study to evaluate safety, tolerability, pharmacodynamics, and pharmacokinetics of ocular GLH8NDE in healthy male adults. Subjects randomly received topical ocular dosing of GLH8NDE or its matching placebo for a day, then for 7 consecutive days with a 62-h washout at one of the following daily doses: 9, 18, 36 (Koreans), and 36 mg (Whites). The study drug was administered in divided doses over 10 h with 2- or 5-h intervals. Thirty-nine (97.5%) out of 40 subjects completed the study. A total of 17 subjects experienced 31 treatment-emergent adverse events, all of which were mild in severity and recovered without sequelae. Neither pathological changes in eye compartments nor clinically significant systemic effects were observed. GLH8NDE was rapidly absorbed reaching the peak concentration within 0.25-0.75 h postdose. The systemic exposure as measured by area under the concentration-time curve from time of administration up to the time of the last quantifiable concentration (AUC_last ) after single-day administration of the same dose was 109% higher in Koreans than in Whites. In conclusion, GLH8NDE was safe and well-tolerated in healthy Korean and White male adults at 9-36 mg/day after single- and multiple-day administrations.

Hydrogen sulfide: a novel gaseous signaling molecule and intracellular Ca2+ regulator in rat parotid acinar cells

In addition to nitric oxide (NO), hydrogen sulfide (H2S) is recognized as a crucial gaseous messenger that exerts many biological actions in various tissues. An attempt was made to assess the roles and underlying mechanisms of both gases in isolated rat parotid acinar cells. Ductal cells and some acinar cells were found to express NO and H2S synthases. Cevimeline, a muscarinic receptor agonist upregulated endothelial NO synthase in parotid tissue. NO and H2S donors increased the intracellular Ca2+ concentration ([Ca2+]i). This was not affected by inhibitors of phospholipase C and inositol 1,4,5-trisphosphate receptors, but was decreased by blockers of ryanodine receptors (RyRs), soluble guanylyl cyclase, and protein kinase G. The H2S donor evoked NO production, which was decreased by blockade of NO synthases or phosphoinositide 3-kinase or by hypotaurine, an H2S scavenger. The H2S donor-induced [Ca2+]i increase was diminished by a NO scavenger or the NO synthases blocker. These results suggest that NO and H2S play important roles in regulating [Ca2+]i via soluble guanylyl cyclase-cGMP-protein kinase G-RyRs, but not via inositol 1,4,5-trisphosphate receptors. The effect of H2S may be partially through NO produced via phosphoinositide 3-kinase-Akt-endothelial NO synthase. It was concluded that both gases regulate [Ca2+]i in a synergistic way, mainly via RyRs in rat parotid acinar cells.

Helicobacter pylori γ-glutamyl transpeptidase-induced Ca(2+) release via PLC-IP3 receptors in AGS cells

In our previous study, γ-glutamyl transpeptidase (GGT) isolated from Helicobacter pylori induced apoptosis of AGS cells. Here, we investigate Ca(2+) effects on GGT-induced apoptosis. The GGT transiently and significantly increased intracellular Ca(2+) concentration ([Ca(2+)]i) in AGS cells in a dose-dependent manner (P < 0.05). The GGT-induced Ca(2+) increase resulted from Ca(2+) influx and release through the phospholipase C - inositol 1,4,5-trisphosphate (PLC-IP3) pathway. The GGT-induced apoptosis was significantly reduced by treatment with U73122 (a PLC inhibitor) and xestospongin (an IP3 receptor antagonist) (P < 0.05). These results indicate that GGT could induce apoptosis of AGS cells by high levels of [Ca(2+)]i.