Changes of Chloride Channels in the Lacrimal Glands of a Rabbit Model of Sjögren Syndrome

Abstract

Purpose To test the hypothesis that expression of Na+-K+-2Cl− co-transporter-1 (NKCC1), cystic fibrosis transmembrane conductance regulator (CFTR), and chloride channel 2 γ subunit (ClC2γ) in the lacrimal glands (LG) of rabbits with induced autoimmune dacryoadenitis (IAD) are changed. Methods LGs were obtained from adult female rabbits with IAD, and age-matched female control rabbits. LGs were processed for laser capture microdissection, real time RT-PCR, western blot, and immunofluorescence. Results In rabbits with IAD, mRNA abundances and protein expressions for NKCC1 and CFTR from whole LGs were significantly lower than in controls. mRNA abundances of NKCC1, CFTR, and ClC2γ from rabbits with IAD were significantly different from acini and ductal cells from controls. NKCC1 was localized to the basolateral membranes of all acinar and ductal cells, with weaker staining intensity in ductal cells, and the staining pattern from rabbits with IAD appeared similar to that from controls. CFTR was found as punctate aggregates in the apical cytoplasm of all acinar and ductal cells, with the intensity in ductal cells much stronger, and no significant difference between controls and rabbits with IAD. ClC2γ was also localized to the apical cytoplasm as punctate aggregates of all acinar cells, but not in ductal cells, and similar staining pattern was observed in rabbits with IAD to control rabbits. Conclusions Our data demonstrated significant changes of mRNA and protein expressions of NKCC1, CFTR, and ClC2γ in rabbits with IAD, suggesting that these changes may contribute to the altered lacrimal secretion, particularly Cl− transport, in rabbits with IAD.

Small‐molecule CFTR activators increase tear secretion and prevent experimental dry eye disease

“…CFTR activators may be particularly suited for disorders of the lacrimal gland, such as primary Sjögren's syndrome, by stimulating fluid transport across the intact corneal and conjunctival epithelia. CFTR activators probably exert their major prosecretory effect at the ocular surface, although there is indirect evidence for CFTR expression and function in lacrimal gland (43)(44)(45)(46). We cannot rule out direct stimulation of lacrimal (or Harderian) secretion by CFTR activators because of possible limited penetration of topically delivered compound to intraorbital glandular tissues.…”

Diverse Mediators Modulate the Chloride Ion Fluxes That Drive Lacrimal Fluid Production

“…They depend on H 2 O transport proteins (aquaporins [AQPs]) [25][26][27] and ion transport proteins [28][29][30][31][32] arrayed in the cells' apical-and basallateral plasma membranes. The ion transport proteins in the acini include Na þ /H þ exchangers (NHE), 29 Cl À /HCO 3 À exchangers (AE), 30 and Na þ -K þ -2Cl À cotransporters (NKCC1) 31 which function in the basal-lateral plasma membranes, Cl À selective channels (ClC3 and CFTR) 32,33 -which function in the apical membranes, 34 and Na þ /K þ exchange pumps (Na,KATPase), which some evidence indicates function in both the apical-and the basal-lateral membranes. 28 The mechanism in the acini secretes Cl À ions into the lumens, thereby generating a negative transepithelial voltage difference; the voltage difference presumably drives Na þ ions into the lumens via the zonulae occludens and zonulae adherens that link adjacent epithelial cells, 35 and the osmotic imbalance that results from the net secretion of Cl À and Na þ draws H 2 O through the epithelium.…”

Role of transmembrane chloride transporters in the fluid secretion of lacrimal gland duct cells

“…More detailed understanding of LG function is therefore essential in order to develop novel approaches in the treatment of dry eye disease (9). Unfortunately, duct cells have been understudied for many years as compared to acinar cells, although recent advances clearly indicated that these duct cells play critical and indispensable roles in LG production (12,13,15,(37)(38)(39). Our laboratory is focusing on the clarification of the role of…”