ABSTRACT
OBJECTIVE@#To investigate the effects of topical administration of cyclosporine A (CsA) on salivary secretion and inflammation of the submandibular glands in non-obese diabetic (NOD) mice.@*METHODS@#Female NOD mice, 21 aged 14 weeks and 18 aged 21 weeks were selected and randomly divided into low-dose group, high-dose group and control group on average. CsA was injected into submandibular glands. One week later the saliva stimulated by pilocarpine was collected and measured. The submandibular glands were collected to make paraffin sections. The lymphocyte infiltration in submandi-bular gland was observed by microscope after hematoxylin-eosin (HE) staining. The number of lymphocyte infiltration foci was counted to calculate the focus sore and the ratio of lymphocyte infiltration area to total gland area was figured up by Leica image analysis system. The expressions of inflammatory cytokines tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-4 (IL-4), IL-13, IL-17F, IL22 and IL-23a in the submandibular glands of the NOD mice were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell apoptosis in the submandibular gland was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The levels of serum creatinine (Scr), blood urea nitrogen (BUN), uric acid (UA), alanine aminotransferase (ALT), aspertate aminotransferase (AST), alkaline phosphatase (ALP), albumin (ALB) and γ-glutamyl transferase (GGT) were measured by automatic biochemical analyzer to evaluate liver and kidney functions.@*RESULTS@#After topical injection of CsA in the submandibular gland, the stimulated salivary flow rate of the 14- and 21-week-old NOD mice significantly increased compared with the control group (P < 0.01 or P < 0.05), and the number and area of lymphocyte infiltration foci in the 14-week-old NOD mice low-dose group significantly decreased compared with the control group (P < 0.01). Low and high dose of CsA had similar effects on reducing inflammation and improving salivary secretion. The overall level of inflammatory cytokines in the submandibular gland did not decrease significantly. The number of cell apoptosis of submandibular gland in the NOD mice treated with CsA decreased compared with the control group, but there was no statistically significant difference. Topical injection of CsA had no adverse effect on liver and kidney function in the NOD mice.@*CONCLUSION@#Topical injection of CsA can reduce lymphocyte infiltration in submandibular gland of NOD mice and improve salivary secretion.
Subject(s)
Animals , Female , Mice , Cyclosporine , Diabetes Mellitus, Experimental/drug therapy , Disease Models, Animal , Inflammation , Mice, Inbred NOD , Saliva , Sjogren's Syndrome , Submandibular GlandABSTRACT
Muscarinic acetylcholine receptors (mAChRs), including M1-M5 subtypes, are classic receptors in regulating water, ion, and solute transport in salivary gland. Our work focuses on the studies on the expression pattern and function of mAChR in the submandibular gland (SMG), and the underlying mechanism involved in the mAChR-regulated secretion, together with the effect of parasympathectomy on the salivary secretion. Microvascular autotransplantation of SMG into the temporal fossa provides a continuous and endogenous source of fluids, and is currently an effective method for treating severe keratoconjunctivitis sicca. By using RT-PCR, Western blotting, and immunofluorescence, our data demonstrated that the expression of M1 and M3 subtypes were decreased in latent period in rabbit SMG autotransplantation model, whereas carbachol stimulation promoted the salivary secretion, as well as M1 and M3 expressions. By contrast, mAChRs were hypersensitive in epiphora SMGs, whereas atropine gel and botulinum toxin A application significantly inhibited the hypersecretion in both animal models and patients. Furthermore, the possible intracellular signal molecules involved in the mAChR-modulated salivary secretion were explored. Activation of mAChR upregulated the expression of aquaporin 5 (AQP5), the main transporter that mediated water secretion through transcellular pathway, and led to AQP5 trafficking from lipid rafts to non-lipid microdomain. Extracellular signal-regulated kinase 1/2 (ERK1/2) was involved in the mAChR-regulated AQP5 content. mAChR activation also modulated the expression, distribution, and function of tight junction proteins, and increased paracellular permeability. ERK1/2/β-arrestin2/clathrin/ubiquitin signaling pathway was responsible for the mAChR-regulated downregulation of tight junction molecule claudin-4. Cytoskeleton filamentous actin (F-actin) was also involved in the distribution and barrier function of epithelial tight junctions. Besides, endothelial tight junctions were opened by mAChR agonist-evoked salivation in the mice. Furthermore, parasympathetic denervation increased resting salivary secretion in the long terminrats and minipigs. Taken together, our work demonstrated that mAChR regulated saliva secretion via transcellular and paracellular pathways in SMG epithelium as well as tight junction opening in SMG endothelium. Modulation of mAChR might be a promising strategy to ameliorate SMG dysfunction.