Localization and induced release of potentially therapeutic components of the rat submandibular salivary gland

Abstract

The salivary glands release multiple compounds into the saliva and blood that have potentially therapeutic properties. One aim of this study was to localize rat submandibular gland protein SMR1, a prohormone known to contain anti‐inflammatory and analgesic peptides, and compare to the distribution of other known components within the rat submandibular gland (SMG). We also explored the feasibility of releasing SMR1 by local neurostimulation using electrodes. Our hypothesis is that SMR1 would be found in discrete regions of the SMG and could be stimulated to be released into the saliva and blood using localized electrostimulation.Salivary glands serve as a source of multiple compounds that are essential to health. The prohormone SMR1 is an example of such a compound that is present in the rat SMG and is secreted into the saliva or blood as peptides that have been shown to have analgesic and anti‐inflammatory properties. Neuroactivation using systemically applied drugs have been shown to release these and other SMG components. Focused electrode‐based neurostimulation of specific sites of the autonomic system may be a better strategy to more specifically release therapeutic compounds without affecting off‐target systems. Previous studies supported differential release of components from the acini compared to the duct system. In this study we evaluated the tissue distribution of SMR1 compared to other known components of the rat SMG, a major salivary gland.SMGs from young and mature rats were fixed, cryosectioned and immunostained. SMR1 peptides were immunohistologically detected in the serous acinar cells of the rat SMG with heterogeneous distribution within any particular acinus. The location of other components alpha‐amylase, EGF (marker of the tubogranular duct system), lactoferrin, lysozyme, were compared to the location of SMR1. Smooth muscle cell (anti‐smooth muscle actin), neuronal components (anti‐TuJ1, anti‐TH, anti‐ChAT, and anti‐synapsin) were also localized or co‐localized.Neurostimulation of the superior cervical ganglion (SCG) and adjacent nerve trunk by bipolar electrodes induced marked increases in SMR1 content in the saliva as determined by Western blot. We also discovered that placement of the electrode altered the level of peptide secretion. Intriguingly, the electrode stimulation increased levels of SMR1 collected from adjacent blood vessels. These findings set the stage for additional studies to refine the stimulation parameters and to map the SCG innervation of the SMG.Support or Funding InformationSupported by grants from GSK‐GalvaniThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.