Lysophosphatidic Acid (LPA) Salivary Species Detection and In Situ LPAR Localization in the Intact Mouse Salivary Gland

Abstract

<b>Abstract ID 25340</b> <b>Poster Board 79</b> Our laboratory has pioneered studying the biology of lysophosphatidic acid (LPA) in oral homeostasis and periodontal disease. LPA is the simplest lipid mediator and plays key homeostatic and inflammatory roles. Saliva is essential for maintaining oral health, and salivary glands are thus pivotal, as they participate in regulating immunity and inflammation, especially in oral disease prevention, oral infection control (Papagerakis et&nbsp;al., 2014), and autoimmunity. Salivary gland secretion and function is also affected by many pharmacological agents. We (Bathena et&nbsp;al. 2011) and others have reported the presence of multiple LPA species in human healthy normal and in periodontal disease saliva. Therefore, we hypothesized that the same LPA species would also be present in mouse saliva, and that mouse salivary glands would also express multiple LPARs. <b>Methods:</b> the simple, sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method we developed in 2011 was used to quantify LPA species (LPA 18:0, LPA 16:0, and LPA 18:1) in C57BL/6 mouse saliva. To further our work, we previously also developed whole-mount <i>in situ</i> LPA receptor (LPAR) subtype localization for various oral soft and hard tissues (Cerutis et&nbsp;al. 2016). Polyclonal antibodies against LPA1, LPA3, and LPA4 were used in indirect immunofluorescence for labeling normal mouse salivary glands using this whole-mount i<i>n situ</i> technique. <b>Results:</b> As we reported for humans, LPA species are also present in low, homeostatic concentrations in mouse saliva. As periodontal disease develops, paralleling what we reported in Bathena et&nbsp;al. (2011) for human saliva, some of the LPA species increase approximately 10-fold as well. Confocal microscopy confirmed LPA1, LPA3, and substantial LPA4 labeling; similar but different patterns of distribution were seen for each GPCR. In conclusion, this confirms LPA1 and LPA3 expression (like in NOD mice, Park et&nbsp;al., (2017) but is the first report of the presence of LPA4 in mouse salivary gland tissue. The presence of multiple confirmed LPARs in mouse salivary glands suggests that these receptors need to be factored into not only studies of autoimmune conditions but also for pharmacological studies of drugs affecting salivary gland biology and secretion. <b>Support:</b> NIDCR/NIGMS 1R15DE028687-01(D.R.C).