Prosaposin in the rat oviductal epithelial cells

Proteomics profiling reveals lipid metabolism abnormalities during oogenesis in unexplained recurrent pregnancy loss

Background

Unexplained recurrent pregnancy loss (URPL) is a clinical dilemma in reproductive fields. Its diagnosis is mainly exclusionary after extensive clinical examination, and some of the patients may still face the risk of miscarriage.

Methods

We analyzed follicular fluid (FF) from in vitro fertilization (IVF) in eight patients with URPL without endocrine abnormalities or verifiable causes of abortion and eight secondary infertility controls with no history of pregnancy loss who had experienced at least one normal pregnancy and delivery by direct data-independent acquisition (dDIA) quantitative proteomics to identify differentially expressed proteins (DEPs). In this study, bioinformatics analysis was performed using online software including g:profiler, String, and ToppGene. Cytoscape was used to construct the protein-protein interaction (PPI) network, and ELISA was used for validation.

Results

Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEPs are involved in the biological processes (BP) of complement and coagulation cascades. Apolipoproteins (APOs) are key proteins in the PPI network. ELISA confirmed that APOB was low-expressed in both the FF and peripheral blood of URPL patients.

Conclusion

Dysregulation of the immune network intersecting coagulation and inflammatory response is an essential feature of URPL, and this disequilibrium exists as early as the oogenesis stage. Therefore, earlier intervention is necessary to prevent the development of URPL. Moreover, aberrant lipoprotein regulation appears to be a key factor contributing to URPL. The mechanism by which these factors are involved in the complement and coagulation cascade pathways remains to be further investigated, which also provides new candidate targets for URPL treatment.

Neurotoxic stimulation alters prosaposin levels in the salivary systems of rats

Prosaposin (PSAP), a potent neurotrophic factor, is found in neuronal and non-neuronal tissues and various biological fluids. Neuropathological conditions often alter PSAP production in neural tissues. However, little is known about its alterations in non-neural tissues, particularly in the salivary glands, which are natural reservoirs of various neurotrophic factors. In this study, we explored whether neurotoxic stimulation by kainic acid (KA), a glutamate analog, altered PSAP levels in the salivary system of rats. The results revealed that KA injection did not alter total saliva production. However, KA-induced neurotoxic stimulation significantly increased the PSAP level in the secreted saliva but decreased it in the serum. In addition, KA-induced elevated immunoreactivities of PSAP and its receptors have been observed in the granular convoluted tubule (GCT) cells of the submandibular gland (SMG), a major salivary secretory organ. Indeed, a large number of PSAP-expressing immunogold particles were observed in the secretory granules of the SMG. Furthermore, KA-induced overexpression of PSAP was co-localized with secretogranin in secretory acini (mostly in GCT cells) and the ductal system of the SMG, suggesting the release of excess PSAP from the salivary glands into the oral cavity. In conclusion, the salivary system produces more PSAP during neurotoxic conditions, which may play a protective role in maintaining the secretory function of the salivary glands and may work in distant organs.

Expression patterns of prosaposin and its receptors, G protein-coupled receptor (GPR) 37 and GPR37L1, in the mouse olfactory organ

Prosaposin is a glycoprotein conserved widely in vertebrates, because it is a precursor for saposins that are required for normal lysosomal function and thus for autophagy, and acts as a neurotrophic factor. Most tetrapods possess two kinds of olfactory neuroepithelia, namely, the olfactory epithelium (OE) and the vomeronasal epithelium (VNE). This study examined the expression patterns of prosaposin and its candidate receptors, G protein-coupled receptor (GPR) 37 and GPR37L1, in mouse OE and VNE by immunofluorescence and in situ hybridization. Prosaposin immunoreactivity was observed in the olfactory receptor neurons, vomeronasal receptor neurons, Bowman's gland (BG), and Jacobson's gland (JG). Prosaposin expression was mainly observed in mature neurons. Prosaposin mRNA expression was observed not only in these cells but also in the apical region of the VNE. GPR37 and GPR37L1 immunoreactivities were found only in the BG and/or the JG. Prosaposin was suggested to secrete and facilitate the autophagic activities of the neurons and modulate the mucus secretion in mouse olfactory organ.