OATP2A1/SLCO2A1-mediated prostaglandin E₂ loading into intracellular acidic compartments of macrophages contributes to exocytotic secretion

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• 作者：Hiroaki Shimada ; Yoshinobu Nakamura ; Takeo Nakanishi ; ^{nakanish@p.kanazawa-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Ikumi Tamai
• 关键词：BSP ; bromosulfophthalein ; COX ; cyclooxygenase ; EGTA ; ethylene glycol tetra-acetic acid ; LPS ; lipopolysaccharides ; MRP ; multidrug resistance associated protein ; NSAIDs ; non-steroidal anti-inflammatory drugs ; NAG ; N-acetyl-β-d-glucosaminidase ; OATP ; organic anion transporting polypeptide ; PMs ; peritoneal macrophages ; PBS ; phosphate-buffered saline ; PG ; prostaglandin ; 15-PGDH ; 15-hydroxyprostaglandin dehydrogenase ; PGE2 ; prostaglandin E2 ; PGES ; prostaglandin E synthase ; rt ; room temperature ; TGBz
• 刊名：Biochemical Pharmacology
• 出版年：2015
• 出版时间：15 December 2015
• 年：2015
• 卷：98
• 期：4
• 页码：629-638
• 全文大小：1779 K

文摘

There is significant evidence that the inducible cyclooxygenase isoform (COX-2) regulates the pericellular concentration of PGE₂; however, the mechanism of the secretory process remains unclear. The present study, therefore, aimed to evaluate the role of prostaglandin transporter (OATP2A1) in PGE₂ secretion from macrophages. Immunofluorescence staining for Oatp2a1 (Slco2a1) was primarily detected in cytoplasmic domains, and was partially co-localized with anti-PGE₂ antibody, LysoTracker^®, and anti-lysosome-associated membrane protein (Lamp) 1 antibody in murine macrophage-derived RAW264 cells and peritoneal macrophages (PMs). PGE₂ uptake by subcellular fraction containing light lysosomes was reduced significantly in the presence of an OATP inhibitor and in Slco2a1^+/− PMs. Secretion of PGE₂ and lysosome-specific N-acetyl-β-d-glucosaminidase was enhanced in activated macrophagic cells, and diminished significantly under the Ca²⁺-depleted condition. The amount of PGE₂ secreted from lipopolysaccharide-activated Slco2a1^−/− PMs was significantly lower than that from PMs from wild type (WT) mice. Expression of Cox-2 and 15-hydroxyprostaglandin dehydrogenase (15-Pgdh) was unchanged between PMs from Slco2a1^−/− and WT mice. These results suggest that OATP2A1 is involved in PGE₂-loading into intracellular acidic compartments, including light lysosomes. Thus, OATP2A1 contributes to PGE₂ secretion by macrophages via exocytosis induced by Ca²⁺ influx, independently of PGE₂ synthesis and metabolism.