Lactate produced during labor modulates uterine inflammation via GPR81 (HCA1).
BACKGROUND
Uterine inflammatory processes trigger prolabor pathways and orchestrate on-time labor onset. Although essential for successful labor, inflammation needs to be regulated to avoid uncontrolled amplification and resolve postpartum. During labor, myometrial smooth muscle cells generate ATP mainly via anaerobic glycolysis, resulting in accumulation of lactate. Aside from its metabolic function, lactate has been shown to activate a G protein-coupled receptor, GPR81, reported to regulate inflammation. We therefore hypothesize that lactate produced during labor may act via GPR81 in the uterus to exert in a feedback manner antiinflammatory effects, to resolve or mitigate inflammation.


OBJECTIVE
We sought to investigate the role of lactate produced during labor and its receptor, GPR81, in regulating inflammation in the uterus.


METHODS
We investigated the expression of GPR81 in the uterus and the pharmacological role of lactate acting via GPR81 during labor, using shRNA-GPR81 and GPR81-/-mice.


RESULTS
(1) Uterine lactate levels increased substantially from 2 to 9 mmol/L during labor. (2) Immunohistological analysis revealed expression of GPR81 in the uterus with high expression in myometrium. (3) GPR81 expression increased during gestation, and peaked near labor. (4) In primary myometrial smooth muscle cell and ex vivo uteri from wild-type mice, lactate decreased interleukin-1β-induced transcription of key proinflammatory Il1b, Il6, Ccl2, and Pghs2; suppressive effects of lactate were not observed in cells and tissues from GPR81-/-mice. (5) Conversely, proinflammatory gene expression was augmented in the uterus at term in GPR81-/-mice and wild-type mice treated intrauterine with lentiviral-encoded shRNA-GPR81; GPR81 silencing also induced proinflammatory gene transcription in the uterus when labor was induced by endotoxin (lipopolysaccharide). (6) Importantly, administration to pregnant mice of a metabolically stable specific GPR81 agonist, 3,5-dihydroxybenzoic acid, decreased endotoxin-induced uterine inflammation, preterm birth, and associated neonatal mortality.


CONCLUSIONS
Collectively, our data uncover a novel link between the anaerobic glycolysis and the control of uterine inflammation wherein the high levels of lactate produced during labor act on uterine GPR81 to down-regulate key proinflammatory genes. This discovery may represent a novel feedback mechanism to regulate inflammation during labor, and conveys a potential rationale for the use of GPR81 agonists to attenuate inflammation and resulting preterm birth.
Department of Pediatrics, Ophthalmology, and Pharmacology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada; Department of Pediatrics and Ophthalmology, Université de Montréal, Montréal, Québec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.
Ankush
A
Madaan
Department of Pediatrics, Ophthalmology, and Pharmacology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada; Department of Pediatrics and Ophthalmology, Université de Montréal, Montréal, Québec, Canada; Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada.
Mathieu
M
Nadeau-Vallée
Maisonneuve-Rosemont Hospital, Research Center, Montreal, Québec, Canada.
Jose Carlos
JC
Rivera
Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada.
Dima
D
Obari
Department of Pediatrics, Ophthalmology, and Pharmacology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada; Department of Pediatrics and Ophthalmology, Université de Montréal, Montréal, Québec, Canada.
Xin
X
Hou
Department of Pediatrics, Ophthalmology, and Pharmacology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada; Department of Pediatrics and Ophthalmology, Université de Montréal, Montréal, Québec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.
Estefania Marin
EM
Sierra
Department of Obstetrics and Gynecology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada.
Sylvie
S
Girard
Departments of Obstetrics and Gynecology, Pediatrics, and Physiology, University of Alberta, Edmonton, Alberta, Canada.
David M
DM
Olson
Department of Pediatrics, Ophthalmology, and Pharmacology, CHU Sainte-Justine Research Center, Montréal, Québec, Canada; Department of Pediatrics and Ophthalmology, Université de Montréal, Montréal, Québec, Canada; Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada; Maisonneuve-Rosemont Hospital, Research Center, Montreal, Québec, Canada. Electronic address: sylvain.chemtob@umontreal.ca.
Sylvain
S
Chemtob
D000818:Animals; D018932:Chemokine CCL2 / Q000187:drug effects / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000235:genetics; D005260:Female; D062385:Hydroxybenzoates / Q000494:pharmacology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007249:Inflammation; D053583:Interleukin-1beta / Q000187:drug effects / Q000235:genetics / Q000494:pharmacology; D015850:Interleukin-6 / Q000235:genetics; D007743:Labor, Obstetric / Q000276:immunology* / Q000378:metabolism; D019344:Lactic Acid / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D018345:Mice, Knockout; D009215:Myometrium / Q000276:immunology* / Q000378:metabolism; D011247:Pregnancy; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000276:immunology; D012118:Resorcinols / Q000494:pharmacology; D014599:Uterus / Q000276:immunology / Q000378:metabolism
C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; C529424:Hcar1 protein, mouse; D062385:Hydroxybenzoates; C587672:IL1B protein, mouse; D053583:Interleukin-1beta; D015850:Interleukin-6; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D012118:Resorcinols; C577686:interleukin-6, mouse; C076950:alpha-resorcylic acid; D019344:Lactic Acid; D051546:Cyclooxygenase 2
CCL2; GPR81; PGHS2; chemokine; chorioamnionitis; cytokine; endotoxin; inflammation; interleukin; interleukin-1; interleukin-6; labor; lactate; lactic acid; lipopolysaccharide; mouse; myometrium; parturition; preterm labor; pyruvate; spontaneous labor