Palmitic acid activates NLRP3 inflammasome and induces placental inflammation during pregnancy in mice

Abstract

23Maternal obesity is one of the major risk factors for pregnancy complications and is associated with 24 low-grade chronic systemic inflammation due to higher levels of pro-inflammatory cytokines such 25 as interleukin (IL)-1β. Pregnant women with obesity have abnormal lipid profiles, characterized by 26 higher levels of free fatty acids, especially palmitic acid (PA). Previously, we reported that PA 27 stimulated IL-1β secretion via activation of NLRP3 inflammasome in human placental cells. These 28 observations led us to hypothesize that higher levels of PA induce NLRP3 inflammasome activation 29 and placental inflammation, resulting in pregnancy complications. However, the effects of PA on 30 NLRP3 inflammasome during pregnancy in vivo remain unclear. Therefore, PA solutions were 31 administered intravenously into pregnant mice on day 12 of gestation. Maternal body weight was 32 significantly decreased and absorption rates were significantly higher in PA-injected mice. The 33 administration of PA significantly increased IL-1β protein and the mRNA expression of NLRP3 34 inflammasome components (NLRP3, ASC, and caspase-1) within the placenta. In murine placental 35 cell culture, PA significantly stimulated IL-1β secretion, and this secretion was suppressed by a 36 specific NLRP3 inhibitor (MCC950). Simultaneously, the number of macrophages/monocytes and 37 neutrophils, together with the mRNA expression of these chemokines increased significantly in the 38 placentas of PA-treated mice. Treatment with PA induced ASC assembling and IL-1β secretion in 39 macrophages, and this PA-induced IL-1β secretion was significantly suppressed in NLRP3-knockout 40 macrophages. These results indicate that transient higher levels of PA exposure in pregnant mice 41 activates NLRP3 inflammasome and induces placental inflammation, resulting in the incidence of 42 absorption. 43 44 48 is a low-grade chronic systemic inflammation and associated with insulin resistance, cardiovascular 49 diseases, and diabetes [3]. Pregnant women with obesity are associated with elevated serum levels of 50 pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α, 51compared to pregnant women with normal weight [4][5][6][7]. Pregnant women with obesity have 52 abnormal lipid profiles, characterized by higher levels of free fatty acids (FFAs) [8, 9]. It has been 53 reported that palmitic acid (PA), the most abundant saturated FFAs in the blood, promotes 54 inflammatory responses by directly engaging toll-like receptors (TLR), and inducing nuclear factor-55 κB (NF-κB)-dependent production of inflammatory cytokines [10, 11]. Previously, we reported that 56 PA caused inflammatory cytokine secretion, inducing IL-1β, IL-6, and IL-8 in human placental cells 57 [12], suggesting that obesity-related PA accumulation induces placental inflammation. 58Recently, there have been numerous reports of inflammasome mechanisms that control 59 sterile inflammation involved in pregnancy pathologies [13][14][15][16]. Inflammasomes are l...

Long Chain Fatty Acids as Modulators of Immune Cells Function: Contribution of FFA1 and FFA4 Receptors

“…Wanten et al, 2002;Khan et al, 2018;Tam et al, 2020 ↑ adhesion, apoptosis, NLRP3, NO, IL-1β, IL-6, TNF-α, NF-κB, JNK, MKK4/7, IL-10, CCL2, IFN-γ M1 polarization, CD36; ↓ phagocytosis in macrophages. Calder et al, 1990a;de Lima et al, 2006;Kim et al, 2017;Lu et al, 2017;Wang et al, 2017Wang et al, , 2021Karasawa et al, 2018;Lancaster et al, 2018;Korbecki and Bajdak-Rusinek, 2019;Fu et al, 2020;Sano et al, 2020;Youk et al, 2021 Synthetic agonist GW9508 ↑ ROS, MMP-9, COX-2, IL-8, chemotaxis in neutrophils. Hidalgo et al, 2011;Manosalva et al, 2015;Mena et al, 2016;Souza et al, 2020 ↑ PLC, PLA2, AMPK, AA; ↓ IL-6 in macrophages.…”

“…Numerous studies exist detailing the pro-inflammatory effects of palmitic acid on macrophages (Kim et al, 2017 ; Wang et al, 2017 ; Karasawa et al, 2018 ; Korbecki and Bajdak-Rusinek, 2019 ; Sano et al, 2020 ; Youk et al, 2021 ). High-fat diet (HFD) may promote hepatocarcinogenesis through an exacerbated inflammatory response that affects the liver function.…”

“…In vivo experiments demonstrated that HFD affected liver function in mice, induced liver infiltration of macrophages, and increased expression of inflammatory factors, such as proliferating cell nuclear antigen (PCNA), NF-κB, cyclin D1, TNF-α, and IL-1β in the liver (Fu et al, 2020 ). In addition, to understand the link between obesity and inflammation, and its effects in pregnancy, Sano et al ( 2020 ) studied the in vivo and in vitro effects of palmitic acid in pregnant mice. The authors observed that palmitic acid induced ASC assembly and IL-1β release in murine macrophages.…”

Gestational Diabetes Mellitus and Maternal Immune Dysregulation: What We Know So Far

“…MCC950, a specific inhibitor of the NLRP3 inflammasome predominantly expressed in macrophages, reduces IL-1β and IL-18 expression by blocking inflammasome assembly and caspase-1 activation [ 179 ]. In murine models of obese, hyperglycaemic pregnancies, MCC950 successfully supressed lipid-induced hyperactivation of the NLRP3 inflammasome in placental cultures [ 180 ]. MCC950 also reduced cholesterol crystal-induced IL-1β response in explants cultures of human placental tissue, demonstrating attenuation of NLRP3-mediated placental inflammation [ 181 ].…”

Advanced maternal age induces fetal growth restriction through decreased placental inflammatory cytokine expression and immune cell accumulation in mice

“…To analyze the populations of inflammatory cells within the placental tissue and spleen of pregnant mice, the mice were sacrificed under general anesthesia. Placental and splenic cells were isolated from mice, as described previously [30,31]…”