D-Lactate Increases Cytokine Production in Bovine Fibroblast-Like Synoviocytes via MCT1 Uptake and the MAPK, PI3K/Akt, and NFκB Pathways

Abstract

Acute ruminal acidosis (ARA) is caused by the excessive intake of highly fermentable carbohydrates, followed by the massive production of D-lactate and the appearance of neutrophilic aseptic polysynovitis. Bovines with ARA develop different lesions, such as ruminitis, polioencephalomalacia (calves), liver abscess and lameness. Lameness in cattle with ARA is closely associated with the presence of laminitis and polysynovitis. However, despite decades of research in bovine lameness as consequence of ruminal acidosis, the aetiology and pathogenesis remain unclear. Fibroblast-like synoviocytes (FLSs) are components of synovial tissue, and under pathological conditions, FLSs increase cytokine production, aggravating inflammatory responses. We hypothesized that D-lactate could induce cytokine production in bovine FLSs. Analysis by qRT-PCR and ELISA revealed that D-lactate, but not L-lactate, increased the expression of IL-6 and IL-8 in a monocarboxylate transporter-1-dependent manner. In addition, we observed that the inhibition of the p38, ERK1/2, PI3K/Akt, and NF-κB pathways reduced the production of IL-8 and IL-6. In conclusion, our results suggest that D-lactate induces an inflammatory response; this study contributes to the literature by revealing a potential key role of D-lactate in the polysynovitis of cattle with ARA.

Role of Lactate in Inflammatory Processes: Friend or Foe

“…The evidence suggest that lactate would be involved in the pathophysiology of lameness in cattle (14). In fact, D-lactic acidosis has been closely associated with the appearance of laminitis and polysynovitis (15)(16)(17)(18)(19).…”

Metabolic Reprogramming and Inflammatory Response Induced by D-Lactate in Bovine Fibroblast-Like Synoviocytes Depends on HIF-1 Activity

“…The results of the study demonstrated that inactivation of the NF-κB pathway strongly decreased mRNA levels of IL-6 induced by Dlactate and bTNF-α in exposed bFLS. Recently, we demonstrated that D-lactate and bTNF-α induced the degradation of IκBα after 30 min of stimulation in bFLS, and treatment with BAY 11-7082 significantly reduced the expression and secretion of IL-6 and IL-8 induced by both stimuli, supporting that the NF-κB pathway is induced by D-lactate in bFLS (23). The NF-κB activity was also shown to be key for the expression of several pro-inflammatory cytokines in bovines, including IL-6, TNF-α, and IL-1β (83)(84)(85)(86)(87).…”

“…Similarly, the inhibition of HIF-1 also significantly decreased extracellular secretion of IL-6 induced by D-lactate and bTNF-α ( Figure 7B ). Since D-lactate and bTNF-α also increased the mRNA expression and secretion of IL-8 ( 23 ), we assessed the involvement of HIF-1 in this pro-inflammatory response. However, preincubation with YC-1 did not decrease the IL-8 expression or secretion ( Supplementary Figure 3 ).…”

“…Consequently, Akt regulates several processes associated with glucose metabolism, including Glut-1 localization to the cell membrane, pentose phosphate shuttle activity, and the activation of various glycolytic enzymes such as HK and phosphofructokinase ( 73 , 74 ). We recently described that D-lactate induced Akt phosphorylation, and inhibition of the PI3K/Akt pathway reduced the mRNA expression and secretion of IL-6 and IL-8 ( 23 ). In the present study, PI3K/Akt pathway inhibition by LY294002 ( 30 ) significantly reduced the mRNA levels of IL-6, HIF-1α, Glut-1, and PDK-1 induced by D-lactate and bTNF-α.…”

“…Bovine FLS (#CDD-B-2910, Articular Engineering, Northbrook, IL, USA) were cultured in sterile 25 cm 2 plastic tissue culture flasks (#70025, SPL Life Sciences, Pocheon-si, Korea) with Dulbecco's Modified Eagle/Ham's F-12 (DMEM/F-12; #12400016, Gibco, Thermo Fischer Scientific, Waltham, MA, USA) supplemented with 10% fetal bovine serum (FBS; #S1810, Biowest, Nuaillé, France) at 37°C under an atmosphere with 5% CO 2 . Cell linage was confirmed by the presence of Vimentin and the absence of CD14, according to Manosalva et al ( 23 ). During passages 3–6, bFLS were cultured in DMEM/F-12 supplemented with 10% FBS in sterile 21.5 cm 2 plastic tissue culture plates (#20060, SPL Life Sciences, Pocheon-si, Korea) for metabolomics and lactate and immunoblot analyses, while sterile 6-well plates (#31006, SPL Life Sciences, Pocheon-si, Korea) were used for reverse transcription-quantitative PCR (RT-qPCR) and ELISA analysis.…”