Inhibition of microsomal prostaglandin E-synthase-1 (mPGES-1) selectively suppresses PGE 2 in an in vitro equine inflammation model

Abstract

Inhibition of prostaglandin E2 (PGE2) production effectively limits inflammation in horses, however nonspecific prostaglandin blockade via cyclooxygenase (COX) inhibition elicits deleterious gastrointestinal side effects in equine patients. Thus, more selective PGE2 targeting therapeutics are needed to treat inflammatory disease in horses. One potential target is microsomal prostaglandin E-synthase-1 (mPGES-1), which is the terminal enzyme downstream of COX-2 in the inducible PGE2 synthesis cascade. This enzyme has yet to be studied in equine leukocytes, which play a pivotal role in equine inflammatory disease. The objective of this study was to determine if mPGES-1 is a PGE2-selective anti-inflammatory target in equine leukocytes. To evaluate this objective, leukocyte-rich plasma (LRP) was isolated from equine whole blood collected via jugular venipuncture of six healthy adult horses of mixed breeds and genders. LRP was primed with granulocyte-monocyte colony-stimulating factor (GM-CSF) and stimulated with lipopolysaccharide (LPS) in the presence or absence of an mPGES-1 inhibitor (MF63), a COX-2 inhibitor (NS-398), or a nonselective COX inhibitor (indomethacin). Following treatment, mPGES-1 and COX-2 mRNA and protein levels were measured via qPCR and western blot, respectively, and PGE2, thromboxane (TXA2) and prostacyclin (PGI2) levels were measured in cellular supernatants via ELISA. This study revealed that LPS significantly increased mPGES-1 mRNA, but not protein levels in equine LRP as measured by qPCR and western blot, respectively. In contrast, COX-2 mRNA and protein were coordinately induced by LPS. Importantly, treatment of LPS-stimulated leukocytes with indomethacin and NS-398 significantly reduced extracellular concentrations of multiple prostanoids (PGE2, TXA2 and PGI2), while the mPGES-1 inhibitor MF63 selectively inhibited PGE2 production only. mPGES-1 inhibition also preserved higher basal levels of PGE2 production when compared to either COX inhibitor, which might be beneficial in a clinical setting. In conclusion, this work identifies mPGES-1 as a key regulator of PGE2 production and a PGE2-selective target in equine leukocytes. This study demonstrates that mPGES-1 is a potentially safer and effective therapeutic target for treatment of equine inflammatory disease when compared to traditional non-steroidal anti-inflammatory drugs.

Inhibition of mPGES-1 attenuates efficient resolution of acute inflammation by enhancing CX3CL1 expression

“…Since Cox-2 inhibitors attenuate the production of all prostanoids, we feel confident that the use of a mPGES-1 inhibitor allows delineating the role of PGE 2 more specifically. While mPGES-1 inhibitors were reported to redirect the PGE 2 precursor PGH 2 to other prostanoids in vitro 26 , 43 , we did not observe such shunting in vivo, in line with other reports 44 , 45 . Epithelial CX3CL1 expression further corroborates previous reports, demonstrating that CX3CL1 is produced by peritoneal epithelial upon peritoneal dialysis, where it contributed to a fibrotic phenotype 27 , 46 .…”

Exploring relationships between body condition score, body fat, activity level and inflammatory biomarkers

“…Our PGE 2 values were consistent with those previously published for equine plasma (Martin & Jones, ) and synovial fluid (Frisbie, Al‐Sobayil, Billinghurst, Kawcak, & McIlwraith, ), as were our PL‐GAG (Calatroni, Avenoso, Ferlazzo, Lindner, & Campo, ) and SF‐GAG (Frisbie et al., ). While there was a significant relationship between BCS and FM and FP, the only outcome measures significantly correlated with inflammation biomarkers (i.e., PL‐PGE 2 ) were BCS, AL and BW.…”

Expression of mPGES1 and p16 in feline and human oral squamous cell carcinoma: A comparative oncology approach

“…In the veterinary literature, Kandefer‐Gola et al (2015) found that in canine mast cell carcinoma, a positive relationship between COX‐2 and mPGES1 exists and the authors suggested that mPGES1 inhibitors could be helpful in canine cancer treatment 68 . In an in vitro equine inflammation model, it was found that mPGES1 has an important role in inflammation and the authors indicated that mPGES1 inhibitors as a novel therapy in equine medicine are worthy of clinical trial 69 . Interestingly, mPGES1 Is not well studied in FOSCC, and even though we didn't see evidence for its expression being coupled to COX‐2 expression, it may still be an important driver of inflammation in the FOSCC microenvironment, and more investigations of feline mPGES1 as a potential therapeutic target are justified.…”