Comparison of Absolute Expression and Turnover Number of COX-1 and COX-2 in Human and Rodent Cells and Tissues

Abstract

Objective We aim to quantify the absolute protein expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in various cells and tissues to determine the relative contribution of COX-1 and COX-2 to PGE 2 production. Methods An LC-MS method was developed and validated, then used for quantifying the absolute amounts of COX-1 and COX-2 in recombinant human COX-1 and COX-2, lysates from different cells, tissue microsomes of rodents and humans, Pirc rat colonic polyps, and biopsy specimens from squamous cell carcinoma (SCC) patients. The COX-1 and COX-2 turnover numbers were subsequently calculated based on apparent formation rates of PGE 2 . Results A robust LC-MS method for quantification of COX-1 and COX-2 was developed and validated and then used to calculate their apparent turnover numbers. The results showed that COX-1 expression levels were much higher than that of COX-2 in all the tested tissues including the colonic epithelium of F344 (28-fold) and Pirc rats (20-fold), colonic polyps of Pirc rats (8-fold), and biopsy specimens of SCC patients (11–17-fold). In addition, both COX-1 and COX-2 were higher in polyps when compared to adjacent mucosa of Pirc rats. The turnover number of recombinant human COX-2 was 14-fold higher than that of recombinant human COX-1. LPS stimulation increased COX-2 protein expression in three cell lines (Raw 264.7, SCC9 and EOMA) as expected but unexpectedly increased COX-1 protein expression (13.8-fold) in EOMA cells. Conclusion In human oral cancer tissues and cells as well as Pirc rat colon, COX-1 plays an unexpectedly but more important role than COX-2 in abnormal PGE 2 production since COX-1 expression is much higher than COX-2. In addition, COX-1 expression levels are inducible in cells, and higher in polyps than surrounding mucosa in Pirc rat colon. These results indicate that targeted suppression of local COX-1 should be considered to reduce colon-specific PGE 2 -mediated inflammation.

The Contribution of Type 2 Diabetes to Parkinson’s Disease Aetiology

“…COX1-regulated prostaglandins are involved in various homeostatic functions throughout the body. COX2-regulated prostaglandins mediate pain and inflammation [432]. Reduced levels of COX 2-regulated prostaglandins are associated with reduced inflammatory cytokine levels and attenuated PD neuroinflammation [433].…”

The crucial role that hippocampus Cyclooxygenase‐2 plays in memory

“…COX‐1 is constitutively expressed in most cells (O'Banion et al, 1992). In contrast, COX‐2 is an inducible enzyme expressed due to pro‐inflammatory stimuli (Ahmed & Gilani, 2011), associated with inflammation and injury response (Li et al, 2022). However, recent studies indicate a greater functional significance of COX‐2 (Ju et al, 2022; Morton & Dongari‐Bagtzoglou, 2001; Zidar et al, 2009).…”

All That Glitters Is Not Gold: Assessment of Bee Pollen Supplementation Effects on Gastric Mucosa

“…Cyclooxygenases (COX) consist of two isoforms, COX-1 and COX-2 [ 14 ]. They are closely related (they share >60% sequence identity) and catalyze the same reaction—the conversion of arachidonic acid to form prostaglandins, including PGD2, PGE2, PGF2α, prostacyclin (PGI2), and thromboxane [ 14 , 15 , 16 , 17 ]. COX-1 is constitutively expressed and it is involved in cytoprotective and regulatory functions in the gastrointestinal mucosa, platelets, kidneys, and the uterus [ 16 ].…”