Genomic and lipidomic analyses differentiate the compensatory roles of two COX isoforms during systemic inflammation in mice

Synthesis of new multitarget-directed ligands containing thienopyrimidine nucleus for inhibition of 15-lipoxygenase, cyclooxygenases, and pro-inflammatory cytokines

A new series of thieno[2,3-d]pyrimidine derivatives 4, 5, 6a-o, and 11 was designed and synthesized starting from cyclohexanone under Gewald condition with the aim to develop multitarget-directed ligands (MTDLs) having anti-inflammatory properties against both 15-LOX and COX-2 enzymes. Moreover, the potential of the compounds against the proinflammatory mediators NO, ROS, TNF-α, and IL-6 were tested in LPS-activated RAW 264.7 macrophages. Compound 6o showed the greatest 15-LOX inhibitory effect (IC50 = 1.17 μM) which was superior to that of the reference nordihydroguaiaretic acid (NDGA, IC50 = 1.28 μM); meanwhile, compounds 6h, 6g, 11, and 4 exhibited potent activities (IC50 = 1.29-1.77 μM). The ester 4 (SI = 137.37) and the phenyl-substituted acetohydrazide 11 (SI = 132.26) showed the highest COX-2 selectivity, which was about 28 times more selective than the reference drug diclofenac (SI = 4.73), however, it was lower than that of celecoxib (SI = 219.25). Interestingly, compound 6o, which showed the highest 15-LOX inhibitory activity and 5 times higher COX-2 selectivity than diclofenac, showed a greater poteny in reducing NO (IC50 = 7.77 μM) than both celecoxib (IC50 = 22.89 μM) and diclofenac (IC50 = 25.34), but comparable activity in inhibiting TNF-α (IC50 = 11.27) to diclofenac (IC50 = 10.45 μM). Similarly, compounds 11 and 6h were more potent in reducing TNF-α and IL6 levels than diclofenac, meanwhile, compound 4 reduced ROS, NO, IL6, and TNF-α levels with comparable potency to the reference drugs celecoxib and diclofenac. Furthermore, docking studies for our compounds within 15-LOX and COX-2 active sites revealed good agreement with the biological evaluations. The proposed compounds could be promising multi-targeted anti-inflammatory candidates to treat resistant inflammatory conditions.

Marrubium persicum İmproved the Biological Parameters Associated with Angiogenesis and İnflammation in Mice

The genus Marrubium, belonging to the family Lamiaceae, is highly praised in herbal medicine of different countries for having renowned healing properties. Herein, the anti-inflammatory and anti-angiogenesis potential of Marrubium persicum methanol extract was evaluated in a mouse air pouch model of inflammation. Aerial parts of M. persicum were solvent extracted using the Soxhlet apparatus. Subsequently, air injections were performed (for 3 days) into the mice's backs to bring about an air pouch, while carrageenan was used to induce inflammation. The mice were divided into four groups, including; negative control (normal saline into the pouch), control (carrageenan), treatment and positive control (dexamethasone). The inflammatory markers were analyzed 48h after injecting carrageenan, and a haemoglobin assay kit assessed the quantification of angiogenesis in granulation tissue. M. persicum methanol extract at doses of 3.5, 5, 7.5 and 10 mg/kg represented significant decreases in inflammatory parameters. Compared to the control group, the optimum dose (3.5 mg/kg) lessened the myeloperoxidase (MPO) and angiogenesis activity, as well as haemoglobin levels. In sum, the methanol extract of M. persicum exhibited anti-inflammatory effects against carrageenan-induced inflammation, which could be related to its antioxidant and inhibitory effects on neutrophils' infiltration.

Hydroxytriazenes incorporating sulphonamide derivatives: evaluation of antidiabetic, antioxidant, anti-inflammatory activities, and computational study

The existent investigation deals with synthesis, characterization, computational analysis, and biological activities of some hydroxytriazene derivatives containing sulphonamide moiety. The compounds were screened for antidiabetic, antioxidant, and anti-inflammatory activities. The antidiabetic activity was assessed using α-glucosidase and α-amylase inhibition assays with IC₅₀ values ranging from 32.0 to 759.13 μg/mL and 157.77 to 340.47 μg/mL while standard drug acarbose showed IC₅₀ values 12.21 and 69.74 μg/mL, respectively. The antioxidant activity was evaluated using DPPH and ABTS radical scavenging assays with IC₅₀ value ranging from 54.01 to 912.66 μg/mL and 33.22 to 128.11 μg/mL, and standard drug ascorbic acid showed IC₅₀ values 29.12 μg/mL and 69.13 μg/mL, respectively. Anti-inflammatory activity was investigated using the carrageenan-induced paw edema method, where percentage inhibition was up to 93.0 and 98.57 for 2 h and 4 h, respectively, and all the compounds were found to exhibit excellent anti-inflammatory activity. Moreover, prediction of activity spectra for substance and molecular docking were also performed. The PASS prediction hypothesized the potential of the compounds for anti-inflammatory activity, and docking results suggested the best binding pose for compounds 1b and 2b with the least energy value from which compounds can be considered as potent COX-2 inhibitors. Furthermore, possible interactions between hydroxytriazene analogues and the targets of antioxidant NADPH oxidase and antidiabetic human maltase-glucoamylase enzyme have been identified. The HOMO and LUMO analysis revealed charge transfer within the compounds. These findings suggested that the synthesized compounds can be potential agents for the treatment of diabetes and inflammation.

Bioactive substances inhibiting COX-2 and cancer cells isolated from the fibrous roots of Alangium chinense (Lour.) Harms

Alangium chinense has been used as a traditional folk medicine for centuries to treat rheumatism, skin diseases, and diabetes by the people of Southeast Asia. However, the bioactive constituents inhibiting COX-2 and cancer cells (HepG2, Caco-2, HeLa) remain unclear. In this study one new (14) along with twenty-four known compounds (1-13, 15-25) were isolated from the fibrous roots of Alangium chinense by chromatographic methods, and identified by NMR, and Gaussian and CD calculation. Compounds 1, 2, 13, 16, 17, 19, 20, 23, and 24 were isolated from this plant for the first time. Their inhibition effects on COX-2 enzyme and cancer cells were evaluated by MTT assay. Compounds 1-4, 13-14, and 16-18 can be used as good inhibitors against COX-2 enzyme, and compounds 1, 13, 14, and 17 were stronger than the positive control (celecoxib). In addition, molecular docking suggested that compounds 13, 17, and 18 belong to ellagic acids and have good inhibition against COX-2 enzyme. While compounds 1, 5, 13 and 21 showed cytotoxicity against HepG2 cells, compounds 2 and 21 showed cytotoxicity against Caco-2 cells, and compound 20 showed cytotoxicity against HeLa cells.

Network pharmacology and in vivo experiments reveal the pharmacological effects and molecular mechanisms of Simiao Powder in prevention and treatment for gout

Background

Gout is a common disease with high incidence due to unhealthy diet and living habits. Simiao Powder, as a classic formula consisted of four common herbs, has been widely used in clinical practice since ancient times to prevent and treat gout. However, the pharmacological mechanism of Simiao Powder is still unclear.

Methods

Based on network pharmacology, Simiao Powder active compounds were identified in TCMSP, ETCM and BATMAN database, used to establish a network of interaction between potential targets of Simiao Powder and known therapeutic targets of gout. Subsequently, the key potential targets are being used for protein–protein interaction, GO enrichment analysis and KEGG pathway enrichment analysis through several authoritative open databases. Molecular docking through AutoDockTools software can verify interaction between molecules. Finally, to validate the predicted results, in vivo experiments based on hyperuricemic-gout mice model were designed and treated with Simiao powder and allopurinol. Serum levels of uric acid (UA), creatinine (Cr), blood urea nitrogen (BUN) and xanthine oxidase (XOD) were determined using a customized assay kit while the expression of PPAR-γ, PTGS1, IL-6 and Bcl2 mRNA were analyzed through qRT-PCR.

Results

Disease-target-compound network was visualized basing on the 20 bioactive compounds and the 19 potential targets using Cytoscape software. The results of PPI analysis, GO enrichment and KEGG pathway enrichment analysis indicate that the potential mechanism of Simiao Powder in treating gout may be achieved by regulating immune and inflammatory reactions, improving metabolism and endocrine. The results of molecular docking show that most of the targets and components have good binding activity. In vivo experiments revealed that Simiao powder can decreased serum UA and XOD levels in hyperuricemic-gout mice, and improved renal function. Furthermore, Simiao powder certainly regulates the expression of PPAR-γ, PTGS1, IL-6 and Bcl2 mRNA in ankle tissue in hyperuricemic-gout mice.

Conclusion

Collectively, this research predicted a multiple compounds, targets, and pathways model mechanism of Simiao Powder in the prevention and treatment of gout, providing new ideas and methods for in-depth research, via vivo experiments.

Increased COX-1 expression in benign prostate epithelial cells is triggered by mitochondrial dysfunction

BACKGROUND

Prostatic inflammation is closely linked to the development and progression of benign prostatic hyperplasia (BPH). Clinical studies of non-steroidal anti-inflammatory drugs, which inhibit cyclooxygenase-2 (COX-2), targeting prostate inflammation patients with symptomatic BPH have demonstrated conflicting results, with some studies demonstrating symptom improvement and others showing no impact. Thus, understanding the role of the cyclooxygenases in BPH and prostatic inflammation is important.

METHODS

The expression of COX-1 was analyzed in a cohort of donors and BPH patients by immunohistochemistry and compared to previously determined characteristics for this same cohort. The impact of mitochondrial dysfunction on COX-1 and COX-2 was determined in experiments treating human benign prostate epithelial cell lines BPH-1 and RWPE-1 with rotenone and MitoQ. RWPE-1 cells were transfected with small interfering RNA specific to complex 1 gene NDUFS3.

RESULTS

COX-1 expression was increased in the epithelial cells of BPH specimens compared to young healthy organ donor and normal prostate adjacent to BPH and frequently co-occurred with COX-2 alteration in BPH patients. COX-1 immunostaining was associated with the presence of CD8+ cytotoxic T-cells, but was not associated with age, prostate size, COX-2 or the presence of CD4+, CD20+ or CD68+ inflammatory cells. In cell line studies, COX protein levels were elevated following treatment with inhibitors of mitochondrial function. MitoQ significantly decreased mitochondrial membrane potential in RWPE-1 cells. Knockdown of NDUFS3 stimulated COX-1 expression.

CONCLUSION

Our findings suggest COX-1 is elevated in BPH epithelial cells and is associated with increased presence of CD8+ cytotoxic T-cells. COX-1 can be induced in benign prostate epithelial cells in response to mitochondrial complex I inhibition, and knockdown of the complex 1 protein NDUFS3. COX-1 and mitochondrial dysfunction may play more of a role than previously recognized in the development of age-related benign prostatic disease.

Signaling Pathways Mediating Bradykinin-Induced Contraction in Murine and Human Detrusor Muscle

Bradykinin (BK) has been proposed to modulate urinary bladder functions and implicated in the pathophysiology of detrusor overactivity. The present study aims to elucidate the signaling pathways of BK-induced detrusor muscle contraction, with the goal of better understanding the molecular regulation of micturition and identifying potential novel therapeutic targets of its disorders. Experiments have been carried out on bladders isolated from wild-type or genetically modified [smooth muscle-specific knockout (KO): Gαq/11-KO, Gα12/13-KO and constitutive KO: thromboxane prostanoid (TP) receptor-KO, cyclooxygenase-1 (COX-1)-KO] mice and on human bladder samples. Contractions of detrusor strips were measured by myography. Bradykinin induced concentration-dependent contractions in both murine and human bladders, which were independent of secondary release of acetylcholine, ATP, or prostanoid mediators. B2 receptor antagonist HOE-140 markedly diminished contractile responses in both species, whereas B1 receptor antagonist R-715 did not alter BK's effect. Consistently with these findings, pharmacological stimulation of B2 but not B1 receptors resembled the effect of BK. Interestingly, both Gαq/11- and Gα12/13-KO murine bladders showed reduced response to BK, indicating that simultaneous activation of both pathways is required for the contraction. Furthermore, the Rho-kinase (ROCK) inhibitor Y-27632 markedly decreased contractions in both murine and human bladders. Our results indicate that BK evokes contractions in murine and human bladders, acting primarily on B2 receptors. Gαq/11-coupled and Gα12/13-RhoA-ROCK signaling appear to mediate these contractions simultaneously. Inhibition of ROCK enzyme reduces the contractions in both species, identifying this enzyme, together with B2 receptor, as potential targets for treating voiding disorders.

Traditional Chinese Medicine Aconiti Radix Cocta Improves Rheumatoid Arthritis via Suppressing COX-1 and COX-2

According to Traditional Chinese Medicine (TCM), Aconiti Radix Cocta (AC) is clinically employed to expel wind, remove dampness, and relieve pain. We evaluated the antirheumatoid arthritis (RA) activities and underlying mechanisms of AC. The chemical constituents of AC were analyzed by high-performance liquid chromatography (HPLC) using three reference compounds (benzoylaconitine, benzoylmesaconine, and benzoylhypacoitine). The anti-RA effects of AC were evaluated in adjuvant-induced arthritis (AIA) rats by hind paw volume and histopathological analysis. The effects of AC on inflammatory cytokines (IL-1β and IL-17A) were determined by enzyme-linked immunosorbent assay. The regulation of cyclooxygenases (COX-1 and/or COX-2) was determined by Western blot and real-time quantitative reverse transcription polymerase chain reaction analyses. AC significantly reduced paw swelling, attenuated the inflammation and bone destruction in joint tissues, and reduced IL-1β and IL-17A in the serum. Moreover, AC downregulated the expression of COX-1 and COX-2 in the synovial tissues. We also identified that AC possesses significant anti-RA activities on AIA, which may be ascribed to the regulation of inflammatory cytokines IL-1β and IL-17, as well as to the inhibition of arachidonic acid signaling pathways. Our findings provide theoretical support for AC as an effective nature-derived therapeutic agent for RA treatment.

Identification of Potential Bioactive Ingredients and Mechanisms of the Guanxin Suhe Pill on Angina Pectoris by Integrating Network Pharmacology and Molecular Docking

The Guanxin Suhe pill (GSP), a traditional Chinese medicine, has been widely used to treat angina pectoris (AP) in Chinese clinical practice. However, research on the bioactive ingredients and underlying mechanisms of GSP in AP remains scarce. In this study, a system pharmacology approach integrating gastrointestinal absorption (GA) evaluation, drug-likeness (DL) evaluation, target exploration, protein-protein-interaction analysis, Gene Ontology (GO) enrichment analysis, network construction, and molecular docking was adopted to explore its potential mechanisms. A total of 481 ingredients from five herbs were collected, and 242 were qualified based on GA and DL evaluation. Target exploration identified 107 shared targets between GSP and AP. Protein-protein interaction identified VEGFA (vascular endothelial growth factor A), TNF (tumor necrosis factor), CCL2 (C-C motif chemokine ligand 2), FN1 (fibronectin 1), MMP9 (matrix metallopeptidase 9), PTGS2 (prostaglandin-endoperoxide synthase 2), IL10 (interleukin 10), CXCL8 (C-X-C motif chemokine ligand 8), IL6 (interleukin 6), and INS (insulin) as hub targets for GSP, which were involved in the inflammatory process, ECM proteolysis, glucose metabolism, and lipid metabolism. GO enrichment identified top pathways in the biological processes, molecular functions, and cell components, explaining GSP's potential AP treatment mechanism. Positive regulation of the nitric oxide biosynthetic process and the response to hypoxia ranked highest of the biological processes; core targets that GSP can regulate in these two pathways were PTGS2 and NOS2, respectively. Molecular docking verified the interactions between the core genes in the pathway and the active ingredients. The study lays a foundation for further experimental research and clinical application.

Mechanism of Shuang-Huang-Lian Oral Liquid for Treatment of Mycoplasmal Pneumonia in Children on Network Pharmacology

BACKGROUND AND OBJECTIVE

Mycoplasmal pneumonia (MP) can lead to inflammation, multiple system immune damage, and mixed infection in children. The pathogenesis is still unclear. Shuang-Huang-Lian (SHL) oral liquid can treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. However, our current understanding of the molecular mechanisms supporting its clinical application still lags behind due to the lack of researches. It is difficult to understand the overall sensitization mechanism of SHL oral liquid. The purpose is to explain the mechanism of action of drugs in this study, which is useful to ensure the safety of medication for children.

METHODS

The therapeutic mechanism of SHL oral liquid was investigated by a system pharmacology approach integrating drug-likeness evaluation, oral bioavailability prediction, ADMET, protein-protein interaction worknet, Gene Ontology enrichment analysis, Kyoto Encyclopedia of Genes and Genomes database pathway performance, C-T-P network construction and molecular docking.

RESULTS

A total of 18 active ingredients contained in SHL oral liquid and 53 major proteins were screened out as effective players in the treatment of M. pneumoniae disease through some related pathways and molecular docking. The majority of targets, hubs and pathways were highly related to anti-mycoplasma therapy, immunity and inflammation process.

CONCLUSION

This study shows that the anti-bacterial effect of SHL oral liquid has multicomponent, multi-target and multi-pathway phenomena. The proposed approach may provide a feasible tool to clarify the mechanism of traditional Chinese medicines and further develop their therapeutic potentials.

Synthesis, Inhibitory Activity, and In Silico Modeling of Selective COX-1 Inhibitors with a Quinazoline Core

Selective cyclooxygenase-1 (COX-1) inhibition has got into the spotlight with the discovery of COX-1 upregulation in various cancers and the cardioprotective role of COX-1 in control of thrombocyte aggregation. Yet, COX-1-selective inhibitors are poorly explored. Thus, three series of quinazoline derivatives were prepared and tested for their potential inhibitory activity toward COX-1 and COX-2. Of the prepared compounds, 11 exhibited interesting COX-1 selectivity, with 8 compounds being totally COX-1-selective. The IC50 value of the best quinazoline inhibitor was 64 nM. The structural features ensuring COX-1 selectivity were elucidated using in silico modeling.

Effect of celecoxib in treatment of burn-induced hypermetabolism

Background: Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step of prostanoid biosynthesis. Under pathologic conditions, COX-2 activity can produce reactive oxygen species and toxic prostaglandin metabolites that exacerbate injury and metabolic disturbance. The present study was performed to investigate the effect of Celecoxib (the inhibitor of COX-2) treatment on lipolysis in burn mice.

Methods: One hundred male BALB/c mice were randomly divided into sham group, burn group, celecoxib group, and burn with celecoxib group (25 mice in each group). Thirty percent total body surface area (TBSA) full-thickness injury was made for mice to mimic burn injuries. Volume of oxygen uptake (VO₂), volume of carbon dioxide output (VCO₂), respiratory exchange ratio (RER), energy expenditure (EE), COX-2 and uncoupled protein-1 (UCP-1) expression in brown adipose tissue (BAT) were measured for different groups.

Results: Adipose tissue (AT) activation was associated with the augmentation of mitochondria biogenesis, and UCP-1 expression in isolated iBAT mitochondria. In addition, VO₂, VCO₂, EE, COX-2, and UCP-1 expression were significantly higher in burn group than in burn with celecoxib group (P<0.05).

Conclusion: BAT plays important roles in burn injury-induced hypermetabolism through its morphological changes and elevating the expression of UCP-1. Celecoxib could improve lipolysis after burn injury.

COX-2 in liver fibrosis

As a vital inducible sensor, cyclooxygenase-2 (COX-2) plays an important role in the progress of hepatic fibrogenesis. Activation of hepatic stellate cells (HSCs) in the liver can significantly accelerate the onset and development of liver fibrosis. COX-2 overexpression triggers inflammation that is an important inducer in hepatic fibrosis. Increasing evidence indicates that COX-2 is involved in the main pathogenesis of liver fibrosis, such as inflammation, apoptosis, and cell senescence. Moreover, COX-2 expression is altered in patients and animal models with non-alcoholic fatty liver disease or cirrhosis. These findings suggest that COX-2 has a broad and critical role in the development of liver fibrosis. In this review, we summarize the latest advances in the regulation and signal transduction of COX-2 and its impact on liver fibrosis.

Deciphering the Active Compounds and Mechanisms of Qixuehe Capsule on Qi Stagnation and Blood Stasis Syndrome: A Network Pharmacology Study

BACKGROUND

Qixuehe capsule (QXH), a Chinese patent medicine, has been demonstrated to be effective in the treatment of menstrual disorders. In traditional Chinese medicine (TCM) theory, qi stagnation and blood stasis syndrome (QS-BSS) is the main syndrome type of menstrual disorders. However, the pharmacodynamic effect of QXH in treating QS-BSS is not clear, and the main active compounds and underlying mechanisms remain unknown.

METHODS

A rat model of QS-BSS was established to evaluate the pharmacodynamic effect of QXH. Thereafter, a network pharmacology approach was performed to decipher the active compounds and underlying mechanisms of QXH.

RESULTS

QXH could significantly reduce the rising whole blood viscosity (WBV) and plasma viscosity (PV) but also normalize prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and fibrinogen (FIB) content in QS-BSS rats. Based on partial least-squares-discriminant analysis (PLS-DA), the low-dose QXH-intervened (QXH-L) and the high-dose QXH-intervened (QXH-H) groups seemed the most effective by calculating the relative distance to normality. Through network pharmacology, QXH may improve hemorheological abnormality mainly via 185 compounds-51 targets-28 pathways, whereas 184 compounds-68 targets-28 pathways were associated with QXH in improving coagulopathy. Subsequently, 25 active compounds of QXH were verified by UPLC-Q/TOF-MS. Furthermore, 174 active compounds of QXH were shared in improving hemorheological abnormality and coagulopathy in QS-BSS, each of which can act on multiple targets to be mainly involved in complement and coagulation cascades, leukocyte transendothelial migration, PPAR signaling pathway, VEGF signaling pathway, and arachidonic acid metabolism. The attribution of active compounds indicated that Angelicae Sinensis Radix (DG), Paeoniae Radix Rubra (CS), Carthami Flos (HH), Persicae Semen (TR), and Corydalis Rhizoma (YHS) were the vital herbs of QXH in treating QS-BSS.

CONCLUSION

QXH can improve the hemorheology abnormality and coagulopathy of QS-BSS, which may result from the synergy of multiple compounds, targets, and pathways.

The anti-inflammatory influence of Cinnamomum burmannii against multi-walled carbon nanotube-induced liver injury in rats

Carbon nanotubes (CNTs) are extensively used in nanotechnology due to their unique physico-chemical properties. CNTs were implicated in many disorders connected with human health. So, we aimed in this study to provide new insight into the role of aqueous C. burmannii in treating the possible hepatotoxic effects of multi-walled carbon nanotube (MWCNTs) exposure. A total of 32 male albino rats were divided into 4 groups: control group, cinnamon-treated group, MWCNT-treated, and cinnamon- and MWCNT-treated group. To achieve the aim of this study, evaluation of percentage change of body weight, oxidant, and antioxidant status including lipid peroxidation (LPO), nitrite, total thiols, glutathione contents (GSH), the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S transferase (GST) was done. Histopathological examination and the rate of pro-inflammatory cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β), cyclooxygenase-1 (COX-1), and tumor necrotic factor-α were performed. Oral administration of aqueous C. burmannii to those MWCNT-treated rats resulted in a significant reduction in LPO and total thiol contents with a significant elevation in the activities of SOD, CAT, and GPX, while GSH content and GST activity were not significantly affected. We observed a significant downregulation in the rate of previous pro-inflammatory cytokines. All this improvement in these examined markers resulted in a significant modulation in the hepatic histopathological lesions caused by MWCNTs. Aqueous C. burmannii extract exhibited a potential defensive effect on the hepatic injury triggered by MWCNTs through upgrading the antioxidant system and downregulating the rate of pro-inflammatory cytokines.

Isoform-Specific Compensation of Cyclooxygenase (Ptgs) Genes during Implantation and Late-Stage Pregnancy

The participation of cyclooxygenase (COX) in embryo implantation and parturition has been studied extensively. However, the distinct role of the two COX isoforms in these processes still remains unclear. Using three characterized mouse lines where the Ptgs1 and Ptgs2 genes substitute for one another, this study focused on the reproductive significance of their distinct roles and potential biological substitution. In both non-gravid and gravid uteri, the knock-in COX-2 is expressed constitutively, whereas the knock-in COX-1 is slightly induced in early implantation. The delayed onset of parturition previously found in COX-1 null mice was corrected by COX-2 exchange in COX-2>COX-1 mice, with normal term pregnancy, gestation length and litter size. In contrast, loss of native COX-2 in COX-1>COX-2 mice resulted in severely impaired reproductive functions. Knock-in COX-1 failed to substitute for the loss of COX-2 in COX-1>COX-2 mice during implantation, indicating that COX-1 may be replaced by COX-2, but not vice versa. A panel of prostaglandins detected in uterus and ovary demonstrates that prostaglandin biosynthesis preferentially depends on native COX-1, but not COX-2. More interestingly, preferential compensations by the COX isoforms were sustained despite weak dependency on their role in prostaglandin biosynthesis in the uterus and ovary.

Differential compensation of two cyclooxygenases in renal homeostasis is independent of prostaglandin-synthetic capacity under basal conditions

The distinct functions of each cyclooxygenase (COX) isoform in renal homeostasis have been the subject of intense investigation for many years. We took the novel approach of using 3 characterized mouse lines, where the prostaglandin (PG)-endoperoxide synthase genes 1 and 2 ( Ptgs1 and Ptgs2) substitute for one another to delineate distinct roles and the potential for COX isoform substitution. Flipped Ptgs genes generate a reversed COX-expression pattern in the kidney, where the knockin COX-2 is highly expressed. Normal nephrogenesis was sustained in all 3 strains at the postnatal stage d 8 (P8). Knockin COX-1 can temporally restore renal function and delay but not prevent renal pathology consequent to COX-2 deletion. Loss of COX-2 in adult COX-1 > COX-2 mice results in severe nephropathy, which leads to impaired renal function. These defects are partially rescued by the knockin COX-2 in Reversa mice, whereas COX-2 can compensate for the loss of COX-1 in COX-2 > COX-1 mice. Intriguingly, the highly expressed knockin COX-2 enzyme barely makes any PGs or thromboxane in neonatal P8 or adult mice, demonstrating that prostanoid biosynthesis requires native COX-1 and cannot be rescued by the knockin COX-2. In summary, the 2 COX isoforms can preferentially compensate for some renal functions, which appears to be independent of the PG-synthetic capacity.-Li, X., Mazaleuskaya, L. L., Ballantyne, L. L., Meng, H., FitzGerald, G. A., Funk, C. D. Differential compensation of two cyclooxygenases in renal homeostasis is independent of prostaglandin-synthetic capacity under basal conditions.

Flipping the cyclooxygenase (Ptgs) genes reveals isoform-specific compensatory functions

Two prostaglandin (PG) H synthases encoded by Ptgs genes, colloquially known as cyclooxygenase (COX)-1 and COX-2, catalyze the formation of PG endoperoxide H₂, the precursor of the major prostanoids. To address the functional interchangeability of these two isoforms and their distinct roles, we have generated COX-2>COX-1 mice whereby Ptgs2 is knocked in to the Ptgs1 locus. We then "flipped" Ptgs genes to successfully create the Reversa mouse strain, where knock-in COX-2 is expressed constitutively and knock-in COX-1 is lipopolysaccharide (LPS) inducible. In macrophages, flipping the two Ptgs genes has no obvious impact on COX protein subcellular localization. COX-1 was shown to compensate for PG synthesis at high concentrations of substrate, whereas elevated LPS-induced PG production was only observed for cells expressing endogenous COX-2. Differential tissue-specific patterns of expression of the knock-in proteins were evident. Thus, platelets from COX-2>COX-1 and Reversa mice failed to express knock-in COX-2 and, therefore, thromboxane (Tx) production in vitro and urinary Tx metabolite formation in COX-2>COX-1 and Reversa mice in vivo were substantially decreased relative to WT and COX-1>COX-2 mice. Manipulation of COXs revealed isoform-specific compensatory functions and variable degrees of interchangeability for PG biosynthesis in cells/tissues.