Inhibition of COX-1 attenuates the formation of thromboxane A2 and ameliorates the acute decrease in glomerular filtration rate in endotoxemic mice

Plasma proteomic characterization of the development of acute kidney injury in early sepsis patients

Acute kidney injury (AKI) develops frequently in the course of patients with sepsis and strongly associates with in-hospital mortality. However, diagnosing AKI involves a considerable lag-time because it depends on assessing an increase in serum creatinine, and offers no insight in the underlying pathophysiology. Consequently, identifying a set of proteins reflecting the development of AKI may improve earlier recognition of AKI and the understanding of its pathophysiology. A targeted plasma proteomic approach was performed in early sepsis patients with and without subsequent AKI development in a matched pair design (n = 19 each). Principal component analysis identified 53 proteins associated with development of AKI, which were further analysed using Enrichr gene ontology and pathway analysis. Nine differentially expressed proteins from the targeted proteomics were increased among patients who subsequently developed AKI and correlated with principal components, namely CALCA, CALR, CA12, CLEC1A, PTK7, KIM-1, NPPC, NUCB2 and PGF. We demonstrated the biological insight in the development of AKI in early sepsis compared to non-AKI sepsis.

Therapeutic implications of cyclooxygenase (COX) inhibitors in ischemic injury

INTRODUCTION

Ischemia-reperfusion injury (IRI) is the inexplicable aggravation of cellular dysfunction that results in blood flow restoration to previously ischemic tissues. COX mediates the oxidative conversion of AA to various prostaglandins and thromboxanes, which are involved in various physiological and pathological processes. In the pathophysiology of I/R injuries, COX has been found to play an important role. I/R injuries affect most vital organs and are characterized by inflammation, oxidative stress, cell death, and apoptosis, leading to morbidity and mortality.

MATERIALS AND METHODS

A systematic literature review of Bentham, Scopus, PubMed, Medline, and EMBASE (Elsevier) databases was carried out to understand the Nature and mechanistic interventions of the Cyclooxygenase modulations in ischemic injury. Here, we have discussed the COX Physiology and downstream signalling pathways modulated by COX, e.g., Camp Pathway, Peroxisome Proliferator-Activated Receptor Activity, NF-kB Signalling, PI3K/Akt Signalling in ischemic injury.

CONCLUSION

This review will discuss the various COX types, specifically COX-1 and COX-2, which are involved in developing I/R injury in organs such as the brain, spinal cord, heart, kidney, liver, and intestine.

Renal microvascular endothelial cell responses in sepsis-induced acute kidney injury

Microvascular endothelial cells in the kidney have been a neglected cell type in sepsis-induced acute kidney injury (sepsis-AKI) research; yet, they offer tremendous potential as pharmacological targets. As endothelial cells in distinct cortical microvascular segments are highly heterogeneous, this Review focuses on endothelial cells in their anatomical niche. In animal models of sepsis-AKI, reduced glomerular blood flow has been attributed to inhibition of endothelial nitric oxide synthase activation in arterioles and glomeruli, whereas decreased cortex peritubular capillary perfusion is associated with epithelial redox stress. Elevated systemic levels of vascular endothelial growth factor, reduced levels of circulating sphingosine 1-phosphate and loss of components of the glycocalyx from glomerular endothelial cells lead to increased microvascular permeability. Although coagulation disbalance occurs in all microvascular segments, the molecules involved differ between segments. Induction of the expression of adhesion molecules and leukocyte recruitment also occurs in a heterogeneous manner. Evidence of similar endothelial cell responses has been found in kidney and blood samples from patients with sepsis. Comprehensive studies are needed to investigate the relationships between segment-specific changes in the microvasculature and kidney function loss in sepsis-AKI. The application of omics technologies to kidney tissues from animals and patients will be key in identifying these relationships and in developing novel therapeutics for sepsis.

Evaluation of Anti-Inflammatory Components of Guizhi Fuling Capsule, an Ancient Chinese Herbal Formula, in Human Umbilical Vein Endothelial Cells

Background

Guizhi Fuling capsule (GFC), a well-known formula composed of five medicinal herbs, is commonly prescribed to treat primary dysmenorrhea, as well as to achieve good clinical efficacy in China. However, the active components of GFC have not been identified. Here, the anti-inflammatory functions of GFC, as well as its major ingredients, were evaluated in human umbilical vein endothelial cells (HUVECs).

Methods

Lipopolysaccharide (LPS) was used in HUVECs to imitate the cellular inflammation. Then, GFC-triggered mRNA expressions of cyclooxygenase-1 (COX-1) and COX-2 were determined by real-time PCR, while the expression of COX-2 protein was revealed by western blotting. Besides, nine components of GFC were evaluated for their contribution value in the anti-dysmenorrhea effects.

Results

The application of GFC downregulated the mRNA expressions of COX-1 and COX-2 mRNAs. Nine major components of GFC were tested in the inflammatory system, and three compounds, including paeoniflorin, benzoylpaeoniflorin, and amygdalin, exhibited robust activation in HUVECs. The combination of paeoniflorin, benzoylpaeoniflorin, and amygdalin showed over 80% of the anti-inflammatory activation.

Conclusion

Our study supports that GFC plays a promising role in anti-dysmenorrhea function by decreasing COXs' expression. Besides, paeoniflorin, benzoylpaeoniflorin, and amygdalin could be considered as major regulators for the anti-dysmenorrhea effects of GFC.

Retinoic Acid-Platinum (II) Complex [RT-Pt(II)] Protects Against Rheumatoid Arthritis in Mice via MEK/Nuclear Factor kappa B (NF-κB) Pathway Downregulation

Background

Rheumatoid arthritis (RA) is an inflammatory disorder that is present in approximately 1% of the world’s population. This study was aimed to investigate the effect of retinoic acid-platinum (II) complex [RT-Pt(II)] on rheumatoid arthritis (RA) and to explore the mechanism involved.

Material/Methods

MH7A cell viability was determined by MTT assay and apoptosis was assessed using FACSCalibur flow cytometry. RT-PCR and Western blot assays were used for assessment of mRNA and proteins levels.

Results

Treatment of rheumatoid arthritis with RT-Pt(II) significantly reduced the levels of IL-1β, IL-6, IL-8, MMP-1, and MMP-13 in synovial fluid of mice in a dose-dependent manner. The expression of iNOS and COX-2 mRNA and protein in rheumatoid arthritis rats was also significantly inhibited by treatment with RT-Pt(II). The TNF-α-induced proliferation of MH7A cells was alleviated by RT-Pt(II) treatment in a concentration-dependent manner. Moreover, RT-Pt(II) treatment induced apoptosis and caused arrest of cell cycle in MH7A cells. The activation of MEK/NF-κB pathway was downregulated by RT-Pt(II) treatment in MH7A cells.

Conclusions

In summary, the present study demonstrated that RT-Pt(II) inhibits TNF-α-induced inflammatory response, suppresses cell viability, and induces apoptosis in rheumatoid arthritis synovial cells. Moreover, RT-Pt(II) exhibited its effect through targeting the MEK/NF-κB pathway. Therefore, RT-Pt(II) can be used for the development of treatments for rheumatoid arthritis.

The role of platelets in acute kidney injury

Acute kidney injury (AKI), a major public health problem associated with high mortality and increased risk of progression towards end-stage renal disease, is characterized by the activation of intra-renal haemostatic and inflammatory processes. Platelets, which are present in high numbers in the circulation and can rapidly release a broad spectrum of bioactive mediators, are important acute modulators of inflammation and haemostasis, as they are the first cells to arrive at sites of acute injury, where they interact with endothelial cells and leukocytes. Diminished control of platelet reactivity by endothelial cells and/or an increased release of platelet-activating mediators can lead to uncontrolled platelet activation in AKI. As increased platelet sequestration and increased expression levels of the markers P-selectin, thromboxane A₂, CC-chemokine ligand 5 and platelet factor 4 on platelets have been reported in kidneys following AKI, platelet activation likely plays a part in AKI pathology. Results from animal models and some clinical studies highlight the potential of antiplatelet therapies in the preservation of renal function in the context of AKI, but as current strategies also affect other cell types and non-platelet-derived mediators, additional studies are required to further elucidate the extent of platelet contribution to the pathology of AKI and to determine the best therapeutic approach by which to specifically target related pathogenic pathways.

Platelets in Sepsis: An Update on Experimental Models and Clinical Data

Beyond their important role in hemostasis, platelets play a crucial role in inflammatory diseases. This becomes apparent during sepsis, where platelet count and activation correlate with disease outcome and survival. Sepsis is caused by a dysregulated host response to infection, leading to organ dysfunction, permanent disabilities, or death. During sepsis, tissue injury results from the concomitant uncontrolled activation of the complement, coagulation, and inflammatory systems as well as platelet dysfunction. The balance between the systemic inflammatory response syndrome (SIRS) and the compensatory anti-inflammatory response (CARS) regulates sepsis outcome. Persistent thrombocytopenia is considered as an independent risk factor of mortality in sepsis, although it is still unclear whether the drop in platelet count is the cause or the consequence of sepsis severity. The role of platelets in sepsis development and progression was addressed in different experimental in vivo models, particularly in mice, that represent various aspects of human sepsis. The immunomodulatory function of platelets depends on the experimental model, time, and type of infection. Understanding the molecular mechanism of platelet regulation in inflammation could bring us one step closer to understand this important aspect of primary hemostasis which drives thrombotic as well as bleeding complications in patients with sterile and infectious inflammation. In this review, we summarize the current understanding of the contribution of platelets to sepsis severity and outcome. We highlight the differences between platelet receptors in mice and humans and discuss the potential and limitations of animal models to study platelet-related functions in sepsis.

Deregulated renal magnesium transport during lipopolysaccharide-induced acute kidney injury in mice

Magnesium (Mg²⁺) abnormalities during sepsis have been reported, but the underlying mechanisms during acute inflammation are poorly understood. We hypothesized that a decrease in GFR and/or changes in transporters or channels for Mg²⁺ could be responsible for the observed Mg²⁺ abnormalities. Therefore, we studied the metabolism of Mg²⁺ in a murine model of endotoxemia. LPS-induced hypermagnesemia was paralleled by a decrease in creatinine clearance and an increase in the fractional excretion of Mg²⁺. In agreement with an altered renal Mg²⁺ handling, endotoxemia decreased the renal expression of claudin (Cldn) 10b, Cldn16, Cldn19, parvalbumin, and of the solute carrier family (Slc) 41a3. Further, LPS increased the renal expression of Cldn14 and Slc41a1. The renal expression of the transient receptor potential melastin (Trpm) 6, Trpm7, and of cyclin M (Cnnm) 2 was unaltered in response to LPS. In vitro studies support a direct effect on the expression of Cldn10b, Cldn14, Cldn16, and Cldn19. Further, endotoxemia increased the fractional excretion of sodium, which was paralleled by a decrease of important renal sodium transporters. In the large intestine, the expression of Trpm7 was increased in response to LPS, whereas the expression of Trpm6 was decreased. Cnnm4 mRNA levels were unchanged in the large intestine. Further, Cldn12 and Na⁺-H⁺ exchanger 3 (Slc9a3) expressions were decreased in the small intestine in response to LPS. Our findings indicate that endotoxemia is associated with hypermagnesemia and a disturbed Mg²⁺ handling. It seems likely that LPS-induced hypermagnesemia is due to the decrease in renal function in response to LPS.

Endotoxaemia differentially regulates the expression of renal Ca2+ transport proteins in mice

AIM

Alterations in parathyroid hormone (PTH) and/or vitamin D signalling are frequently reported in patients with sepsis. The consequences on renal and intestinal Ca²⁺ and P_i regulatory mechanisms are still unclear. We hypothesized that endotoxaemia alters the expression of important renal and intestinal Ca²⁺ and P_i transport proteins.

METHODS

Male C57BL/6 mice were treated with lipopolysaccharide (LPS; 3 mg/kg; i.p.). The mRNA and protein levels of renal and intestinal Ca²⁺ and P_i transport proteins were measured by RT-qPCR, immunohistochemistry and western blot analysis.

RESULTS

Lipopolysaccharide-induced hypocalcaemia and hyperphosphataemia was paralleled by a decrease in glomerular filtration rate and urinary excretion of Ca²⁺ and P_i . Endotoxaemia augmented plasma levels of PTH and affected the fibroblast growth factor 23 (FGF23)-klotho-vitamin D axis by increasing plasma levels of FGF23 and downregulation of renal klotho expression. Renal expression of CYP27b1 and plasma levels of 1,25-dihydroxyvitamin D₃ were increased in response to LPS. Endotoxaemia augmented the renal expression of TRPV5, TRPV6 and PiT1, whereas the renal expression of calbindin-D_28K , NCX1, NaP_i -2a and NaP_i -2c were decreased. Incubation of primary distal tubule cells with LPS increased TRPV6 mRNA levels. Furthermore, LPS decreased the intestinal expression of TRPV6, calbindin-D_9K and of NaP_i -2b.

CONCLUSION

Our findings indicate that endotoxaemia is associated with hypocalcaemia and hyperphosphataemia and a disturbed FGF23-klotho-vitamin D signaling. Further, LPS-induced acute kidney injury was accompanied by an increased or decreased expression of specific renal and intestinal Ca²⁺ and P_i transporters respectively. It seems unlikely that LPS-induced hypocalcaemia is due to renal loss of Ca²⁺ .

Significance of urinary 11-dehydro-thromboxane B2 in age-related diseases: Focus on atherothrombosis

Platelet activation plays a key role in atherogenesis and atherothrombosis. Biochemical evidence of increased platelet activation in vivo can be reliably obtained through non-invasive measurement of thromboxane metabolite (TXM) excretion. Persistent biosynthesis of TXA₂ has been associated with several ageing-related diseases, including acute and chronic cardio-cerebrovascular diseases and cardiovascular risk factors, such as cigarette smoking, type 1 and type 2 diabetes mellitus, obesity, hypercholesterolemia, hyperhomocysteinemia, hypertension, chronic kidney disease, chronic inflammatory diseases. Given the systemic nature of TX excretion, involving predominantly platelet but also extraplatelet sources, urinary TXM may reflect either platelet cyclooxygenase-1 (COX-1)-dependent TX generation or COX-2-dependent biosynthesis by inflammatory cells and/or platelets, or a combination of the two, especially in clinical settings characterized by low-grade inflammation or enhanced platelet turnover. Although urinary 11-dehydro-TXB₂ levels are largely suppressed with low-dose aspirin, incomplete TXM suppression by aspirin predicts the future risk of vascular events and death in high-risk patients and may identify individuals who might benefit from treatments that more effectively block in vivo TX production or activity. Several disease-modifying agents, including lifestyle intervention, antidiabetic drugs and antiplatelet agents besides aspirin have been shown to reduce TX biosynthesis. Taken together, these aspects may contribute to the development of promising mechanism-based therapeutic strategies to reduce the progression of atherothrombosis. We intended to critically review current knowledge on both the pathophysiological significance of urinary TXM excretion in clinical settings related to ageing and atherothrombosis, as well as its prognostic value as a biomarker of vascular events.

Prostaglandins in the pathogenesis of kidney diseases

Prostaglandins (PGs) are important lipid mediators produced from arachidonic acid via the sequential catalyzation of cyclooxygenases (COXs) and specific prostaglandin synthases. There are five subtypes of PGs, namely PGE2, PGI2, PGD2, PGF2α, and thromboxane A2 (TXA2). PGs exert distinct roles by combining to a diverse family of membrane-spanning G protein-coupled prostanoid receptors. The distribution of these PGs, their specific synthases and receptors vary a lot in the kidney. This review summarized the recent findings of PGs together with the COXs and their specific synthases and receptors in regulating renal function and highlighted the insights into their roles in the pathogenesis of various kidney diseases.

Effect of Platelet-derived P-selectin on Neutrophil Recruitment in a Mouse Model of Sepsis-induced Acute Kidney Injury

Background:

Acute kidney injury (AKI) is a severe disease in critically ill patients. Neutrophil infiltration into kidney was associated with the development of AKI, and P-selectin may be involved in the process of neutrophil recruitment in kidney. This study aimed to explore the potential effect of platelet-derived P-selectin on neutrophil recruitment in a mouse model of sepsis-induced AKI.

Methods:

A total of 30 C57BL/6 male mice were divided into five groups (n = 6 in each): sham group, sepsis group, anti-Ly6G group, anti-P-selectin group, and platelet depletion group. Sepsis was induced by cecal ligation and puncture. Serum creatinine concentration and platelet activity were measured by biochemical detector and flow cytometry, respectively. Histological and pathological features were analyzed using hematoxylin-eosin (H&E) and immunohistochemistry (IHC) staining, respectively. Myeloperoxidase (MPO) activity was detected with MPO assay. Unpaired t-test was used for data analysis.

Results:

Serum creatinine increased significantly in septic group compared to sham group (2.68 ± 0.27 mg/dl vs. 0.82 ± 0.19 mg/dl, t = 12.06, P = 0.0000) but attenuated in antibodies-treated animals compared to septic group (anti-Ly6G: 1.62 ± 0.30 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 5.76, P = 0.0004; anti-P-selectin: 1.76 ± 0.31 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 4.92, P = 0.0012; and platelet depletion: 1.93 ± 0.29 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 4.14, P = 0.0032). Platelet amount significantly decreased compared to sham group (658.20 ± 60.64 × 10⁹/L vs. 822.00 ± 48.60 × 10⁹/L, t = 4.71, P = 0.0015) in septic mice, especially in platelet depletion group (240.80 ± 44.98 × 10⁹/L vs. 822.00 ± 48.60 × 10⁹/L, t = 19.63, P = 0.0000). P-selectin activity was significantly increased in septic group compared to sham group (16.54 ± 1.60% vs. 1.90 ± 0.29%, t = 15.64, P = 0.0000) but decreased significantly in platelet depletion group compared to septic group (3.62 ± 0.68% vs. 16.54 ± 1.60%, t = 12.89, P = 0.0002). IHC analysis shown that neutrophil infiltration increased in septic mice compared to sham group (36.67 ± 3.79% vs. 9.17 ± 1.61%, t = 11.58, P = 0.0003) and function-blocked groups (anti-Ly6G: 36.67 ± 3.79% vs. 15.33 ± 1.53%, t = 9.05, P = 0.0008; anti-P-selectin: 36.67 ± 3.79% vs. 21.33 ± 1.53%, t = 6.51, P = 0.0029; and platelet depletion: 36.67 ± 3.79% vs. 23.33 ± 3.06%, t = 4.75, P = 0.0090). MPO increased significantly in septic group compared to control (49.73 ± 1.83 ng/mg prot vs. 13.04 ± 2.16 ng/mg prot, t = 19.03, P = 0.0000) but decreased in function-blocked groups compared to septic group (anti-Ly6G: 26.52 ± 3.86 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 9.59, P = 0.0000; anti-P-selectin: 33.06 ± 6.75 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 4.85, P = 0.0013; and platelet depletion: 33.37 ± 2.25 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 5.33, P = 0.0007).

Conclusion:

Platelets-derived P-selectin may be involved in the development of septic AKI through inducing neutrophil infiltration into kidney.

The protective effect of ticagrelor on renal function in a mouse model of sepsis-induced acute kidney injury

Platelets are traditionally considered to be essential components of primary hemostasis. Recent investigations have revealed that platelets can be activated in patients with sepsis and are implicated in the development of sepsis and sepsis-induced-acute kidney injury (SAKI). In the present study, ticagrelor was used to induce a mouse model of SAKI by cecal ligation and puncture. It was found that ticagrelor could inhibit platelet activity, decrease the levels of interleukin-1β and serum creatinine, reduce infiltration of neutrophils in renal tissue, and attenuate cell apoptosis in the kidney. The results suggested that ticagrelor could protect renal function by inhibiting inflammation, recruitment of neutrophils into the kidney, and cell apoptosis in renal tissue. Thus, the findings might provide new strategies for preventing SAKI.

Downregulation of Thromboxane A2 Receptor Occurs Mainly via Nuclear Factor-KappaB Signaling Pathway in Rat Renal Artery

Thromboxane A₂ (TXA₂) acts on TXA₂ receptors (TP) to regulate renal artery blood flow and subsequently contributes to the pathogenesis of renal ischemia. The present study was designed to examine if nuclear factor-kappaB (NF-κB) signaling pathway is involved in the downregulation of TP receptors in rat renal artery. Rat renal artery segments were organ cultured for 6 or 24 h. Downregulation of TP receptors was monitored using myograph (contractile function), real-time PCR (receptor mRNA), and immunohistochemistry (receptor protein). Specific inhibitors (MG-132 and BMS345541) for NF-κB signaling pathway were used to dissect the underlying molecular mechanisms involved. Compared to fresh (noncultured) segments, organ culture of the renal artery segments for 24 h induced a significant rightward shift of U46619 (TP receptor agonist) contractile response curves (pEC₅₀: 6.89 ± 0.06 versus 6.48 ± 0.04, P < 0.001). This decreased contractile response to U46619 was paralleled with decreased TP receptor mRNA and protein expressions in the renal artery smooth muscle cells. Specific inhibitors (MG-132 and BMS345541) for NF-κB signaling pathway significantly abolished the decreased TP protein expression and receptor-mediated contractions. In conclusion, downregulation of TP receptors in the renal artery smooth muscle cells occurs mainly via the NF-κB signaling pathway.

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

Paeoniflorin ameliorates rheumatoid arthritis in rat models through oxidative stress, inflammation and cyclooxygenase 2

Paeoniflorin has anti-inflammatory, anti-allergy, immune regulatory and pain-relieving effects, amongst other roles. However, the mechanisms underlying the protective effects of paeoniflorin on rheumatoid arthritis (RA) remain under investigation; the objective of the current study was to evaluate these protective effects in the context of an RA model. Rats were randomly divided into 5 groups, as follows: The control group, the RA rat model group, and the paeoniflorin groups, in which paeoniflorin was administered at concentrations of 5, 10 and 20 mg/kg for 3 weeks. The pain thresholds and arthritic symptoms of the RA rats were measured. Oxidative stress and inflammatory cytokines were also analyzed and western blot analysis was used to evaluate cyclooxygenase-2 (COX-2) protein expression levels. Paeoniflorin significantly increased the pain threshold and decreased the arthritic symptoms in the RA rat model. Notably, paeoniflorin reduced the malondialdehyde concentration and increased the activity of superoxide dismutase, catalase and glutathione peroxidase. Furthermore, paeoniflorin attenuated the activity of nuclear factor-κB p65 unit, tumor necrosis factor-α, interleukin (IL)-1β and IL-6, and reduced the COX-2 protein expression level. The present study indicates that paeoniflorin ameliorates disease in rat models of RA through oxidative stress, inflammation and alterations to COX-2 expression.

Circadian CLOCK Mediates Activation of Transforming Growth Factor-β Signaling and Renal Fibrosis through Cyclooxygenase 2

The circadian rhythm regulates blood pressure and maintains fluid and electrolyte homeostasis with central and peripheral clock. However, the role of circadian rhythm in the pathogenesis of tubulointerstitial fibrosis remains unclear. Here, we found that the amplitudes of circadian rhythm oscillation in kidneys significantly increased after unilateral ureteral obstruction. In mice that are deficient in the circadian gene Clock, renal fibrosis and renal parenchymal damage were significantly worse after ureteral obstruction. CLOCK-deficient mice showed increased synthesis of collagen, increased oxidative stress, and greater transforming growth factor-β (TGF-β) expression. TGF-β mRNA expression oscillated with the circadian rhythms under the control of CLOCK-BMAL1 heterodimers. The expression of cyclooxygenase 2 was significantly higher in kidneys from CLOCK-deficient mice with ureteral obstruction. Treatment with a cyclooxygenase 2 inhibitor celecoxib significantly improved renal fibrosis in CLOCK-deficient mice. Taken together, these data establish the importance of the circadian rhythm in tubulointerstitial fibrosis and suggest CLOCK/TGF-β signaling as a novel therapeutic target of cyclooxygenase inhibition.