Recent advances in the development of celecoxib analogs as anticancer agents: A review

Celecoxib is a nonsteroidal anti-inflammatory drug (NSAID) designed to be a selective cyclooxygenase-2 (COX-2) inhibitor. It was approved by the U.S. Food and Drug Administration for the treatment of inflammatory diseases such as osteoarthritis and rheumatoid arthritis. Additionally, celecoxib demonstrated potent antitumor and chemopreventive effects in vitro, in vivo, and in patients. The mechanism of celecoxib's chemopreventive effect is still not fully identified, but it is assumed to be multifactorial. Celecoxib's anticancer activity has been described both as independent of and dependent on its COX-2 inhibitory activity. The current review summarizes the recent advances published between 2000 and 2022 on the structure-based optimization of celecoxib to develop compounds with promising anticancer activity. The structure-activity relationships of celecoxib analogs are discussed, which may be beneficial in the design and development of novel analogs as potent antiproliferative agents in the future.

Glomerular Biomechanical Stress and Lipid Mediators during Cellular Changes Leading to Chronic Kidney Disease

Hyperfiltration is an important underlying cause of glomerular dysfunction associated with several systemic and intrinsic glomerular conditions leading to chronic kidney disease (CKD). These include obesity, diabetes, hypertension, focal segmental glomerulosclerosis (FSGS), congenital abnormalities and reduced renal mass (low nephron number). Hyperfiltration-associated biomechanical forces directly impact the cell membrane, generating tensile and fluid flow shear stresses in multiple segments of the nephron. Ongoing research suggests these biomechanical forces as the initial mediators of hyperfiltration-induced deterioration of podocyte structure and function leading to their detachment and irreplaceable loss from the glomerular filtration barrier. Membrane lipid-derived polyunsaturated fatty acids (PUFA) and their metabolites are potent transducers of biomechanical stress from the cell surface to intracellular compartments. Omega-6 and ω-3 long-chain PUFA from membrane phospholipids generate many versatile and autacoid oxylipins that modulate pro-inflammatory as well as anti-inflammatory autocrine and paracrine signaling. We advance the idea that lipid signaling molecules, related enzymes, metabolites and receptors are not just mediators of cellular stress but also potential targets for developing novel interventions. With the growing emphasis on lifestyle changes for wellness, dietary fatty acids are potential adjunct-therapeutics to minimize/treat hyperfiltration-induced progressive glomerular damage and CKD.

Profiling the interaction of 1-phenylbenzimidazoles to cyclooxygenases

In the design of 1-phenylbenzimidazoles as model cyclooxygenase (COX) inhibitors, docking to a series of crystallographic COX structures was performed to evaluate their potential for high-affinity binding and to reproduce the interaction profile of well-known COX inhibitors. The effect of ligand-specific induced fit on the calculations was also studied. To quantitatively compare the pattern of interactions of model compounds to the profile of several cocrystallized COX inhibitors, a geometric parameter, denominated ligand-receptor contact distance (LRCD), was developed. The interaction profile of several model complexes showed similarity to the profile of COX complexes with inhibitors such as iodosuprofen, iodoindomethacin, diclofenac, and flurbiprofen. Shaping of high-affinity binding sites upon ligand-specific induced fit mostly determined both the affinity and the binding mode of the ligands in the docking calculations. The results suggest potential of 1-phenylbenzimidazole derivatives as COX inhibitors on the basis of their predicted affinity and interaction profile to COX enzymes. The analyses also provided insights into the role of induced fit in COX enzymes. While inhibitors produce different local structural changes at the COX ligand binding site, induced fit allows inhibitors in diverse chemical classes to share characteristic interaction patterns that ensure key contacts to be achieved. Different interaction patterns may also be associated with different inhibitory mechanisms.

The Cardiovascular Pharmacology of Nonsteroidal Anti-Inflammatory Drugs

The principal molecular mechanisms underlying the cardiovascular (CV) and renal adverse effects of nonsteroidal anti-inflammatory drugs (NSAIDs), such as myocardial infarction and hypertension, are understood in more detail than most side effects of drugs. Less is known, however, about differences in the CV safety profile between chemically distinct NSAIDs and their relative predisposition to complications. In review article, we discuss how heterogeneity in the pharmacokinetics and pharmacodynamics of distinct NSAIDs may be expected to affect their CV risk profile. We consider evidence afforded by studies in model systems, mechanistic clinical trials, a meta-analysis of randomized controlled trials, and two recent large clinical trials, Standard Care vs. Celecoxib Outcome Trial (SCOT) and Prospective Randomized Evaluation of Celecoxib Integrated Safety versus Ibuprofen or Naproxen (PRECISION), designed specifically to compare the CV safety of the cyclooxygenase-2-selective NSAID, celecoxib, with traditional NSAIDs. We conclude that SCOT and PRECISION have apparently not compared equipotent doses and have other limitations that bias them toward underestimation of the relative risk of celecoxib.

Hyperfiltration-associated biomechanical forces in glomerular injury and response: Potential role for eicosanoids

Hyperfiltration is a well-known risk factor in progressive loss of renal function in chronic kidney disease (CKD) secondary to various diseases. A reduced number of functional nephrons due to congenital or acquired cause(s) results in hyperfiltration in the remnant kidney. Hyperfiltration-associated increase in biomechanical forces, namely pressure-induced tensile stress and fluid flow-induced shear stress (FFSS) determine cellular injury and response. We believe the current treatment of CKD yields limited success because it largely attenuates pressure-induced tensile stress changes but not the effect of FFSS on podocytes. Studies on glomerular podocytes, tubular epithelial cells and bone osteocytes provide evidence for a significant role of COX-2 generated PGE₂ and its receptors in response to tensile stress and FFSS. Preliminary observations show increased urinary PGE₂ in children born with a solitary kidney. FFSS-induced COX2-PGE₂-EP₂ signaling provides an opportunity to identify targets and, for developing novel agents to complement currently available treatment.

Cyclooxygenase-2, prostaglandin E2, and prostanoid receptor EP2 in fluid flow shear stress-mediated injury in the solitary kidney

Hyperfiltration subjects podocytes to increased tensile stress and fluid flow shear stress (FFSS). We showed a 1.5- to 2.0-fold increase in FFSS in uninephrectomized animals and altered podocyte actin cytoskeleton and increased synthesis of prostaglandin E2 (PGE2) following in vitro application of FFSS. We hypothesized that increased FFSS mediates cellular changes through specific receptors of PGE2. Presently, we studied the effect of FFSS on cultured podocytes and decapsulated isolated glomeruli in vitro, and on solitary kidney in uninephrectomized sv129 mice. In cultured podocytes, FFSS resulted in increased gene and protein expression of cyclooxygenase (COX)-2 but not COX-1, prostanoid receptor EP2 but not EP4, and increased synthesis and secretion of PGE2, which were effectively blocked by indomethacin. Next, we developed a special flow chamber for applying FFSS to isolated glomeruli to determine its effect on an intact glomerular filtration barrier by measuring change in albumin permeability (Palb) in vitro. FFSS caused an increase in Palb that was blocked by indomethacin (P < 0.001). Finally, we show that unilateral nephrectomy in sv129 mice resulted in glomerular hypertrophy (P = 0.006), increased glomerular expression of COX-2 (P < 0.001) and EP2 (P = 0.039), and increased urinary albumin excretion (P = 0.001). Activation of the COX-2-PGE2-EP2 axis appears to be a specific response to FFSS in podocytes and provides a mechanistic basis for alteration in podocyte structure and the glomerular filtration barrier, leading to albuminuria in hyperfiltration-mediated kidney injury. The COX-2-PGE2-EP2 axis is a potential target for developing specific interventions to ameliorate the effects of hyperfiltration-mediated kidney injury in the progression of chronic kidney disease.

Use of NSAIDs in treating patients with arthritis

Patients with rheumatic diseases, including rheumatoid arthritis and osteoarthritis, almost universally describe pain and stiffness as important contributors to reduced health-related quality of life. Of the treatment options available, NSAIDs are the most widely used agents for symptomatic treatment. NSAIDs are effective anti-inflammatory and analgesic drugs by virtue of their ability to inhibit biosynthesis of prostaglandins at the level of the cyclooxygenase enzyme. However, many of the adverse effects of NSAIDs are also related to inhibition of prostaglandin production, making their use problematic in some patient populations. For the clinician, understanding the biology of prostaglandin as it relates to gastrointestinal, renal, and cardiovascular physiology and the pharmacologic properties of specific NSAIDs is key to using these drugs safely. Of particular importance is the recognition of co-morbid conditions and concomitant drugs that may increase the risk of NSAIDs in particular patients. In patients with risk factors for NSAID toxicity, using the lowest dose of a drug with a short half-life only when it is needed is likely to be the safest treatment option. For those patients whose symptoms cannot be managed with intermittent treatment, using protective strategies is essential.

Prostaglandins: modulators of inflammation and cardiovascular risk

Cyclooxygenase (COX)-2-specific drugs such as rofecoxib and celecoxib and the newer agents, etoricoxib and valdecoxib, were developed to provide a safer alternative to traditional nonsteroidal antiinflammatory drugs (tNSAIDs). These drugs have been shown significantly to reduce endoscopically visualized gastrointestinal ulcers, and one of them, rofecoxib, has demonstrated a 50% reduction in clinically important gastrointestinal outcomes compared with a tNSAID. However, COX-derived prostaglandins also have complex interactions with the cardiovascular system. This article briefly reviews our current understanding of the interactions between prostaglandins and cardiovascular physiology, and addresses some of the concerns that recently have been raised regarding coxibs and the risk of cardiovascular events.

Prostaglandin E(2) is crucial in the response of podocytes to fluid flow shear stress

Podocytes play a key role in maintaining and modulating the filtration barrier of the glomerulus. Because of their location, podocytes are exposed to mechanical strain in the form of fluid flow shear stress (FFSS). Several human diseases are characterized by glomerular hyperfiltration, such as diabetes mellitus and hypertension. The response of podocytes to FFSS at physiological or pathological levels is not known. We exposed cultured podocytes to FFSS, and studied changes in actin cytoskeleton, prostaglandin E(2) (PGE(2)) production and expression of cyclooxygenase-1 and-2 (COX-1, COX-2). FFSS caused a reduction in transversal F-actin stress filaments and the appearance of cortical actin network in the early recovery period. Cells exhibited a pattern similar to control state by 24 h following FFSS without significant loss of podocytes or apoptosis. FFSS caused increased levels of PGE(2) as early as 30 min after onset of shear stress, levels that increased over time. PGE(2) production by podocytes at post-2 h and post-24 h was also significantly increased compared to control cells (p < 0.039 and 0.012, respectively). Intracellular PGE(2) synthesis and expression of COX-2 was increased at post-2 h following FFSS. The expression of COX-1 mRNA was unchanged. We conclude that podocytes are sensitive and responsive to FFSS, exhibiting morphological and physiological changes. We believe that PGE(2) plays an important role in mechanoperception in podocytes.

Cyclooxygenase-2-dependent prostacyclin formation and blood pressure homeostasis: targeted exchange of cyclooxygenase isoforms in mice

RATIONALE

Cyclooxygenase (COX)-derived prostanoids (PGs) are involved in blood pressure homeostasis. Both traditional nonsteroidal antiinflammatory drugs (NSAIDs) that inhibit COX-1 and COX-2 and NSAIDs designed to be selective for inhibition of COX-2 cause sodium retention and elevate blood pressure.

OBJECTIVE

To elucidate the role of COX-2 in blood pressure homeostasis using COX-1>COX-2 mice, in which the COX-1 expression is controlled by COX-2 regulatory elements.

METHODS AND RESULTS

COX-1>COX-2 mice developed systolic hypertension relative to wild types (WTs) on a high-salt diet (HSD); this was attenuated by a PGI(2) receptor agonist. HSD increased expression of COX-2 in WT mice and of COX-1 in COX-1>COX-2 mice in the inner renal medulla. The HSD augmented in all strains urinary prostanoid metabolite excretion, with the exception of the major PGI(2) metabolite that was suppressed on regular chow and unaltered by the HSD in both mutants. Furthermore, inner renal medullary expression of the receptor for PGI(2), but not for other prostanoids, was depressed by HSD in WT and even more so in both mutant strains. Increasing osmolarity augmented expression of COX-2 in WT renal medullary interstitial cells and again the increase in formation of PGI(2) observed in WTs was suppressed in cells derived from both mutants. Intramedullary infusion of the PGI(2) receptor agonist increased urine volume and sodium excretion in mice.

CONCLUSIONS

These studies suggest that dysregulated expression of the COX-2 dependent, PGI(2) biosynthesis/response pathway in the renal inner renal medulla undermines the homeostatic response to a HSD. Inhibition of this pathway may contribute directly to the hypertensive response to NSAIDs.

Comparative cardiovascular safety of traditional nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for their anti-inflammatory and analgesic effects. Unfortunately, these drugs are not without toxicity, namely on the gastric mucosa, but also on the cardiovascular system. In this context, the marketing of the coxibs, a new series of NSAIDs that selectively inhibit COX-2, resulted in a large debate around their cardiovascular safety, because they may increase the incidence of myocardial infarction and stroke. The recent suspension of a large, randomised, controlled trial comparing celecoxib, naproxen and placebo in Alzheimer patients (the ADAPT trial) because of an apparent elevated cardiovascular risk in the naproxen group revived the debate on the cardiovascular safety of these drugs, but this time with special emphasis on the effect of traditional nonselective NSAIDs (tNSAIDs). In this paper that reviews and discusses the cardiovascular safety profile of tNSAIDs, essentially naproxen and ibuprofen in view of the most recent experimental and clinical data, the authors note that the published data are quite discordant and one cannot conclude that there is clear evidence to support a cardiovascular hazard from the administration of naproxen or non-naproxen NSAIDs unless additional information is provided. In addition, the results of retrospective case-control studies have to be interpreted very carefully because of the risk of confounding factors that are not always taken into account when subjects were classified either as cases or controls. Thus, in the absence of clear cut data, physicians will have to use traditional NSAIDs (or coxibs) in patients with a high cardiovascular risk on the basis of their common sense rather than on evidence-based medicine. For these patients, one should not forget that an inadequate long-term control of cardiovascular risk factors such as a hypertension, dyslipidaemia, diabetes, smoking and weight excess is more deleterious in terms of cardiovascular mortality than the administration of NSAIDs itself.

Vasoactive prostanoids are generated from arachidonic acid by COX-1 and COX-2 in the mouse

Generation of vasoactive prostanoids from arachidonic acid by cyclooxygenase (COX)-1 and COX-2 was investigated in anesthetized mice. Intravenous injections of the prostanoid precursor arachidonic acid increased pulmonary arterial pressure and decreased systemic arterial pressure. Pulmonary pressor and systemic depressor responses were attenuated by SC-560 and nimesulide, inhibitors of COX-1 and COX-2, in doses that did not alter responses to injected prostanoids. Pulmonary pressor responses to arachidonic acid were blocked and a depressor response was unmasked, whereas systemic depressor responses were not altered, by a thromboxane receptor antagonist. Pulmonary and systemic pressor responses to angiotensin II injections and systemic pressor responses to angiotensin II infusion were not modified by COX-1 or COX-2 inhibitors but were attenuated by losartan. Systemic depressor responses to arachidonic acid were smaller in COX-1 and COX-2 knockout mice, whereas responses to angiotensin II, norepinephrine, U-46619, endothelin-1, and PGE1were not different in COX-1 and COX-2 knockout and wild-type control mice. These results suggest that vasoactive prostanoids with pulmonary pressor and systemic vasodepressor activity are formed by COX-1 and COX-2 and are consistent with Western blot analysis and immunostaining showing the presence of COX-1 and COX-2. These data suggest that thromboxane A2(TxA2) is formed from the precursor by COX-1 and COX-2 in the lung and are in agreement with immunofluorescence studies showing thromboxane synthase. The present data suggest that COX-1- or COX-2-derived prostanoids do not modulate responses to angiotensin II or other vasoactive agents and that prostanoid responses are similar in CD-1 and C57BL/6 and in male and female mice.

Role of COX-1 and -2 in prostanoid generation and modulation of angiotensin II responses

The role of cyclooxygenase (COX)-1 and -2 in prostanoid formation and modulation of pressor responses to ANG II was investigated in the pulmonary and systemic vascular beds in the rat. In the present study, selective COX-1 and -2 inhibitors attenuated increases in pulmonary arterial pressure and decreases in systemic arterial pressure in response to arachidonic acid but did not alter responses to PGE1 or U-46619. The selective COX-1 and -2 inhibitors did not modify systemic pressor responses to injections or infusions of ANG II or pulmonary pressor responses to injections of the peptide. COX-2 inhibitors did not alter, whereas a COX-1 inhibitor depressed, arachidonic acid-induced platelet aggregation. These data provide evidence in support of the hypothesis that prostanoid synthesis occurs by way of the COX-1 and -2 pathways in the pulmonary and systemic vascular beds but that pressor responses to ANG II are not mediated or modulated by these pathways in the rat.

The kallikrein-kinin and the renin-angiotensin systems have a multilayered interaction

Understanding the physiological role of the plasma kallikrein-kinin system (KKS) has been hampered by not knowing how the proteins of this proteolytic system, when assembled in the intravascular compartment, become activated under physiological conditions. Recent studies indicate that the enzyme prolylcarboxypeptidase, an ANG II inactivating enzyme, is a prekallikrein activator. The ability of prolylcarboxypeptidase to act in the KKS and the renin-angiotensin system (RAS) indicates a novel interaction between these two systems. This interaction, along with the roles of angiotensin converting enzyme, cross talk between bradykinin and angiotensin-(1-7) action, and the opposite effects of activation of the ANG II receptors 1 and 2 support a hypothesis that the plasma KKS counterbalances the RAS. This review examines the interaction and cross talk between these two protein systems. This analysis suggests that there is a multilayered interaction between these two systems that are important for a wide array of physiological functions.

PGE2 reduces arachidonic acid release in murine podocytes: evidence for an autocrine feedback loop

Increased glomerular prostaglandin E(2) (PGE(2)) production is associated with the progression of diseases such as membranous nephropathy, nephrotic syndrome, and anti-Thy1 nephritis. We investigated the signaling pathways that regulate the synthesis and actions of PGE(2) in glomerular podocytes. To study its actions, we assessed the ability of PGE(2) to regulate the production of its own precursor, arachidonic acid (AA), in a mouse podocyte cell line. PGE(2) dose-dependently reduced phorbol ester (PMA)-mediated AA release. Inhibition of PMA-stimulated AA release by PGE(2) was found to be cAMP/PKA-dependent, because PGE(2) significantly increased levels of this second messenger, whereas the inhibitory actions of PGE(2) were reversed by PKA inhibition and reproduced by the cAMP-elevating agents forskolin and IBMX. PGE(2) synthesis in this podocyte cell line increased fourfold at 60 min in response to PMA, coinciding with upregulation of cyclooxygenase (COX)-2 but not COX-1 levels. However, PGE(2) synthesis was significantly reduced by COX-1-selective inhibition, yet to a lesser extent by COX-2-selective inhibition. Our findings suggest that PMA-stimulated PGE(2) synthesis in mouse podocytes requires both basal COX-1 activity and induced COX-2 expression, and that PGE(2) reduces PMA-stimulated AA release in a cAMP/PKA-dependent manner. Such an autocrine regulatory loop might have important consequences for podocyte and glomerular function in the context of renal diseases involving PGE(2) synthesis.