Selective COX-2 Inhibitors and Renal Injury in Salt-Sensitive Hypertension

Postoperative Complications Associated with Non-Steroidal Anti-Inflammatory Combinations Used Status-Post Total Hip and Knee Arthroplasty

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used in multimodal pain control following total joint arthroplasty (TJA). However, few studies have assessed the complications associated with the combinations of NSAIDs in this population despite the known risks associated with this class of medications. The Premier Healthcare Database was queried to identify adults who underwent primary total hip or knee arthroplasty from 2005-2014. The following most common inpatient combinations of NSAIDs were chosen for analysis: aspirin + celecoxib (A + C), toradol + aspirin (T + A), toradol + ibuprofen (T + I), celecoxib + ibuprofen (C + I), ibuprofen + aspirin (I + A), and toradol + celecoxib (T + C). Primary outcomes included acute kidney injury (AKI), gastrointestinal bleed, and stroke. Secondary outcomes included periprosthetic joint infection (PJI), deep vein thrombosis, and pulmonary embolism. Univariate and multivariate regression analyses were used to compare differences and address confounds. Overall, 195,833 patients were identified. After controlling for confounds, increased odds of AKI was associated with A + C (adjusted odds ratio [aOR]: 1.20, 95% confidence interval [CI]: 1.09-1.34, p < 0.001) and decreased odds was associated with T + A (aOR 0.76, 95% CI: 0.69-0.83, p < 0.001). Increased odds of stroke was associated with A + C (aOR: 1.80, 95% CI: 1.15-2.84, p = 0.011); T + I (aOR 3.48, 95% CI: 1.25-9.73, p = 0.017); and I + A (aOR 4.29, 95% CI: 1.06-17.9, p = 0.046). Increased odds of PJI was associated with C + I (aOR: 10.3, 95% CI: 1.35-78.3, p = 0.024). In the TJA patient population, NSAID pairings should be regarded as distinct entities. Our results suggest that combinations including A + C, T + I, I + A, and C + I should be used cautiously. With this knowledge, providers should consider tailoring NSAID prescriptions appropriately.

Actions of immune cells in the hypertensive kidney

PURPOSE OF REVIEW

Inflammatory processes play a critical role in the pathogenesis of hypertension. Innate and adaptive immune responses participate in blood pressure (BP) elevation and end-organ damage. In this review, we discuss recent studies illustrating mechanisms through which immune cells and cytokines regulate BP via their actions in the kidney.

RECENT FINDINGS

Cells of the innate immune system, including monocytes, neutrophils, and dendritic cells, can all promote BP elevation via effects on kidney function. These innate immune cells can directly impact oxidative stress and cytokine generation in the kidney and/or present antigens to lymphocytes for the engagement of the adaptive immune system. Once activated by dendritic cells, effector memory T cells accumulate in the hypertensive kidney and facilitate renal salt and water retention. Individual subsets of activated T cells can secrete tumor necrosis factor-alpha (TNF-α), interleukin-17a (IL-17a), and interferon-gamma (IFN-γ), each of which has augmented the elevation of blood pressure in hypertensive models by enhancing renal sodium transport. B cells, regulate blood pressure via vasopressin receptor 2 (V2R)-dependent effects on fluid transport in the kidney.

SUMMARY

Immune cells of the innate and adaptive immune systems drive sodium retention and blood pressure elevation in part by altering renal solute transport.

Cyclo-Oxygenase (COX) Inhibitors and Cardiovascular Risk: Are Non-Steroidal Anti-Inflammatory Drugs Really Anti-Inflammatory?

Cyclo-oxygenase (COX) inhibitors are among the most commonly used drugs in the western world for their anti-inflammatory and analgesic effects. However, they are also well-known to increase the risk of coronary events. This area is of renewed significance given alarming new evidence suggesting this effect can occur even with acute usage. This contrasts with the well-established usage of aspirin as a mainstay for cardiovascular prophylaxis, as well as overwhelming evidence that COX inhibition induces vasodilation and is protective for vascular function. Here, we present an updated review of the preclinical and clinical literature regarding the cardiotoxicity of COX inhibitors. While studies to date have focussed on the role of COX in influencing renal and vascular function, we suggest an interaction between prostanoids and T cells may be a novel factor, mediating elevated cardiovascular disease risk with NSAID use.

Cardio-renal safety of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used therapeutic class in clinical medicine. These are sub-divided based on their selectivity for inhibition of cyclooxygenase (COX) isoforms (COX-1 and COX-2) into: (1) non-selective (ns-NSAIDs), and (2) selective NSAIDs (s-NSAIDs) with preferential inhibition of COX-2 isozyme. The safety and pathophysiology of NSAIDs on the renal and cardiovascular systems have continued to evolve over the years following short- and long-term treatment in both preclinical models and humans. This review summarizes major learnings on cardiac and renal complications associated with pharmaceutical inhibition of COX-1 and COX-2 with focus on preclinical to clinical translatability of cardio-renal data.

The effect of celecoxib on blood pressure and plasma oxidant/antioxidant status in co-administration with glucocorticoid in rat

There is limited information about the concomitant uses of selective COX-2 inhibitors with corticosteroids or with antihypertensive medications. The aim of this study was to investigate the effect of celecoxib on blood pressure and plasma oxidant/antioxidant status in glucocorticoid-induced hypertension and in co-administration with captopril. Male Wistar rats received dexamethasone (30 μg/kg/day, s.c.) for 14 days. The tested groups received dexamethasone and orally treated with celecoxib (10, 25 or 50 mg/kg) or captopril (10, 20 or 40 mg/kg) or celecoxib (50 mg/kg) + captopril from day 8 to 14. Heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) were measured using tail-cuff method. Hydroperoxides concentration and ferric reducing antioxidant power (FRAP) value were determined in plasma samples. Dexamethasone significantly increased BP and plasma hydroperoxides level and decreased body weights. High dose of celecoxib resulted in a small but significant increase in SBP, DBP and MAP in normotensive rats however it did not alter BP markers in dexamethasone-induced hypertensive rats. Celecoxib reduced the hypotensive effect of all doses of captopril in dexamethasone-induced hypertensive rats however the SBP and MAP was preserved near to normal at low and middle doses of captopril but DBP was more than normal at low dose of captopril. Heart rate was not significantly altered by different treatments. High dose of celecoxib also increased plasma hydroperoxides concentration without effect on FRAP level. In conclusion, celecoxib did not change blood pressure in glucocorticoid-induced hypertensive rats but may blunt the hypotensive effect of low dose of captopril. Further studies are needed for detailed information addressing the effects of COX-2 inhibitors on blood pressure in concomitant uses with corticosteroids.

Role of the Immune System in Hypertension

High blood pressure is present in more than one billion adults worldwide and is the most important modifiable risk factor of death resulting from cardiovascular disease. While many factors contribute to the pathogenesis of hypertension, a role of the immune system has been firmly established by a large number of investigations from many laboratories around the world. Immunosuppressive drugs and inhibition of individual cytokines prevent or ameliorate experimental hypertension, and studies in genetically-modified mouse strains have demonstrated that lymphocytes are necessary participants in the development of hypertension and in hypertensive organ injury. Furthermore, immune reactivity may be the driving force of hypertension in autoimmune diseases. Infiltration of immune cells, oxidative stress, and stimulation of the intrarenal angiotensin system are induced by activation of the innate and adaptive immunity. High blood pressure results from the combined effects of inflammation-induced impairment in the pressure natriuresis relationship, dysfunctional vascular relaxation, and overactivity of the sympathetic nervous system. Imbalances between proinflammatory effector responses and anti-inflammatory responses of regulatory T cells to a large extent determine the severity of inflammation. Experimental and human studies have uncovered autoantigens (isoketal-modified proteins and heat shock protein 70) of potential clinical relevance. Further investigations on the immune reactivity in hypertension may result in the identification of new strategies for the treatment of the disease.

Unusual Cause and Presentation of Collapsing Focal Segmental Glomerulosclerosis

Collapsing focal segmental glomerulosclerosis (c-FSGS), a structural variant of focal segmental glomeruloslecrosis (FSGS), is considered to be the most aggressive FSGS form. Most patients present with severe nephrotic syndrome and often have rapidly progressing renal failure and progression to end-stage kidney disease. We are reporting a 28-year-old previously healthy woman, who was started on griseofulvin for onchomycosis; she subsequently developed acute renal failure with significant proteinuria. Exposure to the drug caused dramatic decline in the renal function. Renal biopsy was compatible with c-FSGS. To the best of our knowledge, this is the first case of biopsy-proven griseofulvin-associated c-FSGS. Our patient showed rapid improvement in renal function after discontinuation of griseofulvin. Universally, c-FSGS carries poor prognosis, but this case is unique because patient showed rapid improvement in renal function with a short duration after cessation of griseofulvin.

HSPA12B: a novel facilitator of lung tumor growth

Lung tumor progression is regulated by proangiogenic factors. Heat shock protein A12B (HSPA12B) is a recently identified regulator of expression of proangiogenic factors. However, whether HSPA12B plays a role in lung tumor growth is unknown. To address this question, transgenic mice overexpressing HSPA12B (Tg) and wild-type littermates (WT) were implanted with Lewis lung cancer cells to induce lung tumorigenesis. Tg mice showed significantly higher number and bigger size of tumors than WT mice. Tg tumors exhibited increased angiogenesis and proliferation while reduced apoptosis compared with WT tumors. Interestingly, a significantly enhanced upregulation of Cox-2 was detected in Tg tumors than in WT tumors. Also, Tg tumors demonstrated upregulation of VEGF and angiopoietin-1, downregulation of AKAP12, and increased eNOS phosphorylation compared with WT tumors. Celecoxib, a selective Cox-2 inhibitor, suppressed the HSPA12B-induced increase in lung tumor burden. Moreover, celecoxib decreased angiogenesis and proliferation whereas increased apoptosis in Tg tumors. Additionally, celecoxib reduced angiopoietin-1 expression and eNOS phosphorylation but increased AKAP12 levels in Tg tumors. Our results indicate that HSPA12B stimulates lung tumor growth via a Cox-2-dependent mechanism. The present study identified HSPA12B as a novel facilitator of lung tumor growth and a potential therapeutic target for the treatment of lung cancer.

Analgesic use and the risk for progression of chronic kidney disease

PURPOSE

The chronic effect of various analgesics on the progression of chronic kidney disease (CKD) is inconclusive. There is also lack of information on the renal safety of selective cyclooxygenase-2 (COX-2) inhibitors. This study aimed to clarify the renal risk of analgesic use in CKD patients.

METHODS

A cohort study using a nationally representative database randomly sampled from National Health Insurance (NHI) enrollees was performed. The study population included a total of 19,163 newly diagnosed CKD patients. Clinical conditions were defined by diagnostic codes and exposure information on analgesics was derived from service claims. Cox proportional hazard model was used to assess the association between analgesic use and the risk of progression to end stage renal disease (ESRD).

RESULTS

CKD patients using acetaminophen, aspirin, and non-selective non-steroidal anti-inflammatory drugs (NSAIDs) had an increased risk for ESRD with multivariable-adjusted HRs (95%CIs) of 2.92 (2.47-3.45), 1.96 (1.62-2.36), and 1.56 (1.32-1.85), respectively. The trends toward higher risk with increasing exposure dose were significant for all classes of analgesics (all P for trend < 0.001). Among COX-2 inhibitors, only rofecoxib, but not celecoxib, shows a significant risk association with ESRD (HR = 1.98; 95%CI, 1.15-3.40).

CONCLUSIONS

Our data indicated exacerbating effects of acetaminophen, aspirin, and non-selective NSAIDs on CKD in a dose-dependent manner. For COX-2 inhibitors, only rofecoxib showed an increased risk for ESRD. Although the possibility of residual confounding cannot be completely ruled out, given the common use of analgesics, the possible relation suggested by this study warrants further investigation.

Pathophysiology of cyclooxygenases in cardiovascular homeostasis

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandin H(2) (PGH(2)), which is subsequently converted to the prostanoids PGE(2), PGI(2), PGF(2alpha), and thromboxane A(2). COX has 2 distinct membrane-anchored isoenzymes: COX-1 and COX-2. COX-1 is constitutively expressed in most normal tissues; COX-2 is highly induced by proinflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include conventional nonselective nonsteroidal anti-inflammatory drugs and selective nonsteroidal anti-inflammatory drugs, such as COX-2 inhibitors. The adverse effects of COX inhibitors on the cardiovascular system have been addressed in the last few years. In general, COX inhibitors have many effects, but those most important to the cardiovascular system can be direct (through the effects of prostanoids) and indirect (through alterations in fluid dynamics). Despite reports of detrimental human cardiovascular events associated with COX inhibitors, short, long, and lifetime preclinical toxicology studies in rodents and nonrodents have failed to identify these risks. This article focuses on the expression and function of COX enzymes in normal and pathologic conditions of the cardiovascular system and discusses the cardiovascular pathophysiologic complications associated with COX inhibition.

The effect of parecoxib on kidney function at laparoscopic hysterectomy

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs) have a well-documented nephrotoxic action. Still, there are only few studies that have investigated the nephrotoxicity of cyclo-oxycenase-2-inhibitors during the perioperative period. Thirty patients scheduled for elective laparoscopic hysterectomy were enrolled in this prospective, randomized double-blind study. Patients were randomized into two groups: a saline-treated control group (placebo) and 80 mg parecoxib-treated group (parecoxib). The samples for the analyses of serum and urine were collected at the induction of anesthesia, two hours thereafter, two hours from the end of anesthesia, and on the first postoperative day (POD). S-crea, S-urea, S-cystatin C, S-Na, S-K, U-1mikroglobulin/U-crea, U-GST/U-crea, and U-GST/U-crea were analyzed from the samples. Urine output was measured every hour for the first five hours, and total amount of urine was measured until the first postoperative day. There were no clinical and few statistical significant differences between the two groups in the renal measurements during the study period. The urinary output was also similar in the two groups. A single dose of 80 mg of parecoxib was well tolerated by the kidneys in the short-term perioperative use in patients undergoing laparoscopic hysterectomy with ASA physiological status I-II and age under 60 years.

Distinct roles for basal and induced COX-2 in podocyte injury

Transgenic mice that overexpress cyclooxygenase-2 (COX-2) selectively in podocytes are more susceptible to glomerular injury by adriamycin and puromycin (PAN). To investigate the potential roles of COX-2 metabolites, we studied mice with selective deletion of prostanoid receptors and generated conditionally immortalized podocyte lines from mice with either COX-2 deletion or overexpression. Podocytes that overexpressed COX-2 were virtually indistinguishable from wild-type podocytes but were significantly more sensitive to PAN-induced injury, produced more prostaglandin E(2) and thromboxane B(2), and had greater expression of prostaglandin E(2) receptor subtype 4 (EP(4)) and thromboxane receptor (TP). Treatment of COX-2-overexpressing podocytes with a TP antagonist reduced apoptosis, but treatment with an EP(4) antagonist did not. In contrast, podocytes from COX-2-knockout mice exhibited increased apoptosis, markedly decreased cell adhesion, and prominent stress fibers. In vivo, selective deletion of podocyte EP(4) did not alter the increased sensitivity to adriamycin-induced injury observed in mice overexpressing podocyte COX-2. In contrast, genetic deletion of TP in these mice prevented adriamycin-induced injury, with attenuated albuminuria and foot process effacement. These results suggest that basal COX-2 may be important for podocyte survival, but overexpression of podocyte COX-2 increases susceptibility to podocyte injury, which is mediated, in part, by activation of the thromboxane receptor.

Defining the problem of treating the patient with hypertension and arthritis pain

As osteoarthritis and hypertension coexist often in patients aged >60 years, the coadministration of nonsteroidal anti-inflammatory drugs (NSAIDs) with hypertension therapies is common practice in clinical medicine. Clinical trials in patients with arthritis have shown that many agents within the NSAID class may induce significant increases in systolic blood pressure, particularly when patients are using renin-angiotensin-blocking agents, beta-blockers, or diuretics as antihypertensives. The increases in blood pressure caused by NSAIDs are large enough to be of clinical concern. Sustained blood pressure elevations in the elderly are associated with increases in the risk of both ischemic and hemorrhagic stroke, congestive heart failure, and ischemic cardiac events. Recognition of the development of destabilization of blood pressure control in clinical practice and an awareness of those NSAIDs that place patients at risk for the development of hypertension could lead to reductions in cardiovascular morbidity.

Redox control of renal function and hypertension

Loss of redox homeostasis and formation of excessive free radicals play an important role in the pathogenesis of kidney disease and hypertension. Free radicals such as reactive oxygen species (ROS) are necessary in physiologic processes. However, loss of redox homeostasis contributes to proinflammatory and profibrotic pathways in the kidney, which in turn lead to reduced vascular compliance and proteinuria. The kidney is susceptible to the influence of various extracellular and intracellular cues, including the renin-angiotensin-aldosterone system (RAAS), hyperglycemia, lipid peroxidation, inflammatory cytokines, and growth factors. Redox control of kidney function is a dynamic process with reversible pro- and anti-free radical processes. The imbalance of redox homeostasis within the kidney is integral in hypertension and the progression of kidney disease. An emerging paradigm exists for renal redox contribution to hypertension.

Gq-dependent signaling upregulates COX2 in glomerular podocytes

Accumulating evidence suggests that upregulation of cyclooxygenase 2 (COX2) in glomerular podocytes promotes podocyte injury. Because Gq signaling activates calcineurin and calcineurin-dependent mechanisms are known to mediate COX2 expression, this study investigated the role of Gqalpha in promoting COX2 expression in podocytes. A constitutively active Gq alpha subunit tagged with the TAT HIV protein sequence was introduced into an immortalized podocyte cell line by protein transduction. This stimulated inositol trisphosphate production, activated an nuclear factor of activated T cells-responsive reporter construct, and enhanced levels of both COX2 mRNA and protein compared with cells treated with a Gq protein lacking the TAT sequence. Induction of COX2 was associated with increased prostaglandin E(2) production and podocyte death, both of which were attenuated by selective COX2 inhibition. In vivo, levels of COX2 mRNA and protein were significantly enhanced in podocytes from transgenic mice that expressed podocyte-targeted constitutively active Gqalpha compared with nontransgenic littermates. These data suggest that Gq-dependent signaling cascades stimulate calcineurin and, in turn, upregulate COX2 mRNA and protein, increase eicosanoid production, and cause podocyte injury.

Celecoxib but not the combination of celecoxib+atorvastatin prevents the development of monocrotaline-induced pulmonary hypertension in the rat

The present study aimed to assess the effects of a COX-2 inhibitor, celecoxib, a HMG-CoA reductase inhibitor, atorvastatin, and the association of both on monocrotaline (MC)-induced pulmonary hypertension in rats. Celecoxib (Cib, 25 mg kg(-1) day(-1)), atorvastatin (AS, 10 mg kg(-1) day(-1)) or vehicle, were given orally, separately or in combination, for 26 days to Wistar male rats injected or not with MC (60 mg/kg intraperitoneally). At 4 weeks, MC-injected rats developed a severe pulmonary hypertension, with an increase in lung to body weight ratio (L/BW), right ventricular pressure (RVP in mmHg, 31 +/- 3 and 14 +/- 1 for MC and control groups, respectively, P < 0.05) and right ventricle/left ventricle + septum weight ratio (RV/LV+S) associated with a decrease in acetylcholine- and sodium-nitroprusside-induced pulmonary artery vasodilation in vitro. Hypertensive pulmonary arteries exhibited an increase in wall thickness (wall thickness to external diameter ratio, 0.42 +/- 0.01 vs 0.24 +/- 0.01 for MC and control groups, respectively, P < 0.001). Whole lung eNOS expression was decreased, and an increase in apoptosis, evaluated by cleaved caspase-3 expression, was evidenced by Western blotting. Cib (RVP in mmHg, 19 +/- 3 and 31 +/- 3 for MC+Cib and MC groups, respectively, P < 0.05), but neither AS nor AS+Cib significantly limited the development of pulmonary hypertension (P < 0.05), although the three treatments exhibited protective effects against MC-induced lung and right ventricle hypertrophy evaluated by L/BW and RV/(LV+S) ratios, respectively (P < 0.05). AS, Cib and AS+Cib treatments reduced MC-induced thickening of small intrapulmonary artery wall (0.42 +/- 0.01, 0.24 +/- 0.01, 0.26 +/- 0.01 and 0.28 +/- 0.01 for MC, MC+AS, MC+Cib and MC+AS+Cib groups, respectively, P < 0.001). In control rats, Cib reduced acetylcholine-induced pulmonary artery vasorelaxation. Treatment of MC rats by either Cib or AS did not modify acetylcholine-induced pulmonary artery relaxation, whereas combination of both drugs significantly worsened it (P < 0.05). AS, but neither Cib nor the combination of both, prevented apoptosis (AS, P < 0.05) and partially restored eNOS expression (AS, P < 0.05) in whole lung of MC rats. In conclusion, celecoxib exhibited beneficial effects against the development of monocrotaline-induced pulmonary artery hypertension and right ventricular hypertrophy. These beneficial effects of celecoxib might be, at least partly, explained by its effects on pulmonary artery thickening and pulmonary hypertrophy, even if it did not show any effect on pulmonary artery vasorelaxation and whole lung eNOS expression or apoptosis. The combination of celecoxib and atorvastatin was unable to prevent MC-induced pulmonary hypertension, decreased endothelium-dependent vasorelaxation and showed a trend toward an increased in RVP that deserves further studies.

Signaling pathways modulated by fish oil in salt-sensitive hypertension

Although many studies have indicated that fish oil (FO) improves cardiovascular risk factors and reduces histopathological manifestations of injury in experimental renal injury models, potential mechanisms underlying this protective effect have not been adequately defined. The objective of this study was to identify potential signaling pathways that confer protection in the Dahl rat model of salt-sensitive hypertension. Male Dahl salt-sensitive rats (n = 10/group) were provided with formulated diets containing 8% NaCl, 20% protein, and 25% FO or 25% corn oil (CO) for 28 days. FO reduced blood pressure (-11% at 4 wk; P < 0.05), urine protein excretion (-45% at 4 wk; P < 0.05), plasma cholesterol and triglyceride levels (-54%, P < 0.001; and -58%, P < 0.05), and histopathological manifestations of renal injury, including vascular hypertrophy, segmental and global glomerular sclerosis, interstitial fibrosis, and tubular atrophy. Interstitial inflammation was significantly reduced by FO (-32%; P < 0.001), as assessed by quantitative analysis of ED1-positive cells in sections of the renal cortex. FO reduced tubulointerstitial proliferative activity, as assessed by Western blot analysis of cortical homogenates for PCNA (-51%; P < 0.01) and quantitative analysis of Mib-1-stained sections of the renal cortex (-42%; P < 0.001). Decreased proliferative activity was associated with reduced phospho-ERK expression (-37%; P < 0.005) and NF-kappaB activation (-42%; P < 0.05). FO reduced cyclooxygenase (COX)-2 expression (-63%; P < 0.01) and membrane translocation of the NADPH oxidase subunits p47(phox) and p67(phox) (-26 and -34%; P < 0.05). We propose that FO ameliorates renal injury in Dahl salt-sensitive rats through the inhibition of ERK, decreased NF-kappaB activation, inhibition of COX-2 expression, and decreased NADPH oxidase activation.

Upregulation of cortical COX-2 in salt-sensitive hypertension: role of angiotensin II and reactive oxygen species

Salt-sensitive (SS) hypertension is a vascular diathesis characterized by reduced cardiovascular and renal nitric oxide bioavailability and local upregulation of ANG II. We have demonstrated that rats infused with ANG II manifest increased cortical cyclooxygenase (COX)-2 expression and activity via NADPH oxidase-derived reactive oxygen species (ROS). In the present studies we used Dahl salt-sensitive (DS) rats to test the hypothesis that hypertensive SS rats have increased cortical COX-2 upregulation, which is mediated by ANG II and ROS. DS rats were placed on either a normal-salt diet (0.5% NaCl) or a high-salt diet (4% NaCl) for 6 wk and treated with either the ANG II type 1 (AT1) receptor blocker candesartan (Can, 10 mg·kg−1·day−1) or the SOD mimetic tempol (1 mmol/l). Hypertensive SS rats had a twofold increase in the cortical expression of COX-2 as assessed by Western blot. These changes in COX-2 expression were accompanied by a 10-fold increase in COX-2 mRNA expression and a 2-fold increase in the urinary excretion of PGE2. Treatment with either the AT1receptor blocker Can or the SOD mimetic tempol did not reduce blood pressure but resulted in significant reductions in the cortical expression of COX-2 and the urinary excretion of PGE2. In conclusion, we have demonstrated that local activation of the renin-angiotensin system, via increased ROS generation, mediates COX-2 upregulation in hypertensive SS rats. These studies unveil novel mechanistic pathways that may play a role in the pathogenesis of hypertensive renal injury.

Cardiovascular risk, hypertension, and NSAIDs

During the past 2 years, a great deal of evaluation has been conducted on the cardiovascular (CV) effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase (COX)-2 inhibitors. This review focuses on the effects of the NSAIDs and COX-2 inhibitors on blood pressure and CV events. Clinical trial databases for NSAIDs and COX-2 inhibitors have shown varying levels of destabilization of blood pressure control in treated hypertensive patients as well as variable incident rates of the development of arrhythmias, congestive heart failure, myocardial infarction, and stroke. Nonselective and COX-2 selective NSAIDs can be used carefully in arthritis patients with hypertension and stable CV disorders (excluding congestive heart failure and moderate to severe kidney dysfunction) when the individual clinical benefit of anti-inflammatory therapy outweighs the CV and gastrointestinal risk.

COX-2 selective inhibitors in the treatment of osteoarthritis

OBJECTIVES

To assess the efficacy of cyclooxygenase-2 selective inhibitors (coxibs) in osteoarthritis (OA) and their gastrointestinal, cardiovascular, renovascular, and hepatic side effects compared with traditional nonsteroidal antiinflammatory drugs (NSAIDs) and acetaminophen.

METHODS

Bibliographic database searches for randomized controlled trials, meta-analyses, and literature reviews.

RESULTS

Coxibs are comparable to traditional NSAIDs, providing moderate benefit for OA patients in pain and function versus placebo. NSAIDs, including coxibs, are superior to acetaminophen for OA, particularly in patients with moderate to severe pain. Coxibs decrease gastroduodenal ulcers (74% relative risk reduction) and ulcer complications (61% reduction) versus traditional NSAIDs. Meta-analysis of randomized trials indicates that coxibs increase the risk of myocardial infarctions approximately twofold versus placebo and versus naproxen, but do not increase the risk versus nonnaproxen NSAIDs. NSAIDs, including coxibs, commonly cause fluid retention and increase blood pressure and uncommonly induce congestive heart failure or significant renal dysfunction; risk factors include advanced age, hypertension, and heart or kidney disease. NSAIDs are a rare cause of clinical hepatotoxicity (<1 liver-related death per 100,000 NSAID users in clinical studies). Increased rates of aminotransferase elevations occur with rofecoxib (2%) and high-dose lumiracoxib (3%), and postmarketing cases of clinical liver injury with lumiracoxib have been reported recently.

CONCLUSIONS

Coxibs are as effective as traditional NSAIDs and superior to acetaminophen for the treatment of OA. Coxibs cause fewer gastrointestinal complications than traditional NSAIDs. Coxibs increase cardiovascular risk versus placebo and naproxen-but probably not versus nonnaproxen NSAIDs. Blood pressure commonly increases after initiation of selective or nonselective NSAIDs, especially in hypertensive patients.

Effects of dietary salt on intrarenal angiotensin system, NAD(P)H oxidase, COX-2, MCP-1 and PAI-1 expressions and NF-kappaB activity in salt-sensitive and -resistant rat kidneys

BACKGROUND

Chronic consumption of a high-salt diet causes hypertension (HTN) and renal injury in Dahl salt-sensitive (SSR) but not salt-resistant rats (SRR). These events are, in part, mediated by oxidative stress and inflammation in the kidney and vascular tissues. Activation of the angiotensin II type 1 (AT(1)) receptor plays an important role in the pathogenesis of oxidative stress and inflammation in many hypertensive disorders. However, the systemic renin-angiotensin system (RAS) is typically suppressed in salt-sensitive HTN. This study was designed to test the hypothesis that differential response to a high-salt diet in SSR versus SRR may be related to upregulation of tissue RAS and pathways involved in inflammation and reactive oxygen species (ROS) production.

METHODS AND RESULTS

SSR and SRR were studied 3 weeks after consumption of high- (8%) or low-salt (0.07%) diets. The SSR consuming a low-salt diet exhibited significant increases in AT(1) receptor, cyclooxygenase (COX) 2, plasminogen activator inhibitor (PAI) and phospho-I kappaB in the kidney as compared to those found in SRR. The high-salt diet resulted in severe HTN and proteinuria (in SSR but not SRR) and marked elevations of renal tissue monocyte chemoattractant protein 1, p22(phox), NADPH oxidase subunit 4, angiotensin-II-positive cell count, infiltrating T cells and macrophages and further increases in AT(1) receptor, COX-2, PAI-1 and phospho-I kappaB in the SSR group. The high-salt diet significantly lowered plasma renin activity (PRA) in SRR but not in the SSR. COX-1 abundance was similar on the low-salt diet and rose equally with the high-salt diet in both groups. Among subgroups of animals fed the low-salt diet, kidney glutathione peroxidase (GPX) abundance was significantly lower in the SSR than SRR. The high-salt diet raised GPX and mitochondrial superoxide dismutase (SOD) abundance in the SRR kidneys but failed to do so in SSR. Cu/Zn-SOD abundance was similar in the subgroups of SSR and SRR fed the low-salt diet. The high-salt diet resulted in downregulation of Cu/Zn-SOD in SSR but not SRR.

CONCLUSIONS

Salt sensitivity in the SSR is associated with upregulations of the intrarenal angiotensin system, ROS-generating and proinflammatory/profibrotic proteins and an inability to raise antioxidant enzymes and maximally suppress PRA in response to high salt intake. These events can contribute to renal injury with high salt intake in SSR.

Cardiovascular risk, hypertension, and NSAIDs

During the past 2 years, a great deal of evaluation has been conducted on the cardiovascular (CV) effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase (COX)-2 inhibitors. This review focuses on the effects of the NSAIDs and COX-2 inhibitors on blood pressure and CV events. Clinical trial databases for NSAIDs and COX-2 inhibitors have shown varying levels of destabilization of blood pressure control in treated hypertensive patients as well as variable incident rates of the development of arrhythmias, congestive heart failure, myocardial infarction, and stroke. Nonselective and COX-2 selective NSAIDs can be used carefully in arthritis patients with hypertension and stable CV disorders (excluding congestive heart failure and moderate to severe kidney dysfunction) when the individual clinical benefit of anti-inflammatory therapy outweighs the CV and gastrointestinal risk.

Collapsing glomerulopathy: an inflammatory podocytopathy?

PURPOSE OF REVIEW

Collapsing glomerulopathy is a relatively new and debated podocytopathy. Among several conjectures, inflammatory injury orchestrated by podocytes is emerging to explain the pathogenesis of collapsing glomerulopathy. Here, we briefly summarize recent studies in support of this novel and intriguing hypothesis.

RECENT FINDINGS

Immunohistochemical analyses of markers conventionally used to demarcate podocytes apart from parietal epithelium identified the parietal podocyte. MafB-deficient mice exhibited abnormal podocyte and macrophage differentiation, suggesting ancestral and functional overlap. These apparent developmental anomalies were detected in studies showing an admixture of hyperplastic podocytes with macrophage epitopes and hyperplastic parietal epithelium in pseudocrescents and in true crescents. Experimental antibody-mediated injury of podocytes could trigger capillary collapse and pseudocrescent formation marked by recruitment of epithelial cells from Bowman's capsule. In contrast, experimental stabilization of hypoxia-inducible factors within podocytes--a known inflammatory response by macrophages--could trigger podocyte proliferation and the formation of true necrotizing crescents.

SUMMARY

Preliminary evidence suggests that visceral and parietal podocytes may become macrophage-like inflammatory mediators of proliferative epithelial injury within the glomerulus. This may manifest as collapsing glomerulopathy or crescentic glomerulonephritis--lesions that appear to be anatomically and pathogenically linked.

Overexpression of cyclooxygenase-2 predisposes to podocyte injury

Increased podocyte cyclooxygenase-2 (COX-2) expression is seen in rats after renal ablation and Thy-1 nephritis and in cultured murine podocytes in response to mechanical stress. For investigation of whether COX-2 overexpression plays a role in podocyte injury, transgenic B6/D2 mice in which COX-2 expression was driven by a nephrin promoter were established. Selective upregulation of COX-2 expression in podocytes of transgenic mouse kidneys was confirmed by immunoblotting and immunohistochemistry. Whether upregulation of podocyte-specific COX-2 expression enhanced sensitivity to the development of Adriamycin nephropathy was examined. Adriamycin administration induced dramatically more albuminuria and foot process effacement and reduced glomerular nephrin mRNA and immunoreactivity in transgenic mice compared with wild-type littermates. Adriamycin also markedly increased immunoreactive COX-2 expression in podocytes from transgenic mice compared with the wild-type mice. Reverse transcriptase-PCR indicated that this increase represented a stimulation of endogenous COX-2 mRNA expression rather than COX-2 mRNA driven by the nephrin promoter. Balb/C mice, which are susceptible to renal injury by Adriamycin, also increased podocyte COX-2 expression and reduced nephrin expression in response to administration of the drug. Long-term treatment with the COX-2-specific inhibitor SC58236 ameliorated the albuminuria that was induced by Adriamycin in the transgenic mice. SC58236 also reduced Adriamycin-induced foot process effacement in both the COX-2 transgenic mice and Balb/C mice. Therefore, overexpression of COX-2 may predispose podocytes to further injury.

The Monocyte Chemotactic Protein-1 Gene May Contribute to Hypertension in Dahl Salt-Sensitive Rats

In a previous study, we performed a genome-wide quantitative trait loci (QTLs) analysis for blood pressure using F2 rats derived from Dahl salt-sensitive (DS) and Lewis (LEW) rats and identified two QTLs that influenced blood pressure levels. Although we determined that one of the causative genes in the chromosome (Ch) 1 region seemed to be Klk1, we did not perform detailed analyses on the Ch10 QTL region. The purpose of the present study was to identify candidate genes that influence blood pressure in the Ch10 QTL region. Using microarray analysis, we compiled a list of the genes that are differentially expressed between the two strains and that were localized to the Ch10 QTL region. Subsequent reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis identified that, while the expression levels of Ccl2 mRNA were not different between the kidneys of DS and LEW rats fed a normal diet, those in DS were 10-fold higher than those in LEW under a high-salt diet. Although the promoter reporter assay failed to identify causative nucleotide changes that led to the differential expression, monocyte chemotactic protein-1 (MCP-1) release from isolated monocytes were significantly higher in DS than in LEW. Intriguingly, this Ch10 QTL for blood pressure was also a possible QTL for urinary albumin excretion. Since Ccl2 is well known to be involved in various types of renal injury, it is likely that a higher expression of Ccl2 might aggravate macrophage infiltration, which in turn could aggravate tubulointerstitial injury, and thereby accelerate salt-sensitive hypertension. Thus, Ccl2 appears to be a interesting candidate gene for salt-sensitive hypertension in DS.

Cyclooxygenase-2 and nitric oxide

Nitric oxide (NO) is a simple but pluripotent molecule that is mainly released from vascular endothelial cells where it is formed intracellularly by nitric oxide synthase from L-arginine in response to several stimuli, including shear stress or muscarinic receptor stimulation. NO stimulates guanylyl cyclase to form cyclic guanosine monophosphate, which results in relaxation and vasodilatation of vascular smooth muscle cells (VSMCs). In addition, NO prevents adhesion and aggregation of platelets, and it possesses anti-inflammatory, antiproliferative, and antimigratory effects on leukocytes, endothelial cells, and VSMCs, thus offering protection from atherosclerosis. Dysfunction of the vascular endothelium has been documented in most conditions that promote or are associated with atherosclerosis and is characterized by a reduced bioavailability of NO. The healthy endothelium prevents adhesion and migration of leukocytes, proliferation of VSMCs, and platelet adhesion and aggregation. Maintaining the balance of blood flow and thrombus formation is also a major task of the vascular endothelium. It has been shown that both NO and prostacyclin, a cyclooxygenase-derived relaxing factor, inhibit activation of platelets and regulate vasomotion. Reduced NO and prostacyclin levels can result in endothelial dysfunction, which is recognized as the first step in the atherogenic process. It is of note that chronic inflammation conditions, such as rheumatoid arthritis, are associated with endothelial dysfunction. The reduced NO bioavailability may therefore explain the increased risk for cardiovascular events in patients with chronic low-grade inflammation, such as rheumatoid arthritis and osteoarthritis. Thus, this article provides an overview of the impact of inflammation and anti-inflammatory treatment with cyclooxygenase inhibitors on endothelial function.

Effects of the selective cyclooxygenase-2 inhibitor analgesic celecoxib on renal carbonic anhydrase enzyme activity: a randomized, controlled trial

Rofecoxib and celecoxib were the first cyclooxygenase-2 (COX-2)-specific inhibitors to be marketed as effective anti inflammatory agents. The results of several recent trials and a meta analysis of currently available studies all demonstrate a greater incidence of increased blood pressure, edema, and cardiovascular events in subjects treated with rofecoxib compared with celecoxib. As an approach to the assessment of molecular mechanisms that may contribute to these cardiorenal differences, this study investigated the inhibitory effects of celecoxib on renal carbonic anhydrase enzyme activity in human hypertensive subjects because in vitro enzyme studies demonstrate such an effect. Ten subjects with stable, treated hypertension were randomized to 1 of 3 treatment sequences, which included, in differing order, 200 mg celecoxib twice a day, 250 mg acetazolamide twice a day, or placebo twice a day. Whereas acetazolamide caused a bicarbonate diuresis and a hyperchloremic metabolic acidosis, celecoxib appeared to have no detectable effect on renal carbonic anhydrase or acid-base homeostasis. Thus, in this short-term study of human subjects, therapeutic doses of celecoxib did not appear to have a clinically significant inhibitory action on renal carbonic anhydrase.

The vascular endothelium in hypertension

The vascular endothelium plays a fundamental role in the basal and dynamic regulation of the circulation. Thus, it has a crucial role in the pathogenesis of hypertension. A spectrum of vasoactive substances is synthesised in the endothelium; of these, nitric oxide (NO), prostacyclin (PGI2) and endothelin (ET)-1 are the most important. There is a continuous basal release of NO determining the tone of peripheral blood vessels. Systemic inhibition of NO synthesis or scavenging of NO through oxidative stress causes an increase in arterial blood pressure. Also, the renin-angiotensin-aldosterone system has a major role in hypertension as it has a direct vasoconstrictor effect and important interactions with oxygen free radicals and NO. Prostacyclin, in contrast to NO, does not contribute to the maintenance of basal vascular tone of conduit arteries, but its effect on platelets is most important. ET acts as the natural counterpart to endothelium-derived NO and has an arterial blood pressure-raising effect in man. Anti-hypertensive therapy lowers blood pressure and may influence these different mediators, thus influencing endothelial function. In summary, due to its position between the blood pressure and smooth muscle cells responsible for peripheral resistance, the endothelium is thought to be both victim and offender in arterial hypertension. The delicate balance of endothelium-derived factors is disturbed in hypertension. Specific anti-hypertensive and anti-oxidant treatment is able to restore this balance.

Collapsing glomerulopathy

Collapsing glomerulopathy (CG) has become an important cause of ESRD. First delineated from other proteinuric glomerular lesions in the 1980s, CG is now recognized as a common, distinct pattern of proliferative parenchymal injury that portends a rapid loss of renal function and poor responses to empiric therapy. Notwithstanding, the rise in disorders that are associated with CG, the identification of the first susceptibility genes for CG, the remarkable increase in murine modeling of CG, and promising preclinical testing of new therapeutic strategies suggest that the outlook for CG as a poorly understood and therapeutically resistant renal disease is set to change in the future. This focused review highlights recent advances in research into the pathogenesis and treatment of CG.

Prostaglandin D2 inhibits TGF-beta1-induced epithelial-to-mesenchymal transition in MDCK cells

In a separate study, we identified PGE2 as a potent inhibitor of TGF-beta1induced epithelial-mesenchymal transition (EMT) in cultured Madin-Darby canine kidney (MDCK) cells (Zhang A, Wang M-H, Dong Z, and Yang T. Am J Physiol Renal Physiol 291: F1323-F1331, 2006). This finding prompted us to examine the roles of other prostanoids: PGD2, PGF(2alpha), PGI2, and thromboxane A2 (TXA2). Treatment with 10 ng/ml TGF-beta1 for 3 days induced EMT as reflected by conversion to the spindle-like morphology, loss of E-cadherin, and activation of alpha-smooth muscle actin (alpha-SMA). Treatment with PGD2 remarkably preserved the epithelial-like morphology, restored the expression of E-cadherin, and abolished the activation of alpha-SMA. In contrast, PGF(2alpha), carbocyclic thromboxane A2, PGI2 and its stable analog beraprost were without an effect. MDCK cells expressed DP1 and DP2 receptors; however, the effect of PGD2 was neither prevented by DP1 antagonist BW-A868C or DP2 antagonist BAY-u3405 nor was mimicked by DP1 agonist BW-245C. cAMP-elevating agents forskolin and 8-Br-cAMP blocked EMT. However, cAMP blockers H89 and Rp-cAMP failed to block the effect of PGD2. PGD2 did not seem to act via its metabolites as 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2) levels in the medium following incubation with 3 microM PGD2 were well below the values predicted from the cross activity of the assay. Exposure to TGF-beta1 induced a threefold increase in reactive oxygen species production that was completely abolished by PGD2. We conclude that 1) PGD2, but not PGI2, PGF(2alpha), and TXA2 inhibit EMT, 2) PGD2 inhibits EMT independently of DP1 and DP2 receptors, and 3) PGD2 exhibits antioxidant property which may, in part, account for the antifibrotic action of this PG.

Expectations from patients with rheumatoid arthritis regarding COX-2s: cutting to the heart of the matter

Before the withdrawal of 2 COX-2 selective agents (COX-2s) from the market, many rheumatoid arthritis patients were using these products regularly, with disease-modifying antirheumatic agents. Clinical trials have shown benefit of COX-2s equivalent to nonselective nonsteroidal anti-inflammatory drugs (NS-NSAIDs) in rheumatoid arthritis. Better gastrointestinal (GI) safety has been demonstrated with COX-2s; numerical but not statistical benefit with concomitant use of cardiovascular (CV) doses of aspirin. COX-2 benefit may extend to lower GI blood loss against which proton pump inhibitors are not protective. COX-2s are associated with hypertension and edema of similar magnitude to NS-NSAIDs in predisposed individuals. Epidemiologic studies and clinical trials have confirmed the association of serious thromboembolic (CV) events and congestive heart failure with rofecoxib>25 mg daily, celecoxib, and NS-NSAIDs, although there is a paucity of long-term data. Important questions remain regarding relative GI and CV risks: is concomitant aspirin protective when coadministered with COX-2s? Does this abrogate their GI benefit? As identified many years ago with NS-NSAIDs, patients may respond to one and not another; COX-2s should be considered individually and not as a single "class." Patients deserve the opportunity to make a choice about the perceived benefit/risk assessment when using these therapies, with the collaboration of their physician.

Rofecoxib Increases Susceptibility of Human LDL and Membrane Lipids to Oxidative Damage: A Mechanism of Cardiotoxicity

Clinical investigations have demonstrated a relationship between the extended use of rofecoxib and the increased risk for atherothrombotic events. This has led to the removal of rofecoxib from the market and concern over the cardiovascular safety of other cyclooxygenase (COX)-2 selective agents. Experimental findings from independent laboratories now indicate that the cardiotoxicity of rofecoxib may not be a class effect but because of its intrinsic chemical properties. Specifically, rofecoxib has been shown to increase the susceptibility of human low-density lipoprotein and cellular membrane lipids to oxidative modification, a contributing factor to plaque instability and thrombus formation. Independently of COX-2 inhibition, rofecoxib also promoted the nonenzymatic formation of isoprostanes and reactive aldehydes from biologic lipids. The basis for these observations is that rofecoxib alters lipid structure and readily forms a reactive maleic anhydride in the presence of oxygen. By contrast, other selective (celecoxib, valdecoxib) and nonselective (naproxen, diclofenac) inhibitors did not influence rates of low-density lipoprotein and membrane lipid oxidation. We have now further confirmed these findings by demonstrating that the prooxidant activity of rofecoxib can be blocked by the potent antioxidant astaxanthin in homochiral form (all-trans 3S, 3'S). These findings provide a mechanistic rationale for differences in cardiovascular risk among COX-selective inhibitors because of their intrinsic physicochemical properties.

13-cis retinoic acid inhibits development and progression of chronic allograft nephropathy

Chronic allograft nephropathy is characterized by chronic inflammation and fibrosis. Because retinoids exhibit anti-proliferative, anti-inflammatory, and anti-fibrotic functions, the effects of low and high doses of 13-cis-retinoic acid (13cRA) were studied in a chronic Fisher344-->Lewis transplantation model. In 13cRA animals, independent of dose (2 or 20 mg/kg body weight/day) and start (0 or 14 days after transplantation) of 13cRA administration, serum creatinine was significantly lower and chronic rejection damage was dramatically reduced, including subendothelial fibrosis of preglomerular vessels and chronic tubulointerstitial damage. The number of infiltrating mononuclear cells and their proliferative activity were significantly diminished. The mRNA expression of chemokines (MCP-1/CCL2, MIP-1alpha/CCL3, IP-10/CXCL10, RANTES/CCL5) and proteins associated with fibrosis (plasminogen activator inhibitor-1, transforming growth factor-beta1, and collagens I and III) were strikingly lower in treated allografts. In vitro, activated peritoneal macrophages of 13cRA-treated rats showed a pronounced decrease in protein secretion of inflammatory cytokines (eg, tumor necrosis factor-alpha, interleukin-6). The suppression of the proinflammatory chemokine RANTES/CCL5 x 13cRA in fibroblasts could be mapped to a promoter module comprising IRF-1 and nuclear factor-kappaB binding elements, but direct binding of retinoid receptors to promoter elements could be excluded. In summary, 13cRA acted as a potent immunosuppressive and anti-fibrotic agent able to prevent and inhibit progression of chronic allograft nephropathy.

The kd/kd mouse is a model of collapsing glomerulopathy

Collapsing glomerulopathy (CG) is associated with disorders that markedly perturb the phenotype of podocytes. The kd/kd mouse has been studied for immune and genetic causes of microcystic tubulointerstitial nephritis with little attention to its glomerular lesion. Because histologic examination revealed classic morphologic features of CG, the question arises whether podocytes in kd/kd mice exhibit additional phenotypic criteria for CG. Utilizing Tg26 mice as a positive control, immunohistochemical profiling of the podocyte phenotype was conducted simultaneously on both models. Similar to Tg26 kidneys, podocytes in kd/kd kidneys showed de novo cyclin D1, Ki-67, and desmin expression with loss of synaptopodin and WT-1 expression. Electron micrographs showed collapsed capillaries, extensive foot process effacement, and dysmorphic mitochondria in podocytes. These results indicate that the kd/kd mouse is a model of CG and raise the possibility that human equivalents of the kd susceptibility gene may exist in patients with CG.