Rilonacept in the treatment of acute gouty arthritis: a randomized, controlled clinical trial using indomethacin as the active comparator

Introduction

In phase-3 clinical trials, the interleukin (IL-1) blocker, rilonacept (IL-1 Trap), demonstrated efficacy for gout flare prevention during initiation of urate-lowering therapy. This trial evaluated rilonacept added to a standard-of-care, indomethacin, for treatment of acute gout flares.

Methods

Adults, aged 18-70 years, with gout presenting within 48 hours of flare onset and having at least moderate pain as well as swelling and tenderness in the index joint were randomized to subcutaneous (SC) rilonacept 320 mg at baseline plus oral indomethacin 50 mg TID for 3 days followed by 25 mg TID for up to 9 days (n = 74); SC placebo at baseline plus oral indomethacin as above (n = 76); or SC rilonacept 320 mg at baseline plus oral placebo (n = 75). The primary efficacy endpoint was change in pain in the index joint (patient-reported using a Likert scale (0 = none; 4 = extreme)) from baseline to the average of values at 24, 48 and 72 hours (composite time point) for rilonacept plus indomethacin versus indomethacin alone. Comparison of rilonacept monotherapy with indomethacin monotherapy was dependent on demonstration of significance for the primary endpoint. Safety evaluation included clinical laboratory and adverse event (AE) assessments.

Results

Patient characteristics were comparable among the groups; the population was predominantly male (94.1%), white (75.7%), with mean ± SD age of 50.3 ± 10.6 years. All treatment groups reported within-group pain reductions from baseline (P < 0.0001). Although primary endpoint pain reduction was greater with rilonacept plus indomethacin (-1.55 ± 0.92) relative to indomethacin alone (-1.40 ± 0.96), the difference was not statistically significant (P = 0.33), so formal comparison between monotherapy groups was not performed. Pain reduction over the 72-hour period with rilonacept alone (-0.69 ± 0.97) was less than that in the other groups, but pain reduction was similar among groups at 72 hours. Treatment with rilonacept was well-tolerated with no reported serious AEs related to rilonacept. Across all groups, the most frequent AEs were headache and dizziness.

Conclusions

Although generally well-tolerated, rilonacept in combination with indomethacin and rilonacept alone did not provide additional pain relief over 72 hours relative to indomethacin alone in patients with acute gout flare.

Trial registration

ClinicalTrials.gov registration number NCT00855920.

Novel evidence-based colchicine dose-reduction algorithm to predict and prevent colchicine toxicity in the presence of cytochrome P450 3A4/P-glycoprotein inhibitors

OBJECTIVE

Drug-drug interactions can limit the safety of colchicine for treating rheumatic diseases. Seven separate drug-drug interaction (DDI) studies were performed to elucidate the in vivo effects of concomitant treatment with colchicine and known inhibitors of cytochrome P450 3A4 (CYP3A4)/P-glycoprotein (cyclosporine, ketoconazole, ritonavir, clarithromycin, azithromycin, verapamil ER [extended release]), and diltiazem ER) on the pharmacokinetics of colchicine. The objective was to develop colchicine-dosing algorithms with improved safety.

METHODS

All studies were open-label, non-randomized, single-center, one-sequence, two-period DDI experiments, using two 0.6-mg doses of colchicine, separated by a minimum 14-day washout period, followed by administration of the approved on-label regimen of known CYP3A4/P-glycoprotein inhibitors. Plasma concentrations of colchicine, but not the reference CYP3A4/P-glycoprotein inhibitors, were determined, and the pharmacokinetic parameters were calculated.

RESULTS

The ratios of the maximum concentration and area under the curve from time 0 to infinity for colchicine plus CYP3A4/P-glycoprotein inhibitors versus colchicine alone were >125% across all studies, with the exception of studies involving azithromycin. Significant DDIs were present when single doses of colchicine were coadministered with most of the selected CYP3A4/P-glycoprotein inhibitors. Recommended colchicine dose reductions of 33-66% for the treatment of acute gout and 50-75% for prophylaxis were calculated for concomitant therapy with each agent, with the exception of no dose adjustment when colchicine is used in combination with azithromycin.

CONCLUSION

These studies provide quantitative evidence regarding drug interactions and necessary adjustments in the dose of colchicine if colchicine treatment is continued during therapy with multiple CYP3A4/P-glycoprotein inhibitors. We demonstrated the need for specific reductions in the dose of colchicine when it is used in combination with 2 broadly prescribed calcium channel blockers (verapamil ER and diltiazem ER) and that the dose of colchicine does not need to be adjusted when it is used in combination with azithromycin.

Minimally important differences of the gout impact scale in a randomized controlled trial

OBJECTIVE

The Gout Impact Scale (GIS) is a gout-specific quality of life instrument that assesses impact of gout during an attack and impact of overall gout. The GIS has five scales and each is scored from 0 to 100 (worse health). Our objective was to assess minimally important differences (MIDs) for the GIS administered in a randomized controlled trial (RCT) assessing rilonacept vs placebo for prevention of gout flares during initiation of allopurinol therapy.

METHODS

Trial subjects (n = 83) included those with two or more gout flares (self-reported) in the past year. Of these, 73 had data for Weeks 8 vs 4 and formed the MID analysis group and were analysed irrespective of the treatment assignment. Subjects completed the GIS and seven patient-reported anchors. Subjects with a one-step change (e.g. from very poor to poor) were considered as the MID group for each anchor. The mean change in GIS scores and effect size (ES) was calculated for each anchor's MID group. The average of these created the overall summary MID statistics for each GIS. An ES of 0.2-0.5 was considered to represent MID estimates. Results. Trial subjects (n = 73) were males (96.0%), White (90.4%), with mean age of 50.5 years and serum uric acid of 9.0 mg/dl. The mean change score for the MID improvement group for scales ranged from -5.24 to -7.61 (0-100 scale). The ES for the MID improvement group for the four scales ranged from 0.22 to 0.38.

CONCLUSION

The MID estimates for GIS scales are between 5 and 8 points (0-100 scale). This information can aid in interpreting the GIS results in future gout RCTs. Trial Registration. Clinicaltrials.gov, www.clinicaltrials.gov, NCT00610363.

Predictors of doctor-rated and patient-rated gout severity: gout impact scales improve assessment

RATIONALE, AIMS AND OBJECTIVES

Our objective was to describe the factors associated with doctor-rated and patient-rated gout severity to explain how doctor assessment involving patient-reported outcomes can improve the clinical management of gout.

METHODS

Patients completed a newly validated gout-specific health-related quality of life instrument, the Gout Impact Scale (GIS) and other questions regarding their gout. Both patients and their doctors gave an overall gout severity assessment. We conducted correlation analyses between each predictor of interest and the two different severity ratings (doctor-rated severity and patient-rated severity). Stepwise multiple regressions were performed to determine the best predictors for doctor-rated and patient-rated severity, respectively.

RESULTS

Doctor-rated severity more closely correlated with objective clinical and laboratory findings, particularly the presence of tophi, which was not a leading factor in patient-rated severity assessments. Patient-rated severity more closely correlated with the domains of the GIS, which expressed the impact of gout on health-related quality of life.

CONCLUSION

Doctors might have a better understanding of their patients' level of disease impact if they incorporate an instrument such as the GIS in their evaluation of gout severity and their decisions regarding aggressiveness of treatment. The increased use of patient-reported outcomes measures has the potential to improve quality of care and patient satisfaction, as well as reduce costs of health care utilization.

Arterial calcification is driven by RAGE in Enpp1-/- mice

BACKGROUND/AIMS

Ectopic osteochondral differentiation, driven by ENPP1-catalyzed generation of the chondrogenesis and calcification inhibitor inorganic pyrophosphate (PP(i)), promotes generalized arterial calcification of infancy. The multiligand receptor for advanced glycation end-products (RAGE), which promotes atherosclerosis and diabetic cardiovascular and renal complications, also mediates chondrocyte differentiation in response to RAGE ligand calgranulins such as S100A11. Here, we tested RAGE involvement in ENPP1 deficiency-associated arterial calcification.

METHODS

Because ectopic artery calcification in Enpp1-/- mice is P(i)-dependent and mediated by PP(i) deficiency, in vitro studies on effects of S100A11 and RAGE on mouse aortic explants were conducted using exogenous P(i), as well as alkaline phosphatase to hydrolyze ambient PP(i).

RESULTS

S100A11 induced cartilage-specific collagen IX/XI expression and calcification dependent on RAGE in mouse aortic explants that was inhibited by the endogenous RAGE signaling inhibitor soluble RAGE (sRAGE). Enpp1-/- aortic explants demonstrated decreased P(i)-stimulated release of sRAGE, and increased calcification and type IX/XI collagen expression that were suppressed by exogenous sRAGE and by Rage knockout. Last, Rage knockout suppressed spontaneous aortic calcification in situ in Enpp1-/- mice.

CONCLUSION

Cultured Enpp1-/- aortic explants have decreased P(i)-stimulated release of sRAGE, and RAGE promotes ectopic chondrogenic differentiation and arterial calcification in Enpp1-/- mice.

High versus low dosing of oral colchicine for early acute gout flare: Twenty-four-hour outcome of the first multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose-comparison colchicine study

OBJECTIVE

Despite widespread use of colchicine, the evidence basis for oral colchicine therapy and dosing in acute gout remains limited. The aim of this trial was to compare low-dose colchicine (abbreviated at 1 hour) and high-dose colchicine (prolonged over 6 hours) with placebo in gout flare, using regimens producing comparable maximum plasma concentrations in healthy volunteers.

METHODS

This multicenter, randomized, double-blind, placebo-controlled, parallel-group study compared self-administered low-dose colchicine (1.8 mg total over 1 hour) and high-dose colchicine (4.8 mg total over 6 hours) with placebo. The primary end point was > or = 50% pain reduction at 24 hours without rescue medication.

RESULTS

There were 184 patients in the intent-to-treat analysis. Responders included 28 of 74 patients (37.8%) in the low-dose group, 17 of 52 patients (32.7%) in the high-dose group, and 9 of 58 patients (15.5%) in the placebo group (P = 0.005 and P = 0.034, respectively, versus placebo). Rescue medication was taken within the first 24 hours by 23 patients (31.1%) in the low-dose group (P = 0.027 versus placebo), 18 patients (34.6%) in the high-dose group (P = 0.103 versus placebo), and 29 patients (50.0%) in the placebo group. The low-dose group had an adverse event (AE) profile similar to that of the placebo group, with an odds ratio (OR) of 1.5 (95% confidence interval [95% CI] 0.7-3.2). High-dose colchicine was associated with significantly more diarrhea, vomiting, and other AEs compared with low-dose colchicine or placebo. With high-dose colchicine, 40 patients (76.9%) had diarrhea (OR 21.3 [95% CI 7.9-56.9]), 10 (19.2%) had severe diarrhea, and 9 (17.3%) had vomiting. With low-dose colchicine, 23.0% of the patients had diarrhea (OR 1.9 [95% CI 0.8-4.8]), none had severe diarrhea, and none had vomiting.

CONCLUSION

Low-dose colchicine yielded both maximum plasma concentration and early gout flare efficacy comparable with that of high-dose colchicine, with a safety profile indistinguishable from that of placebo.

Transglutaminase 2 is a marker of chondrocyte hypertrophy and osteoarthritis severity in the Hartley guinea pig model of knee OA

OBJECTIVE

The transglutaminase (TG) isoenzyme TG2, which catalyzes protein cross-linking via transamidation, influences healing phenotype in multiple forms of tissue injury. Moreover, TG2 knockout suppresses cartilage destruction but promotes osteophyte formation in instability-induced mouse knee osteoarthritis (OA). TG2 is marker of growth plate chondrocyte hypertrophy. Moreover, TG2 secreted by chondrocytes acts in part by promoting chondrocyte maturation to hypertrophy, a differentiation state linked with MMP-13 expression and disease progression in OA. Moreover, glucosamine, which is currently under investigation as an OA therapy, binds and inhibits TG2. Here, we examined TG2 as a potential marker of cartilage hypertrophy in the spontaneous guinea pig model of OA.

METHODS

Synovial fluid ELISA and cartilage Immunohistochemistry and quantitative Reverse transcription-polymerase chain reaction (RT-PCR), were used to examine TG2 expression and TG transamidation-catalyzed isopeptide bonds.

RESULTS

TG isopeptide bonds and TG2 were most abundant in articular cartilage in early knee OA. TG2 expression was robust at sites of early but not established osteophytes. Synovial fluid TG2 correlated with knee OA total histological score (r=0.47, P=0.01), as did medial tibial plateau cartilage TG2 mRNA (r=1.0, P=0.003). At 12 months of age, medial tibial plateau cartilage TG2 mRNA expression rose markedly in association with elevated type X collagen, as well as ADAMTS-5, and MMP-13 expression, changes not shared in age-matched Strain 13 guinea pigs that are less susceptible to knee OA.

CONCLUSION

Hartley guinea pig knee TG2 expression associates with enhanced articular chondrocyte hypertrophy and is a biomarker of OA severity.

Hyperalgesia, synovitis and multiple biomarkers of inflammation are suppressed by interleukin 1 inhibition in a novel animal model of gouty arthritis

BACKGROUND

Monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystal-induced interleukin 1 beta (IL1beta) release contributes to inflammation in subcutaneous air pouch and peritoneal models of acute gout and pseudogout. However, consequences of IL1 inhibition have not been explored in more clinically relevant models of crystal-induced arthritis.

OBJECTIVE

To develop a novel mouse model of acute gouty ankle arthritis and use it to assess the effects of genetic deletion of IL1 receptor type (IL1R1) and of exogenous mIL1 Trap (a high-affinity blocker of mouse IL1alpha and IL1beta) on pain, synovitis and systemic inflammatory biomarkers.

METHODS

MSU crystals were injected into the mouse ankle joint and pain and ankle swelling were measured over 4 days. The effects of IL1 inhibition were determined in this model, and in the comparator models of crystal-induced peritonitis and subcutaneous air pouch inflammation.

RESULTS

Both IL1R1-null mice and mice pretreated with mIL1 Trap showed reduced neutrophil influx in MSU and CPPD crystal-induced peritonitis and air pouch models (p<0.05). In the ankle joint model, both IL1R1 knockout mice and pretreatment with mIL1 Trap were associated with significant reductions in MSU crystal-induced elevations in hyperalgesia, inflammation, serum amyloid A and the levels of multiple inflammatory cytokines and chemokines (p<0.05). Additionally, it was found that administration of mIL1 Trap after MSU crystal injection reduced established hyperalgesia and ankle swelling.

CONCLUSIONS

IL1 inhibition both prevented and relieved pain and ankle joint inflammation in response to intra-articular MSU crystals in mice. Results suggested that IL1 Trap has the potential to both prevent and treat gouty arthritis.

Colchicine update: 2008

OBJECTIVES

To review recent advances in the understanding of molecular mechanisms of drug disposition and cellular mechanisms of action and targets of colchicine, and disease applications and guidelines for oral colchicine use.

METHODS

Summarized and interpreted here is the pertinent English and non-English language literature on MEDLINE since the last update of colchicine in this journal in 1998 and published up to July 2008 regarding colchicine pharmacology, toxicology, mechanisms of action, and clinical applications in gout and other medical conditions.

RESULTS

Assessment, after review of 1512 publications, is that oral colchicine therapy is being refined by attention to novel targets such as NALP3 and pyrin. The drug has a narrow therapeutic-toxicity window, and potentially serious drug-drug interactions (eg, with clarithromycin and cyclosporine) are better recognized and therefore preventable. Reviewed here are recent advances in colchicine pharmacogenomics, and recognition of drug-drug interactions and predictors of potential toxicities, including alterations in the P-glycoprotein multidrug transporter ABCB1, cytochrome P450 3A4 isoenzyme, and hepatobiliary and renal function. Current understanding of optimization of colchicine dosing is reviewed, as are recent findings on colchicine therapy of nonrheumatic cardiovascular, hepatic, and renal diseases (eg, lowering of C-reactive protein, and treatment of acute and recurrent pericarditis). Finally, the article reviews the recent U.S. Food and Drug Administration-mandated cessation of marketing of injectable colchicine.

CONCLUSIONS

Oral colchicine has unique anti-inflammatory and antiproliferative effects with broad ramifications for rheumatic and nonrheumatic disease applications. Significant advances in the last decade have increased understanding of predictors of both colchicine efficacy and toxicity.

Factor XIIIA mobilizes transglutaminase 2 to induce chondrocyte hypertrophic differentiation

Two transglutaminases (TGs), factor XIIIA (FXIIIA) and TG2, undergo physiologic upregulation in growth plate hypertrophic chondrocytes, and pathological upregulation in osteoarthritic cartilage. Externalization of guanine-nucleotide-bound TG2 drives chondrocyte maturation to hypertrophy, a state linked to matrix remodeling and calcification. Here, we tested the hypothesis that FXIIIA also promotes hypertrophic differentiation. Using human articular chondrocytes, we determined that extracellular FXIIIA induced chondrocyte hypertrophy associated with rapid movement of TG2 to the cell surface. Site-directed mutagenesis revealed that FXIIIA Pro37 bordering the thrombin endoproteolytic Arg38-Gly39 site, but not intrinsic TG catalytic activity, were necessary for FXIIIA to induce chondrocyte hypertrophy. TGs have been demonstrated to interact with certain integrins and, during osteoarthritis (OA), alpha1beta1 integrin is upregulated and associated with hypertrophic chondrocytes. FXIIIA engaged alpha1beta1 integrin in chondrocytes. Antibody crosslinking of alpha1beta1 integrin mobilized TG2. Conversely, an alpha1beta1-integrin-specific blocking antibody inhibited the capacity of FXIIIA to induce TG2 mobilization to the cell surface, phosphorylation of p38 MAP kinase, and chondrocyte hypertrophy. Our results identify a unique functional network between two cartilage TG isoenzymes that accelerates chondrocyte maturation without requirement for TG-catalyzed transamidation by either TG.

Transglutaminase 2 is central to induction of the arterial calcification program by smooth muscle cells

Arterial calcification is a phenotype of vascular repair in atherosclerosis, diabetes, hyperphosphatemic renal failure, and aging. Arterial calcification is modulated by transition of arterial smooth muscle cells (SMCs) from contractile to chondro-osseous differentiation programmed in response to increases in P(i), bone morphogenetic protein-2, and certain other stimuli. Transglutaminase (TG)2 release modulates tissue repair, partly by transamidation-catalyzed covalent crosslinking of extracellular matrix substrates. TG2 regulates cultured SMC differentiation, resistance artery remodeling to vasoconstriction, and atherosclerotic lesion size. Here, TG2 expression was required for the majority of TG activity in mouse and human aortic SMCs. TG2(-/-) SMCs lost the capacity for P(i) donor-induced formation of multicellular bone-like nodules and for increased expression of the type III sodium-dependent P(i) cotransporter Pit-1 and certain osteoblast and chondrocyte genes (tissue-nonspecific alkaline phosphatase, the osteoblast master transcription factor runx2, and chondrocyte-restricted aggrecan), and for P(i) donor- and bone morphogenetic protein-2-induced calcification. Uniquely in TG2(-/-) SMCs, P(i) donor treatment increased expression of the physiological SMC chondro-osseous differentiation and calcification inhibitors osteoprotegerin, matrix Gla protein, and osteopontin. Conversely, TG2(-/-) SMCs, unlike wild-type SMCs, failed to maintain contractile differentiation on laminin. Exogenous catalytically active TG2 augmented calcification by TG2(-/-) SMC in response to P(i) donor treatment. TG2 expression also drove P(i)-stimulated calcification of mouse aortic ring organ cultures, which was suppressed by the TG2 catalytic site-specific inhibitor Boc-DON-Gln-Ile-Val-OMe (10 micromol/L). Our results suggest that TG2 release in injured arteries is critical for programming chondro-osseous SMC differentiation and calcification in response to increased P(i) and bone morphogenetic protein-2.

Vanin-1 pantetheinase drives increased chondrogenic potential of mesenchymal precursors in ank/ank mice

Widespread endochondral and intramembranous ectopic bone formation is mediated by extracellular PP(i) deficiency that develops in ank/ank mice. Herein we report on the rapid condensation into chondrogenic nodules of cultured ank/ank bone marrow stromal cells (BMSCs). We compared the roles of increased chondrogenic potential versus altered osteoblast function in the ank/ank phenotype. To do so, we crossbred ank/ank mice with mice lacking Vanin-1 pantetheinase, which inhibits synthesis of the chondrogenesis regulator glutathione, since we observed increased Vanin-1 expression and pantetheinase activity and decreased glutathione in ank/ank BMSCs. Vnn1(-/-) BMSCs demonstrated delayed chondrogenesis mediated by increased glutathione. Moreover, increased chondrogenesis of ank/ank BMSCs and increased chondrogenic transdifferentiation and calcification by ank/ank aortic smooth muscle cells and explants were corrected by Vanin-1 knockout. Osteoblastogenesis was accelerated in ank/ank mesenchymal stem cells. However, in cultured ank/ank osteoblasts, Vanin-1 knockout actually increased specific alkaline phosphatase activity and lowered extracellular PP(i), and did not correct increased calcification. Moreover, Vanin-1 knockout failed to correct the ank/ank skeletal soft tissue phenotype. Therefore, ank/ank periskeletal soft tissue calcification appears more dependent on altered osteoblastic function than enhanced chondrogenic potential and is not dependent on Vanin-1; however, Vanin-1 regulates chondrogenesis via glutathione metabolism and is critical for accelerated chondrogenesis of ank/ank mesenchymal precursors and P(i) donor-driven chondrogenic transdifferentiation and calcification of aortic smooth muscle cells.

Calcification of human articular knee cartilage is primarily an effect of aging rather than osteoarthritis

OBJECTIVE

Pathologic calcification of articular cartilage in human knees is often associated with advanced age and conditions of osteoarthritis (OA). Coincidently, most studies that have characterized calcification in joint cartilage have examined populations that are aged and presenting with clinical symptoms. Generally, these studies rely upon relatively insensitive plain radiographs or synovial fluid crystal analyses to quantify calcium levels. The purpose of this study was to examine the relationship between cartilage calcification and aging in an unselected donor population of diverse age using highly sensitive calcification imaging.

METHODS

A group of 106 knee blocks were obtained from 56 individual donors (25 females and 31 males, aged 12-74, avg. 50.3 years). Condylar surfaces were graded on a 4-point OA grading scale for cartilage degeneration. The condyles were cut into approximately 7-10mm thick slabs. Using a Faxitron radiography system, high-resolution images were taken of the slabs to specifically image calcification in cartilage. The quantified calcification areas were then analyzed and correlations with both OA grade and age were assessed.

RESULTS

Every knee presented some measurable calcification. The relative calcium deposition had a significant positive correlation with age. This same positive correlation was seen between condyles showing grade 1 and 2 changes. OA grades higher than 2 did not present any further significant increase in calcium levels.

CONCLUSION

These observations indicate that age rather than OA is the predominant factor driving progressive pathologic calcification in articular cartilage.

Transglutaminase 2 regulates mallory body inclusion formation and injury-associated liver enlargement

BACKGROUND & AIMS

Mallory body (MB) inclusions are a characteristic feature of several liver disorders and share similarities with cytoplasmic inclusions observed in neural diseases and myopathies. MBs consist primarily of keratins 8 and 18 (K8/K18), require a K8-greater-than-K18 ratio for their formation, and contain glutamine-lysine cross-links generated by transglutaminase (TG). We hypothesized that protein transamidation is essential for MB formation.

METHODS

Because TG2 is the most abundant hepatocyte TG, we tested our hypothesis using TG2(-/-) and their wild-type counterpart mice fed 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), an established MB inducer. Keratin cross-linking was further examined using recombinant proteins or transgenic mice that overexpress K8 or K18.

RESULTS

TG2(-/-) livers have markedly reduced TG2 activity as compared with TG2(+/+) livers. The DDC-fed TG2(-/-) mice have dramatic decreases in MB formation and liver hypertrophy response as contrasted with DDC-fed TG2(+/+) mice. Despite similar hepatocellular damage, TG2(-/-) mice had more gallstones, jaundice, and ductal proliferation than wild-type mice. Inhibition of MB formation in TG2(-/-) mice was associated with marked attenuation of ubiquitination and K8-containing protein cross-linking. MB formation and resolution paralleled the generation then disappearance of cross-linked K8, respectively. K8 is a preferential TG2 substrate when compared to K18, as examined in vitro or in DDC-fed transgenic mice that overexpress K8 or K18.

CONCLUSIONS

We demonstrate an essential role for TG2 in determining injury-mediated liver enlargement and the necessity of K8 and TG2 for generating cross-linked keratins and MBs. The role of TG in inclusion formation might extend to nonkeratin intermediate filament protein-related diseases.

New developments in clinically relevant mechanisms and treatment of hyperuricemia

The prevalence of gout has increased markedly in the United States in the past two decades, and new treatments for hyperuricemia are being developed. Recent molecular identification of urate transporter-1 (URAT1) as the central mediator of renal urate reabsorption has provided novel understanding of the pathogenesis of hyperuricemia, and the target site for current and possibly future primary uricosuric agents. Recent studies have also highlighted uricosuric effects of several drugs (losartan, atorvastatin, fenofibrate) that are prescribed for primary indications other than hyperuricemia. The niche of these agents in current management of hyperuricemia is discussed. We also review the ongoing development of recombinant uricase preparations and of novel xanthine oxidase inhibitors exemplified by febuxostat. These agents should provide novel options for patients with chronic, refractory gout and hyperuricemia, particularly in association with allopurinol hypersensitivity and renal insufficiency.

Recent developments in diet and gout

PURPOSE OF REVIEW

Gout is the most common inflammatory arthritis in men, affecting approximately 1-2% of adult men in Western countries. United States gout prevalence has approximately doubled over the past two decades. In recent years, key prospective epidemiological and open-labeled dietary studies, coupled with recent advances in molecular biology elucidating proximal tubular urate transport, have provided novel insights into roles of diet and alcohol in hyperuricemia and gout. This review focuses on recent developments and their implications for clinical practice, including how we advise patients on appropriate diets and alcoholic beverage consumption.

RECENT FINDINGS

Studies have observed an increased risk of gout among those who consumed the highest quintile of meat, seafood and alcohol. Although limited by confounding variables, low-fat dairy products, ascorbic acid and wine consumption appeared to be protective for the development of gout.

SUMMARY

The most effective forms of dietary regimen for both hyperuricemia and gout flares remains to be unidentified. Until confirmed by a large, controlled study, it is prudent to advise patients to consume meat, seafood and alcoholic beverages in moderation, with special attention to food portion size and content of non-complex carbohydrates which are essential for weight loss and improved insulin sensitivity.

Up-regulated expression of the CXCR2 ligand KC/GRO-alpha in atherosclerotic lesions plays a central role in macrophage accumulation and lesion progression

Macrophage-mediated inflammation is central to atherogenesis. We have determined previously that the CXC chemokine receptor CXCR2 is involved in advanced atherosclerosis. We sought to determine whether one of the ligands of CXCR2, KC/GRO-alpha, can also modulate atherogenesis. KC/GRO-alpha(-/-) mice were generated and mated with the atherosclerosis-prone LDLR(-/-) mice. There was a significant reduction in atherosclerosis in mice lacking KC/GRO-alpha; however, this reduction was only approximately half that seen previously in mice lacking CXCR2 in the leukocyte. To determine whether CXCR2 is involved in the early formation of atherosclerosis, leukocyte-specific CXCR2(-/-) chimeric mice on LDLR(-/-) background were generated. Early fatty streak lesion formation in these mice was not affected by leukocyte CXCR2 deficiency whereas lesions were less developed in mice lacking leukocyte CXCR2 when atherosclerosis was allowed to progress to the intermediate stage. Macrophages were relatively sparse in the lesions of leukocyte CXCR2(-/-) mice despite robust MCP-1 expression. These studies indicate that KC/GRO-alpha/CXCR2 does not play a critical role in recruitment of macrophages into early atherosclerotic lesions but both arterial KC/GRO-alpha and leukocyte-specific CXCR2 expression are central to macrophage accumulation in established fatty streak lesions.

Association of sporadic chondrocalcinosis with a -4-basepair G-to-A transition in the 5'-untranslated region of ANKH that promotes enhanced expression of ANKH protein and excess generation of extracellular inorganic pyrophosphate

OBJECTIVE

Certain mutations in ANKH, which encodes a multiple-pass transmembrane protein that regulates inorganic pyrophosphate (PPi) transport, are linked to autosomal-dominant familial chondrocalcinosis. This study investigated the potential for ANKH sequence variants to promote sporadic chondrocalcinosis.

METHODS

ANKH variants identified by genomic sequencing were screened for association with chondrocalcinosis in 128 patients with severe sporadic chondrocalcinosis or pseudogout and in ethnically matched healthy controls. The effects of specific variants on expression of common markers were evaluated by in vitro transcription/translation. The function of these variants was studied in transfected human immortalized CH-8 articular chondrocytes.

RESULTS

Sporadic chondrocalcinosis was associated with a G-to-A transition in the ANKH 5'-untranslated region (5'-UTR) at 4 bp upstream of the start codon (in homozygotes of the minor allele, genotype relative risk 6.0, P = 0.0006; overall genotype association P = 0.02). This -4-bp transition, as well as 2 mutations previously linked with familial and sporadic chondrocalcinosis (+14 bp C-to-T and C-terminal GAG deletion, respectively), but not the French familial chondrocalcinosis kindred 143-bp T-to-C mutation, increased reticulocyte ANKH transcription/ANKH translation in vitro. Transfection of complementary DNA for both the wild-type ANKH and the -4-bp ANKH protein variant promoted increased extracellular PPi in CH-8 cells, but unexpectedly, these ANKH mutants had divergent effects on the expression of extracellular PPi and the chondrocyte hypertrophy marker, type X collagen.

CONCLUSION

A subset of sporadic chondrocalcinosis appears to be heritable via a -4-bp G-to-A ANKH 5'-UTR transition that up-regulates expression of ANKH and extracellular PPi in chondrocyte cells. Distinct ANKH mutations associated with heritable chondrocalcinosis may promote disease by divergent effects on extracellular PPi and chondrocyte hypertrophy, which is likely to mediate differences in the clinical phenotypes and severity of the disease.

External GTP-bound transglutaminase 2 is a molecular switch for chondrocyte hypertrophic differentiation and calcification

Chondrocyte maturation to hypertrophy, associated with up-regulated transglutaminase 2 (TG2) expression, mediates not only physiologic growth plate mineralization but also pathologic matrix calcification and dys-regulated matrix repair in osteoarthritic articular cartilage. TG2-/- mouse chondrocytes demonstrate markedly inhibited progression to hypertrophic differentiation in response to both retinoic acid and the chemokine CXCL1. Here, our objectives were to test if up-regulated TG2 alone is sufficient to promote chondrocyte hypertrophic differentiation and to identify TG2 molecular determinants and potential downstream signals involved. TG2 activities, regulated by nucleotides and calcium, include cross-linking of cartilage matrix proteins, binding of fibronectin, and hydrolysis of GTP and ATP. Following transfection of TG2 site-directed mutants into chondrocytic cells, we observed that wild type TG2, and TG catalytic site and fibronectin-binding mutants promoted type X collagen expression and matrix calcification consistent with chondrocyte hypertrophic differentiation. In contrast, transfected mutants of TG2 GTP binding (K173L) and externalization (Y274A) sites did not stimulate chondrocyte hypertrophy. Recombinant TG2 treatment of bovine cartilage explants demonstrated that extracellular TG2 induced hypertrophy more robustly in the GTP-bound state, confirming an essential role of TG2 GTP binding. Finally, TG2 treatment induced type X collagen in a beta1 integrin-mediated manner, associated with rapid phosphorylation of both Rac1 and p38 kinases that were inhibited by mutation of the TG2 GTP binding site. In conclusion, externalized GTP-bound TG2 serves as a molecular switch for differentiation of chondrocytes to a hypertrophic, calcifying phenotype in a manner that does not require either TG2 transamidation activity or fibronectin binding.

Central role of complement membrane attack complex in monosodium urate crystal-induced neutrophilic rabbit knee synovitis

OBJECTIVE

Monosodium urate monohydrate (MSU) crystals promote gouty inflammation that is critically mediated by neutrophil recruitment and activation. Interleukin-8 (IL-8) and closely related chemokines are major neutrophil chemotaxins in experimental gout. But MSU crystals also activate the classical and alternative pathways of complement, and MSU crystals directly cleave C5 on the crystal surface. Unlike IL-8, the roles in acute gout of individual complement-derived peptides and of the terminal C5b-9 complement components that comprise the membrane attack complex (MAC) are unclear. Hence, we studied rabbits deficient in the MAC component C6 to determine if MAC mediated urate crystal-induced arthritis.

METHODS

We injected C6-deficient and C6-sufficient rabbit knee joints with 10 mg of pyrogen-free urate crystals and analyzed IL-8 levels, leukocyte influx, and joint inflammation 24 hours later.

RESULTS

There was a significant decrease (>60%) in swelling in MSU crystal-injected knees of C6-deficient animals as compared with C6-sufficient animals (P < 0.05). An attenuated rise in MSU crystal-induced joint effusion levels of IL-8 also was observed, which was concordant with diminished numbers of neutrophils (P < 0.05) but not monocytes in MSU crystal-induced knee synovial fluid from C6-deficient animals. Synovial tissue analysis confirmed mononuclear leukocyte infiltration in response to MSU crystal injection in all animals, but substantial neutrophil infiltration only in C6-sufficient animals.

CONCLUSION

MAC activation appears to play a major role in intraarticular IL-8 generation and in neutrophil recruitment in experimental acute gouty arthritis of the rabbit knee. C6 and MAC activation may represent novel therapeutic targets for suppression of neutrophil-mediated joint inflammation in gout.

IL-8-mediated cell migration in endothelial cells depends on cathepsin B activity and transactivation of the epidermal growth factor receptor

Microvascular endothelial cells (HMECs) express both the CXCR1 and the CXCR2, but cell migration is almost entirely mediated by the CXCR2. Similarly, NIH 3T3 cells transfected with the CXCR2 migrated toward IL-8, whereas CXCR1-transfected cells failed to do so. This situation differs from that seen in leukocytes, where chemotaxis is primarily a function of the CXCR1. To define signal transduction pathways that explain this difference in behavior, various inhibitors were used to block cell migration. Apart from inhibitors of phosphatidylinositol 3-kinase, which blocked migration in all cases, inhibition of the epidermal growth factor (EGF) receptor blocked IL-8-mediated cell migration in HMECs and in CXCR2-transfected NIH 3T3 cells, but not in RBL2H3 cells, which do not express an EGFR. Blocking Abs against the EGFR or against heparin-binding EGF-like growth factor similarly blocked IL-8-mediated cell migration and in vitro tubulogenesis in HMECs. Furthermore, inhibition of the EGFR also attenuated focus formation in NIH 3T3 expressing the CXCR2. Immunoprecipitations of the EGFR in HMECs and in NIH 3T3 cells expressing the CXCR2 confirmed that the EGFR was phosphorylated following stimulation with IL-8. However, in contrast to previous reports, e.g., for the thrombin receptor, inhibition of matrix metalloproteases blocked IL-8-mediated cell migration only partially, whereas it was ablated by inhibition of cathepsin B. These results indicate that IL-8-induced transactivation of the EGFR is mediated by the CXCR2 and involves cathepsin B, and that this pathway is important for the migratory and tumorigenic effects of IL-8.

Distinct transglutaminase 2-independent and transglutaminase 2-dependent pathways mediate articular chondrocyte hypertrophy

Altered chondrocyte differentiation, including development of chondrocyte hypertrophy, mediates osteoarthritis and pathologic articular cartilage matrix calcification. Similar changes in endochondral chondrocyte differentiation are essential for physiologic growth plate mineralization. In both articular and growth plate cartilages, chondrocyte hypertrophy is associated with up-regulated expression of certain protein-crosslinking enzymes (transglutaminases (TGs)) including the unique dual-functioning TG and GTPase TG2. Here, we tested if TG2 directly mediates the development of chondrocyte hypertrophic differentiation. To do so, we employed normal bovine chondrocytes and mouse knee chondrocytes from recently described TG2 knockout mice, which are phenotypically normal. We treated chondrocytes with the osteoarthritis mediator IL-1 beta, with the all-trans form of retinoic acid (ATRA), which promotes endochondral chondrocyte hypertrophy and pathologic calcification, and with C-type natriuretic peptide, an essential factor in endochondral development. IL-1 beta and ATRA induced TG transamidation activity and calcification in wild-type but not in TG2 (-/-) mouse knee chondrocytes. In addition, ATRA induced multiple features of hypertrophic differentiation (including type X collagen, alkaline phosphatase, and MMP-13), and these effects required TG2. Significantly, TG2 (-/-) chondrocytes lost the capacity for ATRA-induced expression of Cbfa1, a transcription factor necessary for ATRA-induced chondrocyte hypertrophy. Finally, C-type natriuretic peptide, which did not modulate TG activity, comparably promoted Cbfa1 expression and hypertrophy (without associated calcification) in TG2 (+/+) and TG2 (-/-) chondrocytes. Thus, distinct TG2-independent and TG2-dependent mechanisms promote Cbfa1 expression, articular chondrocyte hypertrophy, and calcification. TG2 is a potential site for intervention in pathologic calcification promoted by IL-1 beta and ATRA.

Inorganic pyrophosphate generation and disposition in pathophysiology

Inorganic pyrophosphate (PP(i)) regulates certain intracellular functions and extracellular crystal deposition. PP(i) is produced, degraded, and transported by specialized mechanisms. Moreover, dysregulated cellular PP(i) production, degradation, and transport all have been associated with disease, and PP(i) appears to directly mediate specific disease manifestations. In addition, natural and synthetic analogs of PP(i) are in use or currently under evaluation as prophylactic agents or therapies for disease. This review summarizes recent developments in the understanding of how PP(i) is made and disposed of by cells and assesses the body of evidence for potentially significant physiological functions of intracellular PP(i) in higher organisms. Major topics addressed are recent lines of molecular evidence that directly link decreased and increased extracellular PP(i) levels with diseases in which connective tissue matrix calcification is disordered. To illustrate in depth the effects of disordered PP(i) metabolism, this review weighs the roles in matrix calcification of the transmembrane protein ANK, which regulates intracellular to extracellular movement of PP(i), and the PP(i)-generating phosphodiesterase nucleotide pyrophosphatase family isoenzyme plasma cell membrane glycoprotein-1 (PC-1).

Interleukin-8 and its receptor CXCR2 in atherosclerosis

The participation of inflammatory cells in atherosclerosis is a well-known process that involves numerous molecules including chemotactic cytokines (chemokines) for their entry into the vessel wall. Although the C-C chemokine monocyte chemoattractant protein-1 and its receptor, CCR2, have been implicated in atherosclerosis, the role of the classic C-X-C chemokine, interleukin-8 (KC/growth-related oncogene alpha in mice) and its receptor CXCR2 has not been studied in the pathogenesis of atherosclerosis. Our research has shown that CXCR2 is strongly expressed on macrophages (Mphi) in atherosclerotic lesion. This CXCR2 expression is proatherogenic in that CXCR2 deficiency significantly reduces the progression of advanced atherosclerosis in mice. Although the mechanism still needs to be worked out, it appears that CXCR2 expression on lesion Mphi is essential for these cells to be retained in the lesion.

Lyme disease 2000. Emerging zoonoses complicate patient work-up and treatment

Lyme disease and other tick-borne diseases affect all age groups, including active persons age 50 and older. There has been a steady expansion in case numbers and the geographic borders of Lyme disease over the last two decades. Better recognition of two emerging tick-borne zoonoses (babesiosis and human granulocytic ehrlichiosis) that can be co-transmitted with Lyme disease is changing the approach to diagnosis and treatment of Lyme disease. Advances from genetic cloning have improved our understanding of the immune mechanisms associated with treatment-resistant Lyme arthritis and enabled the development of the first Lyme disease vaccine. The available vaccine is less efficacious in persons age 65 and older than in younger adults, but it may be a useful adjunct to other preventive measures in areas endemic for Lyme disease.

New developments in the pathogenesis of articular cartilage calcification

Articular cartilage, unlike growth plate cartilage, is specialized to not undergo matrix calcification. However, articular cartilage mineralization, in the form of CPPD (chondrocalcinosis) and hydroxyapatite crystals, frequently accompanies and complicates osteoarthritis and aging. Recent work has demonstrated that certain features of growth cartilage development and mineralization are shared in degenerative cartilage. These include chondrocyte proliferation, hypertrophy and increased apoptosis. Moreover, parathyroid hormone related protein (PTHrP), one of the central mediators of endochondral development, is abundant in osteoarthritic cartilage. Cartilage PPi elaboration and cytosolic transglutaminase activity are markedly increased with aging. Only recently have the molecular identities been defined for the chondrocyte inorganic pyrophosphate (PPi)-generating isozymes of the phosphodiesterase nucleotide pyrophosphatase (PDNP) family (including PC-1 and B10), and for transglutaminase in articular cartilage. This review focuses on the evolving understanding of the potential roles, in articular cartilage calcification, of PTHrP, PDNP family enzymes, PPi metabolism, and transglutaminase activity.

Clinical trials review: crystal deposition diseases

This review focuses on several recent clinically-related observations concerning Calcium Pyrophosphate Deposition Disease (CPPDD). Developments include new information on the epidemiology of idiopathic CPPDD in aging, on familial CPPDD, and on associated conditions that predispose to secondary CPPDD. Factors that may precipitate pseudogout, including the use of intra-articular hyaluronan and systemic G-CSF, are also discussed.

Noninvasive evaluation of adult onset myopathy from carnitine palmitoyl transferase II deficiency using proton magnetic resonance spectroscopy

OBJECTIVE

The adult onset metabolic myopathy of carnitine palmitoyl transferase II (CPT II) deficiency is under-recognized, in part due to variable degrees of enzyme deficiency and symptomatology, as well as limitations in means for noninvasive evaluation. We describe a proton magnetic resonance spectroscopy (MRS) technique, using a standard clinical magnetic resonance imaging scanner, to diagnose and help monitor the response to therapy in adult CPT II deficiency.

METHODS

A 53-year-old woman presented with a long standing history of diffuse aching and fatigue provoked by high fat intake, fasting, or prolonged exertion. Muscle biopsy revealed myopathic features and a deficiency (33% of control) of CPT II activity with elevated palmitoyl carnitine. Proton MRS of the soleus muscle was performed using a 1.5 Tesla scanner before and during dietary therapy.

RESULTS

Proton MRS revealed shortening of the transverse relaxation time (T2), consistent with increased acetylation of the carnitine pool. The symptoms resolved completely by treatment with frequent feedings of a high carbohydrate diet low in long chain fatty acids supplemented with medium chain triglycerides and L-carnitine. Recovery of normal muscle MRS and carnitine T2 relaxation was documented by the third month of therapy.

CONCLUSION

Proton MRS is a novel, potentially useful, and readily available adjunct in the diagnosis and therapeutic monitoring of muscle CPT II deficiency.

Bone morphogenetic proteins and bFGF exert opposing regulatory effects on PTHrP expression and inorganic pyrophosphate elaboration in immortalized murine endochondral hypertrophic chondrocytes (MCT cells)

A fundamental question in endochondral development is why the expression of parathyroid hormone-related protein (PTHrP), which inhibits chondrocyte maturation and mineralization, becomes attenuated at the stage of chondrocyte hypertrophy. To address this question, we used clonal, phenotypically stable SV40-immortalized murine endochondral chondrocytes that express a growth-arrested hypertrophic phenotype in culture (MCT cells). Addition of individual cytokines to the medium of MCT cells revealed that bone morphogenetic protein (BMP)-6, which commits chondrocytes to hypertrophy, markedly inhibited PTHrP production. This activity was shared by three other osteogenic bone morphogenetic proteins (BMP-2, BMP-4, and BMP-7) and by transforming growth factor beta (TGF-beta), which all inhibited the level of PTHrP mRNA. In contrast, basic fibroblast growth factor (bFGF), an inhibitor of chondrocyte maturation to hypertrophy, induced PTHrP in MCT cells and antagonized the effects of BMP-2, BMP-4, BMP-6, and BMP-7 and TGF-beta on PTHrP expression. Opposing effects of bFGF and BMPs also were exerted on the elaboration of inorganic pyrophosphatase (PPi), which regulates the ability of hypertrophic chondrocytes to mineralize the matrix. Specifically, BMP-2 and BMP-4, but not BMP-6 and BMP-7, shared the ability of TGF-beta to induce PPi release, and this activity was inhibited by bFGF in MCT cells. Our results suggest that effects on PTHrP expression could contribute to the ability of BMP-6 to promote chondrocyte maturation. BMPs and bFGF exert opposing effects on more than one function in immortalized hypertrophic chondrocytes. Thus, the normal decrease in bFGF responsiveness that accompanies chondrocyte hypertrophy may function in part by removing the potential for bFGF to induce PTHrP expression and to oppose the effects of BMPs. MCT cells may be useful in further understanding the mechanisms regulating the differentiation and function of hypertrophic chondrocytes.

A leukocyte homologue of the IL-8 receptor CXCR-2 mediates the accumulation of macrophages in atherosclerotic lesions of LDL receptor-deficient mice

Chronic macrophage-mediated inflammation is central to atherosclerosis. A role of the monocyte chemotactic and activating C-C chemokine JE/monocyte chemotactic protein-1 has been proposed. However, the human C-X-C chemokines growth-regulated oncogene (GROalpha) and IL-8, and their shared receptor, CXCR-2, also can be expressed at sites of chronic inflammation. Because we detected CXCR-2 in the intima of human atherosclerotic lesions, we examined the role of leukocyte CXCR-2 expression in affecting lesion cellularity. Atherosclerosis-susceptible LDL receptor-deficient mice were irradiated, successfully repopulated with bone marrow cells that either lacked or expressed mIL-8RH (the homologue of CXCR-2), and fed an atherogenic diet for 16 wk. In recipients of mIL-8RH+/+ marrow, mIL-8RH colocalized with densely accumulated intimal MOMA-2 positive macrophages. In contrast, lesions in recipients of mIL-8RH-/- marrow lacked mIL-8RH, had little intimal MOMA-2 staining, and were less extensive. The mIL-8RH ligand KC/GROalpha was detected in the intima of all aortic atherosclerotic lesions. Thus, the capacity of leukocytes to express mIL-8RH, and associated intralesional expression of its ligands such as KC/GROalpha, mediated the intimal accumulation of macrophages in atherosclerotic lesions of LDL receptor-deficient mice.

Hypercalcemia and systemic lupus erythematosus

Hypercalcemia is commonly caused by the increased production of parathyroid hormone-related protein (PTHrP) by a malignancy. In fact, the demonstration of increased PTHrP production in a patient with hypercalcemia is virtually pathognomonic of malignancy. We studied a patient with systemic lupus erythematosus (SLE), generalized lymphadenopathy, and hypercalcemia. Immunohistology of 2 biopsied lymph nodes revealed the abundant expression of PTHrP and the absence of malignant transformation. Although apparently rare, PTHrP production by non-malignant lymphoid tissue may occur in SLE and should be considered in the differential diagnosis of hypercalcemia.

Expression of the nucleoside triphosphate pyrophosphohydrolase PC-1 is induced by basic fibroblast growth factor (bFGF) and modulated by activation of the protein kinase A and C pathways in osteoblast-like osteosarcoma cells

The closely related cytokines bFGF and aFGF regulate the function of bone cells and mineralization. Osteoblasts express PPi-generating nucleoside triphosphate pyrophosphohydrolase (NTPPPH)/nucleotide phosphodiesterase I activity. bFGF and aFGF (10 ng/ml) up-regulated NTPPPH in human SaOS-2 and U2OS osteosarcoma cells, which express osteoblast-like features in culture. The induction was selective as alkaline phosphatase activity was down-regulated and specific as insulin-like growth factor-1 (IGF-1) and interleukin-1 beta (IL-1 beta) were not active. Furthermore, IL-1 beta but not IGF-1 inhibited bFGF-induced up-regulation of NTPPPH. The induced NTPPPH remained predominantly associated with cells. bFGF can induce signaling through pathways including protein kinase A (PKA) and protein kinase C (PKC)-mediated transduction. An activator of the PKA pathway (8-bromo cyclic adenosine monophosphate [cAMP]) induced NTPPPH. Furthermore, pretreatment with the PKC activator phorbol myristate acetate (PMA) (80 nM) markedly increased subsequent NTPPPH induction by both bFGF and cAMP. The PMA effect was associated with morphologic changes characterized by long, thin intercellular extensions. PKC desensitization also potentially contributed to this effect because the PKC inhibitors staurosporine and H-7 enhanced bFGF-induced and cAMP-induced NTPPPH expression in the absence of morphologic changes. We observed that bFGF induced expression of PC-1, a member of the NTPPPH gene family. The majority of NTPPPH activity was depleted by immunoadsorption using a monoclonal antibody to native human PC-1. bFGF- and aFGF-induced production of PC-1/NTPPPH in osteoblastoid cells may contribute to the effects of FGFs on bone metabolism.

Oxidized LDL enhances lipopolysaccharide-induced tissue factor expression in human adherent monocytes

Oxidized low-density lipoprotein (oxLDL) has been characterized as an atherogenic molecule responsible for the induction of a variety of gene products. One such gene, tissue factor (TF), the cellular initiator of the coagulation cascade, is not expressed in normal vascular tissue but is expressed by monocytes and foam cells in atherosclerotic lesions. Therefore, we examined the effect of oxLDL on TF expression in cultured human adherent monocytes. Endotoxin-free oxLDL alone did not induce TF expression in adherent monocytes. However, oxLDL significantly enhanced TF expression induced by the inflammatory mediator, bacterial lipopolysaccharide (LPS), in a time- and dose-dependent manner. In contrast, oxLDL did not alter LPS-mediated production of interleukin-8 and actually inhibited LPS-induced secretion of tumor necrosis factor-alpha, suggesting that some aspects of the signaling pathways for TF induction differ from those of other LPS-responsive monocyte/macrophage gene products. Thus, this study documents specific modulation of the expression of LPS-inducible genes in monocytic cells by oxLDL. Factors that enhance TF expression in monocyte/macrophage cells present in atheroma may contribute to the severity of thrombotic episodes and complications observed in atherosclerosis.

Gout and mechanisms of crystal-induced inflammation

Since last year's review of gout and hyperuricemia, investigators have described new potential mechanisms that may contribute to urate crystal deposition and the propagation, self-limitation, and therapeutic control of gouty inflammation. The clinical presentation of gout in women continues to be described in greater detail. Also, new information on oral allopurinol desensitization is now available to help approach the difficult problem of allopurinol hypersensitivity.

Apolipoprotein (apo) E inhibits the capacity of monosodium urate crystals to stimulate neutrophils. Characterization of intraarticular apo E and demonstration of apo E binding to urate crystals in vivo

Factors that modulate the ability of monosodium urate crystals to stimulate leukocytes could regulate gouty inflammation. Lipoproteins that bear apo B-100 and apo E bind to urate crystals and suppress crystal-neutrophil interaction. In this study, we observed that urate crystals, coated with apo E of monocyte origin, had a diminished ability to stimulate neutrophils. Apo E was also detected on the surface of urate crystals recovered from gout patients. Thus, we analyzed apo E in noninflammatory synovial fluid, and found it to be associated with particles of heterogeneous size and of predominantly alpha and pre-beta electrophoretic mobility. Local articular synthesis of at least a portion of synovial fluid apo E was suggested because (a) the synovial fluid/plasma concentration ratio of apo E was significantly higher than that for both apo B and apo A-I, which are not widely synthesized by extrahepatic tissues, (b) cultured rheumatoid synovial cells in first passage secreted apo E, (c) a portion of synovial fluid apo E was heavily sialylated. We conclude that synovial fluids contain apo E that appears partly of local origin. Apo E binds to urate crystals and could modulate gouty inflammation.

Nasal cocaine abuse causing an aggressive midline intranasal and pharyngeal destructive process mimicking midline reticulosis and limited Wegener's granulomatosis

We describe a 36-year-old white man with an aggressive, midline intranasal and naso and oropharyngeal destructive process temporally associated with heavy (3 g/week) abuse of nasal cocaine. Necrosis and atrophy of the inferior and middle nasal turbinates bilaterally, prominent naso and oropharyngeal ulcers, and nasal septal perforation were observed clinically. Biopsies of a necrotic posterior oropharyngeal ulcer revealed focal areas of chronic inflammation and necrosis, but there was no evidence of vasculitis or granuloma formation. Serum was negative for antineutrophil cytoplasmic antibody. The oropharyngeal ulcer improved with abstinence from cocaine. Nasal septal perforation is a well recognized complication of nasal cocaine insufflation. Our case illustrates that a more aggressive midline intranasal and intrapharyngeal destructive process mimicking limited Wegener's granulomatosis and midline reticulosis can be associated with nasal cocaine abuse.

Neutrophil activation by inflammatory microcrystals of monosodium urate monohydrate utilizes pertussis toxin-insensitive and -sensitive pathways

The activation of leukocytes by particulates is a critical event in certain inflammatory syndromes, including acute gout associated with microcrystals of monosodium urate monohydrate. In this study we have evaluated mechanisms of human neutrophil activation by urate crystals. Both N-formyl-nor-leu-leu-phe-nor-leu-tyr-lys and uncoated urate crystals (0.5 to 5 mg/ml) but not urate crystals coated with human low density lipoprotein (which suppresses crystal-induced neutrophil responsiveness), stimulated pertussis toxin (PT)-sensitive GTPase activity in purified preparations of human neutrophil membranes. Hydroxyapatite crystals (up to 5 mg/ml) were inactive. Pretreatment of neutrophil membranes with cholera toxin also inhibited crystal-induced and formylated peptide-induced GTPase activity. Pretreatment of whole neutrophils with PT resulted in nearly complete inhibition of formylated peptide-induced cytosolic calcium mobilization, release of superoxide and release of the azurophil granule constituent alpha-mannosidase. In contrast, identical pretreatment of whole neutrophils with PT only partially suppressed urate crystal-induced alpha-mannosidase and superoxide release and failed to inhibit crystal phagocytosis and increases in cytosolic free calcium. Mechanisms of neutrophil activation by monosodium urate crystals appear to be heterogeneous in comparison with activation by formylated peptides and there is no absolute requirement for PT-sensitive membrane G proteins in neutrophil responsiveness to urate crystals.

Neutrophil activation by inflammatory microcrystals of monosodium urate monohydrate utilizes pertussis toxin-insensitive and -sensitive pathways

The activation of leukocytes by particulates is a critical event in certain inflammatory syndromes, including acute gout associated with microcrystals of monosodium urate monohydrate. In this study we have evaluated mechanisms of human neutrophil activation by urate crystals. Both N-formyl-nor-leu-leu-phe-nor-leu-tyr-lys and uncoated urate crystals (0.5 to 5 mg/ml) but not urate crystals coated with human low density lipoprotein (which suppresses crystal-induced neutrophil responsiveness), stimulated pertussis toxin (PT)-sensitive GTPase activity in purified preparations of human neutrophil membranes. Hydroxyapatite crystals (up to 5 mg/ml) were inactive. Pretreatment of neutrophil membranes with cholera toxin also inhibited crystal-induced and formylated peptide-induced GTPase activity. Pretreatment of whole neutrophils with PT resulted in nearly complete inhibition of formylated peptide-induced cytosolic calcium mobilization, release of superoxide and release of the azurophil granule constituent alpha-mannosidase. In contrast, identical pretreatment of whole neutrophils with PT only partially suppressed urate crystal-induced alpha-mannosidase and superoxide release and failed to inhibit crystal phagocytosis and increases in cytosolic free calcium. Mechanisms of neutrophil activation by monosodium urate crystals appear to be heterogeneous in comparison with activation by formylated peptides and there is no absolute requirement for PT-sensitive membrane G proteins in neutrophil responsiveness to urate crystals.

Serum and plasma inhibit neutrophil stimulation by hydroxyapatite crystals. Evidence that serum alpha 2-HS glycoprotein is a potent and specific crystal-bound inhibitor

Tissue deposits of basic calcium phosphate (BCP) crystals are associated with various clinical manifestations of inflammation. We addressed the possibility that native proteins modify the ability of hydroxyapatite (HA) crystals to stimulate human inflammatory cells. Neutrophil superoxide release and chemiluminescence in response to HA crystals (0.3-4.0 mg/ml) were blunted by serum and plasma. Inhibitory activity was progressively removed from serum by sequential adsorption with HA crystals, suggesting that the inhibitors were crystal-bound proteins. Thus, we characterized HA crystal-bound plasma proteins by O'Farrell gels: Fibronectin, transferrin, albumin, alpha 2-HS glycoprotein (AHSG), alpha 1-proteinase inhibitor, alpha 1-acid glycoprotein, Gc globulin, haptoglobin, and high density lipoprotein apolipoproteins were major bound species. Of these, AHSG was the most active inhibitor of HA-induced neutrophil superoxide release, and this glycoprotein partially (60%) restored inhibitory activity to HA-adsorbed serum. AHSG also bound in vitro to the related BCP crystal, octacalcium phosphate, but only minimally to calcium pyrophosphate dihydrate crystals and monosodium urate crystals. Suppressive effects on neutrophil stimulation exhibited by AHSG were also specific for BCP crystals. AHSG was present in noninflammatory synovial fluids bound to synthetic HA crystals in vitro, and AHSG could be detected on native synovial fluid HA crystals. We conclude that the binding of AHSG may modulate the inflammatory potential of BCP crystals.