The role of miRNAs in viral myocarditis, and its possible implication in induction of mRNA-based COVID-19 vaccines-induced myocarditis

BACKGROUND

Several reports of unheeded complications secondary to the current mass international rollout of SARS-COV-2 vaccines, one of which is myocarditis occurring with the FDA fully approved vaccine, Pfizer, and others.

MAIN BODY OF THE ABSTRACT

Certain miRNAs (non-coding RNA sequences) are involved in the pathogenesis in viral myocarditis, and those miRNAs are interestingly upregulated in severe COVID-19. We hypothesize that the use of mRNA-based vaccines may be triggering the release of host miRNAs or that trigger the occurrence of myocarditis. This is based on the finding of altered host miRNA expression promoting virus-induced myocarditis.

SHORT CONCLUSION

In conclusion, miRNAs are likely implicated in myocarditis associated with mRNA vaccines. Our hypothesis suggests the use of miRNA as a biomarker for the diagnosis of mRNA vaccine-induced myocarditis. Additionally, the interplay between viral miRNA and the host immune system could alter inflammatory profiles, hence suggesting the use of therapeutic inhibition to prevent such complications.

Diastolic dysfunction grading, echocardiographic and electrocardiogram findings in 50 patients with apical hypertrophic cardiomyopathy

INTRODUCTION

Apical Hypertrophic Cardiomyopathy (Apical HCM) is an uncommon variant of hypertrophic cardiomyopathy, but it is relatively more common in Asian countries. This is a retrospective, non-randomised, single centre study of patients with Apical HCM focusing on their diastolic dysfunction grading, echocardiographic parameters and electrocardiograms (ECG).

METHODS

All Apical HCM patients coming for clinic visits at the Institut Jantung Negara from September 2017 to September 2018 were included. We assessed their echocardiography images, grade their diastolic function and reviewed their ECG on presentation.

RESULTS

Fifty patient were included, 82% (n=41) were males and 18% (n=9) females. The diastolic function grading of 37 (74%) patients were able to be determined using the updated 2016 American Society of Echocardiography (ASE) diastolic guidelines. Fifty percent (n=25) had the typical ace-ofspades shape left ventricle (LV) appearance in diastole and 12% (n=6) had apical pouch. All patients had T inversion in the anterior leads of their ECG, and only 52% (n=26) fulfilled the ECG left ventricular hypertrophy (LVH) criteria. Majority of our patients presented with symptoms of chest pain (52%, n=26) and dyspnoea (42%, n=21).

CONCLUSION

The updated 2016 ASE guideline makes it easier to evaluate LV diastolic function in most patients with Apical HCM. It also helps in elucidating the aetiology of dyspnoea, based on left atrial pressure. Clinicians should have a high index of suspicion for Apical HCM when faced with deep T inversion on ECG, in addition to a thick LV apex with an aceof- spades appearance during diastole.

"A system biology" approach to bioinformatics and functional genomics in complex human diseases: arthritis

Human and other annotated genome sequences have facilitated generation of vast amounts of correlative data, from human/animal genetics, normal and disease-affected tissues from complex diseases such as arthritis using gene/protein chips and SNP analysis. These data sets include genes/proteins whose functions are partially known at the cellular level or may be completely unknown (e.g. ESTs). Thus, genomic research has transformed molecular biology from "data poor" to "data rich" science, allowing further division into subpopulations of subcellular fractions, which are often given an "-omic" suffix. These disciplines have to converge at a systemic level to examine the structure and dynamics of cellular and organismal function. The challenge of characterizing ESTs linked to complex diseases is like interpreting sharp images on a blurred background and therefore requires a multidimensional screen for functional genomics ("functionomics") in tissues, mice and zebra fish model, which intertwines various approaches and readouts to study development and homeostasis of a system. In summary, the post-genomic era of functionomics will facilitate to narrow the bridge between correlative data and causative data by quaint hypothesis-driven research using a system approach integrating "intercoms" of interacting and interdependent disciplines forming a unified whole as described in this review for Arthritis.

The role of nitric oxide in tissue destruction

Nitric oxide (NO) is synthesized via the oxidation of arginine by a family of nitric oxide synthases (NOS), which are either constitutive (ie. endothelial (ec)NOS and neuronal (nc)NOS) or inducible (iNOS). The production of nitric oxide plays a vital role in the regulation of physiological processes, host defence, inflammation and immunity. Pro-inflammatory effects include vasodilation, oedema, cytotoxicity and the mediation of cytokine-dependent processes that can lead to tissue destruction. Nitric oxide-dependent tissue injury has been implicated in a variety of rheumatic diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis and osteoarthritis. Conversely, the production of NO by endothelial cell NOS may serve a protective, or anti-inflammatory, function by preventing the adhesion and release of oxidants by activated neutrophils in the microvasculature. In this chapter we describe the multifaceted role of nitric oxide in inflammation and address the potential therapeutic implications of NOS inhibition.

Nitric oxide and inflammatory mediators in the perpetuation of osteoarthritis

Articular chondrocyte production of nitric oxide (NO) and other inflammatory mediators, such as eicosanoids and cytokines, are increased in human osteoarthritis. The excessive production of nitric oxide inhibits matrix synthesis and promotes its degradation. Furthermore, by reacting with oxidants such as superoxide anion, nitric oxide promotes cellular injury and renders the chondrocyte susceptible to cytokine-induced apoptosis. PGE(2) exerts anabolic and catabolic effects on chondrocytes, depending on the microenvironment and physiologic condition. The increased expression of inducible NOS (iNOS) and cyclo-oxygenase-2 (COX-2) in OA chondrocytes is largely due to the increased expression of pro-inflammatory cytokines, particularly IL-1, which act in an autocrine/paracrine fashion to perpetuate a catabolic state that leads to progressive destruction of articular cartilage. The initiating factors for the production of inflammatory mediators include altered biomechanical forces; their continued production may be augmented by an increase in extracellular matrix proteins acting through ligation of surface integrins.

Fibronectin activates matrix metalloproteinase-9 secretion via the MEK1-MAPK and the PI3K-Akt pathways in ovarian cancer cells

Cell adhesion to the extracellular matrix appears to trigger a cascade of intracellular signalings. We have previously shown that treatment of ovarian cancer cells, NOM1, with fibronectin (FN) stimulated matrix metalloproteinase (MMP)-9 secretion and thereby activated the invasiveness of cells via the FAK/Ras signaling pathway. By use of chemical inhibitors, we investigated the downstream effectors critical for FN-dependent secretion of MMP-9. Treatment of cells with MEK1 inhibitors, U0126 and PD98059, dramatically suppressed the secretion of MMP-9 activated by FN. Similarly, P1-3 kinase inhibitors, Wortmannin and LY294002, strongly suppressed the FN-dependent secretion of MMP-9 together with the inhibition of Akt activation. In contrast, a specific PKC inhibitor (GF109203X) showed no inhibitory effect on the FN-dependent MMP-9 secretion. Moreover, we found that both the MEK1 inhibitor and the P13-K inhibitor, but not the PKC inhibitor, strongly suppressed the invasiveness of NOM1 cells. Taken together, our results suggest that activation of dual signaling pathways, MEKI-MAPK and P13K-Akt, is required for the FN-dependent activation of MMP-9 secretion. Our results suggest the importance of these signaling molecules as a chemotherapeutic target for cancer.

Osteopontin: an intrinsic inhibitor of inflammation in cartilage

OBJECTIVE

To identify extracellular and intraarticular matrix components that are differentially expressed in normal and osteoarthritis (OA)-affected cartilage and to investigate their functions with respect to regulation of mediators of inflammation.

METHODS

Differential-display reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of a pool of messenger RNA (mRNA) from 10 human OA cartilage samples and 5 normal cartilage samples was performed using arbitrary primers. Confirmatory analysis of the up-regulated transcripts of fibronectin (FN) and osteopontin (OPN) was performed by RT-PCR of individual RNA samples from a separate set of donors. The effect of recombinant OPN (or anti-OPN antiserum) on chondrocyte function was examined by analyzing the spontaneous or interleukin-1 (IL-1)-induced release of nitric oxide (NO) and prostaglandin E2 (PGE2) from human OA-affected cartilage under ex vivo conditions.

RESULTS

Up-regulation (300-700%) of FN and OPN mRNA was observed in human OA-affected cartilage as compared with normal cartilage. Functional analysis of the role of OPN in OA cartilage showed that 1) Addition of 1 microg/ml (20 nM) of recombinant OPN to human OA-affected cartilage under ex vivo conditions inhibited spontaneous and IL-1beta-induced NO and PGE2 production, and 2) neutralization of intraarticular OPN with anti-OPN antiserum augmented NO production.

CONCLUSION

The data indicate that one of the functions of intraarticular OPN, which is overexpressed in OA cartilage, is to act as an innate inhibitor of IL-1, NO, and PGE2 production. These findings suggest that the production of pleiotropic mediators of inflammation that influence cartilage homeostasis, such as NO and PGE2, is regulated by the interaction of chondrocytes with differentially expressed proteins within the extracellular matrix.

Reversal of autocrine and paracrine effects of interleukin 1 (IL-1) in human arthritis by type II IL-1 decoy receptor. Potential for pharmacological intervention

Interleukin 1 (IL-1), produced by both synovial cells and chondrocytes, plays a pivotal role in the pathogenesis of cartilage destruction in osteoarthritis (OA). We examined the specific expression and function of IL-1 receptor family-related genes in human joint tissues. Gene array analysis of human normal and OA-affected cartilage showed mRNA expression of IL-1 receptor accessory protein (IL-1RAcp) and IL-1 type I receptor (IL-1RI), but not IL-1 antagonist (IL-1ra) and IL-1 type II decoy receptor (IL-1RII). Similarly, human synovial and epithelial cells showed an absence of IL-1RII mRNA. Functional genomic analyses showed that soluble (s) IL-1RII, at picomolar concentrations, but not soluble TNF receptor:Fc, significantly inhibited IL-1beta-induced nitric oxide (NO) and/or prostaglandin E(2) production in chondrocytes, synovial and epithelial cells. In OA-affected cartilage, the IC(50) for inhibition of NO production by sIL-1RII was 2 log orders lower than that for sIL-1RI. Human chondrocytes that overexpressed IL-1RII were resistant to IL-1-induced IL-1beta mRNA accumulation and inhibition of proteoglycan synthesis. In osteoarthritis, deficient expression by chondrocytes of innate regulators or antagonists of IL-1 such as IL-1ra and IL-1RII (soluble or membrane form) may allow the catabolic effects of IL-1 to proceed unopposed. The sensitivity of IL-1 action to inhibition by sIL-1RII has therapeutic implications that could be directed toward correcting this unfavorable tissue(s) dependent imbalance.

COX-2, NO, and cartilage damage and repair

The production of nitric oxide (NO) and prostaglandin E2 (PGE(2)) is increased in human osteoarthritis-affected cartilage. These and other inflammatory mediators are spontaneously released by OA cartilage explants ex vivo. The excessive production of nitric oxide inhibits matrix synthesis, and promotes its degradation. Furthermore, by reacting with oxidants such as superoxide anion, nitric oxide promotes cellular injury, and renders the chondrocyte susceptible to cytokine-induced apoptosis. PGE(2) exerts both anabolic and catabolic effects on chondrocytes, depending on the microenvironment and physiological condition. Thus, NO and PGE(2), produced by activated chondrocytes in diseased cartilage, may modulate disease rogression in osteoarthritis, and should therefore be considered potential targets for therapeutic intervention

A role for FAK in the Concanavalin A-dependent secretion of matrix metalloproteinase-2 and -9

To study the signaling pathway critical for the secretion of matrix metalloproteinases (MMPs), we examined the role of focal adhesion kinase (FAK) in Concanavalin A (Con A)-stimulated cells. We established a cell line in which FAK gene was conditionally inducible by use of FAK-null fibroblasts and the tetracycline repression system. In this cell line, FAK expression was undetectable in the presence of tetracycline but induced within 1 day by the removal of the drug. We found that FAK expression augmented the Con A-dependent secretion of MMP-9 and MMP-2. In contrast, proteolytic activation of MMP-2 by Con A-treatment did not require FAK expression. In addition, activation of MMP-secretion and tyrosine phosphorylation of FAK by Con A, but not the proteolytic activation of MMP-2, required attachment of the cells to the extracellular matrix. Taken together, our results suggest that the FAK signaling pathway play a pivotal role in the secretion of MMPs.

Type II interleukin-1beta receptor: a candidate for gene therapy in human arthritis

Interleukin-1 plays a pivotal role in the pathophysiologic process of arthritis. It is released in an autocrine fashion in joints affected with arthritis. Human cartilage affected with arthritis (but not normal cartilage) showed upregulation of interleukin-1beta messenger ribonucleic acid and protein in ex vivo conditions. Type II interleukin-1 receptor, interleukin-1 receptor antagonist, and Type I soluble interleukin-1 receptor has potent interleukin-1 neutralizing activity. In view of these observations, the role of type II interleukin-1 receptor in chondrocyte function was examined. Human interleukin-1beta (5-10 ng/mL) induced nitric oxide, prostaglandin E2 and matrix metalloprotease production in bovine or human chondrocytes, which could be inhibited by 500 pg/mL of Type II interleukin-1 receptor. Interleukin-1 inhibited proteoglycan synthesis that could be reversed by Type II soluble interleukin-1 receptor. Similarly, 1 ng/mL human interleukin-1 induced (or spontaneously produced) nitric oxide and prostaglandin E2 production in human osteoarthritis-affected cartilage could be inhibited by 50% or greater with 100 pg/mL Type II interleukin-1 receptor in ex vivo conditions. Type II interleukin-1 receptor transfected chondrocytes were immune to the insults of exogenous interleukin-1. These experiments showed that endogenous or exogenous Type II interleukin-1 receptor can attenuate the effects of interleukin-1 with respect to induction of inflammatory mediators, matrix metalloprotease activity and, proteoglycan synthesis in human chondrocytes and cartilage.

Nitric oxide synthase/COX cross-talk: nitric oxide activates COX-1 but inhibits COX-2-derived prostaglandin production

It is recognized that there is molecular cross-talk between the inflammatory mediators NO and PGs that may regulate tissue homeostasis and contribute to pathophysiological processes. However, the literature is divided with respect to whether NO activates or inhibits PG production. In this study, we sought to determine whether conflicting observations could be accounted for by divergent effects of NO on the two cyclooxygenase (COX) isoforms. Exposure of resting macrophages to NO (30 microM) enhanced PGE2 release by 4. 5-fold. This enhancement was inhibited by indomethacin but not by the COX-2 selective inhibitor NS398. To separate the activation of phospholipase A2 and COX, we performed experiments using fibroblasts derived from COX-1-deficient or COX-2-deficient mice. These cells exhibit increased basal PG production, which is due to a constitutively stimulated cytosolic phospholipase A2 and enhanced basal expression of the remaining COX isozyme. The exposure of COX- 2-deficient cells to exogenous NO (10 microM) resulted in a 2.4-fold increase of PGE2 release above controls. Further studies indicated that NO stimulated PGE2 release in COX-2-deficient cells, without altering COX-1 mRNA or protein expression. In contrast, NO inhibited COX-2-derived PGE2 production in both LPS-stimulated macrophages and COX-1 knockout cells. This inhibition was associated with both decreased expression and nitration of COX-2. Thus, these studies demonstrate divergent effects of NO on the COX isoforms. The regulation of PGE production by NO is therefore complex and will depend on the local environment in which these pleiotropic mediators are produced.

Functional genomic analysis in arthritis-affected cartilage: yin-yang regulation of inflammatory mediators by alpha 5 beta 1 and alpha V beta 3 integrins

Osteoarthritis-affected cartilage exhibits enhanced expression of fibronectin (FN) and osteopontin (OPN) mRNA in differential display and bioinformatics screen. Functional genomic analysis shows that the engagement of the integrin receptors alpha 5 beta 1 and alpha v beta 3 of FN and OPN, respectively, have profound effects on chondrocyte functions. Ligation of alpha 5 beta 1 using activating mAb JBS5 (which acts as agonist similar to FN N-terminal fragment) up-regulates the inflammatory mediators such as NO and PGE2 as well as the cytokines, IL-6 and IL-8. Furthermore, up-regulation of these proinflammatory mediators by alpha 5 beta1 integrin ligation is mediated via induction and autocrine production of IL-1 beta, because type II soluble IL-1 decoy receptor inhibits their production. In contrast, alpha v beta 3 complex-specific function-blocking mAb (LM609), which acts as an agonist similar to OPN, attenuates the production of IL-1 beta, NO, and PGE2 (triggered by alpha 5 beta 1, IL-1 beta, IL-18, or IL-1 beta, TNF-alpha, plus LPS) in a dominant negative fashion by osteoarthritis-affected cartilage and activated bovine chondrocytes. These data demonstrate a cross-talk in signaling mechanisms among integrins and show that integrin-mediated "outside in" and "inside out" signaling very likely influences cartilage homeostasis, and its deregulation may play a role in the pathogenesis of osteoarthritis.

Differential anti-inflammatory effects of immunosuppressive drugs: cyclosporin, rapamycin and FK-506 on inducible nitric oxide synthase, nitric oxide, cyclooxygenase-2 and PGE2 production

OBJECTIVE AND DESIGN

Cyclosporin, FK-506 and rapamycin have similar but distinct modes of interaction with cyclophilins, calcineurins and transcription factors. These immunosuppressive drugs have also been shown to inhibit cytotoxic and inflammatory responses in macrophage. Therefore, we evaluated the mechanism of action of these drugs on iNOS and COX-2 expression by macrophages, the products of which (NO and PGE2) have cytotoxic and proinflammatory activities.

MATERIALS AND METHODS

The murine macrophage cell line RAW 264.7 was grown as monolayer cultures. The effects of pharmacologically relevant concentrations of cyclosporin, rapamycin and FK-506 were evaluated in the presence and absence of lipopolysaccharide (LPS) which is a known inducer of iNOS and COX-2. Subsequently the expression of iNOS and COX-2 were analyzed by Western and Northern analysis. The production of NO and PGE2 were assayed by Greiss and RIA respectively.

RESULTS

Cyclosporin (1-5 microg/ml) and rapamycin (1.0-10 nM) but not FK-506 (5-10 nM) inhibited both iNOS and COX-2 expression at mRNA level which led to significant inhibition of NO and PGE2 production.

CONCLUSION

These studies characterize differential mechanistic capacity of the immunophilin-binding immunosuppressive drugs (comparable to hydrocortisone) to inhibit both iNOS and COX-2 expression. Inhibition of iNOS and COX-2 mRNA accumulation by cyclosporin and rapamycin seem to be distinct. These studies also highlight potential anti-inflammatory properties of these drugs in addition to their known immunosuppressive activity.

The pleiotropic functions of aspirin: mechanisms of action

Recent studies have suggested that aspirin and aspirin-like compounds have a variety of actions in addition to their well-studied ability to inhibit cyclooxygenases. These actions include inhibition of the uncoupling of oxidative phosphorylation, decreases in adenosine triphosphate stores. increases in extracellular adenosine, downregulation of the expression and activity of inducible nitric oxide synthetase, inhibition and/or stimulation of various mitogen-activated protein kinase activities and inhibition of nuclear factor binding kappaB site (NF-kappaB) activation. Moreover, aspirin-like compounds have recently been shown to have previously unappreciated clinical and biological effects, some apparently independent of cyclooxygenase. In this review we discuss the various mechanisms of action of aspirin-like compounds and their relevance to clinical disease and therapy.

A novel mechanism of action of chemically modified tetracyclines: inhibition of COX-2-mediated prostaglandin E2 production

Tetracyclines (doxycycline and minocycline) inhibit inducible NO synthase expression and augment cyclooxygenase (COX)-2 expression and PGE2 production. In contrast, chemically modified tetracyclines (CMTs), such as CMT-3 and -8 (but not CMT-1, -2, and -5), that lack antimicrobial activity, inhibit both NO and PGE2 production in LPS-stimulated murine macrophages, bovine chondrocytes, and human osteoarthritis-affected cartilage, which spontaneously produces NO and PGE2 in ex vivo conditions. Furthermore, CMT-3 augments COX-2 protein expression but inhibits net PGE2 accumulation. This coincides with the ability of CMT-3 and -8 to inhibit COX-2 enzyme activity in vitro. The action of CMTs is distinct from that observed with tetracyclines because 1) CMT-3-mediated inhibition of PGE2 production coincides with modification of COX-2 protein, which is distinct from the nonglycosylated COX-2 protein generated in the presence of tunicamycin, as observed by Western blot analysis and 2) CMT-3 and -8 have no significant effect on COX-2 mRNA accumulation. In contrast, CMT-3 and -8 do not inhibit COX-1 expression in A549 human epithelial cells at the level of protein and mRNA accumulation or modification of COX-1 protein. CMT-3 and -8 inhibit the sp. act. of COX-2 (but not COX-1) in cell-free extracts. These results demonstrate differential action of CMT-3 (Metastat) on COX-1 and -2 expression, which is distinct from other tetracyclines.

Regulation of tumor necrosis factor-alpha and tumor necrosis factor converting enzyme in human osteoarthritis

A snake venom-like protease isolated by a differential display screen between normal and osteoarthritis (OA)-affected cartilage (designated as cSVP) has a cDNA sequence identical to tumor necrosis factor (TNF)alpha convertase enzyme (TACE) and belongs to the adamalysin group of proteases. It has unique structural properties and when expressed in baculovirus, cleaves preferentially proTNFalpha to TNFalpha. The OA-affected cartilage has upregulated mRNA for TNFalpha and TACE as compared to normal cartilage. TNFalpha and TACE regulate inflammatory mediators in OA-affected cartilage which can be inhibited by both soluble TNFalpha receptors and inhibitors of TACE. These experiments demonstrate a functional paracrine/autocrine role of TNFalpha in OA-affected cartilage that is modulated by upregulated levels of chondrocyte-derived TACE.

Regulation of nitric oxide and prostaglandin E2 production by CSAIDS (SB203580) in murine macrophages and bovine chondrocytes stimulated with LPS

OBJECTIVE AND DESIGN

To compare two anti-inflammatory drugs: CSAIDS (SB203580) and hydrocortisone on iNOS and COX-2 expression.

MATERIAL OR SUBJECTS

Murine macrophages and bovine chondrocytes stimulated with LPS and human OA-affected cartilage were used in this study.

TREATMENT

The macrophages and chondrocytes were preincubated (30 min) with 0.1-1.0 microM CSAIDS or 10 microM of hydrocortisone before stimulating them with 1-100 microg/ml LPS.

METHODS

The end products of iNOS and COX-2: nitric oxide (NO) and PGE2 were estimated by Greiss method and RIA, respectively.

RESULTS

CSAIDS (1 microM) inhibited the production of NO and PGE2 (p< or =0.01) in bovine chondrocytes, but not in murine macrophages (RAW 264.7) (p< or =0.1). In fact, CSAIDS (in murine macrophages) marginally augmented nitrite accumulation (approximately 20%) at 14-24 h of LPS stimulation. Western blot analysis of COX-2 in bovine chondrocytes show decrease in COX-2 expression by hydrocortisone but not CSAIDS, although hydrocortisone and CSAIDS inhibit PGE2 accumulation. Hydrocortisone inhibited both PGE2 and NO production significantly (p< or =0.01) in murine macrophages. Furthermore, hydrocortisone significantly inhibited (p< or =0.01) PGE2 but marginally (p< or =0.05) NO in bovine chondrocytes.

CONCLUSION

These experiments demonstrate differential action of CSAIDS and hydrocortisone on NO and PGE2 production in bovine chondrocytes and RAW 264.7 cells.

Nitric oxide synthase and cyclooxygenases: distribution, regulation, and intervention in arthritis

Nitric oxide (NO) and prostaglandin E2 (PGE2) are two pleiotropic inflammatory mediators overproduced in arthritis-affected joints. The inducible isoform of nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) are found both in the synovial tissue and in the cartilage. Their expression is regulated by catabolic cytokines, such as interleukin-1beta and tumor necrosis factor-alpha. These inflammatory mediators play a profound role in the pathogenic processes that arise in the pannus of rheumatoid arthritis and also interfere with cartilage homeostasis in osteoarthritis. Several drugs, including nonsteroidal anti-inflammatory drugs, immunosuppressive agents, and tetracyclines, attenuate the activity of NO and PGE2. These pleiotropic mediators are targets for pharmacologic intervention and gene therapy.

Regulation of cytosolic COX-2 and prostaglandin E2 production by nitric oxide in activated murine macrophages

Murine macrophages (RAW 264.7) when stimulated with LPS show 90% distribution of cyclooxygenase-2 (COX-2) in the nuclear fraction and approximately 10% in the cytosolic fraction. Further analysis of this cytosolic fraction at 100,000 x g indicates that the COX-2 is distributed both in the 100,000 x g soluble fraction and membrane fraction. Stimulation of RAW 264.7 cells with LPS in the presence of inducible nitric oxide synthase inhibitor L-NMMA at concentrations that inhibit nitrite accumulation by </=80% is inadequate to augment PGE2 production. However, inhibition of nitrite accumulation by >/=85% with higher concentrations of L-NMMA shows 1) up-regulation of PGE2 production, 2) accumulation of COX-2 protein in the 100,000 x g soluble and membrane fractions of the cytosolic fraction, and 3) with no significant effects on the accumulation of COX-2 mRNA. These experiments suggest that low concentrations of nitric oxide (10-15% of the total) attenuate PGE2 production in response to LPS in RAW 264.7 cells. This inhibition is, in part, due to decreased expression of cytosolic COX-2 protein.

Tetracycline up-regulates COX-2 expression and prostaglandin E2 production independent of its effect on nitric oxide

Tetracyclines (doxycycline and minocycline) augmented (one- to twofold) the PGE2 production in human osteoarthritis-affected cartilage (in the presence or absence of cytokines and endotoxin) in ex vivo conditions. Similarly, bovine chondrocytes stimulated with LPS showed (one- to fivefold) an increase in PGE2 accumulation in the presence of doxycycline. This effect was observed at drug concentrations that did not affect nitric oxide (NO) production. In murine macrophages (RAW 264.7) stimulated with LPS, tetracyclines inhibited NO release and increased PGE2 production. Tetracycline(s) and L-N-monomethylarginine (L-NMMA) (NO synthase inhibitor) showed an additive effect on inhibition of NO and PGE2 accumulation, thereby uncoupling the effects of tetracyclines on NO and PGE2 production. The enhancement of PGE2 production in RAW 264.7 cells by tetracyclines was accompanied by the accumulation of both cyclooxygenase (COX)-2 mRNA and cytosolic COX-2 protein. In contrast to tetracyclines, L-NMMA at low concentrations (< or = 100 microM) inhibited the spontaneous release of No in osteoarthritis-affected explants and LPS-stimulated macrophages but had no significant effect on the PGE2 production. At higher concentrations, L-NMMA (500 microM) inhibited NO release but augmented PGE2 production. This study indicates a novel mechanism of action of tetracyclines to augment the expression of COX-2 and PGE2 production, an effect that is independent of endogenous concentration of NO.

Up-regulation of inducible nitric oxide synthase and production of nitric oxide by the Swarm rat and human chondrosarcoma

Production of nitric oxide by solid tumors may have important ramifications regarding tumor growth and potential metastasis. This study demonstrated that the chondrosarcoma of the Swarm rat has upregulated mRNA for inducible nitric oxide synthase and produces nitric oxide. These results were confirmed by (a) the presence of a 4.4-kb band of mRNA detected by Northern blot using a probe for inducible nitric oxide synthase, (b) a 133-kDa band of protein that was detected with either a polyclonal or monoclonal antibody to the inducible nitric oxide synthase of the murine macrophage, and (c) the detection of nitrites from the culture medium of freshly cultured, isolated chondrosarcoma cells. This study showed that the expression of inducible nitric oxide synthase and the production of nitric oxide by the tumor can be increased by stimulation with endotoxin lipopolysaccharide and can be inhibited by inducible nitric oxide synthase inhibitors (L-N(g)-monomethyl arginine and aminoguanidine). Immunostaining confirmed the presence of inducible nitric oxide synthase within the tumor cells and appeared to localize the enzyme to the cytoplasm of the cells. A human chondrosarcoma was also shown to have an upregulated inducible nitric oxide synthase by both the detection of mRNA for inducible nitric oxide synthase and the presence of nitrites from the culture medium of the tumor in organ culture. Because the chondrosarcoma of the Swarm rat is a well differentiated solid tumor that rarely metastasizes, nitric oxide may be produced by the tumor to promote local growth by effects on vascular supply.

Human T cell IgD receptors react with O-glycans on both human IgD and IgA1

Previous studies on murine T cell IgD-R have shown that these receptors recognize N-glycans of murine IgD, and not of other Ig isotypes. We have now studied the specificity of IgD-R on human T cells. Human IgD digested with proteinase K to fragments of < 5 kDa inhibit the ability of T cells to form rosettes with IgD-coated ox erythrocytes. The same amount of digested IgG does not. We tested all the human Ig isotypes: IgG1, -2, -3, -4, IgA2, IgE and IgM fail to inhibit significantly at 20 microg/assay. However, IgA1 is as effective as IgD itself, showing approximately 60 % and 80 % inhibition at 5 microg and 10 microg/assay. Human IgA1 and IgD both contain Gal-1 --> 3-GalNac-rich O-linked glycans, and on this basis are both bound to ricin and jacalin. The O-linked glycans may therefore also represent the common moiety binding to IgD-R. Disaccharides Gal-1 --> 3-GalNac, and Gal-1 --> 4-Glc at 10 microg/assay blocked IgD rosetting while Gal-1 --> 6-Glc did not. We conclude that the human IgD-R is a lectin, differing from the murine IgD-R in that it has both IgA1 and IgD as ligands.

Regulation of nitric oxide production by salicylates and tenidap in human OA-affected cartilage, rat chondrosarcomas and bovine chondrocytes

OBJECTIVE

To examine the effects of non-steroidal anti-inflammatory drugs (NSAIDS) on nitric oxide (NO) and prostaglandin E2 (PGE2) production in chondrocytes from three different species.

METHODS

We have estimated NO production by Griess method, and PGE2 by RIA from the supernatants of articular cartilage obtained from osteoarthritis joints (OA-affected cartilage), rat chondrosarcomas (in ex vivo conditions) and bovine chondrocytes (stimulated with cytokines + endotoxin in vitro conditions) in the presence or absence of aspirin, indomethacin, sodium salicylate, tenidap and glucocorticoids.

RESULTS

NO, which was spontaneously released in ex vivo conditions by OA-affected cartilage and rat chondrosarcomas (maintained in vivo), was susceptible to inhibition by pharmacologically relevant concentrations of aspirin, sodium salicylate and tenidap, but not to concentrations of indomethacin or glucocorticoids that significantly inhibited PGE2 production under the same conditions. Similarly, the production of NO by bovine chondrocytes grown in monolayer cultures that had been stimulated with cytokines + endotoxins (in vitro) to release both NO and PGE2 (at 48-72 h post stimulation), were inhibited by aspirin, sodium salicylate and tenidap, but not by indomethacin or glucocorticoids at concentrations sufficient to PGE2 production. Inhibition of NO in the cytokines + endotoxin stimulated bovine chondrocytes (like the human OA-affected cartilage) augmented PGE2 production.

CONCLUSION

These experiments demonstrate that NO production by chondrocytes across species show a similar profile of susceptibility to inhibition by selected anti-inflammatory drugs. The insensitivity of NO production to glucocorticoids is an important characteristics of these cells that merits further investigation.

TNF-alpha convertase enzyme from human arthritis-affected cartilage: isolation of cDNA by differential display, expression of the active enzyme, and regulation of TNF-alpha

A snake venom-like protease isolated by a differential display screen between normal and osteoarthritis (OA)-affected cartilage (designated as cSVP) has a cDNA sequence identical to TNF-alpha convertase enzyme (TACE). TACE shows the presence of an unknown prodomain, a cysteine switch, a catalytic domain, a zinc binding region, a disintegrin region, an EGF-like domain, a transmembrane domain, and a unique cytoplasmic region. A TACE construct harboring the signal + prodomain + catalytic region (TACE-SPCdeltaDETCy), expressed in baculovirus could cleave preferentially (approximately 12-fold) the TNF-specific peptide over the matrix metalloproteases peptide in vitro. This recombinant protein also cleaved the natural substrate GST-ProTNF-alpha to TNF-alpha (17 kDa) in vitro. The mRNA for TACE, which is broadly distributed and differentially expressed in a variety of human tissues, is up-regulated in arthritis-affected cartilage, but not normal cartilage. OA-affected cartilage also expressed TNF-alpha mRNA that was not detected in normal cartilage. The OA-affected cartilage (in explant assays) spontaneously released TNF-alpha and IL-8 in ex vivo conditions. Addition of TNF-alphaR fused to IgG Fc fragment (TNF-alphaR:Fc) in the presence or absence of soluble IL-1R (with which it acted additively) significantly attenuated the spontaneous/autocrine release of articular IL-8 in this assay. These experiments demonstrate a functional paracrine/autocrine role of TNF-alpha in OA-affected cartilage that may depend, in part, on up-regulated levels of chondrocyte-derived TACE.

The role of nitric oxide in articular cartilage breakdown in osteoarthritis

It is increasingly appreciated that mediators typically associated with inflammatory arthritis, such as catabolic cytokines and nitric oxide, are produced by synovium and cartilage in osteoarthritis. The role that such mediators play in the progression of cartilage degradation in osteoarthritis is under intensive investigation. Nitric oxide is a highly reactive, cytotoxic free radical that has been implicated in tissue injury in a variety of diseases. Cartilage obtained from patients with osteoarthritis produces significant amounts of nitric oxide ex vivo, even in the absence of added stimuli such as interleukin-1 or lipopolysaccharide. In vitro, nitric oxide exerts detrimental effects on chondrocyte functions, including the inhibition of collagen and proteoglycan synthesis, enhanced apoptosis, and an inhibition of B1 integrin-dependent adhesion to the extra-cellular matrix. This paper reviews recent observations regarding the role of nitric oxide in osteoarthritis and presents evidence suggesting that the inhibition of nitric oxide production could be a desirable future therapeutic strategy.

Studies on myiasis producing flies collected by bait traps at Al Marg (Qalyobia Governorate), Egypt

Myiasis is a real welfare problem. As a disease, it affects man and animals. In a study of myiasis producing flies in Al Marg District, sixteen species of dipterous flies were trapped. The predominant species was Musca domestica followed by Lueilia sericata and the least abundance was Wohlfahrtia magnifica. The overall abundance was in Summer followed by Spring and the least was in Winter. The most attractive bait was liver for members of family Calliphoridae and meat for members of family Muscidae and Family Sarcophagidae.

Autocrine production of IL-1 beta by human osteoarthritis-affected cartilage and differential regulation of endogenous nitric oxide, IL-6, prostaglandin E2, and IL-8

Interleukin-1 beta (IL-1 beta) plays a central role in the pathophysiology of cartilage damage and degradation in arthritis. In noninflammatory arthropathies such as osteoarthritis (OA), the synovial-derived IL-1 beta has been implicated in the disease process. In this study, we report that human OA-affected cartilage demonstrates upregulated IL-1 beta mRNA not seen in normal cartilage. The OA-affected cartilage in ex vivo conditions spontaneously releases detectable amounts of autocrine IL-1 beta, nitric oxide (NO), and prostaglandin E2 (PGE2), known to be involved in cartilage damage and inflammation, that cannot be detected in normal cartilage. The autocrine IL-1 beta released by the OA-affected cartilage (for at least 72 hr in ex vivo conditions) is present in sufficient quantities to modulate NO and PGE2 production because addition of recombinant soluble IL-1 beta receptor (but not soluble tumor necrosis factor-alpha receptor) and cytokine-suppressive antiinflammatory drugs (CSAIDs) significantly attenuates the spontaneous release of NO and PGE2. Furthermore, OA-affected cartilage releases significant amounts of IL-6 and IL-8 in ex vivo conditions. Addition of CSAIDs to OA-affected cartilage differentially regulates IL-6 and IL-8 production by inhibiting the spontaneous release of IL-6 but not IL-8 in ex vivo conditions. These experiments demonstrate that the human OA-affected cartilage itself releases sufficient amounts of functionally active autocrine IL-1 beta that can modulate endogenous NO, PGE2, and IL-6, but not IL-8, all of which are known to be stimulated by IL-1 beta in vitro. These IL-1 beta induced pleotropic inflammatory mediators in OA-affected cartilage may be sufficient to facilitate or augment cartilage degradation and inhibit cartilage repair, and therefore lead the cartilage into an autodestructive pathway in osteoarthritis.

Oestrid head maggots in slaughtered sheep in Cairo abattoir

Oestrosis or infestation of sheep, goats, ibex, argali and sometimes man with Oestrus ovis maggots is a real problem in sheep-farming areas allover the world. Parasitism in sheep may be benign, the majority of cases do not terminate fatally, but death may come within a week after appearance of aggravated symptoms. In man, ophthalmomyiasis (sometimes nasopharyngeal) may be benign to destruction of the eye ball or the entire eye in misdiagnosis. In the present study, examination of 1200 slaughtered sheep heads at Cairo abattoir, showed 104 (8.67%) infested with O. ovis maggots. Sheep were parasitized all the year round with more or less maximum number (12.5%) in September. The sex ratio of parasitized sheep (female to male) was 1:2.71. A total of 556 maggots were recovered allover the year with a peak in March (12.6%). The peak for the first instar larvae recovered was September (17.4%), for the second instar was March (15.7%) and for the third instar was June (11.6%). Older sheep were more infested (12.0%) with oestrosis than smaller ones (6.87%). The whole results were discussed.

Studies of wound myiasis among sheep and goats in North Sinai Governorate, Egypt

Myiasis of man and animals is a real welfare problem of world wide distribution particularly in animal raising countries. Studies of myiasis of sheep and goats in North Sinai resulted in the identification of 21 species of myiasis producing flies. The predominant species was Musca domestica followed by Lucilia sericata and the least abundant was M. albina. In general, sheep were more infested with wound myiasis than goats. The overall infestation rate was high in summer, followed by spring then autumn. The least rate of infestation was winter. As to the different areas examined, the high rate of infestation was in Bir Al-Abd, followed by Al Hasanah, Al Arish, Al Sheikh-Zowaid and lastly Rafah. The factors predisposing to wound myiasis in a descending order of importance in goats were open wound, shearing wound, caseous lymphadenitis, foot rot, faecal staining, ophthalmo or facial eczema, horn fracture, rumen fistula and lastly posterior paralysis. In sheep, the most important cause was caseous lymphadenitis followed by foot rot, then open wound and faecal staining, shearing wound, and ophthalmo or facial eczema otherwise more or less the same as in goats. It is concluded that myiasis among edible animals is a problem of veterinary and economic importance. The clinical features range between mild annoyance to severely disfiguring or fatal. No doubt, poor hygiene, presence of draining wounds, depressed level of farmers' consciousness and immobility presidose to different anatomic types of myiasis which may extend to man.

Post-transcriptional regulation of inducible nitric oxide synthase mRNA in murine macrophages by doxycycline and chemically modified tetracyclines

Chemically modified tetracyclines [CMT-3 (IC50 approximately 6-13 microM = approximately 2.5-5 microg/ml) and CMT-8 (IC50 approximately 26 microM = 10 microg/ml), but not CMT-1, -2 or -5], which lack anti-microbial activity, inhibited nitrite production in LPS-stimulated macrophages. Unlike competitive inhibitors of L-arginine which inhibited the specific activity of inducible nitric oxide synthase (iNOS) in cell-free extracts, CMTs exerted no such direct effect on the enzyme. CMTs could, however, be shown to inhibit both iNOS mRNA accumulation and protein expression in LPS-stimulated cells. Tetracyclines (doxycycline and CMT-3) unlike hydrocortisone had no significant effect on murine macrophages transfected with iNOS promoter (tagged to a luciferase reporter gene) in the presence of LPS. However, doxycycline and CMT-3 augmented iNOS mRNA degradation, in LPS-stimulated murine macrophages. These studies show a novel mechanism of action of tetracyclines which harbours properties to increase iNOS mRNA degradation and decrease iNOS protein expression and nitric oxide production in macrophages. This property of tetracyclines may have beneficial effects in the treatment of various diseases where excess nitric oxide has been implicated in the pathophysiology of these diseases.

Interleukin-17 up-regulation of nitric oxide production in human osteoarthritis cartilage

OBJECTIVE

To examine the effect of human interleukin-17 (IL-17) on nitric oxide (NO) production in human osteoarthritis (OA) cartilage under ex vivo conditions.

METHODS

OA cartilage from patients undergoing knee replacement surgery was used in explant assays to assess the effect of IL-17. NO production was measured by estimating the stable NO metabolite, nitrite, in conditioned medium.

RESULTS

IL-17 augmented the spontaneous production of nitric oxide. This augmentation was sensitive to cycloheximide and pyrrolidine dithiocarbamate, but not to dexamethasone or soluble IL-1 receptor.

CONCLUSION

IL-17 augments nitric oxide production in OA cartilage via nuclear factor kappaB activation, but independently of IL-1beta signaling.

Superinduction of cyclooxygenase-2 activity in human osteoarthritis-affected cartilage. Influence of nitric oxide

Cartilage specimens from osteoarthritis (OA)-affected patients spontaneously released PGE2 at 48 h in ex vivo culture at levels at least 50-fold higher than in normal cartilage and 18-fold higher than in normal cartilage + cytokines + endotoxin. The superinduction of PGE2 production coincides with the upregulation of cyclooxygenase-2 (COX-2) in OA-affected cartilage. Production of both nitric oxide (NO) and PGE2 by OA cartilage explants is regulated at the level of transcription and translation. Dexamethasone inhibited only the spontaneously released PGE2 production, and not NO, in OA-affected cartilage. The NO synthase inhibitor HN(G)-monomethyl-L-arginine monoacetate inhibited OA cartilage NO production by > 90%, but augmented significantly (twofold) the spontaneous production of PGE2 in the same explants. Similarly, addition of exogenous NO donors to OA cartilage significantly inhibited PGE2 production. Cytokine + endotoxin stimulation of OA explants increased PGE2 production above the spontaneous release. Addition of L-NMMA further augmented cytokine-induced PGE2 production by at least fourfold. Inhibition of PGE2 by COX-2 inhibitors (dexamethasone or indomethacin) or addition of exogenous PGE2 did not significantly affect the spontaneous NO production. These data indicate that human OA-affected cartilage in ex vivo conditions shows (a) superinduction of PGE2 due to upregulation of COX-2, and (b) spontaneous release of NO that acts as an autacoid to attenuate the production of the COX-2 products such as PGE2. These studies, together with others, also suggest that PGE2 may be differentially regulated in normal and OA-affected chondrocytes.

Chemically modified tetracyclines inhibit inducible nitric oxide synthase expression and nitric oxide production in cultured rat mesangial cells

Tetracyclines inhibit matrix metalloproteinases (MMP) and attenuate connective tissue degradation in a wide variety of human and animal disorders. Chemically modified tetracyclines (CMT) have been synthesized in which the antibacterial potency has been eliminated but in which the anti-MMP efficacy is retained. Nitric oxide (NO) modulates MMP synthesis and activity in mesangial cells in vitro. Therefore, we examined whether CMT inhibit iNOS gene and protein expression and NO production in cultured rat mesangial cells. Mesangial cells were maintained in media containing IFN-gamma and LPS for 24-72 h. Test media contained either no further additives or CMT-1, 3, 5, or 8 at concentrations of 1, 2.5, 5, and 10 micrograms/ml. iNOS gene and protein expression were assessed and NO production was determined by the Griess reaction. Incubation of mesangial cells with CMT-3 and CMT-8 resulted in time- and dose-dependent inhibition of NO production that was maximal at 48 h (< 20% of control) and at a drug concentration of 5 micrograms/ml (P < 0.05). Addition of CMT-1 had a modest (40%) inhibitory effect and CMT-5 did not alter NO production. The impact of CMT on NO production was directly related to their potency as collagenase inhibitors. Moreover, CMT-induced changes in NO synthesis were associated with parallel alterations in steady-state iNOS mRNA abundance and protein expression. These agents may be useful to ameliorate NO-dependent glomerular inflammation.

A novel mechanism of action of tetracyclines: effects on nitric oxide synthases

Tetracyclines have recently been shown to have "chondroprotective" effects in inflammatory arthritides in animal models. Since nitric oxide (NO) is spontaneously released from human cartilage affected by osteoarthritis (OA) or rheumatoid arthritis in quantities sufficient to cause cartilage damage, we evaluated the effect of tetracyclines on the expression and function of human OA-affected nitric oxide synthase (OA-NOS) and rodent inducible NOS (iNOS). Among the tetracycline group of compounds, doxycycline > minocycline blocked and reversed both spontaneous and interleukin 1 beta-induced OA-NOS activity in ex vivo conditions. Similarly, minocycline > or = doxycycline inhibited both lipopolysaccharide- and interferon-gamma-stimulated iNOS in RAW 264.7 cells in vitro, as assessed by nitrite accumulation. Although both these enzyme isoforms could be inhibited by doxycycline and minocycline, their susceptibility to each of these drugs was distinct. Unlike acetylating agents or competitive inhibitors of L-arginine that directly inhibit the specific activity of NOS, doxycycline or minocycline has no significant effect on the specific activity of iNOS in cell-free extracts. The mechanism of action of these drugs on murine iNOS expression was found to be, at least in part, at the level of RNA expression and translation of the enzyme, which would account for the decreased iNOS protein and activity of the enzyme. Tetracyclines had no significant effect on the levels of mRNA for beta-actin and glyceraldehyde-3-phosphate dehydrogenase nor on levels of protein of beta-actin and cyclooxygenase 2 expression. These studies indicate that a novel mechanism of action of tetracyclines is to inhibit the expression of NOS. Since the overproduction of NO has been implicated in the pathogenesis of arthritis, as well as other inflammatory diseases, these observations suggest that tetracyclines should be evaluated as potential therapeutic modulators of NO for various pathological conditions.

The expression and regulation of nitric oxide synthase in human osteoarthritis-affected chondrocytes: evidence for up-regulated neuronal nitric oxide synthase

Classically, osteoarthritis (OA) has been considered a noninflammatory disease. However, the detection of selected inflammatory mediators in osteoarthritic fluid, in the absence of significant inflammatory cell infiltrate, is increasingly appreciated. We sought to identify the inflammatory component in human OA-affected cartilage that may be involved in cartilage damage/destruction. Using Western blot analysis and an antibody to the conserved region of nitric oxide synthase (NOS), we have observed up-regulation of NOS, one of the "key players" of inflammation, in chondrocytes of OA-affected patients. Remarkably, none of the cartilage samples examined from normal joints demonstrated detectable amounts of this NOS. Western blot analysis using the same alpha-NOS antibody indicated that this NOS from OA-affected cartilage (OA-NOS) was larger in size than (and distinct from) transfected human hepatocyte or murine inducible NOS (iNOS) (150 versus 133 kD) and similar in size to neuronal constitutive NOS (ncNOS). Antibodies specific for iNOS showed binding to murine and human iNOS but not to OA-NOS, endothelial constitutive NOS, or ncNOS. Antibodies specific for ncNOS bound to ncNOS and also to OA-NOS, but not to murine or human iNOS or endothelial constitutive NOS. Incubation of OA cartilage in serum-free medium resulted in spontaneous release, for up to 72 h, of substantial amounts of nitrite (up to approximately 80 microM/100 mg wet tissue), which could be inhibited by at least 80% with various inhibitors of iNOS, including inhibitors of protein synthesis and transcription factor NF-kappa B, but which (unlike murine macrophage iNOS) was not sensitive to hydrocortisone or TGF-beta. Exposure of OA-affected cartilage to interleukin 1 beta, tumor necrosis factor-alpha, and lipopolysaccharide resulted in approximately 20-50% augmentation of nitrite accumulation, which was also sensitive to cycloheximide and pyrrolidine dithiocarbamate. Hence, our data indicate that OA-NOS (based on immunoreactivity and molecular weight) is similar to ncNOS and that it releases nitric oxide, which may contribute to the inflammation and pathogenesis of cartilage destruction in OA.

The mode of action of aspirin-like drugs: effect on inducible nitric oxide synthase

Nitric oxide synthesized by inducible nitric oxide synthase (iNOS) has been implicated as a mediator of inflammation in rheumatic and autoimmune diseases. We report that exposure of lipopolysaccharide-stimulated murine macrophages to therapeutic concentrations of aspirin (IC50 = 3 mM) and hydrocortisone (IC50 = 5 microM) inhibited the expression of iNOS and production of nitrite. In contrast, sodium salicylate (1-3 mM), indomethacin (5-20 microM), and acetaminophen (60-120 microM) had no significant effect on the production of nitrite at pharmacological concentrations. At suprapharmacological concentrations, sodium salicylate (IC50 = 20 mM) significantly inhibited nitrite production. Immunoblot analysis of iNOS expression in the presence of aspirin showed inhibition of iNOS expression (IC50 = 3 mM). Sodium salicylate variably inhibited iNOS expression (0-35%), whereas indomethacin had no effect. Furthermore, there was no significant effect of these nonsteroidal anti-inflammatory drugs on iNOS mRNA expression at pharmacological concentrations. The effect of aspirin was not due to inhibition of cyclooxygenase 2 because both aspirin and indomethacin inhibited prostaglandin E2 synthesis by > 75%. Aspirin and N-acetylimidazole (an effective acetylating agent), but not sodium salicylate or indomethacin, also directly interfered with the catalytic activity of iNOS in cell-free extracts. These studies indicate that the inhibition of iNOS expression and function represents another mechanism of action for aspirin, if not for all aspirin-like drugs. The effects are exerted at the level of translational/posttranslational modification and directly on the catalytic activity of iNOS.

Oligomeric IgD augments and monomeric IgD inhibits the generation of IgG memory antibody responses in normal, but not in IgD-deficient, mice

Dimeric or aggregated IgD causes augmentation of primary and secondary Ab responses in mice when injected a few days before or together with the primary dose of Ag. This effect is mediated by Th cells and seems to be linked to the up-regulation of receptors for IgD on CD4+ T cells. IgD-R cross-linking is needed for receptor up-regulation. Here we show that addition of monomeric IgD to dimeric or aggregated IgD blocks IgD-R up-regulation on T cells in vitro and in vivo, as well as their immunoaugmenting effect in vivo. More importantly, monomeric IgD injected 6 to 24 h before a primary Ag injection also inhibits 1) the up-regulation of IgD-R on T cells induced by Ag injection alone, and 2) the generation of IgG memory, as shown in the response to a second dose of Ag injected on day 10. These results suggest that IgD-R on T cells contribute to the T-B cell interaction involved in the priming for a secondary response. The augmenting effect of oligomeric IgD and the inhibiting effect of monomeric IgD on secondary Ab responses are not observed in IgD-/- (IgD-deficient) mice, although injection of oligomeric IgD leads to IgD-R up-regulation on T cells in these mice. These results indicate that IgD presented in the form of immune complexes, most likely on the surface of B cells, is a prerequisite for the immunoaugmenting effects exerted by IgD-R+ T cells. Thus, IgD is the only physiologic ligand for IgD-R on T cells.

Oligomeric IgD augments and monomeric IgD inhibits the generation of IgG memory antibody responses in normal, but not in IgD-deficient, mice

Dimeric or aggregated IgD causes augmentation of primary and secondary Ab responses in mice when injected a few days before or together with the primary dose of Ag. This effect is mediated by Th cells and seems to be linked to the up-regulation of receptors for IgD on CD4+ T cells. IgD-R cross-linking is needed for receptor up-regulation. Here we show that addition of monomeric IgD to dimeric or aggregated IgD blocks IgD-R up-regulation on T cells in vitro and in vivo, as well as their immunoaugmenting effect in vivo. More importantly, monomeric IgD injected 6 to 24 h before a primary Ag injection also inhibits 1) the up-regulation of IgD-R on T cells induced by Ag injection alone, and 2) the generation of IgG memory, as shown in the response to a second dose of Ag injected on day 10. These results suggest that IgD-R on T cells contribute to the T-B cell interaction involved in the priming for a secondary response. The augmenting effect of oligomeric IgD and the inhibiting effect of monomeric IgD on secondary Ab responses are not observed in IgD-/- (IgD-deficient) mice, although injection of oligomeric IgD leads to IgD-R up-regulation on T cells in these mice. These results indicate that IgD presented in the form of immune complexes, most likely on the surface of B cells, is a prerequisite for the immunoaugmenting effects exerted by IgD-R+ T cells. Thus, IgD is the only physiologic ligand for IgD-R on T cells.

Expression of nitric oxide synthase in human peripheral blood mononuclear cells and neutrophils

It has been clearly demonstrated in rodents that nitric oxide (NO) plays an important role in host defense and immunity. However, evidence that human leukocytes express inducible nitric oxide synthase (iNOS) or its products has been inconclusive and a source of controversy. We report that iNOS could not be detected in human monocytes, HL-60 cells, neutrophils, and T cells by Western blotting analysis (< or = 10 pg) or by radiolabeled L-arginine-to-L-citrulline conversion (< or = 20 pmol L-citrulline) under conditions sufficient to induce iNOS in the rodent system and in human hepatocytes, which include activation with cytokines, endotoxins, and/or chemoattractants. However, sensitive methods such as RT-PCR and Northern blot analysis show "constitutively expressed" iNOS mRNA from human monocytes, neutrophils, Jurkat cells, and HL-60 cells. This iNOS mRNA is 4.4 kb and is similar to that seen in human hepatocytes and rodent macrophages. In spite of the constitutive expression of mRNA in neutrophils and the lack of detectable NOS activity (based on Western blotting and L-arginine-to-L-citrulline conversion assay), stimulation of human neutrophils unit FMLP in vitro induced the ADP-ribosylation of an intracellular NO target, glyceraldehyde-3-PO4 dehydrogenase (GAPDH), in a NO-dependent manner. These studies indicate that low levels of NOS protein are expressed in neutrophils (and perhaps T cells and monocytes) and produce NO following stimulation. The data indicate that, in addition to its phagocytic and tumoricidal activity. NO may also function as an autacoid signaling molecule within the cells.

Biology of germinal centers in lymphoid tissue

Germinal centers in lymphoid tissue are the sites of generation of memory B cells undergoing isotype switching and somatic mutation in their Ig genes. Their formation cannot be induced by stimuli other than immunogenic ones. It seems likely that in the function and possibly also in the formation of germinal centers, one important factor is the localization of immune complexes with fixed complement on the surface of follicular dendritic cells. CD4+ T cells, located primarily in the "apical light zones" of the centers, are necessary for germinal center formation. However, their exact role in the process needs clarification, as both cell to cell contact and cytokine production could be involved at different stages of the germinal center generation. These T cells are usually specific for the antigen inducing the germinal center, but they may sometimes respond to other surface components on the B cell surface. In view of the possible stimulatory role of CD4+ T cells in follicular center-derived lymphomas, the functional significance of these T cells in germinal center proliferation is important to unravel. The B cells in germinal centers proliferate extremely rapidly, especially those located in the "dark zones." Many of them undergo apoptosis, particularly in the "basal light zones." The microenvironment of these centers is well suited to the task of expanding and selecting memory B cells of high affinity for the inducing antigen. The interactions of the proliferating B cells with dendritic cells and T cells, unevenly distributed in the various zones of the germinal center, are thought to determine which cells deserve rescue from apoptosis and induction to differentiation into small resting memory B cells. The memory B cells that emerge from the germinal center bear sIg, usually of "switched" isotype, and exhibit somatic mutations in the variable regions of their rearranged Ig genes.

Regulation of IgD-receptor expression on murine T cells. II. Upregulation of IgD receptors is obtained after activation of various intracellular second-messenger systems; tyrosine kinase activity is required for the effect of IgD

The presence of IgD receptors (IgD-R) on T cells during a primary response to antigen causes augmented antibody production and facilitates priming for a secondary response. Cross-linked, but not monomeric IgD leads to a rapid upregulation of these receptors on T cells. As shown in the present study, the rapid upregulation of IgD-specific receptors is also induced by cross-linking of T cell surface molecules known to mediate triggering of T cell activation, such as CD3, CD2, and Thy 1. Furthermore, IgD-R are also upregulated by pharmacologically active compounds that increase intracellular cAMP and by PMA/DiOG plus ionomycin, but not by either PMA or ionomycin alone. The upregulation of IgD-R by anti-CD3 is inhibited by both calphostin C and herbimycin A, while that due to DiOG plus ionomycin is only inhibited by calphostin C. Upregulation of IgD-R by increased cAMP is blocked by HA1004, but not by low concentrations of staurosporine or herbimycin A. IgD itself does not cause an increase in intracellular cAMP, protein kinase C translocation, influx of extracellular Ca2+, or a change in membrane potential. Relatively specific inhibitors of these activation pathways, HA1004, calphostin C, and neomycin, also fail to interfere with IgD-receptor upregulation by IgD itself. However, tyrosine kinase inhibitors, including herbimycin A, tyrphostin C11, and genistein, completely prevent the effect of IgD on IgD-R expression. Although an influx of Ca2+ is apparently not involved, a role for intracellular Ca2+ in the upregulation of IgD-R by IgD on T cells is indicated by the susceptibility to inhibition by BAPTA, W7, and FK520. We conclude that activation of at least three different second-messenger systems can cause IgD-R upregulation, but that the effect of IgD itself requires tyrosine kinase activity, perhaps in an intracellular Ca(2+)-dependent manner.

Regulation of IgD-receptor expression on murine T cells. I. Characterization and metabolic requirements of the process leading to their expression

Receptors for IgD (IgD-R) are found on murine CD4+ T cells and T cell clones. Previous work has shown that incubation with aggregated (but not monomeric) IgD causes the rapid upregulation of IgD-R and enables the T cells to respond with augmented helper function in antibody production. In the present study, IgD-R upregulation is shown to be (a) rapid, reaching plateau levels by 60 min, (b) independent of de novo protein or RNA synthesis, and (c) only slightly reduced at 4 degrees C. The IgD-R+ T cells present both before and after upregulation of IgD-R expression are predominantly resting T cells, whose ability to rosette with IgD-SRBC is inhibited by soluble IgD. The upregulation of IgD-R, even after overnight exposure to IgD, does not cause any detectable change in the expression of other T cell surface markers. Also characteristic of resting T cells is that they exhibit IgD-R in response to IL-2 and IL-4 only after overnight incubation with these cytokines, and fail to respond at all to IL-1. In contrast, cloned Th2 cells, expressing IL-1 and IL-2 receptors, show IgD-R upregulation after a 2-hr exposure to IL-1 or IL-2. GM-CSF, TNF-alpha, IL-6, and IL-10 do not modulate IgD-R expression. T hybridoma cells constitutively express much higher IgD-R levels than resting splenic T cells and can be stained with aggregated IgD followed by FITC-anti-IgD. Their levels of IgD-R expression decrease, as assayed both by rosetting and by staining, on 4-14 hr of incubation with tunicamycin or deoxynojirimycin, suggesting that N-linked glycosylation and oligosaccharide processing, respectively, are needed for continued expression of IgD-R. Tunicamycin-treated cells without detectable IgD-R on their surface still show IgD-binding protein in the cell extracts, suggesting that surface expression is more dependent on glycosylation of the IgD-R molecules than on the ability to bind IgD. Ca2+ ions are needed for optimal binding of IgD to IgD-R, in line with previous findings showing IgD-R to be lectin-like in binding carbohydrate rather than peptide regions of the IgD molecule.