Robert J. Moots

Neutrophil function in inflammation and inflammatory diseases

In inflammatory conditions such as RA, the neutrophil has tended to be dismissed as a short-lived, terminally differentiated, irrelevant bystander cell. However, this is clearly not the case. A better understanding of the complex heterogeneous pathways and processes that constitute RA, in parallel with a more sophisticated knowledge of neutrophil biology has identified many potential roles for these cells in the persistence of inflammation and progression of joint damage, which should not be underestimated. Not only are neutrophils found in high numbers within the rheumatoid joint, both in synovial tissue and in joint fluid, they have a huge potential to directly inflict damage to tissue, bone and cartilage via the secretion of proteases and toxic oxygen metabolites, as well as driving inflammation through antigen presentation and secretion of cytokines, chemokines, prostaglandins and leucotrienes. Drugs already used to treat RA down-regulate many neutrophil functions, including migration to the joint, degranulation and production of inflammatory mediators, and these cells should be considered as important targets for the development of new therapies in the future.

The Mitochondrial Network of Human Neutrophils: Role in Chemotaxis, Phagocytosis, Respiratory Burst Activation, and Commitment to Apoptosis

It is commonly assumed that human neutrophils possess few, if any, functional mitochondria and that they do not depend on these organelles for cell function. We have used the fluorescent mitochondrial indicators, JC-1, MitoTracker Red, and dihydrorhodamine 123 to show that live neutrophils possess a complex mitochondrial network that extends through the cytoplasm. The membrane potential of these mitochondria was rapidly (within 2 min) disrupted by the addition of FCCP (IC50 = 20 nM), but not by the Fo-ATPase inhibitor, oligomycin (at up to 7 μg/ml). However, inhibition of mitochondrial function with both agents resulted in cell shape changes. Neither activation of the respiratory burst nor phagocytosis of either latex particles or serum-opsonized Staphylococcus aureus was affected by the addition of FCCP or oligomycin. However, FCCP inhibited chemotaxis at concentrations that paralleled disruption of mitochondrial membrane potential. Furthermore, prolonged (2-h) incubation with oligomycin resulted in an impaired ability to activate a respiratory burst and also inhibited chemotaxis. These observations indicate that intact mitochondrial function is required to sustain some neutrophil functions, but not for the rapid initiation of the respiratory burst or phagocytosis. Loss of mitochondrial membrane potential was a very early marker for commitment of neutrophils into apoptosis and preceded the appearance of phosphatidylserine on the cell surface. However, inhibition of mitochondrial function did not accelerate the rate of neutrophil apoptosis. These data shed important insights into the hitherto unrecognized importance of mitochondria in the function of neutrophils during infection and inflammation.

Heavy cigarette smoking is strongly associated with rheumatoid arthritis (RA), particularly in patients without a family history of RA

OBJECTIVES To investigate the potential relation between cumulative exposure to cigarette smoking in patients with or without rheumatoid arthritis (RA) and a positive family history of the disease. METHODS 239 outpatient based patients with RA were compared with 239 controls matched for age, sex, and social class. A detailed smoking history was recorded and expressed as pack years smoked. Conditional logistic regression was used to calculate the association between RA and pack years smoked. The patients with RA were also interviewed about a family history of disease and recorded as positive if a first or second degree relative had RA. The smoking history at the time of the study of the patients with RA with or without a family history of the disease was compared directly with that of their respective controls. Patients with RA with or without a family history of the disease were also compared retrospectively for current smoking at the time of disease onset. RESULTS An increasing association between increased pack years smoked and RA was found. There was a striking association between heavy cigarette smoking and RA. A history for 41–50 pack years smoked was associated with RA (odds ratio (OR) 13.54, 95% confidence interval (95% CI) 2.89 to 63.38; p<0.001). The association between ever having smoked and RA was modest (OR 1.81, CI 1.22 to 2.19; p=0.002). Furthermore, cigarette smoking in the patients with RA without a positive family history of RA was more prevalent than in the patients with a positive family history of RA for ever having smoked (72% v 54%; p=0.006), the number of pack years smoked (median 25.0v 4.0; p<0.001), and for smoking at the time of disease onset (58% v 39%; p=0.003). CONCLUSIONS Heavy cigarette smoking, but not smoking itself, is strongly associated with RA requiring hospital follow up and is markedly more prevalent in patients with RA without a family history of RA.

Dopamine receptor expression on human T- and B-lymphocytes, monocytes, neutrophils, eosinophils and NK cells: a flow cytometric study.

This study documents expression of dopamine (DA) receptors on leukocyte subpopulations using flow cytometric techniques to identify dopamine receptors with subtype-specific antibodies. Of the D1-like receptor family (D(1) and D(5)), only D(5) was detected, and of the D2-like receptor family (D(2), D(3) and D(4)), all dopamine receptors were detected. T-lymphocytes and monocytes had low expression of dopamine receptors, whereas neutrophils and eosinophils had moderate expression. B cells and NK cells had higher and more consistent expression. Dopamine receptors D(3) and D(5) were found in most individuals whereas D(2) and D(4) had more variable expression. D(1) was never found.

The multifactorial role of neutrophils in rheumatoid arthritis.

Of all cells implicated in the pathology of rheumatoid arthritis (RA), neutrophils possess the greatest cytotoxic potential, owing to their ability to release degradative enzymes and reactive oxygen species. Neutrophils also contribute to the cytokine and chemokine cascades that accompany inflammation, and regulate immune responses via cell–cell interactions. Emerging evidence suggests that neutrophils also have a previously unrecognised role in autoimmune diseases: neutrophils can release neutrophil extracellular traps (NETs) containing chromatin associated with granule enzymes, which not only kill extracellular microorganisms but also provide a source of autoantigens. For example, citrullinated proteins that can act as neoepitopes in loss of immune tolerance are generated by peptidylarginine deiminases, which replace arginine with citrulline residues, within neutrophils. Indeed, antibodies to citrullinated proteins can be detected before the onset of symptoms in patients with RA, and are predictive of erosive disease. Neutrophils from patients with RA have an increased tendency to form NETs containing citrullinated proteins, and sera from such patients contain autoantibodies that recognize these proteins. Thus, in addition to their cytotoxic and immunoregulatory role in RA, neutrophils may be a source of the autoantigens that drive the autoimmune processes underlying this disease.

Intestinal permeability and inflammation in patients on NSAIDs

Background—The frequency with which non-steroidal anti-inflammatory drugs (NSAIDs) increase small intestinal permeability and cause inflammation is uncertain. Aims—To examine small intestinal permeability and inflammation in a large number of patients on long term NSAIDs. Methods—Sixty eight patients receiving six different NSAIDs for over six months underwent combined absorption-permeability tests at three different test dose osmolarities (iso-, hypo-, and hyperosmolar). Two hundred and eighty six patients on 12 different NSAIDs underwent indium-111 white cell faecal excretion studies to assess the prevalence and severity of intestinal inflammation. Results—The iso- and hyperosmolar tests showed significant malabsorption of 3–0-methyl-d-glucose, d-xylose, andl-rhamnose. Intestinal permeability changes were significantly more pronounced and frequent with the hypo- and hyperosmolar as opposed to the iso-osmolar test. Sequential studies showed that four and nine patients (of 13) developed inflammation after three and six months treatment with NSAIDs, respectively. There was no significant difference (p>0.1) in the prevalence (54–72%) or severity of intestinal inflammation in the 286 patients taking the various NSAIDs apart from those on aspirin and nabumetone, these having no evidence of intestinal inflammation. There was no significant correlation between the inflammatory changes and age, sex, dose of NSAID, length of disease, or NSAID ingestion. Conclusions—Intestinal permeability test dose composition is an important factor when assessing the effects of NSAIDs on intestinal integrity. All the conventional NSAIDs studied were equally associated with small intestinal inflammation apart from aspirin and nabumetone which seem to spare the small bowel.

Corticosteroids: do they damage the cardiovascular system?

Since their introduction for the treatment of rheumatoid arthritis, corticosteroids have become widely used as effective agents in the control of inflammatory diseases. Although there have been undoubted benefits upon mortality in diseases such as systemic lupus erythematosus, many patients survive only to suffer a high incidence of premature atherosclerosis. There is also evidence of increased rates of vascular mortality in other corticosteroid-treated diseases, such as rheumatoid arthritis, reversible airways obstruction and transplant recipients. Possible mechanisms of damage include elevated blood pressure, impaired glucose tolerance, dyslipidaemia, and imbalances in thrombosis and fibrinolysis. This paper reviews the clinical evidence supporting the contention that there is an excess cardiovascular mortality in steroid-treated patients and the underlying mechanisms, and points to further areas of research.

'The Many Faces of Interleukin-6: The Role of IL-6 in Inflammation, Vasculopathy, and Fibrosis in Systemic Sclerosis'

Interleukin-6 is currently attracting significant interest as a potential therapeutic target in systemic sclerosis (SSc). In this paper, the biology of interleukin-6 is reviewed, and the evidence for interleukin-6 dysregulation in SSc is explored. The role of inteleukin-6 classical and trans signalling pathways in SSc relevant phenomena such as chronic inflammation, autoimmunity, endothelial cell dysfunction, and fibrogenesis is discussed. The existing evidence that interventions designed to block interleukin-6 signalling are of therapeutic relevance in SSc is evaluated.

Regulation of neutrophil apoptosis by Mcl-1.

Neutrophils rapidly undergo spontaneous apoptosis, but this process can be considerably delayed by exposure to a variety of agents such as pro-inflammatory cytokines. The anti-apoptotic protein of the Bcl-2 family, Mcl-1, plays a key role in the regulation of neutrophil apoptosis. The protein has some unusual properties compared with other family members, including an extremely high turnover rate. Many factors, such as cytokines and local oxygen concentrations, can regulate cellular levels of Mcl-1 via transcription and post-transcriptional modification, control the survival time of neutrophils within tissues and thereby influence the inflammatory response.

Patient-reported outcomes improve with etanercept plus methotrexate in active early rheumatoid arthritis and the improvement is strongly associated with remission: the COMET trial

Objectives: To compare the effects of etanercept (ETN) 50 mg once weekly plus methotrexate (MTX) versus MTX alone on patient-reported outcomes (PROs) and the relationship between remission and PRO improvement. Methods: In this double-blind, randomised clinical trial (COMET), PROs included: the Health Assessment Questionnaire (HAQ), EuroQoL health status, fatigue and pain visual analogue scales, Hospital Anxiety and Depression Scale, and Medical Outcomes Short-Form-36. Mean changes from baseline were analysed by analysis of covariance using the last observation carried forward method. Results from week 52 are presented. Results: Most PROs demonstrated significantly greater improvements with ETN+MTX than MTX alone, including physical functioning, pain, fatigue and overall health status. A significantly greater improvement in HAQ score was observed in the ETN+MTX than the MTX group (−1.02 vs −0.72; p<0.001) and a greater proportion reached the minimal clinically important difference of 0.22 (88% vs 78%; p<0.006). The relationship between PRO score and clinical status indicated that improvement was greatest among patients achieving remission. Conclusions: Early treatment with ETN+MTX leads to significantly greater improvements in multiple dimensions of PROs than MTX alone. The close relationship between disease activity and PRO improvement suggests that early treatment, with remission as a goal, should maximise the chance of restoring normal functioning and HRQoL.