More Night Than Day — Circadian Rhythms in Polymyalgia Rheumatica and Ankylosing Spondylitis

Chronobiology and Chronotherapy in Inflammatory Joint Diseases

Circadian rhythm perturbations can impact the evolution of different conditions, including autoimmune diseases. This narrative review summarizes the current understanding of circadian biology in inflammatory joint diseases and discusses the potential application of chronotherapy. Proinflammatory cytokines are key players in the development and progression of rheumatoid arthritis (RA), regulating cell survival/apoptosis, differentiation, and proliferation. The production and secretion of inflammatory cytokines show a dependence on the human day–night cycle, resulting in changing cytokine plasma levels over 24 h. Moreover, beyond the circadian rhythm of cytokine secretion, disturbances in timekeeping mechanisms have been proposed in RA. Taking into consideration chronotherapy concepts, modified-release (MR) prednisone tablets have been introduced to counteract the negative effects of night-time peaks of proinflammatory cytokines. Low-dose MR prednisone seems to be able to improve the course of RA, reduce morning stiffness and morning serum levels of IL-6, and induce significant clinical benefits. Additionally, methotrexate (MTX) chronotherapy has been reported to be associated with a significant improvement in RA activity score. Similar effects have been described for polymyalgia rheumatica and gout, although the available literature is still limited. Growing knowledge of chronobiology applied to inflammatory joint diseases could stimulate the development of new drug strategies to treat patients in accordance with biological rhythms and minimize side effects.

Glucocorticoid circadian rhythms in immune function

Adrenal glucocorticoid (GC) hormones are important regulators of energy metabolism, brain functions, and the immune system. Their release follows robust diurnal rhythms and GCs themselves serve as entrainment signals for circadian clocks in various tissues. In the clinics, synthetic GC analogues are widely used as immunosuppressive drugs. GC inhibitory effects on the immune system are well documented and include suppression of cytokines and increased immune cell death. However, the circadian dynamics of GC action are often neglected. Synthetic GC medications fail to mimic complex GC natural rhythms. Several recent publications have shown that endogenous GCs and their daily concentration rhythms prepare the immune system to face anticipated environmental threats. That includes migration patterns that direct specific cell population to organs and tissues best exemplified by the rhythmic expression of chemoattractants and their receptors. On the other hand, chronotherapeutic approaches may benefit the treatment of immunological diseases such as asthma. In this review, we summarise our current knowledge on the circadian regulation of GCs, their role in innate and adaptive immune functions and the implications for the clinics.

Measuring Spinal Mobility Using an Inertial Measurement Unit System: A Reliability Study in Axial Spondyloarthritis

The objectives of this study were to evaluate the reliability of wearable inertial motion unit (IMU) sensors in measuring spinal range of motion under supervised and unsupervised conditions in both laboratory and ambulatory settings. A secondary aim of the study was to evaluate the reliability of composite IMU metrology scores (IMU-ASMI (Amb)). Forty people with axSpA participated in this clinical measurement study. Participant spinal mobility was assessed by conventional metrology (Bath Ankylosing Spondylitis Metrology Index, linear version—BASMI_Lin) and by a wireless IMU sensor-based system which measured lumbar flexion-extension, lateral flexion and rotation. Each sensor-based movement test was converted to a normalized index and used to calculate IMU-ASMI (Amb) scores. Test-retest reliability was evaluated using intra-class correlation coefficients (ICC). There was good to excellent agreement for all spinal range of movements (ICC > 0.85) and IMU-ASMI (Amb) scores (ICC > 0.87) across all conditions. Correlations between IMU-ASMI (Amb) scores and conventional metrology were strong (Pearson correlation ≥ 0.85). An IMU sensor-based system is a reliable way of measuring spinal lumbar mobility in axSpA under supervised and unsupervised conditions. While not a replacement for established clinical measures, composite IMU-ASMI (Amb) scores may be reliably used as a proxy measure of spinal mobility.

Depression and depressive symptoms in patients with polymyalgia rheumatica: discussion points, grey areas and unmet needs emerging from a systematic review of published literature

Objectives

In 1979, Bird et al. proposed depression as a diagnostic criterion for polymyalgia rheumatica (PMR). More recently, the significance of depression in PMR patients has been re-proposed, , and some researchers have suggested that PMR may increase the risk of depression. The aim of our article is to evaluate the relationship between PMR and depression.

Material and methods

Systematic literature searches were performed on 19^th and 20^th May 2020 based on Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. The search was restricted to all studies and case reports with English abstract, published in any language, since 1979 (when depression was first proposed as a diagnostic criterion for PMR) describing the association of PMR with depression. Exclusion criteria were as follows: reviews, conference abstracts, comments, non-original articles; and articles discussing giant cell arteritis (GCA) and PMR when data and observations for the two conditions were not clearly subdivided.

Results

The initial search yielded 812 papers, of which 115 duplicates were removed. A total of 697 articles had a first screening and 506 were excluded based on title and abstract reviews; 117 articles underwent full-length scrutiny, and 99 full-text articles were excluded because they did not meet the inclusion and exclusion criteria (reviews and comments = 58; articles with outcome of interest not reported = 34; low-quality articles = 7). At least, 18 articles were included in this review.

Conclusions

The review did not find any studies that clarified the prevalence rates of depression in patients with PMR. Furthermore, the studies reviewed did not offer any clarity as to whether patients suffered from just depressive symptoms or clinical depression, and that accepted diagnostic criteria for depression had not been employed, indicating that a robust method for diagnosing depression had not been employed. Collaboration of different professionals should be improved through shared guidelines.

Potential Chronotherapeutic Optimization of Antimalarials in Systemic Lupus Erythematosus: Is Toll-Like Receptor 9 Expression Dependent on the Circadian Cycle in Humans?

Toll-like receptor 9 (TLR9) belongs to the group of endosomal receptors of the innate immune system with the ability to recognize hypomethylated CpG sequences from DNA. There is scarce information about TLR9 expression and its association with the circadian cycle (CC). Different patterns of TLR9 expression are regulated by the CC in mice, with an elevated expression at Zeitgeber time 19 (1:00 a.m.); nevertheless, we still need to corroborate this in humans. In systemic lupus erythematosus (SLE), the inhibitory effect of chloroquine (CQ) on TLR9 is limited. TLR9 activation has been associated with the presence of some autoantibodies: anti-Sm/RNP, anti-histone, anti-Ro, anti-La, and anti-double-stranded DNA. Treatment with CQ for SLE has been proven to be useful, in part by interfering with HLA-antigen coupling and with TLR9 ligand recognition. Studies have shown that TLR9 inhibitors such as antimalarial drugs are able to mask TLR9-binding sites on nucleic acids. The data presented here provide the basic information that could be useful for other clinical researchers to design studies that will have an impact in achieving a chronotherapeutic effect by defining the ideal time for CQ administration in SLE patients, consequently reducing the pathological effects that follow the activation of TLR9.

Glucocorticoid management in rheumatoid arthritis: morning or night low dose?

Morning symptoms of rheumatoid arthritis (RA) are linked to circadian increase of night inflammation, supported by inadequate cortisol secretion in active disease. Therefore, exogenous glucocorticoid administration in RA is recommended by EULAR and ACR from the beginning of the diagnosis, since may partially act like a "replacement therapy". In addition, the prevention/treatment of the night up-regulation of the immune/inflammatory reaction has been shown more effective when exogenous glucocorticoid administration is managed with a night-time-release formulation. Despite a considerably higher cost than conventional prednisone (immediate release), chronotherapy with night-time-release prednisone has been recognized a cost-effective option for RA patients not on glucocorticoids who are eligible for therapy with biologic disease-modifying antirheumatic drugs (DMARDs). Interestingly, since different cell populations involved in the inflammatory process are particularly activated during the night (i.e. monocytes, macrophages), other therapeutical approaches used in RA, such as conventional DMARDs and non-steroidal anti-inflammatory drugs (NSAIDs) should follow the same concepts of glucocorticoid chronotherapy. Therefore, bedtime methotrexate chronotherapy was found to better manage RA symptoms, and several available NSAIDs (i.e. indomethacin, aceclofenac, ketoprofen, flurbiprofen, lornoxicam) have been recently modified in their formulation, in order to obtain more focused night action.

Modified-release prednisone for polymyalgia rheumatica: a multicentre, randomised, active-controlled, double-blind, parallel-group study

Objective

To assess the efficacy and safety of modified-release (MR) versus immediate-release (IR) prednisone in newly diagnosed glucocorticoid (GC)-naïve patients with polymyalgia rheumatica (PMR).

Methods

Patients were randomised to double-blind MR prednisone (taken at approximately 22:00) or IR prednisone (taken in the morning), 15 mg/day for 4 weeks. The primary end point was complete response rate (≥70% reduction in PMR visual analogue scale, duration of morning stiffness and C reactive protein (CRP) (or CRP <2× upper limit of normal (ULN))) at week 4. Non-inferiority was decided if the lower 95% confidence limit (MR vs IR prednisone) was above −15%. 400 patients were planned but only 62 were enrolled due to difficulties in recruiting GC-naïve patients with PMR with CRP ≥2×ULN.

Results

The percentage of complete responders at week 4 was numerically greater for MR prednisone (53.8%) than for IR prednisone (40.9%). Non-inferiority of MR versus IR prednisone was not proven in the primary analysis on the per protocol population (N=48; treatment difference: 12.22%; 95% CI −15.82% to 40.25%). However, sensitivity analysis on the full analysis population showed an evident trend favouring MR prednisone (N=62; treatment difference: 15.56%; 95% CI −9.16% to 40.28%). Adverse events were generally mild and transient with no unexpected safety observations.

Conclusions

The study showed a clear trend for favourable short-term efficacy of MR prednisone versus IR prednisone in early treatment of PMR. Further studies are warranted.

Trial registration number

EudraCT number 2011-002353-57; Results.

Circadian variations in clinical symptoms and concentrations of inflammatory cytokines, melatonin, and cortisol in polymyalgia rheumatica before and during prednisolone treatment: a controlled, observational, clinical experimental study

BACKGROUND

In contrast to rheumatoid arthritis (RA), no systematic investigation of diurnal variation has been carried out in polymyalgia rheumatica (PMR). The aim of the study was to provide the often-requested documentation of the 24-h time course of clinical symptoms in PMR and relate them to concentrations during the day of melatonin, inflammatory cytokines, and cortisol. Furthermore, the effects of 14 days of prednisolone treatment were studied.

METHODS

Ten glucocorticoid-naive patients newly diagnosed with PMR and seven non-PMR control subjects were studied for 24 h before treatment and during the 14th day of treatment with 20 mg/day of prednisolone. Global pain and generalized muscle stiffness were monitored by using visual analogue scales, and blood was drawn repeatedly.

RESULTS

In untreated patients, pain and stiffness peaked in the early morning, showing a plateau between 04:00 and 08:00, and then declined to a nadir at 16:00 (2P < 0.05). Plasma concentrations of interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, IL-1β, and IL-4 varied with time in both groups (2P < 0.05) and peaked between 04:00 and 08:00. Furthermore, except for IL-1β, concentrations of these cytokines and of IL-10 were higher throughout the 24-h observation period in patients than in control subjects (2P < 0.05). Also, melatonin and cortisol were consistently higher in patients (2P < 0.05) and varied with time (2P < 0.05), peaking around 02:00 and 08:00, respectively. In patients, prednisolone abolished symptoms, normalized C-reactive protein, and reduced melatonin, IL-6, IL-8, and TNF-α concentrations (2P < 0.05), while IL-10 increased between 10:00 and 14:00.

CONCLUSIONS

In PMR, key symptoms show diurnal variation. Furthermore, in PMR, concentrations of melatonin, several pro- and anti-inflammatory cytokines, and cortisol are increased throughout the day and show diurnal variation, as also seen in healthy subjects. The time courses and the inhibitory effects of prednisolone indicate that in PMR, as proposed for RA, melatonin stimulates cytokine production, which in turn accounts at least partly for the symptoms. Furthermore, overall, cortisol may downregulate cytokine production and symptoms. Stimulation of IL-10 secretion may participate in the anti-inflammatory effects of prednisolone. These findings support use of chronotherapy in PMR and encourage study of circadian variations in other inflammatory autoimmune diseases.

Glucocorticoids and chronotherapy in rheumatoid arthritis

It is evident that the morning symptoms of rheumatoid arthritis (RA) are linked to the circadian abnormal increase in night inflammation, favoured by inadequate cortisol secretion under conditions of active disease. Therefore, exogenous glucocorticoid treatment is recommended in RA at low doses since it may partially act like a ‘replacement therapy’. The prevention/treatment of the night upregulation of the immune/inflammatory reaction (and related flare of cytokine synthesis) has been shown to be more effective when exogenous glucocorticoid administration is obtained with a night-time-release formulation. Large-scale trials documented that modified-release prednisone has greater efficacy then morning prednisone for long-term low-dose glucocorticoid treatment in patients with RA, showing at least a more significant reduction in morning joint stiffness. Interestingly, despite a considerably higher cost than conventional prednisone, chronotherapy with night-time-release prednisone was recognised as a cost-effective option for patients with RA not on glucocorticoids who are eligible for therapy with biological disease-modifying antirheumatic drugs (DMARDs). Moreover, since different cell populations involved in the inflammatory process are particularly activated during the night, other therapeutical approaches used in RA, for example, conventional DMARDs and non-steroidal anti-inflammatory drugs (NSAIDs), should follow the same concepts of glucocorticoid chronotherapy. Indeed, bedtime methotrexate chronotherapy was found to improve RA symptoms compared to the current standard dosing methods, and several available NSAIDs (ie, indomethacin, aceclofenac, ketoprofen, flurbiporfen, lornoxicam) have been very recently modified in their formulation, in order to obtain chronotherapeutical effects in RA.

Reappraisal of the diagnostic and prognostic value of morning stiffness in arthralgia and early arthritis: results from the Groningen EARC, Leiden EARC, ESPOIR, Leiden EAC and REACH

Introduction

Morning stiffness is assessed daily in the diagnostic process of arthralgia and arthritis, but large-scale studies on the discriminative ability are absent. This study explored the diagnostic value of morning stiffness in 5,202 arthralgia and arthritis patients and the prognostic value in early rheumatoid arthritis (RA).

Methods

In arthralgia patients referred to the Early Arthritis Recognition Clinics (EARC) of Leiden (n = 807) and Groningen (n = 481) or included in the Rotterdam Early Arthritis Cohort (REACH) study (n = 353), the associations (cross-sectional analyses) between morning stiffness and presence of arthritis at physical examination were studied. In early arthritis patients, included in the Leiden Early Arthritis Clinic (EAC) (n = 2,748) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n = 813), associations with fulfilling the 2010-RA criteria after one year were assessed. In 2010-RA patients included in the EAC (n = 1,140) and ESPOIR (n = 677), association with the long-term outcomes of disease-modifying antirheumatic drug (DMARD)-free sustained remission and radiological progression were determined. Morning stiffness was defined as a duration ≥60 minutes; sensitivity analyses were performed for other definitions.

Results

In arthralgia, morning stiffness (≥60 minutes) associated with the presence of arthritis; Leiden EARC odds ratio (OR) 1.49 (95% CI 1.001 to 2.20), Groningen EARC OR 2.21 (1.33 to 3.69) and REACH OR 1.55 (0.97 to 2.47) but the areas under the receiver operating characteristic curve (AUCs) were low (0.52, 0.57, 0.54). In early arthritis, morning stiffness was associated with 2010-RA independent of other predictors (Leiden EAC OR 1.72 (95% CI 1.31 to 2.25, AUC 0.68), ESPOIR OR 1.68 (1.03 to 2.74, AUC 0.64)). Duration of ≥30 minutes provided optimal discrimination for RA in early arthritis. Morning stiffness was not associated with radiological progression or DMARD-free sustained remission.

Conclusions

Morning stiffness in arthralgia and early arthritis is associated with arthritis and RA respectively. This supports the incorporation of morning stiffness in the diagnostic process.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0616-3) contains supplementary material, which is available to authorized users.

Circadian use of glucocorticoids in rheumatoid arthritis

A clear temporal relationship exists in rheumatoid arthritis (RA) patients between increased nocturnal levels of pro-inflammatory cytokines, such as TNF-α and interleukin (IL)-6, pro-inflammatory hormones (i.e. melatonin, prolactin) and insufficient night production of the anti-inflammatory cortisol (circadian rhythm). Under long-standing chronic stress of disease, insufficient cortisol is available to inhibit an ongoing nocturnal immune/inflammatory reaction. Clinical RA symptoms follow the same circadian rhythm with highest morning severity. Chronotherapy with nighttime glucocorticoid (GC) availability optimizes the treatment of RA patients with low-dose GCs through more efficient targeting of mediators of the immune/inflammatory reaction during the night to be available on arising. Circadian use of low-dose, long-term prednisone, by using night-release formulations (ingested at 10 to 11 p.m.) especially in early RA patients, appears characterized by a significantly superior efficacy on decreasing morning stiffness and IL-6 serum levels, compared to conventional daytime immediate-release prednisone. Shift from medium-dose, immediate-release prednisone (over 7.5-10 mg/day) to night-release formulations GC low-dose, long-term chronotherapy requires a gradual passage, since the hypothalamic-pituitary-adrenal axis of the treated RA patients, potentially altered by a negative feedback induced by the medium/high daily exogenous GC administration, needs time to re-synchronize control of endogenous GC production into a circadian and more physiological nocturnal hormone availability/optimized efficacy.

Behavioral trait of morningness-eveningness in association with articular and spinal diseases in a population

Earlier studies have revealed that the more the preference to schedule daily activities towards the evening hours is, the higher the odds for a range of health hazards are. Therefore, we wanted to analyze, whether the behavioral trait of morningness-eveningness is associated with articular and spinal diseases or those with musculoskeletal disorders. Participants (n = 6089), as part of the National FINRISK 2007 Study, were derived from the general population, aged 25 to 74 years, living in Finland. Chronotype was assessed based on six items from the original Horne-Östberg Morningness-Eveningness Questionnaire. Information about risk factors and the diagnoses of articular and spinal diseases were based on the self-reported information. Our results suggest that Evening-types have higher odds for articular and spinal diseases as compared with Morning-types, and this risk is heightened especially regarding spinal disease and backache (odds ratios of 1.8 to 2.1, and 1.6 to 1.8, respectively) and remains significant after controlling for the sex, age, education, civil status, physical activity, alcohol use, and smoking, and additionally for the body-mass index, insufficient sleep, or depressive symptoms.

Circadian rhythms in rheumatology--a glucocorticoid perspective

The hypothalamic-pituitary-adrenal (HPA) axis plays an important role in regulating and controlling immune responses. Dysfunction of the HPA axis has been implicated in the pathogenesis of rheumatoid arthritis (RA) and other rheumatic diseases. The impact of glucocorticoid (GC) therapy on HPA axis function also remains a matter of concern, particularly for longer treatment duration. Knowledge of circadian rhythms and the influence of GC in rheumatology is important: on the one hand we aim for optimal treatment of the daily undulating inflammatory symptoms, for example morning stiffness and swelling; on the other, we wish to disturb the HPA axis as little as possible. This review describes circadian rhythms in RA and other chronic inflammatory diseases, dysfunction of the HPA axis in RA and other rheumatic diseases and the recent concept of the hepato-hypothalamic-pituitary-adrenal-renal axis, the problem of adrenal suppression by GC therapy and how it can be avoided, and evidence that chronotherapy with modified release prednisone effective at 02:00 a.m. can inhibit proinflammatory sequelae of nocturnal inflammation better compared with GC administration in the morning but does not increase the risk of HPA axis insufficiency in RA.

Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men

BACKGROUND

Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance.

METHODS

Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments.

RESULTS

IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag.

CONCLUSIONS

This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

Circadian endocrine rhythms: the hypothalamic-pituitary-adrenal axis and its actions

The stress system effectively restores the internal balance--or homeostasis--of living organisms in the face of random external or internal changes, the stressors. This highly complex system helps organisms to provide a series of neuroendocrine responses to stressors--the stress response--through coordinated activation of the hypothalamic-pituitary-adrenal (HPA) axis and the locus coeruleus/norepinephrine autonomic nervous systems. In addition to stressors, life is influenced by daily light/dark changes due to the 24-h rotation of Earth. To adjust to these recurrent day/night cycles, the biological clock system employs the heterodimer of transcription factors circadian locomotor output cycle kaput/brain-muscle-arnt-like protein 1 (CLOCK/BMAL1), along with a set of other transcription factors, to regulate the circadian pattern of gene expression. Interestingly, the stress system, through the HPA axis, communicates with the clock system; therefore, any uncoupling or dysregulation could potentially cause several disorders, such as metabolic, autoimmune, and mood disorders. In this review, we discuss the biological function of the two systems, their interactions, and the clinical implications of their dysregulation or uncoupling.

Delayed-release prednisone - a new approach to an old therapy

INTRODUCTION

Despite the widespread use of glucocorticoid (GC) treatment for inflammatory conditions, there remains a need to optimize use by improving efficacy and/or reducing adverse consequences. The most advanced approach, already licensed for clinical use, is delayed-release prednisone.

AREAS COVERED

Delayed-release prednisone consists of an inert outer coat containing an inner core of active drug (1, 2, or 5 mg) taken at bedtime (approximately 22:00 h). After a lag time of 4 - 6 h, the coat opens to release prednisone, at the appropriate time to counteract elevated nocturnal levels of pro-inflammatory cytokines associated with the circadian pattern of symptoms seen in rheumatoid arthritis (RA) and other inflammatory conditions. Clinical trials in RA have demonstrated the improved efficacy of delayed-release prednisone with respect to morning stiffness compared with conventional immediate-release prednisone tablets taken in the morning and compared with placebo in patients on disease-modifying antirheumatic treatment; the incidence of adverse events was similar to the comparator. Preliminary studies in polymyalgia rheumatica and asthma suggest that delayed-release prednisone may also have benefits in these conditions.

EXPERT OPINION

Delayed-release prednisone offers an effective way to improve the benefit:risk ratio of GC treatment for inflammatory conditions with circadian features.

Polymyalgia rheumatica in 2011

Polymyalgia Rheumatica (PMR) is an inflammatory rheumatic disease that commonly affects individuals over 50 years of age, characterised by pain and morning stiffness of the shoulder and pelvic girdle. PMR can present as 'isolated' form or may be associated with giant cell arteritis. The progress of imaging techniques has helped in understanding different clinical patterns: subclinical vasculitis can occur in at least one-third of PMR patients, causing ischaemic complications. It is considered a polygenic disease and environmental factors may play a role in its pathogenesis, such as viral or bacterial triggers, both in the 'wide' form or assembled with adjuvants in vaccines. The response to steroid therapy is generally dramatic and side effects may occur, as well as the development of glucocorticoid resistance. The optimisation of therapy may require steroid-sparing agents as well as modified-release prednisone as 'nighttime' replacement therapy.

Intense focused ultrasound as a potential research tool for the quantification of diurnal inflammatory pain

Quantifying pain through assay of a human's or animal's response to a known stimulus as a function of time of day is a critical means of advancing chronotherapeutic pain management. Current methods for quantifying pain, even in the context of etiologies involving deep tissue, generally involve stimulation by quantifiable means of either cutaneous (heat-lamp tests, electrical stimuli) or both cutaneous and subcutaneous tissue (von Frey hairs, tourniquets, etc.) or study of proxies for pain (such as stress, via assay of cortisol levels). In this study, we evaluate the usefulness of intense focused ultrasound (iFU), already shown to generate sensations and other biological effects deep to the skin, as a means of quantifying deep diurnal pain using a standard animal model of inflammation. Beginning 5 days after injection of Complete Freund's Adjuvant into the plantar surface of the rat's right hind paw to induce inflammation, the rats were divided into two groups, the light-phase test group (09:00-18:00h) and the dark-phase test group (23:00-06:00h), both of which underwent iFU application deep to the skin. We used two classes of iFU protocol, motivated by the extant literature. One consisted of a single pulse (SP) lasting 0.375s. The other, a multiple pulse (MP) protocol, consisted of multiple iFU pulses each of length 0.075s spaced 0.075s apart. We found the night group's threshold for reliable paw withdrawal to be significantly higher than that of the day group as assayed by each iFU protocol. These results are consistent with the observation that the response to mechanical stimuli by humans and rodents display diurnal variations, as well as the ability of iFU to generate sensations via mechanical stimulation. Since iFU can provide a consistent method to quantify pain from deep, inflamed tissue, it may represent a useful adjunct to those studying diurnal pain associated with deep tissue as well as chronotherapeutics targeting that pain.

Chronobiology and the treatment of rheumatoid arthritis

PURPOSE OF REVIEW

As circadian rhythms and biological signaling occur in a complex network with cyclical 24-h period interactions (chronobiology) between the central and the autonomic nervous systems, the endocrine glands and the immune system, this review will explore the involvement of this emerging network in the disease pathophysiology and management.

RECENT FINDINGS

Recent advances regarding nocturnal hormones such as melatonin and prolactin that activate the nighttime immune response, and the successive rise of cortisol that dowregulates the ongoing immune reactivity very early in the morning, will be discussed within the circadian neuroendocrine immune network. In addition, the role of sleep and the daily distribution of body energy, which are important factors for the homoeostatic regulation of circadian physiological/pathological processes of the immune network will be reviewed.In chronic immune/inflammatory conditions such as rheumatoid arthritis (RA), stiffness and functional disability are evident in the early morning hours as under the chronic stress of the disease the nighttime adrenal cortisol production becomes insufficient to inhibit ongoing nocturnal immune/inflammatory activity.

SUMMARY

Currently, the most advanced approach to optimizing the risk-benefit ratio for long-term glucocorticoid treatment in RA seems to be low-dose chronotherapy with modified nighttime release prednisone (release at 3 a.m.). A similar chronotherapeutical approach could also be effective with disease-modifying antirheumatic drugs such as methotrexate.

Polymyalgia rheumatica and giant cell arteritis: management of two diseases of the elderly

Both polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) present with a broad spectrum of clinical manifestations and almost exclusively occur in the population aged over 50 years. After rheumatoid arthritis, PMR is the second most common autoimmune rheumatic disorder. Visual loss is the most feared complication in temporal arteritis, and extracranial arteries and/or aorta are more often involved in GCA than previously estimated. No specific laboratory parameter exists for diagnosis of PMR. Imaging techniques such as ultrasonography, MRI or 18F-fluorodeoxyglucose PET may be helpful in the diagnosis and evaluation of the extent of vascular involvement in these diseases. This article highlights upcoming new classification criteria for PMR, recent advances of diagnostic and therapeutic procedures as well as ongoing research on biomarkers and corticosteroid-sparing medications, which should improve management of PMR and GCA.