Pathophysiology of vascular dysfunction in a rat model of chronic joint inflammation

Losartan protects endothelium-dependent relaxation in vivo in a murine model of rheumatoid arthritis

Angiotensin II-type 1 receptor stimulation is recognised to promote inflammation, a state central to the development and maintenance of rheumatoid arthritis. Herein we examined the use of losartan, an angiotensin II-type 1 receptor antagonist, on vascular reactivity, knee joint diameter and behavioural assessment of pain in a Freund's complete adjuvant (FCA) mouse model of joint inflammation. Monoarthritis was induced via FCA in the presence or absence of losartan with naive mice serving as controls. Knee joint swelling, joint pain (assessed by dynamic weight bearing of limb use), knee joint artery reactivity (assessed ex vivo) and blood perfusion of the knee joint (assessed in vivo) were determined. FCA mediated a significant increase in knee joint diameter and reduced weight-bearing (a surrogate for pain sensation) of the affected limb. Notably, these phenomena were substantially reduced when mice were prophylactically treated with losartan. Assessment of arterial relaxation and blood perfusion with acetylcholine stimulation revealed that FCA resulted in significant vascular dysfunction, which was resolved to naïve levels with losartan treatment. Through the actions of losartan, these findings indicate that the angiotensin II-type 1 receptor is a likely therapeutic target of importance in the development of the physical changes, pain sensation and vascular dysfunction found in inflammatory arthritis.

Hydrogen peroxide mediates pro-inflammatory cell-to-cell signaling: a new therapeutic target for inflammation?

Nitric oxide is now universally recognized as an extracellular signaling molecule. Nitric oxide, produced in one cell, diffuses across the extracellular space and acts with targets in an adjoining cell. In this study, we present proof that hydrogen peroxide – like nitric oxide – acts as a true first (intercellular) messenger for a multitude of pro-inflammatory ligands. RAW 264.7 macrophages were activated with three different ligands, lipopolysaccharide, interferon-gamma or advanced glycation end products in the presence of increasing concentrations of (hydrogen peroxide scavenging) catalase. As inflammatory readouts, nitric oxide and tumor necrosis factor were determined. We hypothesize that hydrogen peroxide travels between cells propagating the signal, then a certain percentage of the readout should be inhibited by catalase in a concentration-dependent manner. The experiment showed concentration-dependent inhibition of nitric oxide and tumor necrosis factor-α production in response to all three ligands/ligand combinations (interferon-gamma, lipopolysaccharide, and chicken egg albumin-derived advanced glycation end product) in the presence of increasing concentration of catalase. For example, catalase inhibited 100% of nitric oxide and 40% of tumor necrosis factor-α production at its highest concentration. Our results suggest that hydrogen peroxide travels through cell membranes into the extracellular space and enters and activates adjacent cells. Like nitric oxide, we suggest that it is a ubiquitous first messenger, able to transmit cell-to-cell pro-inflammatory signals such as nitric oxide and tumor necrosis factor-α. In a therapeutic setting, our data suggest that compounds acting as hydrogen peroxide scavengers might not even need to enter the cell to act as anti-inflammatory drugs.

Effect of mesenchymal precursor cells on the systemic inflammatory response and endothelial dysfunction in an ovine model of collagen-induced arthritis

Background and Aim

Mesenchymal precursor cells (MPC) are reported to possess immunomodulatory properties that may prove beneficial in autoimmune and other inflammatory conditions. However, their mechanism of action is poorly understood. A collagen-induced arthritis model has been previously developed which demonstrates local joint inflammation and systemic inflammatory changes. These include not only increased levels of inflammatory markers, but also vascular endothelial cell dysfunction, characterised by reduced endothelium-dependent vasodilation. This study aimed to characterise the changes in systemic inflammatory markers and endothelial function following the intravenous administration of MPC, in the ovine model.

Methods

Arthritis was induced in sixteen adult sheep by administration of bovine type II collagen into the hock joint following initial sensitisation. After 24h, sheep were administered either 150 million allogeneic ovine MPCs intravenously, or saline only. Fibrinogen and serum amyloid-A were measured in plasma to assess systemic inflammation, along with pro-inflammatory and anti-inflammatory cytokines. Animals were necropsied two weeks following arthritis induction. Coronary and digital arterial segments were mounted in a Mulvaney-Halpern wire myograph. The relaxant response to endothelium-dependent and endothelium-independent vasodilators was used to assess endothelial dysfunction.

Results and Conclusion

Arthritic sheep treated with MPC demonstrated a marked spike in plasma IL-10, 24h following MPC administration. They also showed significantly reduced plasma levels of the inflammatory markers, fibrinogen and serum amyloid A, and increased HDL. Coronary arteries from RA sheep treated with MPCs demonstrated a significantly greater maximal relaxation to bradykinin when compared to untreated RA sheep (253.6 ± 17.1% of pre-contracted tone vs. 182.3 ± 27.3% in controls), and digital arteries also demonstrated greater endothelium-dependent vasodilation. This study demonstrated that MPCs given intravenously are able to attenuate systemic inflammatory changes associated with a monoarthritis, including the development of endothelial dysfunction.

Hippocampal neuronal metal ion imbalance related oxidative stress in a rat model of chronic aluminum exposure and neuroprotection of meloxicam

Neurodegenerative diseases remain a significant unresolved societal burden afflicting millions of people worldwide. Neurons in the brain are highly sensitive to oxidative stress, which can be induced by metal toxicity. In this paper, a chronic aluminum overload-induced model of neurodegeneration was used to investigate whether metal ions (Al, Fe, Mn, Cu and Zn)-related oxidative stress was involved in neurodegenerative mechanism and to identify the protective action of meloxicam against rat hippocampal neuronal injury. The metal ion contents, activity of superoxide dismutase (SOD), and content of malondialdehyde (MDA) were detected. The results showed that the spatial learning and memory (SLM) function was significantly impaired in chronic aluminum overload rats. Considerable karyopycnosis was observed in hippocampal neurons. The SOD activity was weakened and the MDA content increased both significantly. In the hippocampus, Al, Fe, Mn, Cu, and Zn contents increased by 184.1%, 186.1%, 884.2%, 199.4% and 149.2%, respectively. Meloxicam administration (without Al) had no effect compared with the control group, while meloxicam treatment with aluminum exposure significantly protected rats from SLM function impairment, neuron death, lower SOD activity, higher MDA content and brain metal ion imbalance. Our findings suggest that the cerebral metal ion imbalance-related oxidative stress is involved in mechanism of cerebral injury and neurodegeneration induced by chronic Al overload in rats, and that meloxicam protects neurons by reducing metal ion imbalance-related oxidative stress.

Total sleep deprivation alters endothelial function in rats: a nonsympathetic mechanism

STUDY OBJECTIVES

Sleep loss is suspected to induce endothelial dysfunction, a key factor in cardiovascular risk. We examined whether sympathetic activity is involved in the endothelial dysfunction caused by total sleep deprivation (TSD).

DESIGN

TWO GROUPS: TSD (24-h wakefulness), using slowly rotating wheels, and wheel control (WC).

PARTICIPANTS

Seven-month-old male Wistar rats.

INTERVENTIONS

Pharmacological sympathectomy (reserpine, 5 mg/kg, intraperitoneal), nitric oxide synthase (NOS) inhibition (N (G)-nitro-L-arginine, 20 mg/kg, intraperitoneally 30 min before experiment) and cyclooxygenase (COX) inhibition (indomethacin, 5 mg/kg, intraperitoneally 30 min before experiment).

MEASUREMENTS AND RESULTS

In protocol 1, changes in heart rate (HR) and blood pressure were continuously recorded in the sympathectomized and non-sympathectomized rats. Blood pressure and HR increased during TSD in non-sympathectomized rats. In protocol 2, changes in skin blood flow (vasodilation) were assessed in the sympathectomized and non-sympathectomized rats using laser-Doppler flowmetry coupled with iontophoretic delivery of acetylcholine (ACh), sodium nitroprusside (SNP), and anodal and cathodal currents. ACh- and cathodal current-induced vasodilations were significantly attenuated after TSD in non-sympathectomized and sympathectomized rats (51% and 60%, respectively). In protocol 3, ACh-induced vasodilation was attenuated after NOS and COX inhibition (66% and 49%, respectively). Cathodal current-induced vasodilation decreased by 40% after COX inhibition. In TSD compared to WC a decrease in ACh-induced vasodilation was still observed after COX inhibition. No changes in SNP- and anodal current-induced vasodilation were detected.

CONCLUSION

These results demonstrate that total sleep deprivation induces a reduction in endothelial-dependent vasodilation. This endothelial dysfunction is independent of blood pressure and sympathetic activity but associated with nitric oxide synthase and cyclooxygenase pathway alterations.

Evaluation of anti-inflammatory effect of Withania somnifera root on collagen-induced arthritis in rats

CONTEXT

Withania somnifera (Linn.) Dunal (Solanaceae) has long been used as an herb in Ayurvedic and indigenous medicine and has received intense attention in recent years for its chemopreventive properties.

OBJECTIVE

The present study focuses on the effect of W. somnifera root powder on the behavioral and radiological changes in collagen-induced arthritic rats.

MATERIALS AND METHODS

The rats were randomly divided into five groups: normal control, arthritic control, arthritic rats treated with W. somnifera root powder (at dose levels 600 and 800 mg kg⁻¹) and arthritic rats treated with methotrexate (at dose level 0.3 mg kg⁻¹). The treatment with W. somnifera (daily) and methotrexate (weekly) was initiated from the 20th day post collagen immunization and continued up until the 45th day. Arthritis was assessed macroscopically by measuring paw thickness, ankle size and body weight. Arthritic pain was assessed by toe-spread and total print length of the affected paw. Functional recovery due to the oral treatment of W. somnifera and methotrexate was assessed by sciatic functional index and rota rod activity.

RESULTS

Administration of W. somnifera root powder (600 mg kg⁻¹) to the arthritic rats significantly decreased the severity of arthritis by effectively suppressing the symptoms of arthritis and improving the functional recovery of motor activity and radiological score.

DISCUSSION AND CONCLUSION

W. somnifera root has a protective effect against collagen-induced arthritis (CIA) in rats. The results suggest that W. somnifera root powder acts as an anti-inflammatory and antioxidant agent in decreasing the arthritic effects in collagen-induced arthritic rats.

Endothelial dysfunction in joint disease

Inflammatory joint diseases and autoimmune diseases with joint manifestations are associated with premature and accelerated atherogenesis. Patients with rheumatoid arthritis (RA) have a 5- to 10-year decrease in life expectancy compared to the general population, and those exhibiting extraarticular manifestations have the greatest excess mortality. RA is now established as an independent cardiovascular risk factor. Complex interactions linking conventional cardiovascular risk factors, systemic inflammation, and vascular function may explain the increased cardiovascular risk among RA patients. Endothelial dysfunction is now recognized as both the key step in early atherogenesis and a contributor to atheroma plaque progression at later stages. Endothelial dysfunction is defined as impaired endothelium-dependent blood-vessel dilation in response to a stimulus. The underlying mechanisms remain speculative. Over the last decade, a role for endothelial dysfunction in the cardiovascular complications of inflammatory joint disease has been hypothesized and several maintenance drugs targeting this phenomenon have been tested, with promising results.

Endothelial dysfunction in an ovine model of collagen-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) induces systemic inflammation, producing a range of co-morbidities including cardiovascular disease. An early vascular change is endothelial dysfunction, characterized by reduced endothelium-dependent vasodilation. The aim of this study was to assess endothelial function in isolated coronary and digital arteries using an ovine model of collagen-induced RA.

METHODS

Sheep were culled following induction of arthritis, and their endothelial function was compared to that of normal sheep. Paired arterial segments were mounted in a wire myograph and dilated with endothelium-dependent vasodilators [bradykinin, serotonin, carbachol and adenosine diphosphate (ADP); linked to either Gi or Gq signalling pathways] and endothelium-independent dilators (adenosine and sodium nitroprusside) to construct cumulative concentration-response curves.

RESULTS

Coronary arteries from arthritic sheep exhibited a significantly greater EC50 value for bradykinin-induced relaxation compared to non-arthritic controls (2.9 × 10(-8) M for arthritic sheep vs. 8.6 × 10(-9) M for controls). Digital arteries from arthritic sheep also exhibited a significantly greater EC50 for relaxation to ADP and a significant decrease in the carbachol maximal response. Responses to sodium nitroprusside were unchanged in both coronary and digital arteries.

CONCLUSION

Sheep with RA demonstrated attenuated arterial relaxation to endothelium-dependent vasodilators. This may provide a useful model of endothelial dysfunction in chronic inflammatory conditions. The dysfunction did not appear to be associated with one specific G-protein signalling pathway.

Angiotensin II Type 1 receptor blockade protects endothelium-derived hyperpolarising factor-mediated relaxation in a rat model of monoarthritis

AIMS

Rheumatoid arthritis (RA) is associated with high cardiovascular mortality. Impaired endothelial cell (EC) function and elevated angiotensin II levels may be central to the link between vascular dysfunction and RA. Here we investigated the action of angiotensin type 1 receptor (AT1R) blockade on endothelium-dependent relaxation of the isolated saphenous artery in a rat model of monoarthritis.

MAIN METHODS

Adjuvant arthritis was induced in rats with and without prophylactic losartan (AT1R antagonist) treatment. Vehicle-treated rats were used as controls. Wire myography was employed to investigate EC function of isolated rings of saphenous artery.

KEY FINDINGS

EC-dependent relaxation in arteries from non-inflamed control rats was mediated by both nitric oxide (NO) and endothelium-derived hyperpolarising factor (EDHF) with the EDHF response dependent principally on functional myoendothelial gap junctions. While NO-dependent relaxation remained unaffected, the EDHF-mediated response was abolished in arteries from arthritic rats (P<0.001), however, substantial protection (approximately 50%) of the EDHF-relaxation was found in arthritic rats treated with losartan (P<0.01). Thus, the attenuated EDHF response found in the saphenous artery of arthritic rats was significantly reversed by AT1R blockade.

SIGNIFICANCE

These results suggest a key role for the angiotensin system in the EC dysfunction found in chronic joint inflammation and highlights AT1R as a potential therapeutic target to redress the vascular impairment and mortality associated with RA.

Treatment with the arginase inhibitor Nw-hydroxy-nor-L-arginine restores endothelial function in rat adjuvant-induced arthritis

Introduction

Endothelial dysfunction (ED) participates to atherogenesis associated to rheumatoid arthritis. We recently reported increased arginase activity/expression in vessels from adjuvant-induced arthritis (AIA) rats. In the present study, we investigated the effects of a curative treatment with the arginase inhibitor N_w-hydroxy-nor-L-arginine (nor-NOHA) on vascular dysfunction in AIA rats.

Methods

AIA rats were treated with nor-NOHA (40 mg/kg/d, ip) for 21 days after the onset of arthritis. A group of untreated AIA rats and a group of healthy rats served as controls. ED was assessed by the vasodilatory effect of acetylcholine (Ach) on aortic rings. The role of superoxide anions, prostanoids, endothelium-derived hyperpolarizing factor (EDHF) and nitric oxide synthase (NOS) pathway was studied. Plasma levels of IL-6 and vascular endothelial growth factor (VEGF) were determined by ELISA kits. Arthritis severity was estimated by a clinical, radiological and histological analysis.

Results

Nor-NOHA treatment fully restored the aortic response to Ach to that of healthy controls. The results showed that this beneficial effect is mediated by an increase in NOS activity and EDHF and reduced superoxide anion production as well as a decrease in the activity of cyclooxygenase (COX)-2, thromboxane and prostacyclins synthases. In addition, nor-NOHA decreased IL-6 and VEGF plasma levels in AIA rats. By contrast, the treatment did not modify arthritis severity in AIA rats.

Conclusions

The treatment with an arginase inhibitor has a potent effect on ED in AIA independently of the severity of the disease. Our results suggest that this new pharmacological approach has the potential as a novel add-on therapy in the treatment of RA.

Cartilage degeneration is associated with augmented chemically-induced joint pain in rats: a pilot study

BACKGROUND

Osteoarthritis arising from cartilage degeneration is the most common cause of joint pain. However, the relationship between joint pain and cartilage degeneration is not well understood.

QUESTIONS/PURPOSES

We asked whether the inflammatory mediators participate in the joint pain in the presence of cartilage degeneration.

METHODS

We observed electromyographic responses of hindlimb flexors to four inflammatory mediators (bradykinin, ATP, acetylcholine, and serotonin) injected in normal rat knees and in those with monosodium iodoacetate (MIA)-induced arthritis.

RESULTS

Joint cartilage of all the rats with MIA-induced arthritis histologically showed severe degeneration. We observed greater magnitude and longer duration responses in the MIA-induced arthritis than normal joints with all four mediators.

CONCLUSIONS

The data suggested nociceptors in osteoarthritic joints are more sensitive to inflammatory mediators than in normal joints. Such nociceptive sensitization to inflammatory mediators may participate in the joint pain in osteoarthritis.

The effect of genetic polymorphisms of cyclooxygenase 2 on acute pancreatitis in Turkey

OBJECTIVES

The aims of our study were to determine if polymorphisms in the cyclooxygenase 2 (COX-2) gene is associated with acute pancreatitis (AP) and to evaluate if inflammation risk is associated with specific COX-2 gene haplotypes containing these polymorphisms.

METHODS

The COX-2 genotypes for 7 polymorphisms (rs5275, rs2206593, rs4648262, rs4648261, rs2066826, rs5277, rs2745557) were determined using polymerase chain reaction-restriction fragment length polymorphism analysis in 103 patients with AP and 92 healthy controls.

RESULTS

Except for rs5275, the frequencies of COX-2 polymorphisms were both similar in patients with mild or severe pancreatitis, so were in pancreatitis patients and in controls. Only rs5275 was statistically significantly associated with AP risk. The association was seen with rs5275 (P = 0.03); specifically, patients carrying the TT genotype in comparison with patients carrying the CC genotype had a significantly lower risk of disease (odds ratio, 1.88; 95% confidence interval, 1.06-3.34). Haplotypes with nucleotide T at the -18491961 position (rs5275) and A at the 184915627 position (rs4648261) of COX-2 promoter seem to increase susceptibility (odds ratio, 2.46; 95% confidence interval, 1.15-5.29; P = 0.02).

CONCLUSIONS

These findings suggest that the rs5275 polymorphism in the 3'-untranslated region of the COX-2 gene may be used as 1 marker for defining the risk of AP.

Impact of chronic inflammation on the pharmacokinetic-pharmacodynamic relationship of naproxen

OBJECTIVES

The use of biomarkers for predicting the clinical doses of analgesic drugs relies on the understanding of the relationship between drug exposure and response under disease conditions. In this study, we demonstrate the relevance of such a relationship for COX-inhibitors by modelling the effect of naproxen on prostaglandin E2 (PGE(2)) and thromboxane B2 (TXB(2)) in a chronic inflammation model in rats.

METHODS

Rats were treated with Freund's complete adjuvant (FCA) by intraplantar injection. On post-inoculation days (PID) 7-21, animals received single or chronic (qd until day 21) doses of naproxen (10mg/kg). Blood samples were collected at various intervals after dosing to characterise naproxen pharmacokinetics and its effects on PGE(2) and TXB(2) production. PK-PD modelling was performed using nonlinear mixed effects in NONMEM.

RESULTS

The inhibition of PGE(2) and TXB(2) could be described by a sigmoid E(max) model. A decrease in the potency estimates of both biomarkers was observed under chronic inflammation, as compared to healthy animals. IC(50) values for PGE(2) inhibition showed a shift from 2840+/-510 to 4000+/-677ng/ml(mean+/-SD), whilst IC(50) values for TXB(2) inhibition increased from 1180+/-323 to 3360+/-453ng/ml in healthy and FCA-inoculated animals, respectively.

CONCLUSIONS

Our results show that chronic inflammation causes a significant change in the potency estimates for COX-inhibition. These findings illustrate the implications of pathophysiological processes on pharmacodynamics and consequently on the required exposure levels for achieving response during chronic treatment.

Experimental arthritis inhibits the insulin-like growth factor-I axis and induces muscle wasting through cyclooxygenase-2 activation

Chronic arthritis induces cachexia associated with an inhibition of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) system and an activation of the E3 ubiquitin-ligating enzymes muscle atrophy F-box (MAFbx) and muscle Ring finger 1 (MuRF1) in the skeletal muscle. The aim of this work was to study the role of cyclooxygenase (COX)-2 in chronic arthritis-induced cachexia. Arthritis was induced in rats by Freund's adjuvant injection, and the effects of two COX inhibitors (indomethacin, a nonspecific inhibitor, and meloxicam, a selective COX-2 inhibitor on pituitary GH and on liver and serum IGF-I levels) were tested. Arthritis decreased body weight gain and GH and liver IGF-I gene expression. In the arthritic rats, both inhibitors, indomethacin and meloxicam, prevented the inhibitory effect of arthritis on body weight gain. Indomethacin and meloxicam administration to arthritic rats increased pituitary GH and liver IGF-I mRNA as well as serum levels of IGF-I. These data suggest that induction of COX-2 during chronic inflammation is involved in the inhibition of the GH-IGF-I axis and in the body weight loss. In the gastrocnemius muscle, arthritis increased the gene expression of tumor necrosis factor (TNF)-alpha, the E3 ubiquitin-ligating enzymes MAFbx and MuRF1, as well as of IGF-I and IGF-binding protein-5 (IGFBP-5). Inhibition of COX-2 by meloxicam administration increased gastrocnemius weight and decreased MAFbx, MuRF1, TNF-alpha, and IGFBP-5 gene expression. In summary, our data indicate that chronic arthritis-induced cachexia and muscle wasting are mediated by the COX-2 pathway resulting in a decreased GH-IGF-I secretion and increased expression of MAFbx and MuRF1 mRNA.

Linear response range characterization and in vivo application of laser speckle imaging of blood flow dynamics

Noninvasive blood flow imaging can provide critical information on the state of biological tissue and the efficacy of approaches to treat disease. With laser speckle imaging (LSI), relative changes in blood flow are typically reported, with the assumption that the measured values are on a linear scale. A linear relationship between the measured and actual flow rate values has been suggested. The actual flow rate range, over which this linear relationship is valid, is unknown. Herein we report the linear response range and velocity dynamic range (VDR) of our LSI instrument at two relevant camera integration times. For integration times of 1 and 10 ms, the best case VDR was 80 and 60 dB, respectively, and the worst case VDR was 20 and 50 dB. The best case VDR values were similar to those reported in the literature for optical Doppler tomography. We also demonstrate the potential of LSI for monitoring blood flow dynamics in the rodent dorsal skinfold chamber model. These findings imply that LSI can provide accurate wide-field maps of microvascular blood flow rate dynamics and highlight heterogeneities in flow response to the application of exogenous agents.