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Arachidonic acid is the second polyunsaturated fatty acid in brain and the first one belonging to the ω-6 series. Dietary intakes of arachidonic are between 50 and 300 mg/day in western diets but they might be underestimated. Triglycerides from fat would provide similar amounts than phospholipids of lean meat. Alzheimer’s disease is an age-associated degenerative disease and a critical health concern worldwide. Amyloid-β peptide oligomers are presently recognized as the main and earliest agents of Alzheimer’s disease although their neurotoxicity requires the presence of tau protein. We and others established that the arachidonic-specific cytosolic phospholipase A2 is critical for the amyloid-β peptide oligomer neurotoxicity. Then, we showed that an arachidonic acid-rich diet increases the mouse sensitivity to the amyloid-β peptide oligomer deleterious effect without major increase of arachidonic acid levels in brain. This suggests that dietary arachidonic acid can exert its effects in brain through peripheral modifications. Involvement of systemic sub-inflammation and gut-brain communications are discussed based on the recent literature. The various data suggest that dietary arachidonic acid should be taken into account in the design of preventive strategies against Alzheimer’s disease.

Objective To determine the time course of microvascular abnormalities and the link with macrovascular endothelial function and circulating markers of endothelial activation in adjuvant-induced arthritis (AIA) in rats. Methods Microvascular function/structure and mechanics were studied in third-order mesenteric arteries subjected to flow and/or pressure on day 4 (preclinical arthritis), day 11 (very early arthritis), day 33 (severe disease), and day 90 (when inflammation has resolved) after AIA induction. Macrovascular function was studied in aortic rings, and blood pressure, plasma levels of C-reactive protein (CRP), intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1) were measured at each time point. Results Mesenteric flow-mediated vasodilation was significantly reduced from very early arthritis to chronic disease, whereas increased microvascular arterial stiffness was evident only on day 33. Macrovascular endothelial dysfunction was observed only on day 33. Thus, on day 90, whereas rats with AIA recovered normal macrovascular endothelial function, microvascular endothelial function remained impaired. No correlation was found between micro- and macrovascular endothelial function throughout the course of arthritis (r = 0.180, P = 0.229). Furthermore, no correlation was found between CRP levels, ICAM-1 levels, and endothelial function whatever the vascular bed. AIA was not associated with change in blood pressure or VCAM levels. Conclusion Our findings indicate that microvascular endothelial dysfunction occurs earlier than macrovascular endothelial dysfunction and microvascular arterial stiffness during arthritis, suggesting that microvascular endothelial function would be a valuable tool for the early assessment of cardiovascular risk in RA. Neither the ICAM-1 level nor the CRP level is a good marker of micro- or macrovascular endothelial dysfunction.

Summary To determine the effect of glucocorticoids (GCs) on endothelial dysfunction (ED) and on traditional cardiovascular (CV) risk factors in the adjuvant-induced arthritis (AIA) rat model. At the first signs of AIA, a high dose (HD) [10 mg/kg/day, intraperitoneally (i.p.), GC-HD] or low dose (LD) (1 mg/kg/day, i.p., GC-LD) of prednisolone was administered for 3 weeks. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of nitric oxide synthase (NOS), cyclooxygenase 2 (COX-2), arginase, endothelium derived hyperpolarizing factor (EDHF) and superoxide anions (O2–°) production. Aortic expression of endothelial NOS (eNOS), Ser1177-phospho-eNOS, COX-2, arginase-2, p22phox and p47phox was evaluated by Western blotting analysis. Arthritis scores, blood pressure, heart rate and blood levels of cytokines, triglycerides, cholesterol and glucose were measured. GC-HD but not GC-LD reduced arthritis score significantly and improved Ach-induced relaxation (P

ObjectivesLocal cryotherapy is widely and empirically used in the adjuvant setting in rheumatoid arthritis treatment, however its own therapeutic and anti-inflammatory effects are poorly characterized. We aimed to evaluate the effects of local cryotherapy on local and systemic inflammation in Adjuvant-induced arthritis, a murine model of rheumatoid arthritis.MethodsThe effects of mild hypothermia (30°C for 2 hours) on cytokine protein levels (Multiplex/ELISA) were evaluated in vitro in cultured rat adjuvant-induced arthritis patellae. In vivo, local cryotherapy was applied twice a day for 14 days in arthritic rats (ice: n = 10, cold gas: n = 9, non-treated: n = 10). At day 24 after the induction of arthritis, cytokine expression levels were measured in grinded hind paws (Q-RT-PCR) and in the plasma (Multiplex/ELISA).ResultsIn vitro, punctual mild hypothermia down-regulated IL-6 protein expression. In vivo, ice showed a better efficacy profile on the arthritis score and joint swelling and was better tolerated, while cold gas induced a biphasic response profile with initial, transient arthritis worsening. Local cryotherapy also exerted local and systemic anti-inflammatory effects, both at the gene and the protein levels: IL-6, IL-17A and IL-1β gene expression levels were significantly down-regulated in hind paws. Both techniques decreased plasma IL-17A while ice decreased plasma IL-6 protein levels. By contrast, we observed no effect on local/systemic TNF-α pathway.ConclusionsWe demonstrated for the first time that sub-chronically applied local cryotherapy (ice and cold gas) is an effective and well-tolerated treatment in adjuvant-induced arthritis. Furthermore, we provided novel insights into the cytokine pathways involved in Local cryotherapy's local and systemic anti-inflammatory effects, which were mainly IL-6/IL-17A-driven and TNF-α independent in this model.

International audience

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease characterized by articular and extra-articular manifestations involving cardiovascular (CV) diseases. RA increases the CV mortality by up to 50 % compared with the global population and CV disease is the leading cause of death in patients with RA. There is growing evidence that RA favors accelerated atherogenesis secondary to endothelial dysfunction (ED) that occurs early in the course of the disease. ED is a functional and reversible alteration of endothelial cells, leading to a shift of the actions of the endothelium towards reduced vasodilation, proinflammatory state, proliferative and prothrombotic properties. The mechanistic links between RA and ED have not been fully explained, but growing evidence suggests a role for traditional CV factors, auto-antibodies, genetic factors, oxidative stress, inflammation and iatrogenic interventions such as glucocorticoids (GCs) use. GCs have been used in RA for several decades. Whilst their deleterious CV side effects were described in the 1950s, their effect on CV risk associated with inflammatory arthritis remains subject for debate. GC might induce negative effects on endothelial function, via a direct effect on endothelium or via increasing CV risk factors. Conversely, they might actually improve endothelial function by decreasing systemic and/or vascular inflammation. The present review summarizes the available data on the impact of GCs on endothelial function, both in normal and inflammatory conditions, with a special focus on RA patients.

International audience; Objectives. To determine the effect of etanercept on endothelial dysfunction and on traditional cardiovascular (CV) risk factors in the adjuvant- induced arthritis ( AIA) rat model.Methods. At the first signs of arthritis, etanercept (10 mg/kg/3 days, s.c.) or saline was administered for 3 weeks in AIA rats. Body weights and arthritis scores were monitored daily. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of nitric oxide synthase (NOS), cyclo-oxygenase (COX-2), arginase, endothelium-derived hyperpolarizing factor and superoxide anions (O(2)(-)A degrees) production. Aortic expression of endothelial nitic oxide synthase (eNOS), Ser1177-phospho-eNOS, COX-2, arginase-2, p22(phox) and p47(phox) was evaluated by western blotting analysis. Blood pressure, heart rate and blood levels of triglycerides, cholesterol and glucose were measured.Results. Etanercept significantly reduced arthritis score (P < 0.001). It improved Ach-induced relaxation (P < 0.05) as a result of increased NOS activity, decreased COX-2/arginase activities and decreased O(2)(-)A degrees production. These functional effects relied on increased eNOS expression and phosphorylation, and decreased COX-2, arginase-2 and p22(phox) expressions. No correlation was found between arthritis score and Ach-induced relaxation. The treatment did not change triglycerides, cholesterol and glucose levels, but significantly increased systolic blood pressure and heart rate (P < 0.05).Conclusion. Our data demonstrated that efficient dosage of etanercept on inflammatory symptoms improved endothelial function in AIA. This beneficial effect on endothelial function is disconnected from its impact on CV risk factors and relates to pleiotropic effects of etanercept on endothelial pathways. These results suggest that etanercept could be a good choice for patients with rheumatoid arthritis at high risk of CV events.

Both noise and styrene can injure the cochlea, resulting in a reduction of incoming inputs from the cochlea to the central nervous system. In addition, styrene is known to have neurotoxic properties at high doses. The loss of inputs caused by noise has been shown to be compensated by a new equilibrium between excitatory and inhibitory influences within the inferior colliculus (IC). The main goal of this study was to determine whether styrene-induced hearing loss could also be counterbalanced by a GABAergic adjustment in the IC. For this purpose, rats were exposed to noise (97 dB SPL octave band noise centered at 8 kHz), or to a non-neurotoxic dose of styrene for 4 weeks (700 ppm, 6 h/day, 5 days/week). Auditory sensitivity was tested by evoked potentials, and cochlear damage was assessed by hair cell counts. Glutamate decarboxylase (GAD) was dosed in the IC by indirect competitive enzyme-linked immunosorbent assay. Both noise and styrene caused PTSs that reached 27.0 and 14.6 dB respectively. Outer hair cell (OHC) loss caused by noise did not exceed 9% in the first row, on the other hand OHC loss induced by styrene reached 63% in the third row. Only the noise caused a decrease of GAD of 37% compared to that measured in the controls. No significant modification of GAD concentration has been shown after styrene exposure. Thus, central compensation for cochlear damage may depend on the nature of the ototoxic agent. Unless styrene directly affects IC function, it is reasonable to assume that noise causes a modification of inhibitory neurotransmission within the structure because of impairment of afferent supply to the auditory brainstem. The present findings suggest that central compensation for cochlear damage can preferably occur when afferent fibers are altered.

To determine the time course of microvascular abnormalities and the link with macrovascular endothelial function and circulating markers of endothelial activation in adjuvant-induced arthritis (AIA) in rats.Microvascular function/structure and mechanics were studied in third-order mesenteric arteries subjected to flow and/or pressure on day 4 (preclinical arthritis), day 11 (very early arthritis), day 33 (severe disease), and day 90 (when inflammation has resolved) after AIA induction. Macrovascular function was studied in aortic rings, and blood pressure, plasma levels of C-reactive protein (CRP), intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1) were measured at each time point.Mesenteric flow-mediated vasodilation was significantly reduced from very early arthritis to chronic disease, whereas increased microvascular arterial stiffness was evident only on day 33. Macrovascular endothelial dysfunction was observed only on day 33. Thus, on day 90, whereas rats with AIA recovered normal macrovascular endothelial function, microvascular endothelial function remained impaired. No correlation was found between micro- and macrovascular endothelial function throughout the course of arthritis (r = 0.180, P = 0.229). Furthermore, no correlation was found between CRP levels, ICAM-1 levels, and endothelial function whatever the vascular bed. AIA was not associated with change in blood pressure or VCAM levels.Our findings indicate that microvascular endothelial dysfunction occurs earlier than macrovascular endothelial dysfunction and microvascular arterial stiffness during arthritis, suggesting that microvascular endothelial function would be a valuable tool for the early assessment of cardiovascular risk in RA. Neither the ICAM-1 level nor the CRP level is a good marker of micro- or macrovascular endothelial dysfunction.

AIMS: Changes in circulating brain-derived neurotrophic factor (BDNF) levels were reported in patients with or at risk for cardiovascular diseases associated with endothelial dysfunction, suggesting a link between BDNF and endothelial functionality. However, little is known on cardiovascular BDNF. Our aim was to investigate levels/localization, function, and relevance of cardiovascular BDNF. METHODS AND RESULTS: BDNF levels (western blotting) and localization (immunostaining) were assessed in the heart and aorta from rats with impaired (spontaneously hypertensive rats [SHR]), normal (Wistar Kyoto rats [WKY]), and improved (SHR and WKY subjected to physical training) endothelial function. BDNF levels were also measured in cultured endothelial cells (CECs) subjected to low and high shear stress. The cardiovascular effects of BDNF were investigated in isolated aortic rings and hearts. The results showed high BDNF levels in the heart and aorta, the expression being prominent in endothelial cells as compared with other cell types. Exogenous BDNF vasodilated aortic rings but changed neither coronary flow nor cardiac contractility. Hypertension was associated with decreased expression of BDNF in the endothelium, whereas physical training led to endothelial BDNF up-regulation not only in WKY but also in SHR. Exposure of CECs to high shear stress stimulated BDNF production and secretion. CONCLUSION: Cardiovascular BDNF is mainly localized within endothelial cells in which its expression is dependent on endothelial function. These results open new perspectives on the role of endothelial BDNF in cardiovascular health.

Background Rheumatoid Arthritis (RA) is associated with increased cardiovascular risk (CVR) explained in part by accelerated atherosclerosis as a consequence of endothelial dysfunction. Non-steroidal anti-inflammatory drugs (NSAIDs) are widely prescribed in RA patients in case of acute pain. Surprisingly, despite the commonly-held belief that NSAIDs worsen CVR, data regarding their effect on endothelial function in RA are lacking. Objectives The present study investigated the effect of naproxen (a non-selective COX inhibitor), diclofenac (a preferential COX-2 inhibitor) and celecoxib (a selective COX-2 inhibitor) on vascular function in arthritic rats and identified the underlying mechanisms. Methods Adjuvant-induced arthritis (AIA) was induced in 6 weeks-old male Lewis rats by injection of Mycobacterium butyricum in adjuvant at the basis of the tail. At the onset of arthritis, rats were daily treated (i.p.) with naproxen (10 mg/kg/d), diclofenac (5mg/kg twice a day), celecoxib (3 mg/kg/d) or saline (Vehicle) for 21 days. Arthritis scores were daily monitored. At the end of treatment, thoracic aortas were harvested to measure the relaxation to acetylcholine (Ach) on pre-constricted aortic rings in the presence or not of inhibitor of nitric oxide (NO) synthase (L-NAME), arginase (nor-NOHA), EDHF (Apamin/Charybdotoxin), or a superoxide dismutase analog (Tempol). The effects of a NO donor (sodium nitroprussiate, SNP) and norepinephrine (NE) were studied on endothelium-denuded aortic rings. Results All NSAIDs significantly reduced to the same extent arthritis score in AIA (p Conclusions Our study demonstrates for the first time that naproxen and diclofenac have positive effects on endothelial function in case of arthritis whereas celecoxib had no effect, despite a similar reduction of inflammatory symptoms. From a clinical perspective, these data highlight the heterogeneity of effects of NSAIDs as regards CVR in RA and encourage designing clinical trials to confirm our experimental data and help guiding the better choice of NSAIDs for the global management of RA patients. Disclosure of Interest None declared

Background Cryotherapy is widely and empirically used in an adjuvant and symptomatic setting in inflammatory rheumatic diseases, with a low level of evidence [1]. Objectives The aim of this work was to evaluate local and systemic anti-inflammatory effects of local cryotherapy (LC) in adjuvant-induced arthritis (AIA), comparing 2 techniques (ice and cold gas spray). We considered clinical (arthritic score and ankle diameter) and biological effects on IL-6, IL-17A, IL-1β, TNF-α local and systemic levels. Methods Arthritis was induced by a single Mycobacterium butyricum injection in male Lewis rat tails (day 0). At the onset of arthritis (day 11), rats were treated either by 30 minute-ice applications on hind paws (in cages lined with ice pops – n=10) or by 2 minute-cold gas pulverizations on both hind paws (n=9) twice a day for 14 consecutive days. Ten non-treated AIA rats were used as controls. At day 24 (the day after the last cold application), hind paws were grinded in order to measure cytokine gene expression levels by Q-RT-PCR. Plasmatic levels of the same cytokines were also measured in plasma by cytometry (Multiplex Magpix® ebioscience). IL-6 plasma levels were measured by ELISA (rat IL6 platinum ELISA, BMS625®, ebioscience). Results Ice application significantly reduced the mean arthritic score and ankle diameter from day 6 to day 14 (p Conclusions These results demonstrate in vivo previously unknown therapeutic and anti-inflammatory effects of 14 day-LC in AIA. We observed both local (at the gene level in treated hind paws) and systemic (at the protein level in plasma) down-regulation of key cytokine pathways critically involved in the pathogenesis and severity of inflammatory rheumatic diseases. LC local and systemic anti-inflammatory effects were mainly IL-6/IL-17A-driven and TNF-α-independent in this model. References Guillot X, et al. Cryotherapy in inflammatory rheumatic diseases: a systematic review. Expert Rev Clin Immunol. 2014;10(2):281–94. Disclosure of Interest None declared

International audience; Chronic treatment with angiotensin receptor blockers is largely accepted for protecting cerebral circulation during hypertension, but beneficial effects of short-term treatments are questionable, as highlighted by the recent SCAST trial. We compared the impact of 10 days treatment with candesartan (as SCAST) versus telmisartan (previously described to reverse arteriolar remodeling, chronic treatment) on pial arterioles of spontaneously hypertensive rats (SHR). We explored whether PPAR-gamma agonist activity or AT(1) receptor blockade are involved in their differential effects. In the first study, 4-month-old male SHR were treated with telmisartan (TELMI, 2 mg/kg per day) or candesartan cilexetil (CANDE, 10 mg/kg per day) and compared to vehicle treated SHR and normotensive WKY. In a second study, SHR were treated with CANDE, pioglitazone (a PPAR-gamma agonist, PIO 2.5 mg/kg per day) or CANDE+PIO, compared to TELMI. Internal diameter of pial arterioles (ID, cranial window) was measured at baseline, during hemorrhage-induced hypotension, or following suffusion of Ang II (10(-6) mol/L) or EDTA inactivation of smooth muscle cells (passive ID). PPAR-gamma and eNOS (target gene of PPAR-gamma) mRNA were evaluated in brain microvessels. For similar antihypertensive effects, TELMI (+44% versus SHR), but not CANDE, increased baseline ID. During hemorrhage, ID in TELMI group was similar to WKY, while ID in SHR and CANDE remained lower. In the second study, TELMI (+36%, versus SHR) and CANDE+PIO (+43%) increased baseline ID, but not CANDE or PIO alone. TELMI (-66%) and CANDE+PIO (-69%), but neither CANDE nor PIO alone, decreased Ang II-induced vasoconstriction. CANDE+PIO, but not CANDE, increased passive ID. In both studies, PPAR-gamma and eNOS expressions were higher in TELMI than CANDE. Short-term treatment with TELMI, but not with CANDE, reverses narrowing of pial arteriolar ID in SHR. This may involve PPAR-gamma related mechanisms, since CANDE+PIO treatment induced similar effects, and a better blockade of AT(1) receptors.

International audience; Angiotensin II (Ang II) induces constriction (AT(1)) and dilation (AT(2) receptors) of cerebral arterioles. High sodium intake induces changes in receptors expression and loss of AT(2)-mediated vasodilation in extracerebral vessels. We investigated whether high salt modifies the AT(2)-mediated response of cerebral arterioles.Three-month-old male Wistar rats received drinking water supplemented or not with 1% NaCl. We measured at day 4 or 30 plasma aldosterone concentration, AT receptors expression (brain microvessels, western blot, RT-qPCR), internal diameter of pial arterioles (cranial window) following suffusion with Ang II (10(-6) mol/l, or 10(-8) mol/l + losartan 10(-5) mol/l), serotonin (5-HT, 10(-6) mol/l), sodium nitroprusside (10(-5) mol/l) and adenosine diphosphate (ADP, 10(-4) mol/l).High salt did not modify arterial pressure, baseline arteriolar diameter, vasoconstriction to Ang II or 5-HT, nor vasodilation to SNP. High salt lowered plasma aldosterone concentration (d4 138 ± 71 not significant vs. control 338 ± 73; d30 150 ± 21 P < 0.05 vs. control 517 ± 79 μmol/l). AT receptors mRNA did not change while protein level of AT(2) receptors decreased at d4 (64 ± 9% of control, P < 0.05). AT(2)-mediated vasodilation (control d4; d30 8 ± 2; 5 ± 2%) was abolished at d4 (-2 ± 2%, P < 0.05) and reversed to vasoconstriction at d30 (-7 ± 2%, P < 0.05). ADP-induced vasodilation is abolished at d30 (2 ± 2, P < 0.05 vs. control 19 ± 4%).High salt specifically abolishes AT(2)-mediated vasodilation, immediately, via decreased level of AT(2) receptor protein, and after 30 days, in association with abolition of endothelial vasodilation. Such loss of AT(2)-mediated vasodilation may be deleterious in case of stroke.

International audience; Investigation of the redox status in the cerebral circulation is of great importance in order to evaluate intensity of oxidative stress-related diseases and the corresponding therapeutic effects. Changes in levels of reduced glutathione (GSH) are a major indicator of oxidative stress conditions. However, an important limitation for measurement of GSH as a biomarker is the possible presence in samples of gamma-glutamyltransferase (GGT) activity, i.e., the enzyme catalysing GSH breakdown.An accurate assay for the measurement of GSH in rat brain microvessels was developed, taking into account the high GGT activity expressed in this tissue compartment. Based on a sensitive fluorescence-based microtiter plate method using 2,3-naphthalenedicarboxyaldehyde as GSH-selective fluorogenic probe, the assay was applied to brain microvessels isolated from individual male Wistar rats. Pooling of microvessel fractions from several animals, as required by other procedures, could thus be avoided. In order to prevent GSH consumption via GGT activity, serine–boric acid complex (SBC) was added as inhibitor all along the microvessels isolation process. In the absence of GGT inhibition GSH in isolated brain microvessels was below the limit of quantification. Addition of SBC almost completely suppressed GGT activity, thus allowing GSH quantification (4.4 ± 1.6 nmol.mg− 1 protein, n = 3). Following the administration of a GSH depletor (diethyl maleate, 1 g.kg− 1, i.p.), decreased GSH levels were measured in liver, brain tissue and brain microvessels as well, thus confirming the reliability of the method for safe GSH measurements in small-sized, individual samples presenting high GGT activity.

Numerous laboratory-based data have shown the ability of toluene (Tol) to exacerbate noise-induced hearing loss. However, the mechanism responsible for the synergistic effects of a coexposure to noise and Tol has not yet been completely elucidated. Recent investigations in rats have focused on quantifying the anticholinergic effects of certain aromatic solvents and have demonstrated that these solvents can cancel the protective role played by the middle-ear reflex (MER). Voltage-dependent Ca(2+) channels (VDCCs) regulate acetylcholine release in the central synaptic network and control muscular excitation/contraction processes as well. In order to identify the prevailing action of Tol in the central or peripheral compartment of the MER arc, two VDCC antagonists were injected into the common carotid trunk: omega-conotoxin MVIIC, which blocks only the neuronal N- and P/Q-type Ca(2+) channels, or verapamil, which inhibits the muscular L-type Ca(2+) channels. Rats were also implanted with an electrode on the round window membrane to measure the cochlear microphonic potential (CMP) elicited with a band noise centered at 4 kHz and emitted at 85 dB sound pressure level. The variations in CMP recorded during the test compound injection showed that Tol has similar effects to those induced by omega-conotoxin, the neuronal VDCC blocker. The response obtained with the verapamil injection was broader than those obtained with Tol or conotoxin. This investigation therefore revealed that Tol can mimic the effects of VDCC blockers. The antagonist effects of Tol would be closer to neuronal than to muscular blockers and would be presumably located at the level of the integrator centers of the reflex.

While noise exposure is the most significant contributor to occupational hearing loss, evidence gained over the last 10 years, has pointed to organic solvents as additional contributors to occupational hearing disorders. Despite the implications of this finding, no significant measure has been undertaken to limit exposure to occupational solvents, or to occupational solvents and noise, within the European community. Guidelines for improving hearing protection of people exposed to solvents, or to solvents and noise, are addressed in the present article. Recently, it has been shown that the lowest-observed-adverse-effect level (LOAEL) of styrene was 300 ppm in active (working wheel) rats, and that the same amount of styrene-induced hearing loss (SIHL) can be obtained with styrene concentration difference of 200 ppm between active and sedentary (inactive) rats. Supported by a reasonable safety factor (SF) of 10, the authors proposed to decrease the French threshold limit value of styrene from 50 to 30 ppm (RfD=LOAEL/SF) to ensure a higher level of protection for human hearing. It is widely acknowledged that outer hair cells in the organ of Corti can be considered as the first target tissue of solvents, while little is known about the action of aromatic solvents on the auditory efferent system. In a recent experiment using both the cochlear microphonic and compound action potentials, the authors have shown that toluene can inhibit the action of the middle ear reflex by modifying the cholinergic receptors. It is likely that toluene affects the cholinergic receptors at the brainstem level. By its anticholinergic-like effect, toluene could allow higher acoustic energy penetration into the cochlea exposed to both noise and solvent. Based on this phenomenon, the authors recommend the use of hearing protection for the lower exposure action value: Lex,8h=80 dB(A) in noisy environments polluted by solvents.

From previous in vivo investigations, it has been shown that toluene can mimic the effects of cholinergic receptor antagonists and may thereby modify the response of protective acoustic reflexes. The current study aimed to define the relative effects of aromatic solvents on the middle ear and inner ear acoustic reflexes. Toward this end, the cochlear microphonic (CMP) elicited with a band noise centered at 4 kHz, and the compound action potential (CAP) elicited with 4-kHz tone pips was measured in rats. Both potentials were recorded before, during, and after triggering the protective reflexes by a 110-dB SPL contralateral octave band noise centered at 12.5 kHz (12.5 kHz-OBN). In several rats, the middle ear muscles were severed to identify the relative effects of toluene on the two reflexes. While the reflex elicitor was capable of decreasing both the CMP and CAP amplitudes, an injection of 116.2 mM toluene cancelled this suppressor effect induced by the contralateral sound. In the rats with nonfunctional middle ear muscles, a solvent injection did not modify the electrophysiological responses of the cochlea. Different solvents were tested to study the relationship of the chemical structure of the solvents on the acoustic reflexes. The present study showed that aromatic solvents can inhibit the action of the middle ear reflex by their anticholinergic effect on the efferent motoneurons. An aromatic nucleus and the presence of one side chain of no more than 3 C seem to be required in the solvent structure to inhibit the efferent motoneurons.

Human and animal studies have shown that toluene can cause hearing loss. In the rat, the outer hair cells are first disrupted by the ototoxicant. Because of their particular sensitivity to toluene, the cochlear microphonic potential (CMP) was used for monitoring the cochlea activity of anesthetized rats exposed to both noise (band noise centered at 4 kHz) and toluene. In the present experiment, the conditions were specifically designed to study the toluene effects on CMP and not those of its metabolites. To this end, 100-microL injections of a vehicle containing different concentrations of solvent were made into the carotid artery connected to the tested cochlea. Interestingly, an injection of 116.2-mM toluene dramatically increased in the CMP amplitude (approximately 4 dB) in response to an 85-dB SPL noise. Moreover, the rise in CMP magnitude was intensity dependent at this concentration suggesting that toluene could inhibit the auditory efferent system involved in the inner-ear or/and middle-ear acoustic reflexes. Because acetylcholine is the neurotransmitter mediated by the auditory efferent bundles, injections of antagonists of cholinergic receptors (AchRs) such as atropine, 4-diphenylacetoxy-N-methylpiperidine-methiodide (mAchR antagonist) and dihydro-beta-erythroidine (nAchR antagonist) were also tested in this investigation. They all provoked rises in CMP having amplitudes as large as those obtained with toluene. The results showed for the first time in an in vivo study that toluene mimics the effects of AchR antagonists. It is likely that toluene might modify the response of protective acoustic reflexes.

Background Rheumatoid Arthritis (RA) is associated to an increase in cardiovascular risk (CVR) explained in part by accelerated atherosclerosis as a consequence of endothelial dysfunction. Glucocorticoids (GCs) are widely prescribed in RA patients. Surprisingly, despite the commonly held belief that glucocorticoids worsen the CVR, data concerning their impact on endothelial function in RA is lacking. Objectives The present study investigated the effect of a high dose of prednisolone on vascular function in arthritic rats and identified the underlying mechanisms. Methods Adjuvant-induced arthritis (AIA) was induced in 6-week-old male Lewis rats by injection of Mycobacterium butyricum in adjuvant at the basis of the tail. At the onset of arthritis, rats were daily treated (i.p.) with prednisolone (10 mg /kg, AIA-GC) or saline (Vehicle) for 21 days. Arthritis score and tarsus diameter were daily monitored. At the end of treatment, thoracic aortas were harvested to measure the relaxation of pre-constricted aortic rings to acetylcholine in the presence or not of inhibitor of nitric oxide synthase (NOS) (L-NAME), arginase (nor-NOHA), COX-2 (NS-398), EDHF (Apamin/Charybdotoxin) or a superoxide dismutase analog (Tempol). The effect of a NO donor (sodium nitroprussiate, SNP) and norepineprhine (NE) was studied on endothelium-denuded aortic rings. Aortic expression of endothelial NOS (eNOS) and phospho-eNOS (Ser-1177) was evaluated by western blotting. Blood pressure, glycaemia, triglyceride and total cholesterol levels and radiological score of hind paws were also assessed. Results Consistent with the well-known effects of a high dose of GC, AIA-GC exhibited significantly higher blood pressure (p Conclusions Our study demonstrated that a high dose of prednisolone improved endothelial function in case of RA, independently of its deleterious cardio-metabolic effects. From a clinical perspective, these results raise the question of the use of high doses of GC during a short period to overcome CV risk along with a rapid disease control. Whether this beneficial vascular effect of GC depends on the reduction of disease activity or not deserves further investigations. Disclosure of Interest None declared

Numerous experiments have shown that the aromatic solvents can affect the auditory system in the rat, the cochlea being targeted first. Solvents differ in cochleotoxic potency: for example, styrene is more ototoxic than toluene or xylenes. The goal of this study was to determine the relative ototoxicity of the three isomers of xylene (o-, m- or p-xylene). Moreover, by dosing with the two urinary metabolites of xylene, methylhippuric (MHAs) and mercapturic acids (MBAs), this study points toward a causal relationship between the cochleotoxic effects and potential reactive intermediates arising from the biotransformation of the parent molecules. Separate groups of rats were exposed by inhalation to one isomer following this schedule: 1800 ppm, 6 h/d, 5 d/wk for 3 wk. Auditory thresholds were determined with brainstem-auditory evoked potentials. Morphological analysis of the organ of Corti was performed by counting both sensory and spiral ganglion cells. Among the three isomers, only p-xylene was cochleotoxic. A 39-dB permanent threshold shift was obtained over the tested frequencies range from 8 to 20 kHz. Whereas outer hair cells were largely injured, no significant morphological change was observed within spiral ganglia. The concentrations of urinary p-, o- or m-MHA were greater (p-MHA: 33.2 g/g; o-MHA: 7.8 g/g; m-MHA: 20.4 g/g) than those obtained for MBAs (p-MBA: 0.04 g/g; o-MBA: 6.2 g/g; m-MBA: 0.03 g/g). Besides, there is a large difference between o-MBA (6.2 g/g) and p-MBA (0.04 g/g). As a result, since the cysteine conjugates are not determinant in the ototoxic process of xylenes, the location of the methyl groups around the benzene nucleus could play a key role.

Background Rheumatoid arthritis (RA) is associated with increased risk for cardiovascular disease (CVD). Whereas ample evidence demonstrated the presence of endothelial dysfunction (ED) in RA, it is still unclear how early this abnormality develops. Moreover most of studies have been performed on the macrovasculature but little is known about ED in the microvasculature. Objectives The aim of this study is to investigate the time-course of microvascular and macrovascular impairment in adjuvant-induced arthritis (AIA) in rats. Methods AIA was induced by an intradermal injection of Mycobacterium butyricum in the tail of male Lewis rats (Day 0). Arthritis severity was evaluated by clinical and radiological analysis at 4 stages of AIA: day 4 (preclinical stage), day 11 (very early arthritis), day 33 (severe disease), day 90 (chronic disease). At each stage, functional and mechanical properties of third-order mesenteric arteries were determined by assessing flow-mediated dilatation, myogenic tone and stress-strain relationship. Macrovascular function was studied on isolated aortic rings in which the contractile response to norepinephrine (NE) and the vasorelaxant response to Acetylcholine (Ach) and to sodium nitroprussiate (SNP) were evaluated. Results Macrovascular ED became evident at the severe disease. At the chronic phase of AIA the presence of ED was positively correlated to the radiological score. The response of aortic rings to SNP was normal whatever the stage of AIA. By contrast, NE-induced contractility was significantly reduced in AIA at day 4, and recovered the normal values thereafter. In microvascular bed, ED appears at the early arthritis stage. At the severe disease, microvascular ED is still present and is associated with reduced arterial stiffness. At day 90, one group of microvessels from AIA exhibited ED whereas another group did not, but ED was not correlated to the radiological score. Myogenic tone was unchanged during the course of arthritis. Conclusions Our results demonstrated that micro and macrovascular beds are differentially affected during the course of RA. Microvascular ED is a very early event in the course of arthritis. It precedes the occurrence of macrovascular ED and microvascular stiffness. Our data suggest that the measurement of microvascular function would be relevant for the early diagnosis of CV risk in RA patients. They also suggest that mechanisms underlying macro- and microvascular dysfunction are different. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.1687

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease characterized by articular and extra-articular manifestations involving cardiovascular diseases (CVDs), which account for 30% to 50% of all deaths. In patients with RA, atherosclerosis lesions occur earlier and have a more rapid evolution than in the general population. Beyond mortality, the impact of CVD on quality of life, combined with the associated increase in health-care costs, renders CVD in RA a major public health problem. Recent studies showed that patients with RA are characterized by the presence of endothelial dysfunction (ED), which is recognized as a key event in the development of atherosclerosis. By definition, ED is a functional and reversible alteration of endothelial cells, leading to a shift of the actions of the endothelium toward reduced vasodilation, proinflammatory state and proliferative and prothrombotic properties. Although the improvement of endothelial function is becoming an important element of the global management of patients with RA, the mechanistic determinants of ED in RA are still poorly understood. Animal models of RA provide the unique opportunity to unravel the pathophysiological features of ED in RA. The present review summarizes the available data on mechanisms underlying ED in animal models of RA and proposes attractive prospects in order to discover novel therapeutic strategies of RA-associated ED.