Manuel Feria

The CCR2 receptor as a therapeutic target

The strict control of cell recruitment during the physiological inflammatory response fails in autoimmune inflammatory diseases. The chemokine system is a complex and redundant network of small soluble proteins and G-protein-coupled cell surface receptors that participate in the inflammatory response, mainly attracting cells to the inflammatory foci. Data inferred from animal models suggest that the chemokine system might be involved in the physiopathology of several human disorders. CCR2, a chemokine receptor widely expressed in haematopoietic and non-haematopoieic cells, has been functionally implicated in experimental models of rheumatoid arthritis, multiple sclerosis and atherosclerosis amongst others, which has prompted several pharmaceutical companies to develop and patent a number of compounds with anti-CCR2 activity. This review will consider disorders where CCR2 signalling has shown a relevant function in animal models for which correlative data exist in humans, as well as patents of synthetic and biological products with anti-CCR2 activity potentially useful in human pathology.

Magnesium sulphate injected subcutaneously suppresses autotomy in peripherally deafferented rats

&NA; In rats, recent evidence suggests that injury discharge caused by peripheral nerve section releases excitatory amino acids into the spinal cord which in turn influences decisively the development of autotomy, a self‐mutilation behaviour directed towards the denervated areas. Autotomy has been proposed as a behavioural correlate of the neuropathic pain which occurs in humans after complete nerve lesions. Mg2+ ions have been shown to offer protection from neurological and degenerative disorders in which excitatory amino acids are putatively involved. To ascertain the preventive value of Mg2+ administration on autotomy, male rats underwent unilateral ligation and transection of the sciatic and saphenous nerves 30 min after being injected subcutaneously (s.c.) with 300 or 600 mg/kg MgSO4 or saline. Thereafter, autotomy was monitored for 8 weeks. Serum, lumbosacral (L1–S1) and brain magnesium levels were analyzed 0, 30, 60, 120, 180, 240, 360 min and 24 h after the s.c. injection of 600 mg/kg MgSO4. Serum magnesium levels increased quickly from 1.02 mM (0 time) to 4.52 mM (at 60 min) and dropped afterwards to reach physiological levels at 6 h. Peak increments in L1–S1 and brain Mg2+ levels were smaller (32% and 30%, respectively) although maintained for at least 6 h. Magnesium pretreatment in a significant and dose‐dependent manner (1) largely suppressed autotomy, (2) decreased final autotomy scores, (3) delayed autotomy onset, and (4) decreased the percentage of animals engaged in high autotomy behaviors. The data support a role for excitatory amino acids in determining susceptibility to autotomy and suggest a hopeful way to prevent neuropathic pain in humans after peripheral deafferentation.

Chronic amitriptyline decreases autotomy following dorsal rhizotomy in rats

In the rat, unilateral dorsal cervicothoracic rhizotomy (C5-T1), a proposed model of chronic pain, resulted in autotomy of the ipsilateral limb. The self-mutilation lesions were evaluated daily by means of an autotomy score from the 1st to the 80th postoperatory day. The onset of lesions was variable and attained the maximum degree 8-9 weeks after the dorsal roots section. Chronic administration of amitriptyline (5 and 10 mg/kg/day, i.p., over 30 days), started on the 10th day after rhizotomy, decreased autotomy behavior, an effect which persisted 20 days after treatment withdrawal, and lengthened almost two-fold the lag time between rhizotomy and appearance of lesions. A more pronounced effect was observed with the lowest dose of amitriptyline suggesting the existence of a therapeutic window. Possible mechanisms for the antinociceptive effect of amitriptyline in this model are discussed.

Morphine-Methadone Opioid Rotation in Cancer Patients: Analysis of Dose Ratio Predicting Factors

The dose ratio that is effective when switching opioid therapy from morphine to methadone in cancer patients varies widely. There are no conclusive data explaining the source of this variability. We analyzed 54 cancer patients undergoing opioid rotation to clarify those factors that influenced the morphine/methadone dose ratio (MMEDR) at Day 10 after the switch. Reasons for switching were uncontrolled pain (10 patients) or side effects (with or without pain, 44 patients). Initial MMEDR was 5:1 or 10:1 (82% or 18% of patients, respectively). Multivariate regression analysis was used to identify the demographic, cancer-related, and treatment-related variables that were potential predictors of MMEDR. Median previous morphine dose for the entire sample was 220 mg/day (range: 30-1000 mg/day). The stable MMEDR median was 5:1 (range: 2:1-15:1). In the univariate analysis, reasons for opioid rotation, age, and previous morphine doses were associated with MMEDR. Multiple linear regression analysis showed that only the reason for switching (pain vs. side effects; P<0.001) and previous morphine doses (lower vs. upper to 300 mg/day; P<0.001) were associated with MMEDR. From this analysis, the MMEDRs for patients rotated for side effects at 300 mg/day or more or less than 300 mg/day of morphine were 9.1:1 or 5.6:1, respectively, and the MMEDRs for those switched for pain at 300 mg/day or more or less than 300 mg/day of morphine were 4.9:1 or 3:1, respectively. Both the reasons for opioid rotation and previous morphine doses are predictive factors and should be used to select the MMEDR more accurately.

The role of CD69 in acute neutrophil‐mediated inflammation

The leukocyte activation marker CD69 functions as a negative regulator of the immune response, both in NK‐dependent tumor rejection and in the inflammation associated with lymphocyte‐dependent collagen‐induced arthritis. In contrast, it has been reported that CD69‐deficient mice are refractory to the neutrophil‐dependent acute inflammatory response associated with anti‐type II collagen antibody‐induced arthritis (CAIA), suggesting a positive regulatory role for CD69 in neutrophil function during arthritis induction. To clarify this discrepancy, the CAIA response was independently analyzed in our CD69‐deficient mice. In these experiments, the inflammatory response was unaffected by CD69 deficiency. Additionally, the in vivo down‐regulation of CD69 expression by treatment of wild‐type mice with the anti‐CD69 mAb 2.2, which mimics the CD69‐deficient phenotype, did not affect the course of arthritis in this model. Moreover, down‐regulation of CD69 expression increased expression in arthritic joints of key inflammatory mediators, including IL‐1β, IL‐6 and the chemokine MCP‐1. Neutrophil accumulation in zymosan‐treated air pouches and in thioglycolate‐treated peritoneal cavities was also unaffected in CD69‐deficient mice. In addition, CD69 expression was absent in activated neutrophils. Taken together, these results rule out a significant stimulatory role for CD69 in acute inflammatory responses mediated by neutrophils.

Temporary Sedation with Midazolam for Control of Severe Incident Pain

Incident pain frequently complicates cancer-related pain. Its treatment is sometimes very difficult due to poor responsiveness to opioids. Two cases are presented in which a temporary or intermittent sedation with midazolam was successfully used to control excruciating incident pain.

Modulation of neuropathic pain in rats by intrathecally injected serotonergic agonists

THE involvement of spinal cord serotonergic influences in the development of autotomy, a proposed behavioural model of denervation pain, was studied in rats subjected to sciatic and saphenous nerve transection 5min after intrathecal injection of 100 or 200 μg of several serotonergic receptor subtype agonists. Injection of 8-OH- DPAT, m-CPP, 2-m-5-HT and a low dose of 5-HT, significantly shifted one or more of the parameters describing autotomy to less intense behaviour. In contrast, the injection of CGS-12066B and DOI intensified autotomy. These results suggest both a modulatory role for spinal cord serotonin in the events occurring shortly after neurectomy and new therapeutic approaches for the prevention of certain pain syndromes, such as phantom limb pain.

Relationship between autotomy behaviour and spinal cord monoaminergic levels in rats

&NA; In the rat, unilateral neurectomy of the sciatic and saphenous nerves causes autotomy, a self‐mutilation behaviour, against the denervated limb that is variable in both its onset and severity. To study some of the possible neurochemical sources of this variability, spinal cord levels of norepinephrine (NE), dopamine (DA), serotonin (5‐HT) and 5‐hydroxyindoleacetic acid (5‐HIAA) were analysed ipsi‐ and contralateral to the lesioned side by high performance liquid chromatography at C5‐T1 and 2L1‐S1. According to the early or late onset and to the slight or intense autotomy behaviour, the animals were assigned to four different groups: early autotomy, early no autotomy, late autotomy, and late no autotomy. Two sham‐operated groups were sacrificed at an early or late stage in the postoperative period. The spinal cord NE content remained unchanged throughout the different experimental situations. The more conspicuous changes observed were:a generalized increase in spinal 5‐HT metabolism in all deafferented groups;a significant and selective increase in lumbosacral 5‐HT and 5‐HIAA levels of the rats that did not self‐lesion for 8 weeks after deafferentation anda significant fall (30–45%) in DA levels at denervated spinal segments of the rats that actively self‐attacked late in the postoperative period. The data suggest that spinal cord serotonergic and dopaminergic influences play an important role in determining the susceptibility to autotomy (and perhaps chronic pain) after peripheral deafferentation.

Light-induced arousal affects simultaneously EEG and heart rate variability in the rat

In awaken rats, ECG and EEG were simultaneously analysed in order to quantify the cortical EEG and beat-to-beat heart rate variability (HRV) in response to light onset. The HRV bands LF (40-200 mHz), MF (200-600 mHz) and HF (600-2500 mHz) and the EEG bands delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz) and beta (13-32 Hz) were assessed. Light onset induced a significant arousal reaction in the EEG, manifested by a global decrease in total spectral power and a shift towards theta and beta bands, while total HRV spectral power increased, with a shift to the sympathetic-related MF band. This simultaneous changes in HRV and EEG induced by light onset could be triggered by the same common factor that controls both oscillatory responses.

Effects of Nω-monomethyl-L-arginine on short-term RR interval and systolic blood pressure oscillations

The role of endothelium-derived nitric oxide (EDNO) in short-term regulation of RR interval and arterial blood pressure (BP) in conscious rats was studied with N omega-monomethyl-L-arginine (L-NMMA). RR interval and systolic BP (SBP) variability was investigated by spectral analysis procedures. L-NMMA infused intravenously (i.v.) at 1.2 mg/kg/min elicited a clear increase in blood pressure (BP), RR interval (RRI), and respiratory rate. The main spectral modifications observed during L-NMMA infusion were (a) an increase in power of lower frequency (LF, 0.02-0.20 Hz) systolic BP (SBP) oscillations, (b) a decrease in the power of middle frequency (MF, 0.20-0.60 Hz), SBP oscillations, (c) an increase in the power of respiratory (high-frequency, HF) RR oscillations, and (d) an increase in the SBP-RR correlation in the LF band. These results suggest that L-NMMA infusion induced a rearrangement in the lower frequency oscillations of SBP, in which a decrease in sympathetic activity appears to be involved. The increase in HF oscillations of the RR interval appears to be a consequence of the increase in vagal activity in response to the increase in SBP induced by L-NMMA infusion. The suggested autonomic nervous system alterations could account for the increase in the SBP-RRI correlation in the LF band after L-NMMA administration.