Metal-induced inflammation triggers fibromyalgia in metal-allergic patients

BACKGROUND

Fibromyalgia (FM) is a disease of unknown etiology. Inflammation could be one of the mechanisms behind this disease.

OBJECTIVES

We studied the frequency and clinical relevance of metal allergy in FM patients.

METHODS

Fifteen female FM patients were included in the study. Metal allergy was measured by a lymphocyte transformation test, MELISA®. Ten healthy age-matched women were used as controls for in vitro studies. Reduction of metal exposure in the FM patients was achieved by replacement of dental metal restorations and by the avoidance of known sources of metal exposure. Objective health assessment was performed 5 years after treatment. Subjective health assessment was established by a questionnaire, completed 2, 5 and in some cases 10 years after the start of the study. Follow-up MELISA was also performed.

RESULTS

All FM patients tested positive to at least one of the metals tested. The most frequent reactions were to nickel, followed by inorganic mercury, cadmium and lead. Some healthy controls responded to inorganic mercury in vitro but most of the tests were negative. Objective examination 5 years later showed that half of the patients no longer fulfilled the FM diagnosis, 20% had improved and the remaining 30% still had FM. All patients reported subjective health improvement. This correlated with the normalisation of metal-specific responses in vitro.

CONCLUSION

Metal allergy is frequent in FM patients. The reduction of metal exposure resulted in improved health in the majority of metal-sensitized patients. This suggests that metal-induced inflammation might be an important risk factor in a subset of patients with FM.

Neurochemical studies of human narcolepsy: alpha-adrenergic receptor autoradiography of human narcoleptic brain and brainstem

Studies of human and canine narcolepsy-cataplexy syndrome suggest that noradrenergic function may be abnormal. We used quantitative autoradiography to assess noradrenergic alpha-1 and alpha-2 receptors in several regions of seven human narcoleptic and 18 control brains using [3H]prazosin to evaluate alpha-1 receptors, and [3H]UK14304 and [3H]rauwolscine to evaluate alpha-2 receptors. Specific blocking agents were used in combination with the tritiated ligands to assess alpha-1 and alpha-2 receptor subtypes. Although we found few statistically significant differences between narcoleptic and control brains, there were a number of trends. [3H]Prazosin binding to sites in the amygdala, globus pallidus and putamen was reduced by 22-68%, whereas binding was increased by 40% to the inferior olive and by 84% to portions of the dorsal pons. Binding was similar to control values in other regions. In all seven brainstem regions that were evaluated, the ratio of alpha-1b receptor binding to alpha-1a receptor binding was increased. Binding of [3H]UK14304 was increased by 35-74% in the caudate nucleus, putamen and portions of the amygdala and pons. [3H]rauwolscine binding data suggested that increase of alpha-2 receptor binding in the dorsal pons were not due to effects at the imidazole receptor. findings suggest that noradrenergic function may be altered in specific regions of the brain and brainstem in human narcolepsy, although the absence of statistical significance indicates that these trends should be considered preliminary. The trend toward a relative increase of alpha-1b receptor binding in narcoleptic brainstem is consistent with data from studies of canine narcolepsy and suggests that altered activity at this receptor may contribute to the pathogenesis of human narcolepsy. Studies of additional brains will be required to confirm these findings.

Endotoxin stimulates lymphocyte glutaminase expression

BACKGROUND/HYPOTHESIS

Glutamine is the principal fuel used by lymphocytes. It is hydrolyzed by the glutaminase enzyme, which regulates the rate of intracellular glutamine metabolism. Since lymphocyte glutamine utilization is increased during infection to support cellular proliferation, we hypothesized that endotoxin regulates lymphocyte glutaminase expression at the molecular level.

METHODS

Adult rats received Escherichia coli endotoxin (one dose of 7.5 mg/kg) or saline. Total RNA from lymphocytes in the ileocolic lymph node chain was extracted for Northern hybridization and labeled with an alpha-phosphorus 32 rat glutaminase cDNA probe. The mRNA of the constitutively expressed gene beta-actin was the control for RNA loading. Quantitation of glutaminase transcripts was determined by densitometric scanning and values were normalized to actin. Glutaminase-specific activity (nanomoles per milligram of protein per hour) and glutaminase kinetic parameters were also determined.

RESULTS

Treatment with a single dose of endotoxin resulted in a 53% increase in glutaminase activity at 4 hours. Kinetic analysis showed that the increase in glutaminase activity was due to an 84% increase in Vmax (maximal enzyme velocity) with no change in Km (enzyme affinity). Endotoxin increased glutaminase mRNA twofold at 2 hours and more than fourfold at 4 hours. The increase in message preceded the increase in activity consistent with gene transcription prior to enzyme biosynthesis.

CONCLUSION/CLINICAL RELEVANCE

The increase in glutaminase activity provides lymphocytes in the mesenteric lymph nodes with more glutamine for energy and cellular proliferation during times of infection when the gut mucosal barrier may become compromised.

Dexamethasone stimulation of glutaminase expression in mesenteric lymph nodes

Lymphocytes in the mesenteric lymph nodes (MLNs) play a key role in protecting the body from the translocation of bacteria through the bowel during catabolic states. Lymphocytes use glutamine for energy and for DNA synthesis and have high levels of the glutaminase (GA) enzyme that regulates intracellular glutamine metabolism. This study tested the hypothesis that the increase in circulating glucocorticoid hormones that occurs in response to stress states regulates MLN lymphocyte GA expression at the molecular level. Adult male rats (n = 60) received a single dose of dexamethasone (DEX 0.5 mg/kg intraperitoneally) or saline vehicle (CONT). Ileocolic lymph nodes were excised from anesthetized rats via laparotomy at 2, 4, 12, 24, 48, and 72 hours after injection, and GA activity was assayed in MLN homogenates. A second group of rats received repeated doses of DEX (0.5 mg/kg/d for 4 days). GA activity was assayed in MLN homogenates, and total RNA was extracted for quantitation by Northern hybridization using a phosphorus 32-labeled rat GA cDNA probe. GA activity was increased within 2 hours after a single dose of DEX, with a peak after 4 hours, Kinetic analysis at the 4-hour time point showed an increase in the maximum GA activity (maximal transport velocity [Vmax]: 619 +/- 107 nmol/mg protein/hr in DEX versus 380 +/- 53 nmol/mg protein/hr in CONT, p < 0.05), with no change in GA affinity (Michaelis constant [Km]: 2.28 +/- 0.39 mM in DEX versus 2.20 +/- 0.36 mM in CONT, p = NS). Repeated doses of DEX resulted in a twofold increase in GA activity (550 +/- 125 nmol/mg protein/hr versus 1,175 +/- 40, p < 0.01). Simultaneously, GA mRNA levels were increased by 70%. Glucocorticoids stimulate GA activity and gene expression in lymphocytes that reside in MLNs.