Kainate-activated currents in the ventral tegmental area of neonatal rats are modulated by interleukin-2

Association of interleukin-2 and interleukin-10 with the pathophysiology and development of generalized anxiety disorder: a case-control study

BACKGROUND

Generalized anxiety disorder (GAD) is a devastating mental health condition characterized by constant, uncontrolled worrying. Recent hypotheses indicate that pro-inflammatory cytokines and chemokines are potential contributors to the pathogenesis of GAD. Here, we aimed to assess the role of interleukin-2 (IL-2) and interleukin-10 (IL-10) in the pathophysiology and development of GAD.

METHODS

This study recruited 50 GAD patients diagnosed according to the DSM-5 criteria and 38 age-sex-matched healthy controls (HCs). A qualified psychiatrist evaluated all study subjects. The socio-demographic and clinical characteristics of the study population were determined using pre-structured questionnaires or interviews, and cytokine serum levels were estimated using commercially available ELISA kits.

RESULTS

We observed reduced serum IL-10 levels in GAD patients compared to HCs (33.69 ± 1.37 pg/ml vs. 44.12 ± 3.16 pg/ml). Also, we observed a significant negative correlation between altered IL-10 levels and GAD-7 scores (r=-0.315, p = 0.039). Moreover, IL-10 serum measurement exhibited good predictive value in receiver operating characteristics (ROC) analysis with an area under the curve (AUC) value of 0.793 (p < 0.001) with 80.65% sensitivity and 62.79% specificity at a cutoff value of 33.93 pg/ml. Conversely, we noticed elevated serum IL-2 levels in GAD patients than in HCs (14.81 ± 2.88 pg/ml vs. 8.08 ± 1.1 pg/ml); however, it failed to maintain any significant association with GAD-7 scores, implying that IL-2 might not be involved in GAD pathogenesis. The lower AUC value (0.640; p > 0.05) exhibited by IL-2 serum measurement in ROC analysis further supported that IL-2 might not be associated with GAD.

CONCLUSION

This study provides new insights into the complex interplay between anti-inflammatory cytokines and GAD pathogenesis. Based on the present findings, we can assume that IL-10 but not IL-2 may be associated with the pathophysiology and development of GAD. However, further research with a larger population size and longitudinal design is required to confirm the potential diagnostic efficacy of IL-10.

Microarray analysis of rat hippocampus exposed to excitotoxicity: reversal Na(+)/Ca(2+) exchanger NCX3 is overexpressed in glial cells

Multiple factors are involved in the glutamate-induced excitotoxicity phenomenon, such as overload of ionotropic and metabotropic receptors, excess Ca(2+) influx, nitric oxide synthase activation, oxidative damage due to increase in free radicals, and release of endogenous polyamine, among others. In order to attempt a more integrated approach to address this issue, we established, by microarray analysis, the hippocampus gene expression profiles under glutamate-induced excitotoxicity conditions. Increased gene expression is mainly related to excitotoxicity (CaMKII, glypican 2, GFAP, NCX3, IL-2, and Gmeb2) or with cell damage response (dynactin and Ecel1). Several genes that augmented their expression are related to glutamatergic system modulation, in particular with NMDA receptor modulation and calcium homeostasis (IL-2, CaMKII, acrosin, Gmeb2, hAChE, Slc83a, and SP1 factor). Conversely, among genes that diminished their expression, we found the Syngap 1, which is downregulated by CaMKII, and the MHC II, which is downregulated by glutamate. Changes observed in gene expression induced by monosodium glutamate (MSG) neonatal treatment in the hippocampus are consistent with the activation of the mechanisms that modulate NMDA receptor function as well as with the implementation of plastic response to cell damage and intracellular calcium homeostasis. Regarding this aspect, we report here that NCX3/Slc8a3, a Na(+)/Ca(2+) membrane exchanger, is highly expressed in astrocytes, both in vitro and in vivo, in response to glutamate-induced excitotoxicity. Hence, the results of this analysis present a broad view of the expression profile elicited by MSG neonatal treatment, and lead us to suggest the possible molecular pathways of action and reaction involved under this experimental model of excitotoxicity.

Attention-deficit hyperactivity disorder (ADHD) and glial integrity: S100B, cytokines and kynurenine metabolism--effects of medication

BACKGROUND

Children with attention-deficit/hyperactivity disorder (ADHD) show a marked temporal variability in their display of symptoms and neuropsychological performance. This could be explained in terms of an impaired glial supply of energy to support neuronal activity.

METHOD

We pursued one test of the idea with measures of a neurotrophin reflecting glial integrity (S100B) and the influences of 8 cytokines on the metabolism of amino-acids, and of tryptophan/kynurenine to neuroprotective or potentially toxic products that could modulate glial function. Serum samples from 21 medication-naïve children with ADHD, 21 typically-developing controls, 14 medicated children with ADHD and 7 healthy siblings were analysed in this preliminary exploration of group differences and associations.

RESULTS

There were no marked group differences in levels of S100B, no major imbalance in the ratios of pro- to anti-inflammatory interleukins nor in the metabolism of kynurenine to toxic metabolites in ADHD. However, four trends are described that may be worthy of closer examination in a more extensive study. First, S100B levels tended to be lower in ADHD children that did not show oppositional/conduct problems. Second, in medicated children raised interleukin levels showed a trend to normalisation. Third, while across all children the sensitivity to allergy reflected increased levels of IL-16 and IL-10, the latter showed a significant inverse relationship to measures of S100B in the ADHD group. Fourthly, against expectations healthy controls tended to show higher levels of toxic 3-hydroxykynurenine (3 HK) than those with ADHD.

CONCLUSIONS

Thus, there were no clear signs (S100B) that the glial functions were compromised in ADHD. However, other markers of glial function require examination. Nonetheless there is preliminary evidence that a minor imbalance of the immunological system was improved on medication. Finally, if lower levels of the potentially toxic 3 HK in ADHD children were confirmed this could reflect a reduction of normal pruning processes in the brain that would be consistent with delayed maturation (supported here by associations with amino-acid metabolism) and a reduced metabolic source of energy.

Spinal injection of IL-2 or IL-15 alters mechanical and thermal withdrawal thresholds in rats

IL-2 and IL-15 were tested for effects on responses to mechanical or thermal stimuli when spinally administered to male Sprague-Dawley rats with surgically implanted intrathecal catheters. Restricted doses of both IL-2 and IL-15 produced increased responsiveness to mechanical stimulation of the hindpaws. This effect lasted up to 48 h. IL-2 had biphasic effects on thermal responses whereas IL-15 produced thermal hypalgesia alone. These effects dissipated within 24h. These results suggest that IL-2 and IL-15 may participate in the generation of hyperalgesia in some pain conditions.

Cytokines and neuronal ion channels in health and disease

The biophysical properties and the spatial distribution of ion channels define the signaling characteristics of individual neurons. Function, number localization, and ratio of receptor and ion channels are dynamically modulated in response to diverse stimuli and undergo dynamic changes in both physiological and pathological conditions. Increasing evidence indicates that cytokines may specifically interact with receptor and ion channels regulating neuronal excitability, synaptic plasticity, and injury. Interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha, two proinflammatory cytokines implicated in various pathophysiological conditions of the CNS, have been particularly studied. Literature data indicate that these cytokines (1) directly and promptly modulate ion channel activity, (2) exert different (and often opposite) effects on the same channels, and (3) act on ion channels both at physiological and pathological concentrations. Consequently, cytokines are now regarded as novel neuromodulators, opening important perspectives in the current view of brain behavior.

Transient ischemia-induced changes of interleukin-2 and its receptor β immunoreactivity and levels in the gerbil hippocampal CA1 region

Interlukin-2 (IL-2) is an important cytokine in the brain: IL-2 and its receptors are involved with inflammatory processes. Chronological changes in IL-2 level in serum, and IL-2 and its receptor (IL-2 receptor beta, IL-2Rbeta) immunoreactivities and levels were examined in the hippocampal CA1 region after transient forebrain ischemia in gerbils. IL-2 level in serum significantly decreased 12 h after ischemia/reperfusion. IL-2 immunoreactivity was detected in the somata of pyramidal cells in sham-operated group. At 15 min after ischemia, IL-2 immunoreactivity was shown in non-pyramidal cells as well as pyramidal cells. One day after ischemia, IL-2 immunoreactivity was lowest, and IL-2 immunoreactivity is shown in non-pyramidal cells from 2 days after ischemia. Four days after ischemia, IL-2 immunoreactivity was shown in dying pyramidal cells. IL-2Rbeta immunoreactivity in the sham-operated and 15 min-3 min post-ischemic groups is detected in the cell membrane of pyramidal cells. From 3 h after ischemia, IL-2Rbeta immunoreactivity is found in cytoplasm and nuclei, but not in cell membrane. IL-2Rbeta immunoreactivity decreases from 6 h after ischemia and is shown mainly in non-pyramidal cells from 3 days after ischemia. The data of Western blot analyses for IL-2 and IL-2Rbeta was similar to the immunohistochemical data. IL-2 infusion into cerebrospinal fluid did not protect hippocampal neurons from ischemic damage. These results suggest that IL-2 and IL-2Rbeta show malfunction from 3 h after ischemia, and exogenous IL-2 does not protect ischemic neuronal damage.

Δ9-Tetrahydrocannabinol and Endogenous Cannabinoid Anandamide Directly Potentiate the Function of Glycine Receptors

Anandamide (AEA) and delta9-tetrahydrocannabinol (THC) are endogenous and exogenous ligands, respectively, for cannabinoid receptors. Whereas most of the pharmacological actions of cannabinoids are mediated by CB1 receptors, there is also evidence that these compounds can produce effects that are not mediated by the activation of identified cannabinoid receptors. Here, we report that THC and AEA, in a CB1 receptor-independent manner, cause a significant potentiation of the amplitudes of glycine-activated currents (I(Gly)) in acutely isolated neurons from rat ventral tegmental area (VTA) and in Xenopus laevis oocytes expressing human homomeric (alpha1) and heteromeric (alpha1beta1) subunits of glycine receptors (GlyRs). The potentiation of I(Gly) by THC and AEA is concentration-dependent, with respective EC50 values of 86 +/- 9 and 319 +/- 31 nM for alpha1 homomeric receptors, 73 +/- 8 and 318 +/- 24 nM for alpha1beta1 heteromeric receptors, and 115 +/- 13 and 230 +/- 29 nM for native GlyRs in VTA neurons. The effects of THC and AEA are selective for I(Gly), because GABA-activated current in VTA neurons or in X. laevis oocytes expressing alpha2beta3gamma2 GABA(A) receptor subunits were unaffected by these compounds. The maximal potentiation by THC and AEA was observed at the lowest concentration of glycine; with increasing concentrations of glycine, the potentiation significantly decreased. The site for THC and AEA seems to be distinct from that of the alcohol and volatile anesthetics. The results indicate that THC and AEA, in pharmacologically relevant concentrations, directly potentiate the function of GlyRs through an allosteric mechanism.