Knockdown of interleukin-10 induces the redistribution of sigma1-receptor and increases the glutamate-dependent NADPH-oxidase activity in mouse brain neurons

Background

In the central nervous system, interleukin-10 (IL-10) provides trophic and survival effects directly on neurons, modulates neurite plasticity, and has a pivotal importance in the neuronal regeneration in neurodegenerative and neuroinflammatory conditions. This cytokine is primarily produced by glial cells and has beneficial effects on the neuronal viability. However, the mechanisms of IL-10-elicited neuroprotection are not clear.

Results

Membrane preparations, isolated from wild-type (Wt) and IL-10 knockout (KO) mice brain were used in this study. It has been shown that compared to wild-type mice, in IL-10 KO mice brain, the amount of immunoglobulin binding protein (BiP) is greatly increased, whereas the content of sigma receptor-1 (SigR1) is not changed significantly. Co-immunoprecipitation experiments have shown that the association of SigR1 with small GTPase Rac1 (Ras-related C3 botulinum toxin substrate 1), NR2B subunit of NMDA-receptor (NMDAR) and inositol-3-phosphate receptor (IP3R) is higher in the IL-10 KO mice brain than in the Wt mice brain. Besides, we have found that either glutamate or sigma ligands, separately or together, do not change glutamate-induced NADPH-oxidase (NOX) activity in Wt-type mice brain membrane preparations, whereas in IL-10 KO mice high concentration of glutamate markedly increases the NOX-dependent production of reactive oxygen species (ROS). Glutamate-dependent ROS production was decreased to the normal levels by the action of sigma-agonists.

Conclusions

It has been concluded that IL-10 deprivation, at least in part, can lead to the induction of ER-stress, which causes BiP expression and SigR1 redistribution between components of endoplasmic reticulum (ER) and plasma membrane. Moreover, IL-10 deficiency can change the specific organization of NMDAR, increasing the surface expression of SigR1-sensitive NR2B-containing NMDAR. In these conditions, glutamate-dependent ROS production is greatly increased leading to the initiation of apoptosis. In this circumstances, sigma-ligands could play a preventive role against NMDA receptor-mediated excitotoxicity.

Sigma-1 receptor directly interacts with Rac1-GTPase in the brain mitochondria

BACKGROUND

Small Rho-GTPases are critical mediators of neuronal plasticity and are involved in the pathogenesis of several psychiatric and neurological disorders. Rac-GTPase forms a multiprotein complex with upstream and downstream regulators that are essential for the spatiotemporal transmission of Rac signaling. The sigma-1 receptor (Sig1R) is a ligand-regulated membrane protein chaperone, and multiprotein complex assembly is essential to sigma-receptor function.

RESULTS

Using immunoprecipitation techniques, we have shown that in mitochondrial membranes Sig1R could directly interact with Rac1. Besides Rac1, the Sig1R forms complexes with inositol 1,4,5-trisphosphate receptor and Bcl2, suggesting that mitochondrial associated membranes (MAM) are involved in this macromolecular complex formation. Assembly of this complex is ligand-specific and depends on the presence of sigma agonist/antagonist, as well as on the presence of GTP/GDP. Treatment of mitochondrial membranes with (+)-pentazocine leads to the (+)-pentazocine-sensitive phosphorylation of Bad and the pentazocine-sensitive NADPH-dependent production of ROS.

CONCLUSION

We suggest that Sig1R through Rac1 signaling induces mild oxidative stress that possibly is involved in the regulation of neuroplasticity, as well as in the prevention of apoptosis and autophagy.

Thyroid hormones differentially regulate phosphorylation of ERK and Akt via integrin αvβ3 receptor in undifferentiated and differentiated PC-12 cells

The effects of 3,5,3'-triiodo-l-thyronine (T3) and l-thyroxine (T4) on the integrin αvβ3 receptor of thyroid hormones (TH) were investigated in pheochromocytoma PC-12 cells. Differentiation was induced by treatment of PC-12 cells with fisetin and the levels of phosphorylated extracellular signal-regulated kinase (ERK) and Akt in cytoplasm, as well as the content of FoxO6 transcription factor in nuclei was analysed in undifferentiated and differentiated conditions. We have found that in undifferentiated PC-12 cells, tetraiodothyroacetic acid (TETRAC), a known inhibitor of binding of T4 and T3 to plasma membrane integrin αvβ3 receptor inhibits T4-dependent phosphorylation of ERK, whereas in differentiated PC-12 cells, TETRAC abolishes the effect of T3. In undifferentiated PC-12 cells, both TH increase the level of p-Akt, and this enhancement is not sensitive to TETRAC. In differentiated PC-12 cells, both TH increase the level of p-Akt; however, only T3-dependent activation of Akt is sensitive to the TETRAC. Furthermore, our results have shown that in differentiated PC-12 cells, the expression of FoxO6 was higher than in undifferentiated PC-12 cells, and this elevation has not changed under the action of TH. Only in undifferentiated PC-12 cells the T3-dependent expression of FoxO6 was sensitive to the TETRAC. We propose that PC-12 cells contain integrin αvβ3 receptor, which T3 and T3/T4 sites are differentially regulated by TH in undifferentiated and differentiated conditions.

N-methyl-D-aspartate and sigma-ligands change the production of interleukins 8 and 10 in lymphocytes through modulation of the NMDA glutamate receptor

Human T lymphocytes express both ionotropic and metabotropic glutamate receptors that control immune responses, cell activation, maturation and death. In this study, we examined the effect of N-methyl-D-aspartate (NMDA) and sigma1-receptor ligands on the secretion of the proinflammatory chemokine interleukin 8 (IL-8) and the anti-inflammatory cytokine interleukin 10 (IL-10) in human leukemia Jurkat cells and peripheral blood lymphocytes (PBLs). We have shown that NMDA increased IL-8 and decreased IL-10 secretion and that sigma-ligands modulated the action of NMDA. Moreover, the effects of NMDA and sigma-ligands were interrelated with the nitric oxide (NO) content, suggesting that the intracellular concentration of NO could play a major role in the synthesis of cytokines. Western blots against the NR2A and NR2B subunits of the NMDA glutamate receptor revealed that long-term (48 h) treatment of PBLs with glutamate at concentrations within normal plasma levels (1 x 10(-5)M), in contrast to low concentrations (0.3 x 10(-6)M), downregulates the NR2A subunit, probably by internalization. Furthermore, we found that PBLs with noninternalized NR2A secreted less IL-10 than lymphocytes with downregulated NR2A; under these conditions, the transcriptional activity of NF-kappaB was increased whereas the transcriptional activity of c-Fos was decreased. These findings implicate that the activities of NF-kappaB and c-Fos control the expression of the IL8 and IL10 genes, depending on the subunit composition of the NMDA receptor. In conclusion, we suggest that lymphocytes express an active NMDA receptor only in a low-glutamate milieu.

Haloperidol induces neurotoxicity by the NMDA receptor downstream signaling pathway, alternative from glutamate excitotoxicity

The NMDA receptor is believed to be important in a wide range of nervous system functions including neuronal migration, synapse formation, learning and memory. In addition, it is involved in excitotoxic neuronal cell death that occurs in a variety of acute and chronic neurological disorders. Besides of agonist/coagonist sites, other modulator sites, including butyrophenone site may regulate the N-methyl-D-aspartate receptor. It has been shown that haloperidol, an antipsychotic neuroleptic drug, interacts with the NR2B subunit of NMDA receptor and inhibits NMDA response in neuronal cells. We found that NMDA receptor was co-immunoprecipitated by anti-Ras antibody and this complex, beside NR2 subunit of NMDA receptor contained haloperidol-binding proteins, nNOS and Ras-GRF. Furthermore, we have shown that haloperidol induces neurotoxicity of neuronal cells via NMDA receptor complex, accompanied by dissociation of Ras-GRF from membranes and activation of c-Jun-kinase. Inclusion of insulin prevented relocalization of Ras-GRF and subsequent neuronal death. Haloperidol-induced dissociation of Ras-GRF leads to inhibition of membrane-bound form of Ras protein and changes downstream regulators activity that results in the initiation of the apoptotic processes via the mitochondrial way. Our results suggest that haloperidol induces neuronal cell death by the interaction with NMDA receptor, but through the alternative from glutamate excitotoxicity signaling pathway.

Action of a novel pyrrolo[1,2-c][1.3]benzodiazepine on the viability of Jurkat and neuronal/glial cells

We have designed and synthesized several structural isomers of anthramycin (heterocycles 2, 3, 5, 6, and 8) and found that, in particular, pyrrolobenzodiazepine 8 induces DNA cleavage and formation of small fragments of DNA. The cytotoxic effects of 8 were manifested with both non-transformed primary neuronal/glial cells and transformed Jurkat cells. The other compounds did not change the viability either of transformed or of non-transformed cells, and induced DNA cleavage to a lesser extent.

Noninvasive assessment of left ventricular contractility by pacemaker stress echocardiography

BACKGROUND

Estimating contractility of the left ventricle with noninvasive techniques is an important yet elusive goal. Positive inotropic interventions are mirrored by smaller end-systolic volumes and higher end-systolic pressures. An increased heart rate progressively increases the force of ventricular contraction (Bowditch treppe or staircase phenomenon).

AIM

To assess the feasibility of a noninvasive estimation of force-frequency relation (FFR) during pacing stress in the echo lab in patients with permanent pacemaker (PM).

METHODS

Transthoracic stress pacing echocardiography was performed in 26 patients with a permanent pacemaker (age 69+/-11 years; 21 men, 5 women). Seven patients had normal function at baseline and during stress ("normals"); eight had angiographically assessed coronary artery disease (three with and five without induced ischemia with stress echo); eleven patients had dilated cardiomyopathy (DC). To build the FFR, the force was determined at different steps as the ratio of the systolic pressure (SP, cuff sphygmomanometer)/end-systolic volume index (ESV, biplane Simpson rule/body surface area). Heart rate was determined from ECG.

RESULTS

The absolute value of the FFR slope was highest in controls and lowest in DC patients. A flat-downsloping FFR was found in 12/19 patients but not for normals (p<0.01).

CONCLUSIONS

Noninvasive pacemaker stress echocardiography (PASE) is a simple and efficient option to assess left ventricular (LV) contractility in patients with permanent pacemaker.