Role of hypothalamic-pituitary adrenal-axis, toll-like receptors, and macrophage polarization in pre-atherosclerotic changes induced by social isolation stress in mice.

It has been well documented that chronic stress can induce atherosclerotic changes, however, the underlying mechanisms is yet to be established. In this regard, this study aimed to elucidate the relation between hypothalamic-pituitary adrenal-axis (HPA-axis), toll-like receptors (TLRs), as well as M1/M2 macrophage ratio and pre-atherosclerotic changes in social isolation stress (SIS) in mice. We used small interfering RNA against the glucocorticoid receptor (GR) to evaluate the relation between HPA-axis and TLRs. C57BL/6J mice were subjected to SIS and RT-PCR, ELISA, flow cytometry, and immunohistochemistry were used to assess the relations between pre-atherosclerotic changes and TLRs, macrophage polarization, pro-inflammatory cytokines, and cell adhesion molecules in aortic tissue. We used TAK-242 (0.3 mg/kg, intraperitoneally), a selective antagonist of TLR4, as a possible prophylactic treatment for atherosclerotic changes induced by SIS. We observed that isolated animals had higher serum concentration of corticosterone and higher body weight in comparison to normal animals. In isolated animals, results of in vitro study showed that knocking-down of the GR in bone marrow-derived monocytes significantly decreased the expression of TLR4. In vivo study suggested higher expression of TLR4 on circulating monocytes and higher M1/M2 ratio in aortic samples. Pathological study showed a mild pre-atherosclerotic change in isolated animals. Finally, we observed that treating animals with TAK-242 could significantly inhibit the pre-atherosclerotic changes. SIS can possibly increase the risk of atherosclerosis through inducing abnormal HPA-axis activity and subsequently lead to TLR4 up-regulation, vascular inflammation, high M1/M2 ratio in intima. Thus, TLR4 inhibitors might be a novel treatment to decrease the risk of atherosclerosis induced by chronic stress.

The possible role of nitric oxide in anti-convulsant effects of Naltrindole in seizure-induced by social isolation stress in male mice.

Social isolation stress (SIS) as a chronic model of early-life stress could induce proconvulsant effects in mice. In the current study, we evaluated the role of opioid receptors (OPRs) agonists and antagonists in pro-conversant effects of SIS and the common pathway between delta-opioid receptors (DORs) and nitric oxide (NO) in stress-induced seizure. For reaching to this goal, we used pentylenetetrazol (PTZ) model of clonic-seizure to measure seizure threshold and administrated selective and non-selective OPRs agonists and antagonists in both social condition (SC) and isolated condition (IC) animals. In the next step, we administrated sub effective dose of naltrindole (NLT, 0.3 mg/kg) with sub-effective doses of nitric oxide synthesis (NOS) inhibitors including L-NAME (10 mg/kg), aminoguanidine (50 mg/kg) and 7-NI (15 mg/kg). Also, we co-administrated sub-effective dose of SNC80 (0.5 mg/kg) with sub-effective dose of l-arg (25 mg/kg) to assess the seizure threshold. In addition, we measured nitrite levels of hippocampus following administration of mentioned drugs in both SC and IC mice. Our findings showed that L-NAME and 7-NI (but not AG) increased anti-convulsant activity of NLT and l-arg increased proconvulsant effects of SNC80 in IC animals. Nitrite assay showed that co-administration of NLT plus sub-effective doses of L-NAME and 7-NI (but not AG) decreased and co-administration of SNC80 with sub-effective dose of l-arg increased nitrite levels of hippocampus in IC mice. This study suggests the role of n-NOS in anti-convulsant effects of NLT and pro-convulsant effects of SNC80 in stress-induced seizure.

Protective effect of minocycline on LPS-induced mitochondrial dysfunction and decreased seizure threshold through nitric oxide pathway.

Lipopolysaccharide (LPS) increases inflammatory cytokines of the brain and deregulates the mitochondrial function, thus could increase the seizure susceptibility. Studies have shown that minocycline has neuroprotective and antioxidant properties. In this study, we aimed to evaluate the anticonvulsant properties of minocycline in LPS-treated animals and the possible involvement of nitric oxide and mitochondrial pathways. In a PTZ model of seizure in mice, minocycline was administrated to LPS-treated mice. Then followed by co-injection of its sub-effective dose and NOS inhibitors including 7-Nitroindazole (7-NI), aminoguanidine (AG) and L-NG-Nitroarginine methyl ester (L-NAME) to evaluate the changes in seizure threshold and the possible involvement of nitrergic system. Molecular assessments were used to evaluate the effects of each treatment on inflammation and mitochondrial function in the brain. LPS-treated animals had lower seizure threshold compared to intact animals; injection of minocycline (80 mg/kg) to LPS-treated mice reversed this effect. Co-injection of sub-effective doses of minocycline (40 mg/kg) and L-NAME to LPS-treated animals significantly increased seizure threshold. We observed that co-treatment of minocycline and AG dissimilar to 7-NI could increase the seizure threshold of LPS-treated animals. L-arginine reversed the anticonvulsant effect of minocycline. Also, molecular evaluations showed that LPS could increase the ATP levels, GSH levels, and reactive oxygen species formation. However, minocycline at both doses significantly reversed the effect of LPS. Minocycline counteracts the proconvulsant effects of LPS through regulating of mitochondrial function and decreasing of neuro-inflammation. Also, co-administration of minocycline and i-NOS inhibitors could intensify anticonvulsant effects of minocycline.