Striatal overexpression of ß-arrestin2 counteracts L-dopa-induced dyskinesia in 6-hydroxydopamine lesioned Parkinson's disease rats.

Prolonged administration of Levodopa (L-dopa) therapy can generate L-dopa-induced dyskinesia (LID). Accumulating evidence indicates that hyper-activation of the dopamine D1 receptor (D1R) and the cAMP signaling cascade in the medium spiny neurons (MSNs) of the striatum are involved in LID. Previous studies have shown that striatal ß-arrestin2 overexpression significantly reduces LID severity and have indicated that ß-arrestin2 may play a causal role in the dyskinesia sensitization process. L-dopa-induced changes in the expression of signaling molecules and other proteins in the striatum were examined immunohistochemically and by western blot. A rAAV (recombinant adeno-associated virus) vector was used to overexpress and ablate ß-arrestin2. We found that striatal overexpression of AAV-mediated ß-arrestin2 produced less severe AIMs (abnormal involuntary movements) in response to L-dopa, whereas selective deletion of ß-arrestin2 in the striatal neurons dramatically enhanced the severity of dyskinesia induced by L-dopa. Furthermore, no significant improvements in motor behavior (FFT: forelimb functional test) were seen with the inhibition or overexpression of ß-arrestin2. Finally, overexpression of ß-arrestin2 diminished L-dopa-induced D1R and phosphor-DARPP32/ERK levels. Viral deletion of ß-arrestin2 markedly enhanced the key biochemical markers in the direct pathway. We found that increased availability of ß-arrestin2 ameliorated dyskinesia severity with no influence on the anti-Parkinsonian action of L-dopa, suggesting a promising approach for controlling LID in Parkinson's disease. In addition, overexpression of ß-Arrestin2 prevented the development of LID by inhibiting G protein-dependent D1R and phosphor-DARPP32/ERK signaling in dyskinetic rats.

Limited AT1 Receptor Internalization Is a Novel Mechanism Underlying Sustained Vasoconstriction Induced by AT1 Receptor Autoantibody From Preeclampsia.

Background Angiotensin II type 1 receptor ( AT 1R) autoantibody ( AT 1- AA ) was first identified as a causative factor in preeclampsia. Unlike physiological ligand angiotensin II (Ang II ), AT 1- AA can induce vasoconstriction in a sustained manner, causing a series of adverse effects, such as vascular injury and poor placental perfusion. However, its underlying mechanisms remain unclear. Here, from the perspective of AT 1R internalization, the present study investigated the molecular mechanism of sustained vasoconstriction induced by AT 1R autoantibody. Methods and Results In the current study, we used the vascular-ring technique to determine that AT 1- AA -positive IgG, which was obtained from the sera of preeclamptic patients, induced long-term vasoconstriction in endothelium-intact or endothelium-denuded rat thoracic arteries. The effect was caused by prolonged activation of AT 1R downstream signals in vascular smooth muscle cells, including Ca2+, protein kinase C, and extracellular signal-regulated kinase 1 and 2. Then, using subcellular protein fractionation, cell surface protein biotinylation, and total internal reflection fluorescence, we found that AT 1- AA -positive IgG resulted in significantly less AT 1R internalization than in the Ang II treatment group. Moreover, through use of fluorescent tracing and bioluminescence resonance energy transfer, we found that AT 1- AA -positive IgG cannot induce the recruitment of ß-arrestin1/2, which mediated receptor internalization. Then, the effect of sustained AT 1R activation induced by AT 1- AA -positive IgG was rescued by overexpression of ß-arrestin2. Conclusions These data suggested that limited AT 1R internalization resulting from the inhibition of ß-arrestin1/2 recruitment played an important role in sustained vasoconstriction induced by AT 1- AA -positive IgG, which may set the stage for avoiding AT 1R overactivation in the management of preeclampsia.

Cardiac chronotropic hypo-responsiveness and atrial fibrosis in rats chronically treated with lithium.

Lithium is a widely used mood-stabilizing agent; however, it causes a variety of cardiovascular side effects including sinus node dysfunction. In this study we explored the potential adverse effects of lithium on cardiac chronotropic responsiveness, atrial tissue histology and gene expression in rats that were chronically treated with therapeutic doses of lithium. Male Wistar albino rats were given lithium chloride (2.5 g/kg) orally for 2 or 3 months. Following treatment, the atria were isolated and spontaneously beating rate and chronotropic responsiveness to ß-adrenergic stimulation was evaluated in an organ bath. Development of cardiac fibrosis was examined by histological methods. The expression of atrial Col1a1 (collagen I, alpha 1) and ß-arrestin2 was also assessed using quantitative RT-PCR. Treatment with lithium induced a significant hypo-responsiveness to adrenergic stimulation (P < 0.001) and caused fibrosis in the atrial tissue of treated rats. In addition, the expression of atrial Col1a1 mRNA was significantly increased in atrial tissues of lithium-treated animals, while ß-arrestin2 mRNA expression did not show a significant difference compared with control animals. Altogether, these findings indicate that cardiac chronotropic hypo responsiveness and associated cardiac fibrosis are side effects of chronic lithium treatment. Moreover, it seems that lithium treatment does not influence ß-arrestin2 mRNA expression.

Omega-3 fatty acids regulate NLRP3 inflammasome activation and prevent behavior deficits after traumatic brain injury.

Omega-3 fatty acids (ω-3 FAs) attenuate inflammation and improve neurological outcome in response to traumatic brain injury (TBI), but the specific anti-inflammatory mechanisms remain to be elucidated. Here we found that NLRP3 inflammasome and subsequent pro-inflammatory cytokines were activated in human brains after TBI. Rats treated with ω-3 FAs had significantly less TBI-induced caspase-1 cleavage and IL-1ß secretion than those with vehicle. G protein-coupled receptor 40 (GPR40) was observed to be involved in this anti-inflammation. GW1100, a GPR40 inhibitor, eliminated the anti-inflammatory effect of ω-3 FAs after TBI. ß-Arrestin-2 (ARRB2), a downstream scaffold protein of GPR40, was activated to inhibit inflammation via directly binding with NLRP3 in the ω-3 FAs treatment group. Interestingly, we also observed that ω-3 FAs prevented NLRP3 mitochondrial localization, which was reversed by GW1100. Furthermore, ω-3 FAs markedly ameliorated neuronal death and behavioral deficits after TBI, while GW1100 significantly suppressed this effect. Collectively, these data indicate that the GPR40-mediated pathway is involved in the inhibitory effects of ω-3 FAs on TBI-induced inflammation and ARRB2 is activated to interact with NLRP3.