Background-Perivascular adipose tissue (PVAT)-derived relaxing factor (PVATRF) significantly regulates vascular tone. Its chemical nature remains unknown. We determined whether palmitic acid methyl ester (PAME) was the PVATRF and whether its release and/or vasorelaxing activity decreased in hypertension. Methods and Results-Using superfusion bioassay cascade technique, tissue bath myography, and gas chromatography/mass spectrometry, we determined PVATRF and PAME release from aortic PVAT preparations of Wistar Kyoto rats and spontaneously hypertensive rats. The PVAT of Wistar Kyoto rats spontaneously and calcium dependently released PVATRF and PAME. Both induced aortic vasorelaxations, which were inhibited by 4-aminopyridine (2 mmol/L) and tetraethylammonium 5 and 10 mmol/L but were not affected by tetraethylammonium 1 or 3 mmol/L, glibenclamide (3 mol/L), or iberiotoxin (100 nmol/L). Aortic vasorelaxations induced by PVATRF-and PAME-containing Krebs solutions were not affected after heating at 70°C but were equally attenuated after hexane extractions. Culture mediums of differentiated adipocytes, but not those of fibroblasts, contained significant PAME and caused aortic vasorelaxation. The PVAT of spontaneously hypertensive rats released significantly less PVATRF and PAME with an increased release of angiotensin II. In addition, PAME-induced relaxation of spontaneously hypertensive rats aortic smooth muscle diminished drastically, which was ameliorated significantly by losartan. Conclusions-We found that PAME is the PVATRF, causing vasorelaxation by opening voltage-dependent K ϩ channels on smooth muscle cells. Diminished PAME release and its vasorelaxing activity and increased release of angiotensin II in the PVAT suggest a noble role of PVAT in pathogenesis of hypertension. The antihypertensive effect of losartan is attributed partly to its reversing diminished PAME-induced vasorelaxation. (Circulation. 2011;124:1160-1171.) Key Words: angiotensin II Ⅲ fatty acids Ⅲ hypertension Ⅲ potassium ion channels Ⅲ vasomotor tone Ⅲ vasorelaxation Ⅲ losartan T he systemic blood vessels are surrounded by various amounts of perivascular adipose tissue (PVAT). Since the first report by Soltis and Cassis in 1991 that PVAT attenuated contraction of aortic rings to norepinephrine, 1 it has been well accepted that the anticontractile effect of PVAT is due to release of relaxing factor(s) from these adipocytes. 2 The vasodilation induced by PVAT-derived relaxing factor (PVATRF) is independent of the endothelium, cyclooxygenase, or cytochrome P450 pathway. 2,3 The general consensus is that PVATRFinduced vasodilation is due to opening of potassium channels on the smooth muscle cells. [2][3][4][5] The chemical identity of the PVATRF, however, remains unknown. Clinical Perspective on p 1171Our recent studies using superfusion bioassay cascade technique have demonstrated release of an endogenous potent vasodilator, palmitic acid methyl ester (PAME), from the superior cervical ganglion and retina of the rat. 6,7 Because PAME is hydro...

An inflammatory response in the central nervous system mediated by activation of microglia is a key event in the early stages of the development of neurodegenerative diseases. Silymarin is a polyphenolic flavanoid derived from milk thistle that has anti-inflammatory, cytoprotective and anticarcinogenic effects. In this study, we first investigated the neuroprotective effect of silymarin against lipopolysaccharide (LPS)-induced neurotoxicity in mesencephalic mixed neuron-glia cultures. The results showed that silymarin significantly inhibited the LPS-induced activation of microglia and the production of inflammatory mediators, such as tumour necrosis factor-alpha and nitric oxide (NO), and reduced the damage to dopaminergic neurons. Therefore, the inhibitory mechanisms of silymarin on microglia activation were studied further. The production of inducible nitric oxide synthase (iNOS) was studied in LPS-stimulated BV-2 cells as a model of microglia activation. Silymarin significantly reduced the LPS-induced nitrite, iNOS mRNA and protein levels in a dose-dependent manner. Moreover, LPS could induce the activation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase but not extracellular signal-regulated kinase. The LPS-induced production of NO was inhibited by the selective p38 MAPK inhibitor SB203580. These results indicated that the p38 MAPK signalling pathway was involved in the LPS-induced NO production. However, the activation of p38 MAPK was not inhibited by silymarin. Nevertheless, silymarin could effectively reduce LPS-induced superoxide generation and nuclear factor kappaB (NF-kappaB) activation. It suggests that the inhibitory effect of silymarin on microglia activation is mediated through the inhibition of NF-kappaB activation.

Abstract:Because of the well-documented importance of glutamate clearance by astrocytes in protecting neurons against excitotoxicity, it was interesting to examine whether L-glutamate exerts a toxic action on cultured astrocytes. Cell damage was evaluated by measuring activity of lactate dehydrogenase (LDH) released into the culture medium. Exposure of astrocyte cultures of the neonatal rat cerebral cortex to L-glutamate resulted in a concentration-and time-dependent increase in the release of LDH. L-Glutamate-induced gliotoxicity appeared to be mediated predominantly by the increase of oxidative stress because the reduced glutathione content and its effects were almost completely blocked by vitamin E and pyrrolidinedithiocarbamate. To support this notion further, the supplementation or depletion of intracellular reduced glutathione content attenuated or worsened Lglutamate toxicity, respectively. Activation of the glutamate transporter mimicked the action of L-glutamate on astrocytes. In addition, degrees of cell damage were not directly correlated to the levels of glutamate uptake. Moreover, the mechanism of this toxicity required energy and macromolecular synthesis. Taken together, brief exposure to L-glutamate resulted in glutamate uptake and cell swelling, whereas sustained exposure injured astrocytes via oxidative stress instead of the excitatory mechanism.

Attempts were made to: (1) define the regions of origin of the ansa lenticularis (AL) and the lenticular fasciculus (LF), and (2) determine if particular regions of the medial pallidal segment (MPS) project in an organized fashion to thalamic nuclei. The MPS was divided into rostral and caudal (by a plane through the LF), dorsal and ventral (by an appropriate plane), and medial and lateral (by the accessory medullary lamina) parts. Attempts were made to categorize various lesions of the MPS and degeneration was studied in transverse, sagittal and horizontal sections stained by the Nauta and Wiitanen technics. Corresponding Nissl-stained sections were used to delineate thalamic nuclei.Localized lesions in portions of the MPS (11 rostral and 10 caudal) were worthy of anatomical analysis in 21 monkeys. Data support the thesis that fibers of the AL arise predominantly from the outer part of the MPS and pass ventrally and medially through portions of the inner part of the MPS to their site of emergence. Fibers of the LF appear to arise from the inner part of the MPS and project dorsomedially through the internal capsule.Pallidothalamic projections to the rostral ventral tier thalamic nuclei [the ventral anterior (VApc) and the ventral lateral (VLo)] appear topographically organized in three cardinal dimensions. Rostral parts of the MPS project predominantly to parts of VApc, while caudal parts of the MPS project primarily to parts of VLo. There also is a dorsoventral and mediolateral correspondence in the pallidal projection to VApc and VLo which exhibits overlap. Pallidothalamic projections to the centromedian nucleus (CM) terminate preponderantly in rostral and medial regions of the nucleus, and there appears to be a definite correspondence between parts of the MPS and parts of CM, only in the dorsoventral dimension.