Endogenous methyl palmitate modulates nicotinic receptor-mediated transmission in the superior cervical ganglion

Methyl Palmitate Modulated NMDA-Induced Cerebral Hyperemia in Hypertensive Rats

N-methyl-D-aspartate (NMDA) receptors were found to be dysfunctional in hypertensive rats. Methyl palmitate (MP) has been shown to diminish the nicotine-induced increase in blood flow in the brainstem. The aim of this study was to determine how MP modulated NMDA-induced increased regional cerebral blood flow (rCBF) in normotensive (WKY), spontaneously hypertensive (SHR), and renovascular hypertensive (RHR) rats. The increase in rCBF after the topical application of experimental drugs was measured using laser Doppler flowmetry. Topical NMDA application induced an MK-801-sensitive increase in rCBF in anesthetized WKY rats, which was inhibited by MP pretreatments. This inhibition was prevented by pretreatment with chelerythrine (a PKC inhibitor). The NMDA-induced increase in rCBF was also inhibited by the PKC activator in a concentration-dependent manner. Neither MP nor MK-801 affected the increase in rCBF induced by the topical application of acetylcholine or sodium nitroprusside. Topical application of MP to the parietal cortex of SHRs, on the other hand, increased basal rCBF slightly but significantly. MP enhanced the NMDA-induced increase in rCBF in SHRs and RHRs. These results suggested that MP had a dual effect on the modulation of rCBF. MP appears to play a significant physiological role in CBF regulation.

Palmitic acid methyl ester induces cardiac hypertrophy through activating the GPR receptor-mediated changes of intracellular calcium concentrations and mitochondrial functions

Myocardial hypertrophy is associated with a significant increase in intracellular Ca²⁺ , which can be induced by long-chain fatty acid. Palmitic acid methyl ester (PAME), a fatty acid ester released from adipose tissue, superior cervical ganglion, and retina, has been found to have anti-inflammation, antifibrosis, and peripheral vasodilation effects. However, the effects of PAME on cardiomyocytes are still unclear. The aim of this study was to determine whether PAME could disrupt the intracellular Ca²⁺ balance, leading to cardiomyocyte hypertrophy. Neonatal rat cardiomyocytes were treated with various concentrations (10-100 μM) of PAME for 1-4 days. Cytosolic Ca²⁺ and mitochondrial Ca²⁺ concentrations were examined using Fura-2 AM and Rhod-2, respectively. After treatment with PAME for 4 days, mitochondrial Ca²⁺ , an indicator of the state of mitochondrial permeability transition pore (MPTP), and cell death were monitored by flow cytometric analysis. ATP levels were detected using the ATP assay kit. Cardiomyocyte hypertrophy was analyzed by measuring the cardiac hypertrophy biomarker and cell area using quantitative real time-polymerase chain reaction, Western Blot analysis and immunofluorescence analysis. Our results show that PAME concentration- and time-dependently increased cytosolic and mitochondria Ca²⁺ through the mitochondrial calcium uniporter. Moreover, treatment with PAME for 4 days caused MPTP opening, thereby reducing ATP production and enhancing reactive oxygen species (ROS) generation, and finally led to cardiomyocyte hypertrophy. These effects caused by PAME treatment were attenuated by the G-protein coupled receptor 40 (GPR40) inhibitor. In conclusion, PAME impaired mitochondrial function, which in turn led to cardiomyocyte hypertrophy through increasing the mitochondrial Ca²⁺ levels mediated by activating the GPR40 signaling pathway.

Changes in the level of fatty acids in the brain of rats during memory acquisition

Memory acquisition is accompanied by many cellular and molecular processes, and it is not always clear what role they play. Fatty acids (FAs) are known to be important for cognitive functions, but the details of their involvement in memory processes remain unknown. We investigated FAs in the prefrontal cortex and hippocampus of rats trained to perform a task with food reinforcement. The learning consisted of two training sessions, each of which included 10 trials. The results showed that such training altered individual FAs in the brains. The most significant changes were in the prefrontal cortex, where an increase in the level of many FAs occurred, especially after the second training session: palmitic (16:0), stearic (18:0), docosahexaenoic (22:6, n-3), arachidonic (22:4, n-6), docosapentaenoic (22:5, n-6) acids. Changes in the fatty acid level after training in rats were detected only in the left hippocampus, where the levels of palmitic, docosapentaenoic, and docosahexaenoic acids changed. The changes in the right hippocampus were not significant. In both the prefrontal cortex and the left hippocampus, 72 h after training, all FAs returned to control levels. We believe that the main role of a reversible increase in FA levels during memory acquisition is to support and protect cellular processes involved in memory acquisition. Consolidation of memory traces, which occurs mainly in the neocortex, requires protection from external influences, to which FAs makes a significant contribution. They are able to improve neuronal plasticity, enhance local blood flow, improve mitochondrial processes, and suppress pro-inflammatory signals.

Palmitic Acid Methyl Ester Enhances Adipogenic Differentiation in Rat Adipose Tissue-Derived Mesenchymal Stem Cells through a G Protein-Coupled Receptor-Mediated Pathway

Adipogenic differentiation from stem cells has become a research target due to the increasing interest in obesity. It has been indicated that adipocytes can secrete palmitic acid methyl ester (PAME), which is able to regulate stem cell proliferation. However, the effects of PAME on adipogenic differentiation in stem cell remain unclear. Here, we present that the adipogenic differentiation medium supplemented with PAME induced the differentiation of rat adipose tissue-derived mesenchymal stem cells (rAD-MSCs) into adipocyte. rAD-MSCs were treated with PAME for 12 days and then subjected to various analyses. The results from the present study show that PAME significantly increased the levels of adipogenic differentiation markers, PPARγ and Gpd1, and enhanced adipogenic differentiation in rAD-MSCs. Furthermore, the level of GPR40/120 protein increased during induction of adipocyte differentiation in rAD-MSCs. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced adipogenic differentiation. Moreover, PAME significantly increased phosphorylation of extracellular signal-regulated kinases (ERK), but not AKT and mTOR. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced ERK phosphorylation and adipogenic differentiation. PAME also increased the intracellular Ca²⁺ levels. Cotreatment with PAME and a Ca²⁺ chelator or a phospholipase C (PLC) inhibitor prevented the PAME-enhanced ERK phosphorylation and adipogenic differentiation. Our data suggest that PAME activated the GPR40/120/PLC-mediated pathway, which in turn increased the intracellular Ca²⁺ levels, thereby activating the ERK, and eventually enhanced adipogenic differentiation in rAD-MSCs. The findings from the present study might help get insight into the physiological roles and molecular mechanism of PAME in regulating stem cell differentiation.

Protein arginine methyltransferase 8 modulates mitochondrial bioenergetics and neuroinflammation after hypoxic stress

Protein arginine methyltransferases (PRMTs) are a family of enzymes involved in gene regulation and protein/histone modifications. PRMT8 is primarily expressed in the central nervous system, specifically within the cellular membrane and synaptic vesicles. Recently, PRMT8 has been described to play key roles in neuronal signaling such as a regulator of dendritic arborization, synaptic function and maturation, and neuronal differentiation and plasticity. Here, we examined the role of PRMT8 in response to hypoxia-induced stress in brain metabolism. Our results from liquid chromatography mass spectrometry, mitochondrial oxygen consumption rate (OCR), and protein analyses indicate that PRMT8(-/-) knockout mice presented with altered membrane phospholipid composition, decreased mitochondrial stress capacity, and increased neuroinflammatory markers, such as TNF-α and ionized calcium binding adaptor molecule 1 (Iba1, a specific marker for microglia/macrophage activation) after hypoxic stress. Furthermore, adenovirus-based overexpression of PRMT8 reversed the changes in membrane phospholipid composition, mitochondrial stress capacity, and neuroinflammatory markers. Together, our findings establish PRMT8 as an important regulatory component of membrane phospholipid composition, short-term memory function, mitochondrial function, and neuroinflammation in response to hypoxic stress.

Methyl palmitate modulates the nicotine-induced increase in basilar arterial blood flow

Methyl palmitate (MP) is a fatty acid methyl ester. Our recent study indicated that adrenergic nerve-dependent functional sympathetic-sensory nerve interactions were abolished by MP in mesenteric arteries. However, the effect of MP on perivascular nerves and cerebral blood flow remains unclear. In this study, the increase in basilar arterial blood flow (BABF) after the topical application of nicotinic acetylcholine receptor agonists was measured using laser Doppler flowmetry in anesthetized rats. The choline (a selective α7-nicotinic acetylcholine receptor agonist)-induced increase in BABF was abolished by tetrodotoxin (a neurotoxin), N^G -nitro-L-arginine (a nonselective NO synthase inhibitor), α-bungarotoxin (a selective α7-nicotinic acetylcholine receptor inhibitor), and chronic sympathetic denervation. In addition, the nicotine (a nicotinic acetylcholine receptor agonist)-induced increase in BABF was inhibited by MP in a concentration-dependent manner. The acetylcholine-induced increase in BABF was not affected by MP. The myography results revealed that nicotine-induced vasorelaxation was significantly inhibited by MP, but was reversed by chelerythrine (a protein kinase C inhibitor). MP-induced vasodilation was significantly greater in BA rings without endothelium compared to those with endothelium. Meanwhile, MP did not affect baseline BABF. Our results indicate that MP acts as a neuromodulator in the cerebral circulation where it activates the PKC pathway and causes a diminished nicotine-induced increase in blood flow in the brainstem, and that the vasorelaxation effect of MP may play a minor role.

Palmitic acid methyl ester inhibits cardiac arrest-induced neuroinflammation and mitochondrial dysfunction

We previously discovered that palmitic acid methyl ester (PAME) is a potent vasodilator released from the sympathetic ganglion with vasoactive properties. Post-treatment with PAME can enhance cortical cerebral blood flow and functional learning and memory, while inhibiting neuronal cell death in the CA1 region of the hippocampus under pathological conditions (i.e. cerebral ischemia). Since mechanisms underlying PAME-mediated neuroprotection remain unclear, we investigated the possible neuroprotective mechanisms of PAME after 6 min of asphyxial cardiac arrest (ACA, an animal model of global cerebral ischemia). Our results from capillary-based immunoassay (for the detection of proteins) and cytokine array suggest that PAME (0.02 mg/kg) can decrease neuroinflammatory markers, such as ionized calcium binding adaptor molecule 1 (Iba1, a specific marker for microglia/macrophage activation) and inflammatory cytokines after cardiopulmonary resuscitation. Additionally, the mitochondrial oxygen consumption rate (OCR) and respiratory function in the hippocampal slices were restored following ACA (via Seahorse XF24 Extracellular Flux Analyzer) suggesting that PAME can ameliorate mitochondrial dysfunction. Finally, hippocampal protein arginine methyltransferase 1 (PRMT1) and PRMT8 are enhanced in the presence of PAME to suggest a possible pathway of methylated fatty acids to modulate arginine-based enzymatic methylation. Altogether, our findings suggest that PAME can provide neuroprotection in the presence of ACA to alleviate neuroinflammation and ameliorate mitochondrial dysfunction.

Methyl Palmitate-A suitable adjuvant for Sorafenib therapy to reduce in vivo toxicity and to enhance anti-cancer effects on hepatocellular carcinoma cells

This study focused on evaluating the potency of Methyl Palmitate in reducing in vivo toxicity with enhancement of anti-cancer effects of Sorafenib. In vitro anti-cancer effects on human Hep-G2 cell line were analysed by MTT, Trypan blue, clonogenic, wound scratch migration and TUNEL assays. An in vivo study for anti-angiogenesis effect, toxicity and teratogenicity was analysed in Zebrafish embryos. The combination of Sorafenib (4.5 µmol/L) with Methyl Palmitate (3 mmol/L) significantly enhanced anti-cancer effects on Hep-G2 cell line by increasing cytotoxicity (P ≤ .05 in MTT assay; P ≤ .01 in Trypan blue assay), apoptosis (P ≤ .05) and decreasing the metastatic migration (P ≤ .01) than Sorafenib alone treatment. A prominent inhibition of angiogenesis in vivo was observed for combination treatment. At 5 dpf, only <20% toxicity was observed for 3 mmol/L Methyl palmitate while it was 65.75% for Sorafenib treatment which implies that it is a safer dose for in vivo treatments. A highly significant (P ≤ .001) reduction (43.20%) in toxicity was observed in combination treatment. Thus, the Sorafenib-Methyl Palmitate combination showed a promising treatment effect with significantly reduced in vivo toxicity when compared with Sorafenib alone treatment, and hence the Methyl Palmitate may serve as a good adjuvant for Sorafenib therapy.

Stearic acid methyl ester affords neuroprotection and improves functional outcomes after cardiac arrest

Cardiac arrest causes neuronal damage and functional impairments that can result in learning/memory dysfunction after ischemia. We previously identified a saturated fatty acid (stearic acid methyl ester, SAME) that was released from the superior cervical ganglion (sympathetic ganglion). The function of stearic acid methyl ester is currently unknown. Here, we show that SAME can inhibit the detrimental effects of global cerebral ischemia (i.e. cardiac arrest). Treatment with SAME in the presence of asphyxial cardiac arrest (ACA) revived learning and working memory deficits. Similarly, SAME-treated hippocampal slices after oxygen-glucose deprivation inhibited neuronal cell death. Moreover, SAME afforded neuroprotection against ACA in the CA1 region of the hippocampus, reduced ionized calcium-binding adapter molecule 1 expression and inflammatory cytokines/chemokines, with restoration in mitochondria respiration. Altogether, we describe a unique and uncharted role of saturated fatty acids in the brain that may have important implications against cerebral ischemia.

Putative anti-inflammatory, antioxidant, and anti-apoptotic roles of the natural tissue guardian methyl palmitate against isoproterenol-induced myocardial injury in rats

Background

Myocardial injury is considered as a worldwide main cause of morbidity and mortality. The present study aimed to investigate the probable cardioprotective activity of the naturally occurring endogenous fatty acid ester methyl palmitate (MP) against isoproterenol (ISO)-induced myocardial injury in rats and the possible underlying molecular mechanisms. The study was carried out in two consecutive sets of experiments; the first set screened the cardioprotective dose of MP in ISO-intoxicated rats. In the second set, forty male Sprague Dawley rats received either MP (150 mg/kg, p.o) three times/week for 2 weeks and/or 2 consecutive doses of ISO separated by 24 h (85 mg/kg, s.c) on the 13th and 14th days. Different cardiotoxicity and oxidative stress markers were assessed. Furthermore, endothelial nitric oxide synthase (eNOS) levels were determined. For detection of apoptosis, Bax, Bcl-2, and caspase 3 were estimated. To assess inflammation, toll-like receptor 4 (TLR-4) and tumor necrosis factor-alpha (TNF-α) were measured using ELISA. Meanwhile, nuclear factor kappa B (NF-kB) and cyclooxygenase-2 (COX-2) were detected immunohistochemically.

Results

Pretreatment with MP significantly ameliorated the cardiotoxicity and oxidative stress markers. It also markedly elevated eNOS content, decreased apoptotic marker expression, and mitigated TLR-4 activation and other inflammatory markers. Electrocardiography and histopathological examination also confirmed the cardioprotective effect of MP.

Conclusion

The findings of this study indicated that MP possesses a potent cardioprotective activity against ISO-induced myocardial injury through its significant antioxidant, anti-apoptotic, anti-inflammatory, and vasodilatation activities.

Graphical abstract

Protein Arginine Methyltransferases in Cardiovascular and Neuronal Function

The methylation of arginine residues by protein arginine methyltransferases (PRMTs) is a type of post-translational modification which is important for numerous cellular processes, including mRNA splicing, DNA repair, signal transduction, protein interaction, and transport. PRMTs have been extensively associated with various pathologies, including cancer, inflammation, and immunity response. However, the role of PRMTs has not been well described in vascular and neurological function. Aberrant expression of PRMTs can alter its metabolic products, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA). Increased ADMA levels are recognized as an independent risk factor for cardiovascular disease and mortality. Recent studies have provided considerable advances in the development of small-molecule inhibitors of PRMTs to study their function under normal and pathological states. In this review, we aim to elucidate the particular roles of PRMTs in vascular and neuronal function as a potential target for cardiovascular and neurological diseases.

Palmitic Acid Methyl Ester Induces G2/M Arrest in Human Bone Marrow-Derived Mesenchymal Stem Cells via the p53/p21 Pathway

Bone marrow-derived mesenchymal cells (BM-MSCs) are able to differentiate into adipocytes, which can secrete adipokines to affect BM-MSC proliferation and differentiation. Recent evidences indicated that adipocytes can secrete fatty acid metabolites, such as palmitic acid methyl ester (PAME), which is able to cause vasorelaxation and exerts anti-inflammatory effects. However, effects of PAME on BM-MSC proliferation remain unclear. The aim of this study was to investigate the effect of PAME on human BM-MSC (hBM-MSC) proliferation and its underlying molecular mechanisms. hBM-MSCs were treated with PAME for 48 h and then subjected to various analyses. The results from the present study show that PAME significantly reduced the levels of G₂/M phase regulatory proteins, cyclin-dependent kinase 1 (Cdk1), and cyclin B1 and inhibited proliferation in hBM-MSCs. Moreover, the level of Mdm2 protein decreased, while the levels of p21 and p53 protein increased in the PAME-treated hBM-MSCs. However, PAME treatment did not significantly affect apoptosis/necrosis, ROS generation, and the level of Cdc25C protein. PAME also induced intracellular acidosis and increased intracellular Ca²⁺ levels. Cotreatment with PAME and Na⁺/H⁺ exchanger inhibitors together further reduced the intracellular pH but did not affect the PAME-induced decreases of cell proliferation and increases of the cell population at the G₂/M phase. Cotreatment with PAME and a calcium chelator together inhibited the PAME-increased intracellular Ca²⁺ levels but did not affect the PAME-induced cell proliferation inhibition and G₂/M cell cycle arrest. Moreover, the half-life of p53 protein was prolonged in the PAME-treated hBM-MSCs. Taken together, these results suggest that PAME induced p53 stabilization, which in turn increased the levels of p53/p21 proteins and decreased the levels of Cdk1/cyclin B1 proteins, thereby preventing the activation of Cdk1, and eventually caused cell cycle arrest at the G₂/M phase. The findings from the present study might help get insight into the physiological roles of PAME in regulating hBM-MSC proliferation.

Palmitic acid methyl ester is a novel neuroprotective agent against cardiac arrest

We previously discovered that palmitic acid methyl ester (PAME) is a potent vasodilator first identified and released from the superior cervical ganglion and remain understudied. Thus, we investigated PAME's role in modulating cerebral blood flow (CBF) and neuroprotection after 6 min of cardiac arrest (model of global cerebral ischemia). Our results suggest that PAME can enhance CBF under normal physiological conditions, while administration of PAME (0.02 mg/kg) immediately after cardiopulmonary resuscitation can also enhance CBF in vivo. Additionally, functional learning and spatial memory assessments (via T-maze) 3 days after asphyxial cardiac arrest (ACA) suggest that PAME-treated rats have improved learning and memory recovery versus ACA alone. Furthermore, improved neuronal survival in the CA1 region of the hippocampus were observed in PAME-treated, ACA-induced rats. Altogether, our findings suggest that PAME can enhance CBF, alleviate neuronal cell death, and promote functional outcomes in the presence of ACA.

Palmitic Acid Methyl Ester and Its Relation to Control of Tone of Human Visceral Arteries and Rat Aortas by Perivascular Adipose Tissue

Background: Perivascular adipose tissue (PVAT) exerts anti-contractile effects on visceral arteries by release of various perivascular relaxing factors (PVRFs) and opening voltage-gated K⁺ (K_v) channels in vascular smooth muscle cells (VSMCs). Palmitic acid methyl ester (PAME) has been proposed as transferable PVRF in rat aorta. Here, we studied PVAT regulation of arterial tone of human mesenteric arteries and clarified the contribution of K_v channels and PAME in the effects.

Methods: Wire myography was used to measure vasocontractions of mesenteric artery rings from patients undergoing abdominal surgery. Isolated aortic rings from Sprague-Dawley rats were studied for comparison. PVAT was either left intact or removed from the arterial rings. Vasocontractions were induced by external high K⁺ (60 mM), serotonin (5-HT) or phenylephrine. PAME (10 nM−3 μM) was used as vasodilator. K_v channels were blocked by XE991, a K_v7 (KCNQ) channel inhibitor, or by 4-aminopyridine, a non-specific K_v channel inhibitor. PAME was measured in bathing solutions incubated with rat peri-aortic or human visceral adipose tissue.

Results: We found that PVAT displayed anti-contractile effects in both human mesenteric arteries and rat aortas. The anti-contractile effects were inhibited by XE991 (30 μM). PAME (EC₅₀ ~1.4 μM) was capable to produce relaxations of PVAT-removed rat aortas. These effects were abolished by XE991 (30 μM), but not 4-aminopyridine (2 mM) or NDGA (10 μM), a lipoxygenases inhibitor. The cytochrome P450 epoxygenase inhibitor 17-octadecynoic acid (ODYA 10 μM) and the soluble epoxide hydrolase inhibitor 12-(3-adamantan-1-ylureido)-dodecanoic acid (AUDA 10 μM) slightly decreased PAME relaxations. PAME up to 10 μM failed to induce relaxations of PVAT-removed human mesenteric arteries. 5-HT induced endogenous PAME release from rat peri-aortic adipose tissue, but not from human visceral adipose tissue.

Conclusions: Our data also suggest that K_v7 channels are involved in the anti-contractile effects of PVAT on arterial tone in both rat aorta and human mesenteric arteries. PAME could contribute to PVAT relaxations by activating K_v7 channels in rat aorta, but not in human mesenteric arteries.

Cerebral ischemia and neuroregeneration

Cerebral ischemia is one of the leading causes of morbidity and mortality worldwide. Although stroke (a form of cerebral ischemia)-related costs are expected to reach 240.67 billion dollars by 2030, options for treatment against cerebral ischemia/stroke are limited. All therapies except anti-thrombolytics (i.e., tissue plasminogen activator) and hypothermia have failed to reduce neuronal injury, neurological deficits, and mortality rates following cerebral ischemia, which suggests that development of novel therapies against stroke/cerebral ischemia are urgently needed. Here, we discuss the possible mechanism(s) underlying cerebral ischemia-induced brain injury, as well as current and future novel therapies (i.e., growth factors, nicotinamide adenine dinucleotide, melatonin, resveratrol, protein kinase C isozymes, pifithrin, hypothermia, fatty acids, sympathoplegic drugs, and stem cells) as it relates to cerebral ischemia.

Interruption of perivascular sympathetic nerves of cerebral arteries offers neuroprotection against ischemia

Sympathetic nervous system activity is increased after cardiopulmonary arrest, resulting in vasoconstrictor release from the perivascular sympathetic nerves of cerebral arteries. However, the pathophysiological function of the perivascular sympathetic nerves in the ischemic brain remains unclear. A rat model of global cerebral ischemia (asphyxial cardiac arrest, ACA) was used to investigate perivascular sympathetic nerves of cerebral arteries via bilateral decentralization (preganglionic lesion) of the superior cervical ganglion (SCG). Decentralization of the SCG 5 days before ACA alleviated hypoperfusion and afforded hippocampal neuroprotection and improved functional outcomes. These studies can provide further insights into the functional mechanism(s) of the sympathetic nervous system during ischemia.

NEW & NOTEWORTHY

Interruption of the perivascular sympathetic nerves can alleviate CA-induced hypoperfusion and neuronal cell death in the CA1 region of the hippocampus to enhance functional learning and memory.

Sundew plant, a potential source of anti-inflammatory agents, selectively induces G2/M arrest and apoptosis in MCF-7 cells through upregulation of p53 and Bax/Bcl-2 ratio

The worldwide cancer incidences are remarkable despite the advancement in cancer drug discovery field, highlighting the need for new therapies focusing on cancer cell and its microenvironment, including inflammation. Several species of Drosera (family: Droseraceae) are used in various traditional as well as homeopathic systems of medicine. Drosera burmannii Vahl. is also enlisted in French Pharmacopoeia in 1965 for the treatment of inflammatory diseases, including chronic bronchitis, asthma and whooping cough. The present study is designed to substantiate the potential of D. burmannii in in vitro anticancer activity and its relation with anti-inflammatory property. In vitro anticancer study revealed that DBME is inhibiting the proliferation of MCF-7 cells without affecting the viability of other malignant and non-malignant cells. DBME induced G2/M phase arrest and apoptosis in MCF-7 cells by suppressing the expression of cyclin A1, cyclin B1 and Cdk-1 and increasing the expression of p53, Bax/Bcl-2 ratio leading to activation of caspases and PARP degradation. Presence of caspase-8 (Z-IETD-fmk) and caspase-9 (Z-LEHD-fmk) inhibitors alone did prevent the apoptosis partially while apoptosis prevention was significantly observed when used in combination, suggesting vital role of caspases in DBME-induced apoptosis in MCF-7 cells. DBME also downregulated LPS-induced increased expression of iNOS, COX-2 and TNF-α along with suppression on intracellular ROS production that confirms the potential of DBME as anti-inflammatory extract. GCMS analysis revealed the presence of four major compounds hexadecanoic acid, tetradecanoic acid, hexadecen-1-ol, trans-9 and 1-tetradecanol along with some other fatty acid derivatives and carotenoids (Beta-doradecin) in DBME. These findings confirmed the anti-inflammatory activity of DBME, which is already listed in French Pharmacopeia in 1965. Here we have additionally reported the anti-breast cancer activity of DBME and its relation to the anti-inflammatory potential. Hence, an ethnopharmacological approach can be considered as useful tool for the discovery of new drug leads.

Beneficial effects of calcitriol on hypertension, glucose intolerance, impairment of endothelium-dependent vascular relaxation, and visceral adiposity in fructose-fed hypertensive rats

Besides regulating calcium homeostasis, the effects of vitamin D on vascular tone and metabolic disturbances remain scarce in the literature despite an increase intake with high-fructose corn syrup worldwide. We investigated the effects of calcitriol, an active form of vitamin D, on vascular relaxation, glucose tolerance, and visceral fat pads in fructose-fed rats. Male Wistar-Kyoto rats were divided into 4 groups (n = 6 per group). Group Con: standard chow diet for 8 weeks; Group Fru: high-fructose diet (60% fructose) for 8 weeks; Group Fru-HVD: high-fructose diet as Group Fru, high-dose calcitriol treatment (20 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding; and Group Fru-LVD: high-fructose diet as Group Fru, low-dose calcitriol treatment (10 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding. Systolic blood pressure was measured twice a week by the tail-cuff method. Blood was examined for serum ionized calcium, phosphate, creatinine, glucose, triglycerides, and total cholesterol. Intra-peritoneal glucose intolerance test, aortic vascular reactivity, the weight of visceral fat pads, adipose size, and adipose angiotensin II levels were analyzed at the end of the study. The results showed that the fructose-fed rats significantly developed hypertension, impaired glucose tolerance, heavier weight and larger adipose size of visceral fat pads, and raised adipose angiotensin II expressions compared with the control rats. High- and low-dose calcitriol reduced modestly systolic blood pressure, increased endothelium-dependent aortic relaxation, ameliorated glucose intolerance, reduced the weight and adipose size of visceral fat pads, and lowered adipose angiotensin II expressions in the fructose-fed rats. However, high-dose calcitriol treatment mildly increased serum ionized calcium levels (1.44 ± 0.05 mmol/L). These results suggest a protective role of calcitriol treatment on endothelial function, glucose tolerance, and visceral adiposity in fructose-fed rats.

L-type calcium channels in sympathetic α3β2-nAChR-mediated cerebral nitrergic neurogenic vasodilation

AIM

Nicotine stimulation of α3β2-nicotinic acetylcholine receptors (α3β2-nAChRs) located on sympathetic nerves innervating basilar arteries causes calcium-dependent noradrenaline release, leading to activation of parasympathetic nitrergic nerves and dilation of basilar arteries. This study aimed to investigate the major subtype of calcium channels located on cerebral peri-vascular sympathetic nerves, which is involved in nicotine-induced α3β2-nAChR-mediated nitrergic vasodilation in basilar arteries.

METHODS

Nicotine- and transmural nerve stimulation (TNS)-induced dilation of isolated porcine basilar arteries was examined using in vitro tissue bath. Nicotine-induced calcium influx, nicotine-induced noradrenaline release and nicotine-induced inward currents were evaluated in rat superior cervical ganglion (SCG) neurones, peri-vascular sympathetic nerves of porcine basilar arteries and α3β2-nAChRs-expressing oocytes respectively. mRNA and protein expression of Cav 1.2 and Cav 1.3 channels were detected by RT-PCR, Western blotting and immunohistochemistry.

RESULTS

Nicotine-induced vasodilation was not affected by ω-agatoxin TK (selective P/Q-type calcium channel blocker) or ω-conotoxin GVIA (N-type calcium channel blocker). The vasodilation, however, was inhibited by nicardipine (L-type calcium channel blocker) in concentrations which did not affect TNS-induced vasodilation, suggesting the specific blockade. Nicardipine concentration-dependently inhibited nicotine-induced calcium influx in rat SCG neurones and reduced nicotine-induced noradrenaline release from peri-vascular sympathetic nerves of porcine basilar arteries. Nicardipine (10 μm), which significantly blocked nicotine-induced vasorelaxation by 70%, did not appreciably affect nicotine-induced inward currents in α3β2-nAChRs-expressing oocytes. Furthermore, the mRNAs and proteins of Cav 1.2 and Cav 1.3 channels were expressed in porcine SCG and peri-vascular nerve terminals.

CONCLUSION

The sympathetic neuronal calcium influx through L-type calcium channels is modulated by α3β2-nAChRs. This calcium influx causes noradrenaline release, initiating sympathetic-parasympathetic (axo-axonal) interaction-induced nitrergic dilation of porcine basilar arteries.

Fatty acid methyl esters and Solutol HS 15 confer neuroprotection after focal and global cerebral ischemia

We previously showed that palmitic acid methyl ester (PAME) and stearic acid methyl ester (SAME) are simultaneously released from the sympathetic ganglion and PAME possesses potent vasodilatory properties which may be important in cerebral ischemia. Since PAME is a potent vasodilator simultaneously released with SAME, our hypothesis was that PAME/SAME confers neuroprotection in rat models of focal/global cerebral ischemia. We also examined the neuroprotective properties of Solutol HS15, a clinically approved excipient because it possesses similar fatty acid compositions as PAME/SAME. Asphyxial cardiac arrest (ACA, 6 min) was performed 30 min after PAME/SAME treatment (0.02 mg/kg, IV). Solutol HS15 (2 ml/kg, IP) was injected chronically for 14 days (once daily). Histopathology of hippocampal CA1 neurons was assessed 7 days after ACA. For focal ischemia experiments, PAME, SAME, or Solutol HS15 was administered following reperfusion after 2 h of middle cerebral artery occlusion (MCAO). 2,3,5-Triphenyltetrazolium staining of the brain was performed 24 h after MCAO and the infarct volume was quantified. Following ACA, the number of surviving hippocampal neurons was enhanced by PAME-treated (68%), SAME-treated (69%), and Solutol-treated HS15 (68%) rats as compared to ACA only-treated groups. Infarct volume was decreased by PAME (83%), SAME (68%), and Solutol HS15 (78%) as compared to saline (vehicle) in MCAO-treated animals. PAME, SAME, and Solutol HS15 provide robust neuroprotection in both paradigms of ischemia. This may prove therapeutically beneficial since Solutol HS15 is already administered as a solublizing agent to patients. With proper timing and dosage, administration of Solutol HS15 and PAME/SAME can be an effective therapy against cerebral ischemia.

Direct renin inhibitor prevents and ameliorates insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats

Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers can improve insulin resistance and vascular dysfunction in insulin-resistant rats; however, there are few reports on the effects of direct renin inhibitors on these conditions. We investigated the effects of a direct renin inhibitor, aliskiren, on insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats. Male Wistar-Kyoto rats were divided into four groups (n=6 per group) and studied for 8 weeks: Group Con: standard chow diet; group Fru: high-fructose diet (60% fructose); Group FruA: high-fructose diet with concurrent aliskiren treatment (100 mg kg(-1) per day); and Group FruB: high-fructose diet with subsequent aliskiren treatment 4 weeks later. Blood was collected for biochemical assays, and isolated rings of the thoracic aorta were obtained for analysis of vascular reactivity, vascular structure and lipid peroxide. Rats fed with high-fructose diets developed significant systolic hypertension, decreased plasma nitrite (NO(2); nitric oxide metabolite) levels and increased plasma glucose, insulin, triglyceride, total cholesterol and aortic lipid peroxide levels, and aortic wall thickness compared with control rats. Aliskiren treatment, either concurrent or subsequent, elevated plasma NO(2) levels and reduced systolic hypertension, insulin resistance, dyslipidemia, aortic lipid peroxide levels and aortic wall hypertrophy in FHR. The peak endothelium-dependent aortic relaxations were significantly higher in rats that received aliskiren treatment than in those that did not. In conclusion, our findings suggest that aliskiren prevents and ameliorates insulin resistance, aortic endothelial dysfunction and oxidative vascular remodeling in fructose-fed hypertensive rats.

Memantine inhibits α3β2-nAChRs-mediated nitrergic neurogenic vasodilation in porcine basilar arteries

Memantine, an NMDA receptor antagonist used for treatment of Alzheimer’s disease (AD), is known to block the nicotinic acetylcholine receptors (nAChRs) in the central nervous system (CNS). In the present study, we examined by wire myography if memantine inhibited α3β2-nAChRs located on cerebral perivascular sympathetic nerve terminals originating in the superior cervical ganglion (SCG), thus, leading to inhibition of nicotine-induced nitrergic neurogenic dilation of isolated porcine basilar arteries. Memantine concentration-dependently blocked nicotine-induced neurogenic dilation of endothelium-denuded basilar arteries without affecting that induced by transmural nerve stimulation, sodium nitroprusside, or isoproterenol. Furthermore, memantine significantly inhibited nicotine-elicited inward currents in Xenopous oocytes expressing α3β2-, α7- or α4β2-nAChR, and nicotine-induced calcium influx in cultured rat SCG neurons. These results suggest that memantine is a non-specific antagonist for nAChR. By directly inhibiting α3β2-nAChRs located on the sympathetic nerve terminals, memantine blocks nicotine-induced neurogenic vasodilation of the porcine basilar arteries. This effect of memantine is expected to reduce the blood supply to the brain stem and possibly other brain regions, thus, decreasing its clinical efficacy in the treatment of Alzheimer’s disease.

Differential effects of delta and epsilon protein kinase C in modulation of postischemic cerebral blood flow

Cerebral ischemia causes cerebral blood flow (CBF) derangements resulting in neuronal damage by enhanced protein kinase C delta (δPKC) levels leading to hippocampal and cortical neuronal death after ischemia. Contrarily, activation of εPKC mediates ischemic tolerance by decreasing vascular tone providing neuroprotection. However, whether part of this protection is due to the role of differential isozymes of PKCs on CBF following cerebral ischemia remains poorly understood. Rats pretreated with a δPKC specific inhibitor (δV1-1, 0.5 mg/kg) exhibited attenuation of hyperemia and latent hypoperfusion characterized by vasoconstriction followed by vasodilation of microvessels after two-vessel occlusion plus hypotension. In an asphyxial cardiac arrest (ACA) model, rats treated with δ V1-1 (pre- and postischemia) exhibited improved perfusion after 24 h and less hippocampal CA1 and cortical neuronal death 7 days after ACA. On the contrary, εPKC-selective peptide activator, conferred neuroprotection in the CA1 region of the rat hippocampus 30 min before induction of global cerebral ischemia and decreased regional CBF during the reperfusion phase. These opposing effects of δ v. εPKC suggest a possible therapeutic potential by modulating CBF preventing neuronal damage after cerebral ischemia.

Role of perivascular adipose tissue-derived methyl palmitate in vascular tone regulation and pathogenesis of hypertension

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 μmol/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+ 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.