Peroxisome proliferator-activated receptor-γ activation reduces cyclooxygenase-2 expression in vascular smooth muscle cells from hypertensive rats by interfering with oxidative stress

Ginger protects against vein graft remodeling by precisely modulating ferroptotic stress in vascular smooth muscle cell dedifferentiation

Vein graft (VG) failure (VGF) is associated with VG intimal hyperplasia, which is characterized by abnormal accumulation of vascular smooth muscle cells (VSMCs). Most neointimal VSMCs are derived from pre-existing VSMCs via a process of VSMC phenotypic transition, also known as dedifferentiation. There is increasing evidence to suggest that ginger or its bioactive ingredients may block VSMC dedifferentiation, exerting vasoprotective functions; however, the precise mechanisms have not been fully characterized. Therefore, we investigated the effect of ginger on VSMC phenotypic transition in VG remodeling after transplantation. Ginger significantly inhibited neointimal hyperplasia and promoted lumen (L) opening in a 3-month VG, which was primarily achieved by reducing ferroptotic stress. Ferroptotic stress is a pro-ferroptotic state. Contractile VSMCs did not die but instead gained a proliferative capacity and switched to the secretory type, forming neointima (NI) after vein transplantation. Ginger and its two main vasoprotective ingredients (6-gingerol and 6-shogaol) inhibit VSMC dedifferentiation by reducing ferroptotic stress. Network pharmacology analysis revealed that 6-gingerol inhibits ferroptotic stress by targeting P53, while 6-shogaol inhibits ferroptotic stress by targeting 5-lipoxygenase (Alox5), both promoting ferroptosis. Furthermore, both ingredients co-target peroxisome proliferator-activated receptor gamma (PPARγ), decreasing PPARγ-mediated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1 (Nox1) expression. Nox1 promotes intracellular reactive oxygen species (ROS) production and directly induces VSMC dedifferentiation. In addition, Nox1 is a ferroptosis-promoting gene that encourages ferroptotic stress production, indirectly leading to VSMC dedifferentiation. Ginger, a natural multi-targeted ferroptotic stress inhibitor, finely and effectively prevents VSMC phenotypic transition and protects against venous injury remodeling.

Effect of sacubitril/valsartan on the hypertensive heart in continuous light-induced and lactacystin-induced pre-hypertension: Interactions with the renin-angiotensin-aldosterone system

This study investigated whether sacubitril/valsartan or valsartan are able to prevent left ventricular (LV) fibrotic remodelling and dysfunction in two experimental models of pre-hypertension induced by continuous light (24 hours/day) exposure or by chronic lactacystin treatment, and how this potential protection interferes with the renin-angiotensin-aldosterone system (RAAS). Nine groups of three-month-old male Wistar rats were treated for six weeks as follows: untreated controls (C), sacubitril/valsartan (ARNI), valsartan (Val), continuous light (24), continuous light plus sacubitril/valsartan (24+ARNI) or valsartan (24+Val), lactacystin (Lact), lactacystin plus sacubitil/valsartan (Lact+ARNI) or plus valsartan (Lact+Val). Both the 24 and Lact groups developed a mild but significant systolic blood pressure (SBP) increase, LV hypertrophy and fibrosis, as well as LV systolic and diastolic dysfunction. Yet, no changes in serum renin-angiotensin were observed either in the 24 or Lact groups, though aldosterone was increased in the Lact group compared to the controls. In both models, sacubitril/valsartan and valsartan reduced elevated SBP, LV hypertrophy and fibrosis and attenuated LV systolic and diastolic dysfunction. Sacubitril/valsartan and valsartan increased the serum levels of angiotensin (Ang) II, Ang III, Ang IV, Ang 1-5, Ang 1-7 in the 24 and Lact groups and reduced aldosterone in the Lact group. We conclude that both continuous light exposure and lactacystin treatment induced normal-to-low serum renin-angiotensin models of pre-hypertension, whereas aldosterone was increased in lactacystin-induced pre-hypertension. The protection by ARNI or valsartan in the hypertensive heart in either model was related to the Ang II blockade and the protective Ang 1-7, while in lactacystin-induced pre-hypertension this protection seems to be additionally related to the reduced aldosterone level.

The Melatonin Derivative ITH13001 Prevents Hypertension and Cardiovascular Alterations in Angiotensin II-Infused Mice

Inflammatory mechanisms and oxidative stress seem to contribute to the pathogenesis of hypertension. ITH13001 is a melatonin-phenyl-acrylate hybrid that moderately induces the antioxidant transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) and has a potent oxidant scavenging effect compared with other derivatives of its family. Here we investigated the effect of ITH13001 on hypertension and the associated cardiovascular alterations. Angiotensin II (AngII)-infused mice were treated with ITH13001 (1 mg/kg per day, i.p.) for 2 weeks. The ITH13001 treatment prevented: 1) the development of hypertension, cardiac hypertrophy, and increased collagen and B-type natriuretic peptide (Bnp) expression in the heart; 2) the reduction of elasticity, incremental distensibility, fenestrae area, intraluminal diameter, and endothelial cell number in mesenteric resistance arteries (MRA); 3) the endothelial dysfunction in aorta and MRA; 4) the plasma and cardiovascular oxidative stress and the reduced aortic nitric oxide (NO) bioavailability; 5) the increased cardiac levels of the cytokines interleukin (IL)-1β, IL-6, and C-C motif chemokine ligand 2 (Ccl2), the T cell marker cluster of differentiation 3 (Cd3), the inflammasome NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3), the proinflammatory enzymes inducible nitric oxide synthase (iNOS) and COX-2, the toll-like receptor 4 (TLR4) adapter protein myeloid differentiation primary response 88 (MyD88), and the nuclear factor kappa B (NF-κB) subunit p65; 6) the greater aortic expression of the cytokines tumor necrosis factor alpha (Tnf-α), Ccl2 and IL-6, Cd3, iNOS, MyD88, and NLRP3. Although ITH13001 increased nuclear Nrf2 levels and heme oxygenase 1 (HO-1) expression in vascular smooth muscle cells, both cardiac and vascular Nrf2, Ho-1, and NADPH quinone dehydrogenase 1 (Nqo1) levels remained unmodified irrespective of AngII infusion. Summarizing, ITH13001 improved hypertension-associated cardiovascular alterations independently of Nrf2 pathway activation, likely due to its direct antioxidant and anti-inflammatory properties. Therefore, ITH13001 could be a useful therapeutic strategy in patients with resistant hypertension. SIGNIFICANCE STATEMENT: Despite the existing therapeutic arsenal, only half of the patients treated for hypertension have adequately controlled blood pressure; therefore, the search for new compounds to control this pathology and the associated damage to end-target organs (cerebral, cardiac, vascular, renal) is of particular interest. The present study demonstrates that a new melatonin derivative, ITH13001, prevents hypertension development and the associated cardiovascular alterations due to its antioxidant and anti-inflammatory properties, making this compound a potential candidate for treatment of resistant hypertensive patients.

Identification of an inhibitor for atherosclerotic enzyme NOX-1 to inhibit ROS production

Background

NOX-1 overexpression has been observed in various studies, persons with diabetes or cardiovascular conditions. NOX-1 orchestrates the disease pathogenesis of various cardiovascular conditions such as atherosclerotic plaque development and is a very crucial biomarker. Therefore, this study was carried out to deduce the three-dimensional modelled structure of NOX-1 using DeepMind AlphaFold-2 to find meaningful insight into the structural biology. Extensive in silico approaches have been used to determine the active pocket, virtually screen large chemical space to identify potential inhibitors. The role of the key amino acid residues was also deduced using alanine scanning mutagenesis contributing to the catalytic process and to the overall stability of NOX-1.

Results

The modelled structure of NOX-1 protein was validated using ERRAT. The ERRAT statistics with 9 amino acids sliding window have shown a confidence score of 96.937%. According to the Ramachandran statistics, 96.60% of the residues lie within the most favoured region, and 2.80% of residues lie in the additionally allowed region, which gives an overall of 99.4% residues in the three quadrants in the plot. GKT-831 which is a referral drug in this study has shown a GOLD interaction score of 62.12 with respect to the lead molecule zinc000059139266 which has shown a higher GOLD score of 78.07. Alanine scanning mutagenesis studies has shown that Phe201, Leu98 and Leu76 are found to be the key interacting residues in hydrophobic interactions. Similarly, Tyr324, Arg287 and Cys73 are major amino acid residues in the hydrogen bond interactions.

Conclusions

NOX-1 overexpression leads to heightened ROS production resulting in catastrophic outcomes. The modelled structure of NOX-1 has a good stereochemistry with respect to Ramachandran plot. The lead molecule zinc000059139266 has shown to have a very high interaction score of 78.07 compared to the referral drug GKT-831 with a score of 62.12. There is an excellent scope for the lead molecule to progress further into in vitro and in vivo studies.

Regulation by Nrf2 of IL-1β-induced inflammatory and oxidative response in VSMC and its relationship with TLR4

Introduction: Vascular oxidative stress and inflammation play an important role in the pathogenesis of cardiovascular diseases (CVDs). The proinflammatory cytokine Interleukin-1β (IL-1β) participates in the vascular inflammatory and oxidative responses and influences vascular smooth muscle cells (VSMC) phenotype and function, as well as vascular remodelling in cardiovascular diseases. The Toll-like receptor 4 (TLR4) is also involved in the inflammatory response in cardiovascular diseases. A relationship between Interleukin-1β and Toll-like receptor 4 pathway has been described, although the exact mechanism of this interaction remains still unknown. Moreover, the oxidative stress sensitive transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) promotes the transcription of several antioxidant and anti-inflammatory genes. Nuclear factor-erythroid 2-related factor 2 activators have shown to possess beneficial effects in cardiovascular diseases in which oxidative stress and inflammation are involved, such as hypertension and atherosclerosis; however, the molecular mechanisms are not fully understood. Here, we analysed the role of Toll-like receptor 4 in the oxidative and inflammatory effects of Interleukin-1β as well as whether nuclear factor-erythroid 2-related factor 2 activation contributes to vascular alterations by modulating these effects. Materials: For this purpose, vascular smooth muscle cells and mice aortic segments stimulated with Interleukin-1β were used. Results: Interleukin-1β induces MyD88 expression while the Toll-like receptor 4 inhibitor CLI-095 reduces the Interleukin-1β-elicited COX-2 protein expression, reactive oxygen species (ROS) production, vascular smooth muscle cells migration and endothelial dysfunction. Additionally, Interleukin-1β increases nuclear factor-erythroid 2-related factor 2 nuclear translocation and expression of its downstream proteins heme oxygenase-1, NAD(P)H:quinone oxidoreductase 1 and superoxide dismutase-2, by an oxidative stress-dependent mechanism; moreover, Interleukin-1β reduces the expression of the nuclear factor-erythroid 2-related factor 2 inhibitor Keap1. The nuclear factor-erythroid 2-related factor 2 activator tert-butylhydroquinone (tBHQ) reduces the effects of Interleukin-1β on the increased reactive oxygen species production and the expression of the proinflammatory markers (p-p38, p-JNK, p-c-Jun, COX-2), the increased cell proliferation and migration and prevents the Interleukin-1β-induced endothelial dysfunction in mice aortas. Additionally, tert-butylhydroquinone also reduces the increased MyD88 expression, NADPHoxidase activity and cell migration induced by lipopolysaccharide. Conclusions: In summary, this study reveals that Toll-like receptor 4 pathway contributes to the prooxidant and proinflammatory Interleukin-1β-induced effects. Moreover, activation of nuclear factor-erythroid 2-related factor 2 prevents the deleterious effects of Interleukin-1β, likely by reducing Toll-like receptor 4-dependent pathway. Although further research is needed, the results are promising as they suggest that nuclear factor-erythroid 2-related factor 2 activators might protect against the oxidative stress and inflammation characteristic of cardiovascular diseases.

Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life

The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.

Protective role of irbesartan against cyclophosphamide-induced testicular damage in rats via up-regulating PPAR-γ signaling and ameliorating NF-κB/NLRP3/IL-18 inflammatory axis

BACKGROUND

Cancer and its therapies can impact fertility in various ways, and therefore a growing number of cancer survivors face fertility as a significant concern. The cytotoxic alkylating agent cyclophosphamide (CP) is commonly used as an antineoplastic agent; unfortunately, its use is significantly associated with male infertility and damage to the reproductive system.

AIM

The present study aimed to assess the possible beneficial effects of Irbesartan (IRB) in a rat model of CP-induced testicular toxicity.

MAIN METHODS

The effects of treatment were assessed by measuring peroxisome proliferator-activated receptor gamma (PPAR-γ) expression via qRT-PCR, the immunohistochemical (IHC) assessment of apoptotic markers, NOD-like receptor protein 3 (NLRP3), and nuclear factor-κB (NF-κB), determination of the count and viability of epididymal sperm, oxidative stress markers via biochemical analysis, serum testosterone, caspase-1, and interleukin-18 (IL-18) levels via ELISA, histopathological assessment, and fibrosis by Masson's trichrome (MT) stain.

KEY FINDINGS

There was a significant increase in malondialdehyde (MDA), caspase-1, and IL-18 contents, NF-κB, NLRP3, Bcl-2-associated X protein (Bax), caspase-3, and MT staining in testicular tissue after CP administration compared to the normal control group. Whereas reduced glutathione (GSH), superoxide dismutase (SOD), PPAR-γ expression, B-cell lymphoma-2 (Bcl-2) staining, serum testosterone, and the count and viability of epididymal sperm were decreased compared to the normal control group. The IRB treatment has reversed CP-induced testicular toxicity.

SIGNIFICANCE

It is possible to conclude that IRB revealed a significant testicular protective effect against CP via antioxidant, anti-apoptotic, and anti-inflammatory effects.

A network pharmacology-based approach to explore the active ingredients and molecular mechanism of Lei-gong-gen formula granule on a spontaneously hypertensive rat model

Background

Lei-gong-gen formula granule (LFG) is a folk prescription derived from Zhuang nationality, the largest ethnic minority among 56 nationalities in China. It consists of three herbs, namely Eclipta prostrata (L.) L., Smilax glabra Roxb, and Centella asiatica (L.) Urb. It has been widely used as health protection tea for hundreds of years to prevent hypertension in Guangxi Zhuang Autonomous Region. The purpose of this study is to validate the antihypertensive effect of LFG on the spontaneously hypertensive rat (SHR) model, and to further identify the effective components and anti-hypertension mechanism of LFG.

Methods

The effects of LFG on blood pressure, body weight, and heart rate were investigated in vivo using the SHR model. The levels of NO, ANG II, and ET-1 in the serum were measured, and pathological changes in the heart were examined by H&E staining. The main active components of LFG, their corresponding targets, and hypertension associated pathways were discerned through network pharmacology analysis based on the Traditional Chinese Medicine Systems Pharmacology (TCMSP), Traditional Chinese Medicine Integrated Database (TCMID), and the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM). Then the predicted results were further verified by molecular biology experiments such as RT-qPCR and western blot. Additionally, the potential active compounds were predicted by molecular docking technology, and the chemical constituents of LFG were analyzed and identified by UPLC-QTOF/MS technology. Finally, an in vitro assay was performed to investigate the protective effects of potential active compounds against hydrogen peroxide (H₂O₂) induced oxidative damage in human umbilical vein endothelial cells (HUVEC).

Results

LFG could effectively reduce blood pressure and increase serum NO content in SHR model. Histological results showed that LFG could ameliorate pathological changes such as cardiac hypertrophy and interstitial inflammation. From network pharmacology analysis, 53 candidate active compounds of LFG were collected, which linked to 765 potential targets, and 828 hypertension associated targets were retrieved, from which 12 overlapped targets both related to candidate active compounds from LFG and hypertension were screened and used as the potential targets of LFG on antihypertensive effect. The molecular biology experiments of the 12 overlapped targets showed that LFG could upregulate the mRNA and protein expressions of NOS3 and proto-oncogene tyrosine-protein kinase SRC (SRC) in the thoracic aorta. Pathway enrichment analysis showed that the PI3K-AKT signaling pathway was closely related to the expression of NOS3 and SRC. Moreover, western blot results showed that LFG significantly increased the protein expression levels of PI3K and phosphorylated AKT in SHR model, suggesting that LFG may active the PI3K-AKT signaling pathway to decrease hypertension. Molecular docking study further supported that p-hydroxybenzoic acid, cedar acid, shikimic acid, salicylic acid, nicotinic acid, linalool, and histidine can be well binding with NOS3, SRC, PI3K, and AKT. UPLC-QTOF/MS analysis confirmed that p-hydroxybenzoic acid, shikimic acid, salicylic acid, and nicotinic acid existed in LFG. Pre-treatment of HUVEC with nicotinic acid could alleviate the effect on cell viability induced by H₂O₂ and increase the NO level in cell supernatants.

Conclusions

LFG can reduce the blood pressure in SHR model, which might be attributed to increasing the NO level in serum for promoting vasodilation via upregulating SRC expression level and activating the PI3K-AKT-NOS3 signaling pathway. Nicotinic acid might be the potential compound for LFG antihypertensive effect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-021-00507-1.

Cumulative incidence and risk factors for radiation induced leukoencephalopathy in high grade glioma long term survivors

The incidence and risk factors associated with radiation-induced leukoencephalopathy (RIL) in long-term survivors of high-grade glioma (HGG) are still poorly investigated. We performed a retrospective research in our institutional database for patients with supratentorial HGG treated with focal radiotherapy, having a progression-free overall survival > 30 months and available germline DNA. We reviewed MRI scans for signs of leukoencephalopathy on T2/FLAIR sequences, and medical records for information on cerebrovascular risk factors and neurological symptoms. We investigated a panel of candidate single nucleotide polymorphisms (SNPs) to assess genetic risk. Eighty-one HGG patients (18 grade IV and 63 grade III, 50M/31F) were included in the study. The median age at the time of radiotherapy was 48 years old (range 18-69). The median follow-up after the completion of radiotherapy was 79 months. A total of 44 patients (44/81, 54.3%) developed RIL during follow-up. Twenty-nine of the 44 patients developed consistent symptoms such as subcortical dementia (n = 28), gait disturbances (n = 12), and urinary incontinence (n = 9). The cumulative incidence of RIL was 21% at 12 months, 42% at 36 months, and 48% at 60 months. Age > 60 years, smoking, and the germline SNP rs2120825 (PPARg locus) were associated with an increased risk of RIL. Our study identified potential risk factors for the development of RIL (age, smoking, and the germline SNP rs2120825) and established the rationale for testing PPARg agonists in the prevention and management of late-delayed radiation-induced neurotoxicity.

A Blunted Sympathetic Function and an Enhanced Nitrergic Activity Contribute to Reduce Mesenteric Resistance in Hyperthyroidism

We aimed to determine whether an experimental model of hyperthyroidism could alter the function of sympathetic and nitrergic components of mesenteric innervation. For this purpose, male Wistar rats were divided into (1) control rats (CT) and (2) rats infused with L-Thyroxine (HT). Body weight gain and adipose tissue accumulation were lower in HT rats, while systolic blood pressure and citrate synthase activity in the soleus muscle were increased by HT. In segments from the superior mesenteric artery, the application of an electrical field stimulation (EFS) induced a vasoconstrictor response, which was lower in arteries from HT animals. The alpha-adrenoceptor antagonist phentolamine diminished EFS-induced vasoconstriction to a lower extent in HT arteries, while the purinergic receptor antagonist suramin reduced contractile response to EFS only in segments from CT. In line with this, noradrenaline release, tyrosine hydroxylase expression and activation and dopamine β hydroxylase expression were diminished in HT. The unspecific nitric oxide synthase (NOS) inhibitor L-NAME increased EFS-induced vasoconstriction more markedly in segments from HT rats. NO release was enhanced in HT, probably due to an enhancement in neuronal NOS activity, in which a hyperactivation of both PKC and PI3K-AKT signaling pathways might play a relevant role. In conclusion, perivascular mesenteric innervation might contribute to reduce the vascular resistance observed in hyperthyroidism.

Antioxidant Properties of Egg White Hydrolysate Prevent Mercury-Induced Vascular Damage in Resistance Arteries

Aim: We investigated the antioxidant protective power of egg white hydrolysate (EWH) against the vascular damage induced by mercury chloride (HgCl2) exposure in resistance arteries. Methods: Male Wistar rats received for 60 days: (I) intramuscular injections (i.m.) of saline and tap water by gavage - Untreated group; (II) 4.6 μg/kg of HgCl2 i.m. for the first dose and subsequent doses of 0.07 μg/kg/day and tap water by gavage - HgCl2 group; (III) saline i.m. and 1 g/kg/day of EWH by gavage - EWH group, or (IV) the combination of the HgCl2 i.m. and EWH by gavage - EWH + HgCl2 group. Blood pressure (BP) was indirectly measured and dose-response curves to acetylcholine (ACh), sodium nitroprusside (SNP), and noradrenaline (NE) were assessed in mesenteric resistance arteries (MRA), as in situ production of superoxide anion, nitric oxide (NO) release, vascular reactive oxygen species (ROS), lipid peroxidation, and antioxidant status. Results: Egg white hydrolysate prevented the elevation in BP and the vascular dysfunction after HgCl2 exposure; restored the NO-mediated endothelial modulation and inhibited the oxidative stress and inflammatory pathways induced by HgCl2. Conclusion: Egg white hydrolysate seems to be a useful functional food to prevent HgCl2-induced vascular toxic effects in MRA.

NADPH Oxidases and Their Role in Atherosclerosis

The current view on atherosclerosis positions it as a multifactorial disorder that results from the interplay between lipid metabolism disturbances and inflammatory processes. Oxidative stress is proven to be one of the initiating factors in atherosclerosis development, being implicated both in the inflammatory response and in atherogenic modifications of lipoproteins that facilitate lipid accumulation in the arterial wall. The hallmark of oxidative stress is the elevated level of reactive oxygen species (ROS). Correspondingly, the activity of major ROS-generating enzymes, including nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, and cyclooxygenases, is an important element in atherosclerosis development. In particular, the role of NADPH oxidases in atherosclerosis development has become a subject of intensive research. Aberrant activity of NADPH oxidases was shown to be associated with cardiovascular disease in humans. With regard to atherosclerosis, several important pathological components of the disease development, including endothelial dysfunction, inflammation, and vascular remodeling, involve aberrations in NADPH oxidases functioning. In humans, NADPH oxidases are represented by four isoforms expressed in vascular tissues, where they serve as the main source of ROS during atherogenesis. Moreover, recent studies have demonstrated their impact on vascular remodeling processes. Interestingly, one of the NADPH oxidase isoforms, NOX4, was shown to have an atheroprotective effect. Despite the growing evidence of the crucial involvement of NADPH oxidases in atherosclerosis pathogenesis, the available data still remains controversial. In this narrative review, we summarize the current knowledge of the role of NADPH oxidases in atherosclerosis and outline the future directions of research.

Eicosanoids and Oxidative Stress in Diabetic Retinopathy

Oxidative stress is an important factor to cause the pathogenesis of diabetic retinopathy (DR) because the retina has high vascularization and long-time light exposition. Cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) enzymes can convert arachidonic acid (AA) into eicosanoids, which are important lipid mediators to regulate DR development. COX-derived metabolites appear to be significant factors causative to oxidative stress and retinal microvascular dysfunction. Several elegant studies have unraveled the importance of LOX-derived eicosanoids, including LTs and HETEs, to oxidative stress and retinal microvascular dysfunction. The role of CYP eicosanoids in DR is yet to be explored. There is clear evidence that CYP-derived epoxyeicosatrienoic acids (EETs) have detrimental effects on the retina. Our recent study showed that the renin-angiotensin system (RAS) activation augments retinal soluble epoxide hydrolase (sEH), a crucial enzyme degrading EETs. Our findings suggest that EETs blockade can enhance the ability of RAS blockade to prevent or mitigate microvascular damage in DR. This review will focus on the critical information related the function of these eicosanoids in the retina, the interaction between eicosanoids and reactive oxygen species (ROS), and the involvement of eicosanoids in DR. We also identify potential targets for the treatment of DR.

Pioglitazone Modulates the Vascular Contractility in Hypertension by Interference with ET-1 Pathway

Endothelin-1 (ET-1) is an important modulator of the vascular tone and a proinflammatory molecule that contributes to the vascular damage observed in hypertension. Peroxisome-proliferator activated receptors-γ (PPARγ) agonists show cardioprotective properties by decreasing inflammatory molecules such as COX-2 and reactive oxygen species (ROS), among others. We investigated the possible modulatory effect of PPARγ activation on the vascular effects of ET-1 in hypertension. In spontaneously hypertensive rats (SHR), but not in normotensive rats, ET-1 enhanced phenylephrine-induced contraction through ET_A by a mechanism dependent on activation of TP receptors by COX-2-derived prostacyclin and reduction in NO bioavailability due to enhanced ROS production. In SHR, the PPARγ agonist pioglitazone (2.5 mg/Kg·day, 28 days) reduced the increased ET_A levels and increased those of ET_B. After pioglitazone treatment of SHR, ET-1 through ET_B decreased ROS levels that resulted in increased NO bioavailability and diminished phenylephrine contraction. In vascular smooth muscle cells from SHR, ET-1 increased ROS production through AP-1 and NFκB activation, leading to enhanced COX-2 expression. These effects were blocked by pioglitazone. In summary, in hypertension, pioglitazone shifts the vascular ET_A/ET_B ratio, reduces ROS/COX-2 activation and increases NO availability; these changes explain the effect of ET-1 decreasing phenylephrine-induced contraction.

Indazole-Cl inhibits hypoxia-induced cyclooxygenase-2 expression in vascular smooth muscle cells

Atherosclerosis is the most common root cause of arterial disease, such as coronary artery disease and carotid artery disease. Hypoxia is associated with the formation of macrophages and increased inflammation and is known to be present in lesions of atherosclerotic. Vascular smooth muscle cells (VSMCs) are one of the major components of blood vessels, and hypoxic conditions affect VSMC inflammation, proliferation and migration, which contribute to vascular stenosis and play a major role in the atherosclerotic process. Estrogen receptor (ER)-β is thought to play an important role in preventing the inflammatory response in VSMCs. In this report, we studied the anti-inflammatory effect of indazole (In)-Cl, an ERβ-specific agonist, under conditions of hypoxia. Expression of cyclooxygenase-2 reduced by hypoxia was inhibited by In-Cl treatment in VSMCs, and this effect was antagonized by an anti-estrogen compound. Additionally, the production of reactive oxygen species induced under conditions of hypoxia was reduced by treatment with In-Cl. Increased cell migration and invasion by hypoxia were also dramatically decreased following treatment with In-Cl. The increase in cell proliferation following treatment with platelet-derived growth factor was attenuated by In-Cl in VSMCs. RNA sequencing analysis was performed to identify changes in inflammation-related genes following In-Cl treatment in the hypoxic state. Our results suggest that ERβ is a potential therapeutic target for the suppression of hypoxia-induced inflammation in VSMCs.

Suppressive effects of type I angiotensin receptor antagonists, candesartan and irbesartan on allergic asthma

The effects of candesartan and irbesartan, antagonists of the type I angiotensin II receptor, were investigated on allergic asthma. The antigen-induced degranulation was measured by evaluating β-hexosaminidase activity in vitro. Additionally, a murine ovalbumin-induced allergic asthma model was used to test the in vivo efficacy. It was observed that while candesartan inhibited the antigen-induced degranulation in rat RBL-2H3 mast cells, irbesartan did not. Administration of candesartan and irbesartan decreased the number of immune cells in the bronchoalveolar lavage fluid and reduced the expression of Th2 (IL-4, IL-5, and IL-13) and Th1 cytokines (IL-2 and IFN-γ) in the lung tissues of mice with ovalbumin-induced allergic asthma. Histological studies revealed that both antagonists reduced inflammation and mucin production in the lungs. Therefore, these findings provide evidence that candesartan and irbesartan could have potential applications as anti-allergic agents.

Bradykinin and interleukin-1β synergistically increase the expression of cyclooxygenase-2 through the RNA-binding protein HuR in rat dorsal root ganglion cells

Synergistic expression of cyclooxygenase-2 (COX-2) by interleukin-1β (IL-1β) and bradykinin (BK) in peri-sensory neurons results in the production of prostanoids, which affects sensory neuronal activity and responsiveness and causes hyperalgesia. To evaluate the effects of pro-inflammatory mediators on COX-2 expression, cultured rat dorsal root ganglion (DRG) cells were treated with IL-1β and BK, which caused persistent increased COX-2 expression. Co-treatment increased COX-2 transcriptional activities in an additive manner by a COX-2 promoter luciferase assay. Immunoprecipitated HuR, an RNA-binding protein, in co-treated DRG cells contained more COX-2 mRNA than that of the control. The synergistic effects of IL-1β and BK on COX-2 expression may be a result of RNA stabilization mediated by HuR in peri-sensory neurons. Multiple pro-inflammatory cytokines and mediators are produced during neurogenic inflammation and aberrant control of COX-2 mRNA turnover may be implicated in diseases including chronic inflammation, which results in inflammation-derived hyperalgesia around primary sensory neurons.

Interplay between the renin-angiotensin system, the canonical WNT/β-catenin pathway and PPARγ in hypertension

PURPOSE OF REVIEW

Heterogeneous causes can determinate hypertension.

RECENT FINDINGS

The renin-angiotensin system (RAS) has a major role in the pathophysiology of blood pressure. Angiotensin II and aldosterone are overexpressed during hypertension and lead to hypertension development and its cardiovascular complications. In several tissues, the overactivation of the canonical WNT/β-catenin pathway leads to inactivation of peroxisome proliferator-activated receptor gamma (PPARγ), while PPARγ stimulation induces a decrease of the canonical WNT/β-catenin pathway. In hypertension, the WNT/β-catenin pathway is upregulated, whereas PPARγ is decreased. The WNT/β-catenin pathway and RAS regulate positively each other during hypertension, whereas PPARγ agonists can decrease the expression of both the WNT/β-catenin pathway and RAS. We focus this review on the hypothesis of an opposite interplay between PPARγ and both the canonical WNT/β-catenin pathway and RAS in regulating the molecular mechanism underlying hypertension. The interactions between PPARγ and the canonical WNT/β-catenin pathway through the regulation of the renin-angiotensin system in hypertension may be an interesting way to better understand the actions and the effects of PPARγ agonists as antihypertensive drugs.

Role of peroxisome proliferator-activated receptor-gamma activation on visfatin, advanced glycation end products, and renal oxidative stress in obesity-induced type 2 diabetes mellitus

The present study focused on the role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) activation on renal oxidative damages, serum visfatin, and advanced glycation end products (AGEs) in high-fat diet (HFD)-induced type 2 diabetes mellitus. Following the institutional animal ethics committee guidelines, Wistar rats were categorized into five groups: group 1: fed on a normal rat diet; group 2: HFD-induced obese rats (HFD for 8 weeks); group 3: HFD-fed rats treated with rosiglitazone (RSG; 3 mg/kg orally for 7 days); group 4: T2DM rats induced by HFD and low dose of streptozotocin (i.p. 35 mg/kg); group 5: T2DM rats treated with RSG (3 mg/kg orally for 7 days). Serum levels of AGEs and visfatin, renal damage, and oxidative stress were analyzed. Results showed that HFD-induced obesity and T2DM caused an elevated blood glucose, serum AGEs, visfatin, insulin, urea, creatinine, and tissue malondialdehyde, whereas a decreased catalase and superoxide dismutase activity were observed. The PPAR-γ activation via agonist restored these changes. Our findings suggest that AGEs and visfatin possess an important role in the progression of renal oxidative stress, which can be reduced by the PPAR-γ agonist that impede deleterious effects of HFD and HFD-induced T2DM on renal damage.

Regulator of calcineurin 1 modulates vascular contractility and stiffness through the upregulation of COX-2-derived prostanoids

Cyclooxygenase-2 (COX-2) derived-prostanoids participate in the altered vascular function and mechanical properties in cardiovascular diseases. We investigated whether regulator of calcineurin 1 (Rcan1) participates in vascular contractility and stiffness through the regulation of COX-2. For this, wild type (Rcan1^+/+) and Rcan1-deficient (Rcan1^-/-) mice untreated or treated with the COX-2 inhibitor rofecoxib were used. Vascular function and structure were analysed by myography. COX-2 and phospo-p65 expression were studied by western blotting and immunohistochemistry and TXA₂ production by ELISA. We found that Rcan1 deficiency increases COX-2 and IL-6 expression and NF-κB activation in arteries and vascular smooth muscle cells (VSMC). Adenoviral-mediated re-expression of Rcan1.4 in Rcan1^-/- VSMC normalized COX-2 expression. Phenylephrine-induced vasoconstrictor responses were greater in aorta from Rcan1^-/- compared to Rcan1^+/+ mice. This increased response were diminished by etoricoxib, furegrelate, SQ 29548, cyclosporine A and parthenolide, inhibitors of COX-2, TXA₂ synthase, TP receptors, calcineurin and NF-κB, respectively. Endothelial removal and NOS inhibition increased phenylephrine responses only in Rcan1^+/+ mice. TXA₂ levels were greater in Rcan1^-/- mice. In small mesenteric arteries, vascular function and structure were similar in both groups of mice; however, vessels from Rcan1^-/- mice displayed an increase in vascular stiffness that was diminished by rofecoxib. In conclusion, our results suggest that Rcan1 might act as endogenous negative modulator of COX-2 expression and activity by inhibiting calcineurin and NF-kB pathways to maintain normal contractility and vascular stiffness in aorta and small mesenteric arteries, respectively. Our results uncover a new role for Rcan1 in vascular contractility and mechanical properties.

Chemical and Physical Approaches to Extend the Replicative and Differentiation Potential of Stem Cells

Cell therapies using mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) are increasing in regenerative medicine, with applications to a growing number of aging-associated dysfunctions and degenerations. For successful therapies, a certain mass of cells is needed, requiring extensive ex vivo expansion of the cells. However, the proliferation of both MSCs and EPCs is limited as a result of telomere shortening-induced senescence. As cells approach senescence, their proliferation slows down and differentiation potential decreases. Therefore, ways to delay senescence and extend the replicative lifespan these cells are needed. Certain proteins and pathways play key roles in determining the replicative lifespan by regulating ROS generation, damage accumulation, or telomere shortening. And, their agonists and gene activators exert positive effects on lifespan. In many of the treatments, importantly, the lifespan is extended with the retention of differentiation potential. Furthermore, certain culture conditions, including the use of specific atmospheric conditions and culture substrates, exert positive effects on not only the proliferation rate, but also the extent of proliferation and differentiation potential as well as lineage determination. These strategies and known underlying mechanisms are introduced in this review, with an evaluation of their pros and cons in order to facilitate safe and effective MSC expansion ex vivo.

Lactacystin-Induced Model of Hypertension in Rats: Effects of Melatonin and Captopril

Lactacystin is a proteasome inhibitor that interferes with several factors involved in heart remodelling. The aim of this study was to investigate whether the chronic administration of lactacystin induces hypertension and heart remodelling and whether these changes can be modified by captopril or melatonin. In addition, the lactacystin-model was compared with NG-nitro-l-arginine-methyl ester (L-NAME)- and continuous light-induced hypertension. Six groups of three-month-old male Wistar rats (11 per group) were treated for six weeks as follows: control (vehicle), L-NAME (40 mg/kg/day), continuous light (24 h/day), lactacystin (5 mg/kg/day) alone, and lactacystin with captopril (100 mg/kg/day), or melatonin (10 mg/kg/day). Lactacystin treatment increased systolic blood pressure (SBP) and induced fibrosis of the left ventricle (LV), as observed in L-NAME-hypertension and continuous light-hypertension. LV weight and the cross-sectional area of the aorta were increased only in L-NAME-induced hypertension. The level of oxidative load was preserved or reduced in all three models of hypertension. Nitric oxide synthase (NOS) activity in the LV and kidney was unchanged in the lactacystin group. Nuclear factor-kappa B (NF-κB) protein expression in the LV was increased in all treated groups in the cytoplasm, however, in neither group in the nucleus. Although melatonin had no effect on SBP, only this indolamine (but not captopril) reduced the concentration of insoluble and total collagen in the LV and stimulated the NO-pathway in the lactacystin group. We conclude that chronic administration of lactacystin represents a novel model of hypertension with collagenous rebuilding of the LV, convenient for testing antihypertensive drugs or agents exerting a cardiovascular benefit beyond blood pressure reduction.

Hypertension-Causing Mutation in Peroxisome Proliferator-Activated Receptor γ Impairs Nuclear Export of Nuclear Factor-κB p65 in Vascular Smooth Muscle

Selective expression of dominant negative (DN) peroxisome proliferator-activated receptor γ (PPARγ) in vascular smooth muscle cells (SMC) results in hypertension, atherosclerosis, and increased nuclear factor-κB (NF-κB) target gene expression. Mesenteric SMC were cultured from mice designed to conditionally express wild-type (WT) or DN-PPARγ in response to Cre recombinase to determine how SMC PPARγ regulates expression of NF-κB target inflammatory genes. SMC-specific overexpression of WT-PPARγ or agonist-induced activation of endogenous PPARγ blunted tumor necrosis factor α (TNF-α)-induced NF-κB target gene expression and activity of an NF-κB-responsive promoter. TNF-α-induced gene expression responses were enhanced by DN-PPARγ in SMC. Although expression of NF-κB p65 was unchanged, nuclear export of p65 was accelerated by WT-PPARγ and prevented by DN-PPARγ in SMC. Leptomycin B, a nuclear export inhibitor, blocked p65 nuclear export and inhibited the anti-inflammatory action of PPARγ. Consistent with a role in facilitating p65 nuclear export, WT-PPARγ coimmunoprecipitated with p65, and WT-PPARγ was also exported from the nucleus after TNF-α treatment. Conversely, DN-PPARγ does not bind to p65 and was retained in the nucleus after TNF-α treatment. Transgenic mice expressing WT-PPARγ or DN-PPARγ specifically in SMC (S-WT or S-DN) were bred with mice expressing luciferase controlled by an NF-κB-responsive promoter to assess effects on NF-κB activity in whole tissue. TNF-α-induced NF-κB activity was decreased in aorta and carotid artery from S-WT but was increased in vessels from S-DN mice. We conclude that SMC PPARγ blunts expression of proinflammatory genes by inhibition of NF-κB activity through a mechanism promoting nuclear export of p65, which is abolished by DN mutation in PPARγ.

PPARs in the central nervous system: roles in neurodegeneration and neuroinflammation

Over 25 years have passed since peroxisome proliferators-activated receptors (PPARs), were first described. Like other members of the nuclear receptors superfamily, PPARs have been defined as critical sensors and master regulators of cellular metabolism. Recognized as ligand-activated transcription factors, they are involved in lipid, glucose and amino acid metabolism, taking part in different cellular processes, including cellular differentiation and apoptosis, inflammatory modulation and attenuation of acute and chronic neurological damage in vivo and in vitro. Interestingly, PPAR activation can simultaneously reprogram the immune response, stimulate metabolic and mitochondrial functions, promote axonal growth, induce progenitor cells to differentiate into myelinating oligodendrocytes, and improve brain clearance of toxic molecules such as β-amyloid peptide. Although the molecular mechanisms and cross-talk with different molecular pathways are still the focus of intense research, PPARs are considered potential therapeutic targets for several neuropathological conditions, including degenerative disorders such as Alzheimer's, Parkinson's and Huntington's disease. This review considers recent advances regarding PPARs, as well as new PPAR agonists. We focus on the mechanisms behind the neuroprotective effects exerted by PPARs and summarise the roles of PPARs in different pathologies of the central nervous system, especially those associated with degenerative and inflammatory mechanisms.

NADPH oxidases and vascular remodeling in cardiovascular diseases

Reactive oxygen species (ROS) are key signaling molecules that regulate vascular function and structure in physiological conditions. A misbalance between the production and detoxification of ROS increases oxidative stress that is involved in the vascular remodeling associated with cardiovascular diseases such as hypertension by affecting inflammation, hypertrophy, migration, growth/apoptosis and extracellular matrix protein turnover. The major and more specific source of ROS in the cardiovascular system is the NADPH oxidase (NOX) family of enzymes composed of seven members (NOX1-5, DUOX 1/2). Vascular cells express several NOXs being NOX-1 and NOX-4 the most abundant NOXs present in vascular smooth muscle cells. This review focuses on specific aspects of NOX-1 and NOX-4 isoforms including information on regulation, function and their role in vascular remodeling. In order to obtain a more integrated view about the role of the different NOX isoforms in different types of vascular remodeling, we discuss the available literature not only on hypertension but also in atherosclerosis, restenosis and aortic dilation.

Augmented oxidative stress and preserved vasoconstriction induced by hydrogen peroxide in coronary arteries in obesity: role of COX-2

BACKGROUND AND PURPOSE

Oxidative stress plays a key role in the vascular and metabolic abnormalities associated with obesity. Herein, we assessed whether obesity can increase coronary vasoconstriction induced by hydrogen peroxide (H₂ O₂ ) and the signalling pathways involving COX-2 and superoxide (O₂^.- ) generation.

EXPERIMENTAL APPROACH

Contractile responses to H₂ O₂ and O₂^.- generation were measured in coronary arteries from genetically obese Zucker rats (OZR) and compared to lean Zucker rats (LZR).

KEY RESULTS

Both basal and H₂ O₂ -stimulated O₂^.- production were enhanced in coronary arteries from OZR, but H₂ O₂ -induced vasoconstriction was unchanged. The selective COX-2 inhibitor NS398 significantly reduced H₂ O₂ -induced contractions in endothelium-denuded arteries from LZR and OZR, but only in endothelium-intact arteries from LZR. PGI₂ (IP) receptor antagonism modestly reduced the vasoconstrictor action of H₂ O₂ while antagonism of the PGE₂ receptor 4 (EP₄ ) enhanced H₂ O₂ contractions in arteries from OZR but not LZR. Basal release of COX-2-derived PGE₂ was higher in coronary arteries from OZR where the selective agonist of EP₄ receptors TCS 2519 evoked potent relaxations. COX-2 was up-regulated after acute exposure to H₂ O₂ in coronary endothelium and vascular smooth muscle (VSM) and inhibition of COX-2 markedly reduced H₂ O₂ -elicited O₂^.- generation in coronary arteries and myocardium. Expression of Nox subunits in VSM and NADPH-stimulated O₂^.- generation was enhanced and contributed to H₂ O₂ vasoconstriction in arteries from obese rats.

CONCLUSION AND IMPLICATIONS

COX-2 contributes to cardiac oxidative stress and to the endothelium-independent O₂^.- -mediated coronary vasoconstriction induced by H₂ O₂ in obesity, which is offset by the release of COX-2-derived endothelial PGE₂ acting on EP₄ vasodilator receptors.

Hu antigen R is required for NOX-1 but not NOX-4 regulation by inflammatory stimuli in vascular smooth muscle cells

OBJECTIVE

NOX-1 and NOX-4 are key enzymes responsible for reactive oxygen species (ROS) generation in vascular smooth muscle cells (VSMC). The RNA-binding protein Hu antigen R (HuR) is implicated in posttranscriptional regulation of gene expression; however, its role regulating NOX is unknown. We investigated transcriptional and posttranscriptional mechanisms underlying angiotensin II (AngII) and IL-1β regulation of NOX-1 and NOX-4 in VSMC and their implications in cell migration.

METHODS

Rat and human VSMC were stimulated with AngII (0.1 μmol/l) and/or IL-1β (10 ng/ml). NOX-1 and NOX-4 mRNA and protein levels, NOX-1 and NOX-4 promoter and 3'UTR activities, NADPH oxidase activity, ROS production, and cell migration were studied.

RESULTS

IL-1β increased NOX-1 expression, NADPH oxidase activity and ROS production, and decreased NOX-4 expression and H2O2 production in VSMC. AngII potentiated the IL-1β-mediated induction of NOX-1 expression, NADPH oxidase activity, ROS production, and cell migration. However, AngII did not influence IL-1β-induced NOX-4 downregulation. AngII + IL-1β interfered with the decay of NOX-1 mRNA and promoted HuR binding to NOX-1 mRNA. Moreover, HuR blockade reduced NOX-1 mRNA stability and AngII + IL-1β-induced NOX-1 mRNA levels. IL-1β decreased NOX-4 expression through a transcriptional mechanism that involved response elements situated in the proximal promoter. AngII and/or IL-1β-induced cell migration were prevented by NOX-1 and HuR blockade and were augmented by NOX-4 overexpression.

CONCLUSION

In VSMC HuR-mediated mRNA stabilization is partially responsible for AngII + IL-1β-dependent NOX-1 expression, whereas transcriptional mechanisms are involved in decreased NOX-4 expression induced by IL-1β. NOX4 and HuR regulation of NOX-1 contributes to VSMC migration, important in vascular inflammation and remodeling.

Treatment of Mitochondrial Diabetes with a Peroxisome Proliferator-activated Receptor (PPAR)-gamma Agonist

The 3243 A>G mutation in mitochondrial DNA is the most common cause of monogenic diabetes mellitus in Japan. A 45-year-old woman with mitochondrial diabetes and significant insulin resistance presented with hypoadiponectinemia despite a normal amount of visceral fat. Three months of treatment with pioglitazone (PIO) improved her blood glucose profile and response to the 75-g oral glucose tolerance test. These changes were accompanied by the amelioration of her insulin resistance and the impairment of early-phase insulin secretion. Her serum adiponectin levels increased to the normal range. In this case of mitochondrial diabetes, PIO was effective for glycemic control.

Pioglitazone, a PPARγ agonist, attenuates PDGF-induced vascular smooth muscle cell proliferation through AMPK-dependent and AMPK-independent inhibition of mTOR/p70S6K and ERK signaling

Pioglitazone (PIO), a PPARγ agonist that improves glycemic control in type 2 diabetes through its insulin-sensitizing action, has been shown to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. Although PPARγ-dependent and PPARγ-independent mechanisms have been attributed to its vasoprotective effects, the signaling events associated with PIO action in VSMCs are not fully understood. To date, the likely intermediary role of AMP-activated protein kinase (AMPK) toward PIO inhibition of VSMC proliferation has not been examined. Using human aortic VSMCs, the present study demonstrates that PIO activates AMPK in a sustained manner thereby contributing in part to inhibition of key proliferative signaling events. In particular, PIO at 30μM concentration activates AMPK to induce raptor phosphorylation, which diminishes PDGF-induced mTOR activity as evidenced by decreased phosphorylation of p70S6K, 4E-BP1, and S6 and increased accumulation of p27(kip1), a cell cycle inhibitor. In addition, PIO inhibits the basal phosphorylation of ERK in VSMCs. Downregulation of endogenous AMPK by target-specific siRNA reveals an AMPK-independent effect for PIO inhibition of ERK, which contributes in part to diminutions in cyclin D1 expression and Rb phosphorylation and the suppression of VSMC proliferation. Furthermore, AMPK-dependent inhibition of mTOR/p70S6K and AMPK-independent inhibition of ERK signaling occur regardless of PPARγ expression/activation in VSMCs as evidenced by gene silencing and pharmacological inhibition of PPARγ. Strategies that utilize nanoparticle-mediated PIO delivery at the lesion site may limit restenosis after angioplasty without inducing PPARγ-mediated systemic adverse effects.

Cryptotanshinone attenuates cardiac fibrosis via downregulation of COX-2, NOX-2, and NOX-4

Cryptotanshinone (CTS), a bioactive constituent extracted from a Chinese traditional herb Danshen (Salvia miltiorrhiza), demonstrates multiple protective effects against cardiovascular diseases. The present study was designed to explore the effects of CTS in vitro by cultured adult rat cardiac fibroblasts stimulated with angiotensin II (Ang II) and in vivo by rats with acute myocardial infarction. Our data showed that in cardiac fibroblasts, CTS attenuated Ang II-induced upregulation of fibronectin, connective tissue growth factor, cyclooxygenase-2, and normalized Ang II-induced upregulation of extracellular signal-regulated kinases 1/2 (ERK1/2). Meanwhile, CTS depressed the Ang II-stimulated upregulation of NAD(P)H oxidase 2 and 4 (NOX-2 and NOX-4) and reactive oxygen species production. Similar results were observed in acute myocardial infarction rats with oral administration of CTS, which relieved the pathological changes accompanying myocardial infarction. In conclusion, CTS may exert antifibrotic effects in vitro by inhibiting Ang II-induced extracellular signal-regulated kinases 1/2 phosphorylation and the expression of cyclooxygenase-2, NOX-2, and NOX-4, and also improved the pathological changes and relieved cardiac fibrosis in vivo.

Toll-like receptor 4 contributes to vascular remodelling and endothelial dysfunction in angiotensin II-induced hypertension

BACKGROUND AND PURPOSE

Toll-like receptor 4 (TLR4) signalling contributes to inflammatory cardiovascular diseases, but its role in hypertension and the associated vascular damage is not known. We investigated whether TLR4 activation contributed to angiotensin II (AngII)-induced hypertension and the associated vascular structural, mechanical and functional alterations.

EXPERIMENTAL APPROACH

AngII was infused (1.44 mg · kg(-1) · day(-1), s.c.) for 2 weeks in C57BL6 mice, treated with a neutralizing anti-TLR4 antibody or IgG (1 μg · day(-1); systolic BP (SBP) and aortic cytokine levels were measured. Structural, mechanical and contractile properties of aortic and mesenteric arterial segments were measured with myography and histology. RT-PCR and Western blotting were used to analyse these tissues and cultured vascular smooth muscle cells (VSMC) from hypertensive rats (SHR).

KEY RESULTS

Aortic TLR4 mRNA levels were raised by AngII infusion. Anti-TLR4 antibody treatment of AngII-treated mice normalised: (i) increased SBP and TNF-α, IL-6 and CCL2 levels; (ii) vascular structural and mechanical changes; (iii) altered aortic phenylephrine- and ACh-induced responses; (iv) increased NOX-1 mRNA levels, superoxide anion production and NAD(P)H oxidase activity and effects of catalase, apocynin, ML-171 and Mito-TEMPO on vascular responses; and (v) reduced NO release and effects of L-NAME on phenylephrine-induced contraction. In VSMC, the MyD88 inhibitor ST-2825 reduced AngII-induced NAD(P)H oxidase activity. The TLR4 inhibitor CLI-095 reduced AngII-induced increased phospho-JNK1/2 and p65 NF-κB subunit nuclear protein expression.

CONCLUSIONS AND IMPLICATIONS

TLR4 up-regulation by AngII contributed to the inflammation, endothelial dysfunction, vascular remodelling and stiffness associated with hypertension by mechanisms involving oxidative stress. MyD88-dependent activation and JNK/NF-κB signalling pathways participated in these alterations.

Apocynin decreases AGEs-induced stimulation of NF-κB protein expression in vascular smooth muscle cells from GK rats

CONTEXT

Elevated oxidative stress plays a key role in diabetes-associated vascular disease. Excessive production of reactive oxygen species via advanced glycation end products (AGEs) activates peroxisome proliferator-activated receptor gamma (PPARγ) and the transcription factor nuclear factor-kB (NF-κB) in aortic vascular smooth muscle cells (VSMCs). Apocynin, a drug with an antioxidant effect, has also been proposed as a therapeutic agent for atherosclerotic disease.

OBJECTIVES

This work investigates the effects of apocynin on the PPARγ and NF-κB protein expression evoked by AGEs in cultured VSMCs from Goto-Kakisaki (GK) rats, a non-obese insulin model of both insulin resistance and type 2 diabetes.

MATERIALS AND METHODS

VSMCs, isolated from aortas of GK and non-diabetic rats, were cultured. The expression of proteins was evaluated by Western blot. The blood glucose concentration was measured with a blood glucose test meter. The diabetes of GK rats was controlled by blood glucose and insulin determinations (non-fasting values). The serum insulin concentration was determined by radioimmunoassay.

RESULTS

In VSMCs from non-diabetic and GK rats, apocynin (1 and 10 µM) abolished the protein overexpression of NF-κB induced by glycated bovine serum albumin (AGEs-BSA) incubation. However, apocynin (1 and 10 µM) enhanced the expression of PPARγ protein in the presence of AGEs-BSA (100 μg/mL) in VSMCs from non-diabetic, but not from GK rats.

CONCLUSION

These findings suggest that apocynin decreases the incidence of alterations in VSMCs induced by AGEs through the reduction of NF-κB and may represent an attractive therapeutic approach to treat diabetes mellitus.

HuR mediates the synergistic effects of angiotensin II and IL-1β on vascular COX-2 expression and cell migration

BACKGROUND AND PURPOSE

Angiotensin II (AngII) and IL-1β are involved in cardiovascular diseases through the induction of inflammatory pathways. HuR is an adenylate- and uridylate-rich element (ARE)-binding protein involved in the mRNA stabilization of many genes. This study investigated the contribution of HuR to the increased expression of COX-2 induced by AngII and IL-1β and its consequences on VSMC migration and remodelling.

EXPERIMENTAL APPROACH

Rat and human VSMCs were stimulated with AngII (0.1 μM) and/or IL-1β (10 ng · mL(-1)). Mice were infused with AngII or subjected to carotid artery ligation. mRNA and protein levels were assayed by quantitative PCR, Western blot, immunohistochemistry and immunofluorescence. Cell migration was measured by wound healing and transwell assays.

KEY RESULTS

In VSMCs, AngII potentiated COX-2 and tenascin-C expressions and cell migration induced by IL-1β. This effect of AngII on IL-1β-induced COX-2 expression was accompanied by increased COX-2 3' untranslated region reporter activity and mRNA stability, mediated through cytoplasmic HuR translocation and COX-2 mRNA binding. These effects were blocked by ERK1/2 and HuR inhibitors. VSMC migration was reduced by blockade of ERK1/2, HuR, COX-2, TXAS, TP and EP receptors. HuR, COX-2, mPGES-1 and TXAS expressions were increased in AngII-infused mouse aortas and in carotid-ligated arteries. AngII-induced tenascin-C expression and vascular remodelling were abolished by celecoxib and by mPGES-1 deletion.

CONCLUSIONS AND IMPLICATIONS

The synergistic induction of COX-2 by AngII and IL-1β in VSMCs involves HuR through an ERK1/2-dependent mechanism. The HuR/COX-2 axis participates in cell migration and vascular damage. HuR might be a novel target to modulate vascular remodelling.

Brain metabolite clearance: impact on Alzheimer's disease

Alzheimer's Disease (AD) is a complex neurodegenerative disorder often associated with aging and characterized by several critical molecular changes that take place in the brain. Among the molecular hallmarks of AD, increased levels of amyloid β-peptide (Aβ) and the subsequent Aβ-derived damage are the most well-studied factors; however, despite the large amounts of effort and resources devoted to the study of AD and AD pathophysiology, the scientific community still awaits therapeutic alternatives capable of ensuring a better outcome for AD patients. In 2012, Cramer et al. (Science 335:1503-1506 2012) astonished the scientific community by rescuing behavioral and cognitive impairments in AD mouse models via oral administration of bexarotene, a drug used to treat some types of skin cancer. Moreover, these authors demonstrated that bexarotene, a retinoid X receptor (RXR) agonist, exerts major effects on Aβ levels, mainly through increased apolipoprotein E (ApoE) expression. Apart from the valid questions addressed in Cramer's work, only a few attempts have been made to explain the effects of bexarotene. Most of these explanations have been solely based on the ability of bexarotene to reduce Aβ levels and not on the mechanisms that lead to such a reduction. Although it is well known that an imbalance in the Aβ production/excretion rate is the basis of increased Aβ levels in AD, no further explanations have been proposed to address the potential involvement of the blood-brain barrier (BBB), a critical Aβ-clearance structure, in the bexarotene-mediated effects. Moreover, no attempt has been made to explain how the different effects observed after bexarotene administration are connected to each other. Based on current information and on our own experience with nuclear receptors (NR), we offer new perspectives on the mechanisms of bexarotene action, which should help to improve our knowledge of NRs.

Oxidative stress-induced alterations in PPAR-γ and associated mitochondrial destabilization contribute to kidney cell apoptosis

The mechanism(s) underlying renoprotection by peroxisome proliferator-activated receptor (PPAR)-γ agonists in diabetic and nondiabetic kidney disease are not well understood. Mitochondrial dysfunction and oxidative stress contribute to kidney disease. PPAR-γ upregulates proteins required for mitochondrial biogenesis. Our aim was to determine whether PPAR-γ has a role in protecting the kidney proximal tubular epithelium (PTE) against mitochondrial destabilisation and oxidative stress. HK-2 PTE cells were subjected to oxidative stress (0.2-1.0 mM H₂O₂) for 2 and 18 h and compared with untreated cells for apoptosis, mitosis (morphology/biomarkers), cell viability (MTT), superoxide (dihydroethidium), mitochondrial function (MitoTracker red and JC-1), ATP (luminescence), and mitochondrial ultrastructure. PPAR-γ, phospho-PPAR-γ, PPAR-γ coactivator (PGC)-1α, Parkin (Park2), p62, and light chain (LC)3β were investigated using Western blots. PPAR-γ was modulated using the agonists rosiglitazone, pioglitazone, and troglitazone. Mitochondrial destabilization increased with H₂O₂concentration, ATP decreased (2 and 18 h; P < 0.05), Mitotracker red and JC-1 fluorescence indicated loss of mitochondrial membrane potential, and superoxide increased (18 h, P < 0.05). Electron microscopy indicated sparse mitochondria, with disrupted cristae. Mitophagy was evident at 2 h (Park2 and LC3β increased; p62 decreased). Impaired mitophagy was indicated by p62 accumulation at 18 h (P < 0.05). PPAR-γ expression decreased, phospho-PPAR-γ increased, and PGC-1α decreased (2 h), indicating aberrant PPAR-γ activation and reduced mitochondrial biogenesis. Cell viability decreased (2 and 18 h, P < 0.05). PPAR-γ agonists promoted further apoptosis. In summary, oxidative stress promoted mitochondrial destabilisation in kidney PTE, in association with increased PPAR-γ phosphorylation. PPAR-γ agonists failed to protect PTE. Despite positive effects in other tissues, PPAR-γ activation appears to be detrimental to kidney PTE health when oxidative stress induces damage.

Toll-like receptor 4 upregulation by angiotensin II contributes to hypertension and vascular dysfunction through reactive oxygen species production

Hypertension is considered as a low-grade inflammatory disease, with adaptive immunity being an important mediator of this pathology. TLR4 may have a role in the development of several cardiovascular diseases; however, little is known about its participation in hypertension. We aimed to investigate whether TLR4 activation due to increased activity of the renin-angiotensin system (RAS) contributes to hypertension and its associated endothelial dysfunction. For this, we used aortic segments from Wistar rats treated with a non-specific IgG (1 µg/day) and SHRs treated with losartan (15 mg/kg·day), the non-specific IgG or the neutralizing antibody anti-TLR4 (1 µg/day), as well as cultured vascular smooth muscle cells (VSMC) from Wistar and SHRs. TLR4 mRNA levels were greater in the VSMC and aortas from SHRs compared with Wistar rats; losartan treatment reduced those levels in the SHRs. Treatment of the SHRs with the anti-TLR4 antibody: 1) reduced the increased blood pressure, heart rate and phenylephrine-induced contraction while it improved the impaired acetylcholine-induced relaxation; 2) increased the potentiation of phenylephrine contraction after endothelium removal; and 3) abolished the inhibitory effects of tiron, apocynin and catalase on the phenylephrine-induced response as well as its enhancing effect of acetylcholine-induced relaxation. In SHR VSMCs, angiotensin II increased TLR4 mRNA levels, and losartan reduced that increase. CLI-095, a TLR4 inhibitor, mitigated the increases in NAD(P)H oxidase activity, superoxide anion production, migration and proliferation that were induced by angiotensin II. In conclusion, TLR4 pathway activation due to increased RAS activity is involved in hypertension, and by inducing oxidative stress, this pathway contributes to the endothelial dysfunction associated with this pathology. These results suggest that TLR4 and innate immunity may play a role in hypertension and its associated end-organ damage.

Alzheimer's disease: relevant molecular and physiopathological events affecting amyloid-β brain balance and the putative role of PPARs

Alzheimer’s disease (AD) is the most common form of age-related dementia. With the expected aging of the human population, the estimated morbidity of AD suggests a critical upcoming health problem. Several lines of research are focused on understanding AD pathophysiology, and although the etiology of the disease remains a matter of intense debate, increased brain levels of amyloid-β (Aβ) appear to be a critical event in triggering a wide range of molecular alterations leading to AD. It has become evident in recent years that an altered balance between production and clearance is responsible for the accumulation of brain Aβ. Moreover, Aβ clearance is a complex event that involves more than neurons and microglia. The status of the blood-brain barrier (BBB) and choroid plexus, along with hepatic functionality, should be considered when Aβ balance is addressed. Furthermore, it has been proposed that exposure to sub-toxic concentrations of metals, such as copper, could both directly affect these secondary structures and act as a seeding or nucleation core that facilitates Aβ aggregation. Recently, we have addressed peroxisomal proliferator-activated receptors (PPARs)-related mechanisms, including the direct modulation of mitochondrial dynamics through the PPARγ-coactivator-1α (PGC-1α) axis and the crosstalk with critical aging- and neurodegenerative-related cellular pathways. In the present review, we revise the current knowledge regarding the molecular aspects of Aβ production and clearance and provide a physiological context that gives a more complete view of this issue. Additionally, we consider the different structures involved in AD-altered Aβ brain balance, which could be directly or indirectly affected by a nuclear receptor (NR)/PPAR-related mechanism.

The quest for selective nox inhibitors and therapeutics: challenges, triumphs and pitfalls

SIGNIFICANCE

Numerous studies in animal models and human subjects corroborate that elevated levels of reactive oxygen species (ROS) play a pivotal role in the progression of multiple diseases. As a major source of ROS in many organ systems, the NADPH oxidase (Nox) has become a prime target for therapeutic development.

RECENT ADVANCES

In recent years, intense efforts have been dedicated to the development of pan- and isoform-specific Nox inhibitors as opposed to antioxidants that proved ineffective in clinical trials. Over the past decade, an array of compounds has been proposed in an attempt to fill this void.

CRITICAL ISSUES

Although many of these compounds have proven effective as Nox enzyme family inhibitors, isoform specificity has posed a formidable challenge to the scientific community. This review surveys the most prominent Nox inhibitors, and discusses potential isoform specificity, known mechanisms of action, and shortcomings. Some of these inhibitors hold substantial promise as targeted therapeutics.

FUTURE DIRECTIONS

Increased insight into the mechanisms of action and regulation of this family of enzymes as well as atomic structures of key Nox subunits are expected to give way to a broader spectrum of more potent, efficacious, and specific molecules. These lead molecules will assuredly serve as a basis for drug development aimed at treating a wide array of diseases associated with increased Nox activity.

Pioglitazone reduces angiotensin II-induced COX-2 expression through inhibition of ROS production and ET-1 transcription in vascular cells from spontaneously hypertensive rats

Glitazones have anti-inflammatory properties by interfering with the transcription of proinflammatory genes, such as cyclooxygenase (COX)-2, and with ROS production, which are increased in hypertension. This study analyzed whether pioglitazone modulates COX-2 expression in hypertension by interfering with ROS and endothelin (ET)-1. In vivo, pioglitazone (2.5 mg·kg(-1)·day(-1), 28 days) reduced the greater levels of COX-2, pre-pro-ET-1, and NADPH oxidase (NOX) expression and activity as well as O2 (·-) production found in aortas from spontaneously hypertensive rats (SHRs). ANG II increased COX-2 and pre-pro-ET-1 levels more in cultured vascular smooth muscle cells from hypertensive rats compared with normotensive rats. The ETA receptor antagonist BQ-123 reduced ANG II-induced COX-2 expression in SHR cells. ANG II also increased NOX-1 expression, NOX activity, and superoxide production in SHR cells; the selective NOX-1 inhibitor ML-171 and catalase reduced ANG II-induced COX-2 and ET-1 transcription. ANG II also increased c-Jun transcription and phospho-JNK1/2, phospho-c-Jun, and p65 NF-κB subunit nuclear protein expression. SP-600125 and lactacystin, JNK and NF-κB inhibitors, respectively, reduced ANG II-induced ET-1, COX-2, and NOX-1 levels and NOX activity. Pioglitazone reduced the effects of ANG II on NOX activity, NOX-1, pre-pro-ET-1, COX-2, and c-Jun mRNA levels, JNK activation, and nuclear phospho-c-Jun and p65 expression. In conclusion, ROS production and ET-1 are involved in ANG II-induced COX-2 expression in SHRs, explaining the greater COX-2 expression observed in this strain. Furthermore, pioglitazone inhibits ANG II-induced COX-2 expression likely by interfering with NF-κB and activator protein-1 proinflammatory pathways and downregulating ROS production and ET-1 transcription, thus contributing to the anti-inflammatory properties of glitazones.

Rosiglitazone regulates anti-inflammation and growth inhibition via PTEN

Peroxisome proliferator-activated receptor gamma (PPARγ) agonist has anti-inflammatory and anticancer properties. However, the mechanisms by which PPARγ agonist rosiglitazone interferes with inflammation and cancer via phosphatase and tensin homolog-(PTEN)-dependent pathway remain unclear. We found that lower doses (<25  μ M) of rosiglitazone significantly inhibited lipopolysaccharide-(LPS)-induced nitric oxide (NO) release (via inducible nitric oxide synthase, iNOS), prostaglandin E2 (PGE2) production (via cyclooxygenase-2, COX-2), and activation of Akt in RAW 264.7 murine macrophages. However, rosiglitazone did not inhibit the production of reactive oxygen species (ROS). In PTEN knockdown (shPTEN) cells exposed to LPS, rosiglitazone did not inhibit NO release, PGE2 production, and activation of Akt. These cells had elevated basal levels of iNOS, COX-2, and ROS. However, higher doses (25-100  μ M) of rosiglitazone, without LPS stimulation, did not block NO release and PGE2 productions, but they inhibited p38 MAPK phosphorylation and blocked ROS generation in shPTEN cells. In addition, rosiglitazone caused G1 arrest and reduced the number of cells in S + G2/M phase, leading to growth inhibition. These results indicate that the anti-inflammatory property of rosiglitazone is related to regulation of PTEN independent of inhibition on ROS production. However, rosiglitazone affected the dependence of PTEN-deficient cell growth on ROS.

The effect of FFAR1 on pioglitazone-mediated attenuation of palmitic acid-induced oxidative stress and apoptosis in βTC6 cells

OBJECTIVE

We sought to determine whether free fatty acid receptor 1 (FFAR1), a receptor for free fatty acids on the β-cell membrane, can mediate the pioglitazone (PIO)-attenuating effect on lipoapoptosis in β cells and its relationship to oxidative stress.

METHODS

The glucose-sensitive mouse beta pancreatic cell line βTC6 was used to investigate the effect of FFAR1 on PIO-attenuating palmitic acid (PA)-induced oxidative stress and apoptosis.

RESULTS

(1) PIO reduced PA-induced lipoapoptosis in β cells and upregulated the expression of FFAR1 at the mRNA and protein levels in a dose- and time-dependent manner. Silencing of FFAR1 expression was shown to weaken the protective effect of PIO on PA-induced lipoapoptosis in βTC6 cells; while lentiviral-mediated overexpression of FFAR1 was shown to enhance the protective effect of PIO against lipoapoptosis in β cells. (2) Downregulation of FFAR1 expression reduced the attenuating effect of PIO on the expression of NAPDH oxidase subunit p47(phox), Bax, cleaved caspase 3, and the production of reactive oxygen specific (ROS) induced by lipotoxicity, thereby preventing the upregulation of the expression of bcl-2. Inducing the overexpression of FFAR1 enhanced the anti-oxidative stress effect of PIO. Similarly, these effects of FFAR1 on PIO were reproduced under conditions of oxidative stress and apoptosis in βTC6 cells that were induced by H2O2. (3) PIO was found to increase the expression of PLCγ, ERK1/2, and PPARγ in lipotoxic β cells. Silencing FFAR1 expression reduced the PIO-mediated increases in the expression of above proteins; while inducing FFAR1 overexpression showed the opposite effect. Use of an inhibitor of PLCγ, ERK1/2, PPARγ was shown to restrict the protective effect of PIO on oxidative stress and lipoapoptosis of β cells.

CONCLUSIONS

FFAR1 can mediate PIO suppression of β-cell lipoapoptosis through anti-oxidative stress, which may be related to the activation of the PLCγ-ERK1/2-PPARγ pathway.

Down-regulated peroxisome proliferator-activated receptor γ (PPARγ) in lung epithelial cells promotes a PPARγ agonist-reversible proinflammatory phenotype in chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory condition and a leading cause of death, with no available cure. We assessed the actions in pulmonary epithelial cells of peroxisome proliferator-activated receptor γ (PPARγ), a nuclear hormone receptor with anti-inflammatory effects, whose role in COPD is largely unknown. We found that PPARγ was down-regulated in lung tissue and epithelial cells of COPD patients, via both reduced expression and phosphorylation-mediated inhibition, whereas pro-inflammatory nuclear factor-κB (NF-κB) activity was increased. Cigarette smoking is the main risk factor for COPD, and exposing airway epithelial cells to cigarette smoke extract (CSE) likewise down-regulated PPARγ and activated NF-κB. CSE also down-regulated and post-translationally inhibited the glucocorticoid receptor (GR-α) and histone deacetylase 2 (HDAC2), a corepressor important for glucocorticoid action and whose down-regulation is thought to cause glucocorticoid insensitivity in COPD. Treating epithelial cells with synthetic (rosiglitazone) or endogenous (10-nitro-oleic acid) PPARγ agonists strongly up-regulated PPARγ expression and activity, suppressed CSE-induced production and secretion of inflammatory cytokines, and reversed its activation of NF-κB by inhibiting the IκB kinase pathway and by promoting direct inhibitory binding of PPARγ to NF-κB. In contrast, PPARγ knockdown via siRNA augmented CSE-induced chemokine release and decreases in HDAC activity, suggesting a potential anti-inflammatory role of endogenous PPARγ. The results imply that down-regulation of pulmonary epithelial PPARγ by cigarette smoke promotes inflammatory pathways and diminishes glucocorticoid responsiveness, thereby contributing to COPD pathogenesis, and further suggest that PPARγ agonists may be useful for COPD treatment.

New roles for old pathways? A circuitous relationship between reactive oxygen species and cyclo-oxygenase in hypertension

Elevated production of prostanoids from the constitutive (COX-1) or inducible (COX-2) cyclo-oxygenases has been involved in the alterations in vascular function, structure and mechanical properties observed in cardiovascular diseases, including hypertension. In addition, it is well known that production of ROS (reactive oxygen species) plays an important role in the impaired contractile and vasodilator responses, vascular remodelling and altered vascular mechanics of hypertension. Of particular interest is the cross-talk between NADPH oxidase and mitochondria, the main ROS sources in hypertension, which may represent a vicious feed-forward cycle of ROS production. In recent years, there is experimental evidence showing a relationship between ROS and COX-derived products. Thus ROS can activate COX and the COX/PG (prostaglandin) synthase pathways can induce ROS production through effects on different ROS generating enzymes. Additionally, recent evidence suggests that the COX-ROS axis might constitute a vicious circle of self-perpetuating vasoactive products that have a pathophysiological role in altered vascular contractile and dilator responses and hypertension development. The present review discusses the current knowledge on the role of oxidative stress and COX-derived prostanoids in the vascular alterations observed in hypertension, highlighting new findings indicating that these two pathways act in concert to induce vascular dysfunction.

Pleiotropic effects of peroxisome proliferator-activated receptor γ and δ in vascular diseases

Peroxisome proliferator-activated receptors gamma (PPARγ) and delta (PPARδ) are nuclear receptors that have significant physiological effects on glucose and lipid metabolism. Experimental studies in animal models of metabolic disease have demonstrated their effects on improving lipid profile, insulin sensitivity, and reducing inflammatory responses. PPARγ and -δ are also expressed in the vasculature and their beneficial effects have been examined in various cardiovascular disease models such as atherosclerosis, hypertension, diabetic vascular complications, etc. using pharmacological ligands or genetic tools including viral vectors and transgenic mice. These studies suggest that PPARγ and δ are antiinflammatory, antiatherogenic, antioxidant, and antifibrotic against vascular diseases. Several signaling pathways, effector molecules, as well as coactivators/repressors have been identified as responsible for the protective effects of PPARγ and -δ in the vasculature. We discuss the pleiotropic effect of PPARγ and δ in vascular dysfunction, including atherosclerosis, hypertension, vascular remodeling, vascular injury, and diabetic vasculopathy, in various animal models, and the major underlying mechanisms. We also compare the phenotypes of several endothelial cell/vascular smooth muscle-specific PPARγ and -δ knockout and overexpressing transgenic mice in various disease models, and the implications underlying the functional importance of vascular PPARγ and δ in regulating whole-body homeostasis.

Peroxisome proliferator-activated receptors and Alzheimer's disease: hitting the blood-brain barrier

The blood-brain barrier (BBB) is often affected in several neurodegenerative disorders, such as Alzheimer's disease (AD). Integrity and proper functionality of the neurovascular unit are recognized to be critical for maintenance of the BBB. Research has traditionally focused on structural integrity more than functionality, and BBB alteration has usually been explained more as a consequence than a cause. However, ongoing evidence suggests that at the early stages, the BBB of a diseased brain often shows distinct expression patterns of specific carriers such as members of the ATP-binding cassette (ABC) transport protein family, which alter BBB traffic. In AD, amyloid-β (Aβ) deposits are a pathological hallmark and, as recently highlighted by Cramer et al. (2012), Aβ clearance is quite fundamental and is a less studied approach. Current knowledge suggests that BBB traffic plays a more important role than previously believed and that pharmacological modulation of the BBB may offer new therapeutic alternatives for AD. Recent investigations carried out in our laboratory indicate that peroxisome proliferator-activated receptor (PPAR) agonists are able to prevent Aβ-induced neurotoxicity in hippocampal neurons and cognitive impairment in a double transgenic mouse model of AD. However, even when enough literature about PPAR agonists and neurodegenerative disorders is available, the problem of how they exert their functions and help to prevent and rescue Aβ-induced neurotoxicity is poorly understood. In this review, along with highlighting the main features of the BBB and its role in AD, we will discuss information regarding the modulation of BBB components, including the possible role of PPAR agonists as BBB traffic modulators.