Telmisartan ameliorates lipopolysaccharide-induced innate immune response through peroxisome proliferator-activated receptor-γ activation in human monocytes

Evaluation of the protective effect of losartan in acetaminophen-induced liver and kidney damage in mice

Acetaminophen is widely used among humans as an antipyretic and analgesic. In this study, the protective effect of losartan in hepatotoxicity and nephrotoxicity induced by acetaminophen in mice was investigated owing to its anti-inflammatory and antioxidant effects. An injection of a single dose of 500 mg/kg (i.p.) acetaminophen was administered to induce hepatotoxicity and nephrotoxicity in Groups VI-X. Losartan at doses of 1 mg/kg (Group VII), 3 mg/kg (Group VIII), and 10 mg/kg (Groups III, V, IX, and X) was injected intraperitoneally twice, at 1 and 12 h after the acetaminophen injection. Additionally, a 4 mg/kg dose of GW9662 (peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist) was injected intraperitoneally 30 min before the losartan injections in Groups V and X. At the end of 24 h, the mice were euthanized, and blood, liver, and kidney tissue samples were collected. Levels of AST, ALT, creatinine, and oxidative stress markers including TBARS, SOD, CAT, GPx, TAS, TOS, GSH, and GSSG, along with pro-inflammatory cytokines IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α, were measured using ELISA kits. Additionally, a histological evaluation of the tissue samples was performed. Acetaminophen causes increases in the levels of AST, ALT, creatinine, TBARS, TOS, GSSG, IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α in serum, liver, and kidney tissue. Meanwhile, it led to a decrease in the levels of SOD, CAT, GPx, TAS, and GSH. Losartan injection reversed oxidative and inflammatory damage induced by acetaminophen. Histopathological changes in liver and kidney tissue were alleviated by losartan. The substance GW9662 increased the protective effect of losartan. In light of all the data obtained from our study, it can be said that losartan has a protective effect on liver and kidney damage induced by acetaminophen due to its antioxidant and anti-inflammatory effects. In terms of the study, losartan was found to be an alternative substance that could protect people from the harmful effects of acetaminophen.

Immunomodulation and immunopharmacology in heart failure

The immune system is intimately involved in the pathophysiology of heart failure. However, it is currently underused as a therapeutic target in the clinical setting. Moreover, the development of novel immunomodulatory therapies and their investigation for the treatment of patients with heart failure are hampered by the fact that currently used, evidence-based treatments for heart failure exert multiple immunomodulatory effects. In this Review, we discuss current knowledge on how evidence-based treatments for heart failure affect the immune system in addition to their primary mechanism of action, both to inform practising physicians about these pleiotropic actions and to create a framework for the development and application of future immunomodulatory therapies. We also delineate which subpopulations of patients with heart failure might benefit from immunomodulatory treatments. Furthermore, we summarize completed and ongoing clinical trials that assess immunomodulatory treatments in heart failure and present several therapeutic targets that could be investigated in the future. Lastly, we provide future directions to leverage the immunomodulatory potential of existing treatments and to foster the investigation of novel immunomodulatory therapeutics.

The Renin Angiotensin System as a Therapeutic Target in Traumatic Brain Injury

Traumatic brain injury (TBI) is a major public health problem, with limited pharmacological options available beyond symptomatic relief. The renin angiotensin system (RAS) is primarily known as a systemic endocrine regulatory system, with major roles controlling blood pressure and fluid homeostasis. Drugs that target the RAS are used to treat hypertension, heart failure and kidney disorders. They have now been used chronically by millions of people and have a favorable safety profile. In addition to the systemic RAS, it is now appreciated that many different organ systems, including the brain, have their own local RAS. The major ligand of the classic RAS, Angiotensin II (Ang II) acts predominantly through the Ang II Type 1 receptor (AT1R), leading to vasoconstriction, inflammation, and heightened oxidative stress. These processes can exacerbate brain injuries. Ang II receptor blockers (ARBs) are AT1R antagonists. They have been shown in several preclinical studies to enhance recovery from TBI in rodents through improvements in molecular, cellular and behavioral correlates of injury. ARBs are now under consideration for clinical trials in TBI. Several different RAS peptides that signal through receptors distinct from the AT1R, are also potential therapeutic targets for TBI. The counter regulatory RAS pathway has actions that oppose those stimulated by AT1R signaling. This alternative pathway has many beneficial effects on cells in the central nervous system, bringing about vasodilation, and having anti-inflammatory and anti-oxidative stress actions. Stimulation of this pathway also has potential therapeutic value for the treatment of TBI. This comprehensive review will provide an overview of the various components of the RAS, with a focus on their direct relevance to TBI pathology. It will explore different therapeutic agents that modulate this system and assess their potential efficacy in treating TBI patients.

Angiotensin receptor blocker use is associated with upregulation of the memory-protective angiotensin type 4 receptor (AT4R) in the postmortem brains of individuals without cognitive impairment

The reported primary dementia-protective benefits of angiotensin II type 1 receptor (AT1R) blockers (ARB) are believed, at least in part, to arise from systemic effects on blood pressure. However, there is a specific and independently regulated brain renin-angiotensin system (RAS). Brain RAS acts mainly through three receptor subtypes; AT1R, AT2R, and AT4R. The AT1R promotes inflammation and mitochondrial reactive oxygen species generation. AT2R increases nitric oxide. AT4R is essential for dopamine and acetylcholine release. It is unknown whether ARB use is associated with changes in the brain RAS. Here, we compared the impact of treatment with ARB on not cognitively impaired individuals and individuals with Alzheimer's dementia using postmortem frontal-cortex samples of age- and sex-matched participants (70-90 years old, n = 30 in each group). We show that ARB use is associated with higher brain AT4R, lower oxidative stress, and amyloid-β burden in NCI participants. In AD, ARB use was associated with lower brain AT1R but had no impact on inflammation, oxidative stress, or amyloid-β burden. Our results may suggest a potential role for AT4R in the salutary effects for ARB on the brains of not cognitively impaired older adults.

Neuroprotective effect of angiotensin II receptor blockers on the risk of incident Alzheimer's disease: A nationwide population-based cohort study

Background

Recent studies on renin-angiotensin system (RAS) inhibitors have reported a reduced risk of Alzheimer's disease (AD). Nevertheless, the effect of RAS inhibitor type and blood-brain barrier (BBB) permeability on the risk of AD is still unknown.

Objectives

To assess the effects of RAS inhibitors on the risk of AD based on the type and BBB permeability and investigate the cumulative duration-response relationship.

Methods

This was a population-based retrospective cohort study using the Korean Health Insurance Review and Assessment database records from 2008 to 2019. The data of patients diagnosed with ischemic heart disease between January 2009 and June 2009 were identified for inclusion in the analyses. Propensity score matching was used to balance RAS inhibitor users with non-users. The association between the use of RAS inhibitors and incident AD was evaluated using a multivariate Cox proportional hazard regression model. The results are presented in adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs).

Results

Among the 57,420 matched individuals, 7,303 developed AD within the follow-up period. While the use of angiotensin-converting enzyme inhibitors (ACEIs) was not significantly associated with AD risk, the use of angiotensin II receptor blockers (ARBs) showed a significant association with reduced risk of incident AD (aHR = 0.94; 95% CI = 0.90-0.99). Furthermore, the use of BBB-crossing ARBs was associated with a lower risk of AD (aHR = 0.83; 95% CI = 0.78-0.88) with a cumulative duration-response relationship. A higher cumulative dose or duration of BBB-crossing ARBs was associated with a gradual decrease in AD risk (P for trend < 0.001). No significant association between the use of ACEIs and the risk of AD was observed regardless of BBB permeability.

Conclusion

Long-term use of BBB-crossing ARBs significantly reduced the risk of AD development. The finding may provide valuable insight into disease-modifying drug options for preventing AD in patients with cardiovascular diseases.

Sacubitril/valsartan alleviates sepsis-induced acute lung injury via inhibiting GSDMD-dependent macrophage pyroptosis in mice

Sepsis-induced acute lung injury (ALI) is a life-threatening disorder with intricate pathogenesis. Macrophage pyroptosis reportedly plays a vital role in ALI. Although it has been established that angiotensin receptor blockers (ARBs) can reduce sepsis-induced organ injury, the efficacy of sacubitril/valsartan (SV) for sepsis has been largely understudied. Here, we aimed to investigate the role of SV in sepsis-induced ALI. Caecal ligation and puncture (CLP) were used to induce polymicrobial sepsis and related ALI. The therapeutic effects of SV in CLP mice were subsequently assessed. Gasdermin D (GSDMD)^-/- mice were used to validate the signalling pathways affected by SV. In vitro, mouse bone marrow-derived macrophages (BMDMs) and Raw264.7 cells were treated with SV following exposure to lipopolysaccharide and adenosine triphosphate. Finally, the serum obtained from 42 septic patients was used for biochemical analysis. Compared to the other ARBs, SV yielded more pronounced anti-inflammatory effects on macrophages. In vivo, SV decreased mortality rates, significantly reduced lung damage and prevented the inflammatory response in CLP mice. In addition, SV suppressed GSDMD-mediated macrophage pyroptosis in mice. In BMDMs and Raw264.7 cells, the anti-inflammatory and anti-pyroptosis properties of SV were verified. SV treatment effectively inhibited NLRP3 inflammasome activation and prevented macrophage pyroptosis in a GSDMD-dependent manner. Furthermore, we found that septic individuals had considerably higher serum angiotensin II levels. Overall, we found that SV might prevent ALI in CLP mice by inhibiting GSDMD-mediated pyroptosis of macrophages. Thus, SV might be a viable drug for sepsis-induced ALI.

Comparing the Neuroprotective Effects of Telmisartan, Perindopril, and Nebivolol Against Lipopolysaccharide-Induced Injury in Neuron-Like Cells

The effect of antihypertensive drugs, especially drugs modulating the renin-angiotensin-aldosterone-system (RAAS), on neurodegenerative diseases still needs to be investigated. This study aimed to compare the effects of three different antihypertensive drugs (telmisartan, perindopril, and nebivolol) on neuroprotection and acetylcholine (ACh) levels against lipopolysaccharide (LPS)-induced injury in a differentiated SH-SY5Y cell line. Cells were treated with retinoic acid for differentiation to a neuronal phenotype. LPS 20 (μg/mL) was applied to the cells for one hour. Then, the cells were treated with 1, 5, and 10 µg/mL concentrations of telmisartan, perindopril, and nebivolol separately for 24 hours, except for the control and LPS alone groups. Cell viability was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. ACh levels were analyzed using an enzyme immunosorbent assay in the culture medium. Tumor necrosis factor-alpha (TNF-α), interleukin 1 beta (IL-1β), and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) expressions were evaluated using western blot analysis. Telmisartan demonstrated the highest cell viability against LPS-induced injury, whereas the protective effect of perindopril was moderate. Nebivolol showed no neuroprotective effect. The protective effect of 10-µg/mL telmisartan was superior to 10 µg/mL perindopril (p=0.006), 5 µg/mL perindopril (p=0.001), 1 µg/mL perindopril (p=0.001), and 1, 5, and 10 µg/mL nebivolol (p<0.001). Among all the study drugs, only telmisartan provided a statistically significant increase in ACh levels after LPS-induced injury. Additionally, the administration of telmisartan provided a concentration-dependent reduction in TNF-α, IL-1β, and NFκB expression against LPS-induced neuroinflammation. These findings suggest that telmisartan has a superior neuroprotective effect against LPS-induced injury in neuron-like cells compared with both perindopril and nebivolol.

The immunomodulatory effects of antihypertensive therapy: A review

Hypertension remains the leading preventable risk factor for stroke and coronary artery disease, significantly contributing to all-cause global mortality and predisposing patients to renal and heart failure, as well as peripheral vascular disease. Due to the widespread usage of antihypertensive drugs, global mean blood pressure has remained unchanged or even slightly decreased over the past four decades. However, considering the broad spectrum of mechanisms involved in the action of antihypertensive drugs and the prevalence of their target receptors on immune cells, possible immunomodulatory effects which may exert beneficial effects of lowering blood pressure but also potentially alter immune function should be considered. In this review, we attempt to assess the consequences to immune system function of administering the five most commonly prescribed groups of antihypertensive drugs and to explain the mechanisms behind those interactions. Finally, we show potential gaps in our understanding of the effects of antihypertensive drugs on patient health. With regard to the widespread use of these drugs in the adult population worldwide, the discussed results may be of vital importance to evidence-based decision-making in daily clinical practice.

Addressing Peroxisome Proliferator-Activated Receptor-gamma in 3-Nitropropionic Acid-Induced Striatal Neurotoxicity in Rats

Telmisartan (TEL) is an angiotensin II type 1 receptor blocker and a partial activator of peroxisome proliferator-activated receptor-gamma (PPARγ), which regulates inflammatory and apoptotic pathways. Increasing evidence has demonstrated the PPARγ agonistic property of TEL in several brain disorders. This study aims to explore the neuroprotective impact of TEL in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. The PPARγ effect of TEL was affirmed by using the PPARγ agonist pioglitazone (PIO), and the antagonist GW9662. 3-NP led to a significant reduction in body weight alongside motor and cognitive functioning. The striata of the 3-NP-treated rats showed energy-deficit, microglia-mediated inflammatory reactions, apoptotic damage as well as histopathological lesions. PIO and TEL improved motor and cognitive perturbations induced by 3-NP, as confirmed by striatal histopathological examination, energy restoration, and neuronal preservation. Both drugs improved mitochondrial biogenesis evidenced by elevated mRNA expression of PPARγ, PGC-1α, and TFAM, alongside increased striatal ATP and SDH. The mitochondrial effect of TEL was beyond PPARγ activation. As well, their anti-inflammatory effect was attributed to suppression of microglial activation, and protein expression of pS536 p65 NF-κB with marked attenuation of striatal inflammatory mediator's release. Anti-inflammatory cytokine IL-10 expression was concurrently increased. TEL effectively participated in neuronal survival as it promoted phosphorylation of Akt/GSK-3β, further increased Bcl-2 expression, and inhibited cleavage of caspase-3. Interestingly, co-treatment with GW9662 partially revoked the beneficial effects of TEL. These findings recommend that TEL improves motor and cognitive performance, while reducing neuronal inflammation and apoptosis in 3-NP-induced neurotoxicity via a PPARγ-dependent mechanism.

Systematic Review and Meta-Analysis of Renin-Angiotensin-Aldosterone System Blocker Effects on the Development of Cardiovascular Disease in Patients With Chronic Kidney Disease

Background: Cardiovascular events are one of the most serious complications that increase the risk of mortality and morbidity in pre-dialysis and on-dialysis chronic kidney disease (CKD) patients. Activation of the renin-angiotensin-aldosterone system (RAAS) is considered to contribute to the development of cardiovascular events in these populations. Therefore, several kinds of RAAS blockers have been frequently prescribed to prevent cardiovascular events in patients with CKD; however, their effectiveness remains controversial. This systematic review focuses on whether RAAS blockers prevent cardiovascular events in patients with CKD. Method: PubMed were searched to retrieve reference lists of eligible trials and related reviews. Randomized prospective controlled trials that investigated the effects on cardiovascular events in CKD patients that were published in English from 2010 to 2020 were included. Results: Among 167 identified studies, 11 eligible studies (n = 8,322 subjects) were included in the meta-analysis. The meta-analysis showed that RAAS blockers significantly reduced cardiovascular events in on-dialysis patients with CKD [three studies; odds ratio (OR), 0.52; 95% confidence interval (CI), 0.36 to 0.74; p = 0.0003], but there was no significant difference in pre-dialysis patients with CKD because of the heterogeneity in each study (eight studies). We also investigated the effects of each kind of RAAS blocker on cardiovascular events in CKD patients. Among the RAAS blockers, mineralocorticoid receptor antagonists significantly decreased cardiovascular events in pre-dialysis or on-dialysis patients with CKD (four studies; OR, 0.60; 95%CI, 0.50 to 0.73, p < 0.0001). However, angiotensin receptor blockers did not show significant effects (four studies; OR, 0.65; 95%CI, 0.42 to 1.01; p = 0.0529). The effects of angiotensin converting enzyme inhibitors and direct renin inhibitors on cardiovascular events in patients with CKD could not be analyzed because there were too few studies. Conclusion: Mineralocorticoid receptor antagonists may decrease cardiovascular events in pre-dialysis or on-dialysis patients with CKD.

Angiotensin Receptor Blockers Are Not Just for Hypertension Anymore

Beyond blood pressure control, angiotensin receptor blockers reduce common injury mechanisms, decreasing excessive inflammation and protecting endothelial and mitochondrial function, insulin sensitivity, the coagulation cascade, immune responses, cerebrovascular flow, and cognition, properties useful to treat inflammatory, age-related, neurodegenerative, and metabolic disorders of many organs including brain and lung.

Systemic Candesartan Treatment Modulates Behavior, Synaptic Protein Levels, and Neuroinflammation in Female Mice That Express Human APOE4

Evidence suggests that angiotensin receptor blockers (ARBs) could be beneficial for Alzheimer’s disease (AD) patients independent of any effects on hypertension. However, studies in rodent models directly testing the activity of ARB treatment on behavior and AD-relevent pathology including neuroinflammation, Aβ levels, and cerebrovascular function, have produced mixed results. APOE4 is a major genetic risk factor for AD and has been linked to many of the same functions as those purported to be modulated by ARB treatment. Therefore, evaluating the effects of ARB treatment on behavior and AD-relevant pathology in mice that express human APOE4 could provide important information on whether to further develop ARBs for AD therapy. In this study, we treated female and male mice that express the human APOE4 gene in the absence (E4FAD−) or presence (E4FAD+) of high Aβ levels with the ARB prodrug candesartan cilexetil for a duration of 4 months. Compared to vehicle, candesartan treatment resulted in greater memory-relevant behavior and higher hippocampal presynaptic protein levels in female, but not male, E4FAD− and E4FAD+ mice. The beneficial effects of candesartan in female E4FAD− and E4FAD+ mice occurred in tandem with lower GFAP and Iba1 levels in the hippocampus, whereas there were no effects on markers of cerebrovascular function and Aβ levels. Collectively, these data imply that the effects of ARBs on AD-relevant pathology may be modulated in part by the interaction between APOE genotype and biological sex. Thus, the further development of ARBs could provide therapeutic options for targeting neuroinflammation in female APOE4 carriers.

Protective role of ACE2 and its downregulation in SARS-CoV-2 infection leading to Macrophage Activation Syndrome: Therapeutic implications

In light of the outbreak of the 2019 novel coronavirus disease (COVID-19), the international scientific community has joined forces to develop effective treatment strategies. The Angiotensin-Converting Enzyme (ACE) 2, is an essential receptor for cell fusion and engulfs the SARS coronavirus infections. ACE2 plays an important physiological role, practically in all the organs and systems. Also, ACE2 exerts protective functions in various models of pathologies with acute and chronic inflammation. While ACE2 downregulation by SARS-CoV-2 spike protein leads to an overactivation of Angiotensin (Ang) II/AT1R axis and the deleterious effects of Ang II may explain the multiorgan dysfunction seen in patients. Specifically, the role of Ang II leading to the appearance of Macrophage Activation Syndrome (MAS) and the cytokine storm in COVID-19 is discussed below. In this review, we summarized the latest research progress in the strategies of treatments that mainly focus on reducing the Ang II-induced deleterious effects rather than attenuating the virus replication.

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Protective role of ACE2 in the organs and system

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Downregulation of ACE2 expression by SARS-CoV-2 leads to Ang II-induced organ damage.

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The appearance of MAS in COVID-19 patient

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Suggested treatment to diminish the deleterious effect of Ang II or appearance of MAS

Effect of Telmisartan in the Oxidative Stress Components Induced by Ischemia Reperfusion in Rats

The therapeutic effects of telmisartan, an angiotensin II receptor antagonist and a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, have been demonstrated in several disorders. It has antioxidant and immune response modulator properties and has shown promising results in the treatment of an ischemia/reperfusion (I/R) lesion. In this study, a skeletal muscle (right gastrocnemius muscle) I/R lesion was induced in rats and different reperfusion times (1 h, 24 h, 72 h, 7-day, and 14-day subgroups) were assessed. Furthermore, levels of oxidative markers such as enzymatic scavengers (catalase (CAT) and superoxide dismutase (SOD)) and metabolites (nitrates and 8-oxo-deoxyguanosine) were determined. The degree of tissue injury (total lesioned fibers and inflammatory cell count) was also evaluated. We observed an increase in CAT and SOD expression levels under telmisartan treatment, with a decrease in injury and oxidative biomarker levels in the 72 h, 7-day, and 14-day subgroups. Telmisartan reduced oxidative stress and decreased the damage of the I/R lesion.

Telmisartan Protects a Microglia Cell Line from LPS Injury Beyond AT1 Receptor Blockade or PPARγ Activation

The Angiotensin II Receptor Blocker (ARB) Telmisartan reduces inflammation through Angiotensin II AT1 receptor blockade and peroxisome proliferator-activated receptor gamma (PPARγ) activation. However, in a mouse microglia-like BV2 cell line, imitating primary microglia responses with high fidelity and devoid of AT1 receptor gene expression or PPARγ activation, Telmisartan reduced gene expression of pro-injury factors, enhanced that of anti-inflammatory genes, and prevented LPS-induced increase in inflammatory markers. Using global gene expression profiling and pathways analysis, we revealed that Telmisartan normalized the expression of hundreds of genes upregulated by LPS and linked with inflammation, apoptosis and neurodegenerative disorders, while downregulating the expression of genes associated with oncological, neurodegenerative and viral diseases. The PPARγ full agonist Pioglitazone had no neuroprotective effects. Surprisingly, the PPARγ antagonists GW9662 and T0070907 were neuroprotective and enhanced Telmisartan effects. GW9226 alone significantly reduced LPS toxic effects and enhanced Telmisartan neuroprotection, including downregulation of pro-inflammatory TLR2 gene expression. Telmisartan and GW9662 effects on LPS injury negatively correlated with pro-inflammatory factors and upstream regulators, including TLR2, and positively with known neuroprotective factors and upstream regulators. Gene Set Enrichment Analysis (GSEA) of the Telmisartan and GW9662 data revealed negative correlations with sets of genes associated with neurodegenerative and metabolic disorders and toxic treatments in cultured systems, while demonstrating positive correlations with gene sets associated with neuroprotection and kinase inhibition. Our results strongly suggest that novel neuroprotective effects of Telmisartan and GW9662, beyond AT1 receptor blockade or PPARγ activation, include downregulation of the TLR2 signaling pathway, findings that may have translational relevance.

Azilsartan improves the effects of etanercept in patients with active rheumatoid arthritis: a pilot study

Background and aim

Much evidence has emerged documenting the involvement of the renin-angiotensin system (RAS) in inflammatory processes. The objective of this study was to evaluate the effects of blocking RAS with azilsartan (Azil) on the clinical efficacy of etanercept (Etan) in patients with active rheumatoid arthritis (RA).

Patients and methods

Forty-two patients diagnosed with active RA and poorly responding to methotrexate were enrolled in this pilot clinical study. They were randomly allocated into two groups, and treated with either Etan (50 mg/week) and placebo or the same dose of Etan with Azil (20 mg/day) for 90 days. The clinical outcome was evaluated using the Disease Activity Score-28 joint (DAS-28), simplified disease activity index (SDAI), clinical disease activity index (CDAI) and the health assessment questionnaire disease index (HAQ-DI). Blood samples were obtained for the assessment of C-reactive protein and erythrocyte sedimentation rate at baseline and after 90 days.

Results

The markers of pain and disease activity, C-reactive protein and erythrocyte sedimentation rate were significantly improved when Azil was used, as an adjuvant with Etan, compared with the use of Etan and placebo.

Conclusion

Blocking RAS with azilsartan may improve the effects of etanercept on the clinical markers of pain and disease severity of patients with active RA not responding to methotrexate.

A Dual AMPK/Nrf2 Activator Reduces Brain Inflammation After Stroke by Enhancing Microglia M2 Polarization

AIMS

Microglia-mediated neuroinflammation plays an important role in focal ischemic stroke, a disorder with no effective therapeutic agents. Since microglial polarization to the M2 phenotype and reduction of oxidative stress are mediated through AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (Nrf2) activation, we assessed the dual therapeutic effect of AMPK and Nrf2 activation by a novel neuroprotectant HP-1c in the treatment of ischemic stroke.

RESULTS

We developed a novel class of hybrids (HP-1a-HP-1f) of telmisartan and 2-(1-hydroxypentyl)-benzoate (HPBA) as a ring-opening derivative of NBP. The most promising hybrid, HP-1c, exhibited more potent anti-inflammatory and neuroprotective effects in vitro and reduced brain infarct volume and improved neurological deficits in a rat model of transient focal cerebral ischemia when compared with telmisartan alone, NBP alone, or a combination of telmisartan and NBP. HP-1c had a therapeutic window of up to 24 h, ameliorated ischemic cerebral injury in permanent focal cerebral ischemia, and improved motor function. The beneficial effects of HP-1c in ischemic stroke were associated with microglial polarization to the M2 phenotype and reduced oxidative stress. HP-1c also shifted the M1/M2 polarization in a mouse neuroinflammatory model. The anti-inflammatory and anti-oxidative effects of HP-1c were associated with AMPK-Nrf2 pathway activation for neuroprotection. We showed that HP-1c penetrates the brain, has a plasma half-life of around 3.93 h, and has no toxicity in mice. Innovation and Conclusion: Our study results suggest that HP-1c, with dual AMPK- and Nrf2-activating properties, may have potential in further studies as a novel therapy for ischemic stroke. Antioxid. Redox Signal. 28, 141-163.

Development and validation of a high throughput LC-MS/MS method for simultaneous quantitation of pioglitazone and telmisartan in rat plasma and its application to a pharmacokinetic study

Management of cardiovascular risk factors in diabetes demands special attention due to their co-existence. Pioglitazone (PIO) and telmisartan (TLM) combination can be beneficial in effective control of cardiovascular complication in diabetes. In this research, we developed and validated a high throughput LC-MS/MS method for simultaneous quantitation of PIO and TLM in rat plasma. This developed method is more sensitive and can quantitate the analytes in relatively shorter period of time compared to the previously reported methods for their individual quantification. Moreover, till date, there is no bioanalytical method available to simultaneously quantitate PIO and TLM in a single run. The method was validated according to the USFDA guidelines for bioanalytical method validation. A linear response of the analytes was observed over the range of 0.005-10 µg/mL with satisfactory precision and accuracy. Accuracy at four quality control levels was within 94.27%-106.10%. The intra- and inter-day precision ranged from 2.32%-10.14 and 5.02%-8.12%, respectively. The method was reproducible and sensitive enough to quantitate PIO and TLM in rat plasma samples of a preclinical pharmacokinetic study. Due to the potential of PIO-TLM combination to be therapeutically explored, this method is expected to have significant usefulness in future.

Roles of Peroxisome Proliferator-Activated Receptor Gamma on Brain and Peripheral Inflammation

Peroxisome proliferator-activated receptor gamma (PPARγ) has been implicated in the pathology of numerous diseases involving diabetes, stroke, cancer, or obesity. It is expressed in diverse cell types, including vessels, immune and glial cells, and neurons. PPARγ plays crucial roles in the regulation of cellular differentiation, lipid metabolism, or glucose homeostasis. PPARγ ligands also exert effects on attenuating degenerative processes in the brain, as well as in peripheral systems, and it has been associated with the control of anti-inflammatory mechanisms, oxidative stress, neuronal death, neurogenesis, differentiation, and angiogenesis. This review will highlight key advances in the understanding of the PPARγ-related mechanisms responsible for neuroprotection after brain injuries, both ischemia and traumatic brain injury, and it will also cover the natural and synthetic agonist for PPARγ, angiotensin receptor blockers, and PPARγ antagonists, used in experimental and clinical research. A better understanding of the pleiotropic mechanisms and applications of these drugs to improve the recovery and to repair the acute and chronic induced neuroinflammation after brain injuries will pave the way for more effective therapeutic strategies after brain deficits.

Brain Renin-Angiotensin System and Microglial Polarization: Implications for Aging and Neurodegeneration

Microglia can transform into proinflammatory/classically activated (M1) or anti-inflammatory/alternatively activated (M2) phenotypes following environmental signals related to physiological conditions or brain lesions. An adequate transition from the M1 (proinflammatory) to M2 (immunoregulatory) phenotype is necessary to counteract brain damage. Several factors involved in microglial polarization have already been identified. However, the effects of the brain renin-angiotensin system (RAS) on microglial polarization are less known. It is well known that there is a “classical” circulating RAS; however, a second RAS (local or tissue RAS) has been observed in many tissues, including brain. The locally formed angiotensin is involved in local pathological changes of these tissues and modulates immune cells, which are equipped with all the components of the RAS. There are also recent data showing that brain RAS plays a major role in microglial polarization. Level of microglial NADPH-oxidase (Nox) activation is a major regulator of the shift between M1/proinflammatory and M2/immunoregulatory microglial phenotypes so that Nox activation promotes the proinflammatory and inhibits the immunoregulatory phenotype. Angiotensin II (Ang II), via its type 1 receptor (AT1), is a major activator of the NADPH-oxidase complex, leading to pro-oxidative and pro-inflammatory effects. However, these effects are counteracted by a RAS opposite arm constituted by Angiotensin II/AT2 receptor signaling and Angiotensin 1–7/Mas receptor (MasR) signaling. In addition, activation of prorenin-renin receptors may contribute to activation of the proinflammatory phenotype. Aged brains showed upregulation of AT1 and downregulation of AT2 receptor expression, which may contribute to a pro-oxidative pro-inflammatory state and the increase in neuron vulnerability. Several recent studies have shown interactions between the brain RAS and different factors involved in microglial polarization, such as estrogens, Rho kinase (ROCK), insulin-like growth factor-1 (IGF-1), tumor necrosis factor α (TNF)-α, iron, peroxisome proliferator-activated receptor gamma, and toll-like receptors (TLRs). Metabolic reprogramming has recently been involved in the regulation of the neuroinflammatory response. Interestingly, we have recently observed a mitochondrial RAS, which is altered in aged brains. In conclusion, dysregulation of brain RAS plays a major role in aging-related changes and neurodegeneration by exacerbation of oxidative stress (OS) and neuroinflammation, which may be attenuated by pharmacological manipulation of RAS components.

Alternative Interventions to Prevent Oxidative Damage following Ischemia/Reperfusion

Ischemia/reperfusion (I/R) lesions are a phenomenon that occurs in multiple pathological states and results in a series of events that end in irreparable damage that severely affects the recovery and health of patients. The principal therapeutic approaches include preconditioning, postconditioning, and remote ischemic preconditioning, which when used separately do not have a great impact on patient mortality or prognosis. Oxidative stress is known to contribute to the damage caused by I/R; however, there are no pharmacological approaches to limit or prevent this. Here, we explain the relationship between I/R and the oxidative stress process and describe some pharmacological options that may target oxidative stress-states.

Postconditioning attenuates coronary perivascular and interstitial fibrosis through modulating angiotensin II receptors and angiotensin-converting enzyme 2 after myocardial infarction

BACKGROUND

Postconditioning (Postcon) is known to reduce infarct size. This study tested the hypothesis that Postcon attenuates the perivascular and interstitial fibrosis after myocardial infarction through modulating angiotensin II-activated fibrotic cascade.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to 45-min coronary occlusion followed by 1 and 6 wk of reperfusion. Postcon was applied at the onset of reperfusion with four cycles of 10/10-s reperfusion-ischemia at the onset of reperfusion. Preconditioning (Precon) with two cycles of 5/5-min ischemia-reperfusion was applied before coronary occlusion.

RESULTS

Postcon reduced angiotensin-converting enzyme protein and expression in the perivascular area and intermyocardium, coincident with the less-expressed angiotensin II receptor, type 1, enhanced angiotensin II receptor, type 2, and angiotensin converting enzyme 2. Postcon lowered the monocyte chemoattractant protein-1 and inhibited the populations of interstitial macrophages (60 ± 12 versus 84 ± 9.5 number per high-powered field [HPF] in control, P < 0.05). Along with these modulations, Postcon also downregulated transforming growth factor β1 protein and inhibited proliferation of α-smooth muscle actin expressing myofibroblasts (41 ± 11 versus 79 ± 8.2 number per HPF in control, P < 0.05), consistent with downregulated phospho-Smad2 and phospho-Smad3. Furthermore, the synthesis of collagen I and III was attenuated, and the perivascular-interstitial fibrosis was inhibited by Postcon as demonstrated by reduced perivascular fibrosis ratio (0.6 ± 0.6 versus 1.6 ± 0.5 per HPF in control, P < 0.05) and smaller collagen-rich area (16 ± 4.7 versus 34 ± 9.2% per HPF in control, P < 0.05). Precon conferred a comparable level of protection as Postcon did in all parameters measured, suggesting protection trigged by this endogenous stimulation can be achieved when it was applied either before ischemia or after reperfusion.

CONCLUSIONS

These results suggest that Postcon could be selected as an adjunctive intervention with other existing therapeutic drugs to treat the fibrosis-derived heart failure patients after myocardial infarction.

Type-1 angiotensin receptor signaling in central nervous system myeloid cells is pathogenic during fatal alphavirus encephalitis in mice

BACKGROUND

Alphaviruses can cause fatal encephalitis in humans. Natural infections occur via the bite of infected mosquitos, but aerosol transmissibility makes some of these viruses potential bioterrorism agents. Central nervous system (CNS) host responses contribute to alphavirus pathogenesis in experimental models and are logical therapeutic targets. We investigated whether reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) activity within the CNS contributes to fatal alphavirus encephalitis in mice.

METHODS

Infected animals were treated systemically with the angiotensin receptor-blocking drug, telmisartan, given its ability to cross the blood-brain barrier, selectively block type-1 angiotensin receptors (AT1R), and inhibit Nox-derived ROS production in vascular smooth muscle and other extraneural tissues. Clinical, virological, biochemical, and histopathological outcomes were followed over time.

RESULTS

The importance of the angiotensin II (Ang II)/AT1R axis in disease pathogenesis was confirmed by demonstrating increased Ang II levels in the CNS following infection, enhanced disease survival when CNS Ang II production was suppressed, increased AT1R expression on microglia and tissue-infiltrating myeloid cells, and enhanced disease survival in AT1R-deficient mice compared to wild-type (WT) controls. Systemic administration of telmisartan protected WT mice from lethal encephalitis caused by two different alphaviruses in a dose-dependent manner without altering virus replication or exerting any anti-inflammatory effects in the CNS. Infection triggered up-regulation of multiple Nox subunits in the CNS, while drug treatment inhibited local Nox activity, ROS production, and oxidative neuronal damage. Telmisartan proved ineffective in Nox-deficient mice, demonstrating that this enzyme is its main target in this experimental setting.

CONCLUSIONS

Nox-derived ROS, likely arising from CNS myeloid cells triggered by AT1R signaling, are pathogenic during fatal alphavirus encephalitis in mice. Systemically administered telmisartan at non-hypotensive doses targets Nox activity in the CNS to exert a neuroprotective effect. Disruption of this pathway may have broader implications for the treatment of related infections as well as for other CNS diseases driven by oxidative injury.

Angiotensin receptor blockers are not associated with reduced inflammatory markers in the general population

OBJECTIVE

Angiotensin receptor blockers (ARBs) have been suggested to reduce inflammation in randomized controlled trials. We assessed the association between ARBs and inflammatory markers in a general population setting.

METHODS

This is a population-based prospective study conducted in Lausanne, Switzerland. Baseline data from 933 participants on antihypertensive drugs (424 on ARBs) was collected in 2003-2006. Follow-up data from 1120 participants (572 on ARBs) was collected in 2009-2012. C-reactive protein (CRP), interleukins 1β and 6 and tumor necrosis factor alpha (TNF-α) were assessed and categorized in quartiles.

RESULTS

At baseline, no differences were found between participants taking or not taking ARBs for all inflammatory markers studied, and this association persisted after multivariate adjustment: odds ratios (ORs) and (95% confidence interval) for being in the highest quartile of interleukin-1β, interleukin-6, TNF-α and CRP for participants on ARB compared to participants not on ARB were 1.23 (0.89-1.70), 1.26 (0.93-1.70), 1.14 (0.85-1.53) and 1.27 (0.96-1.69) respectively (P > 0.05). These findings were further replicated in the follow-up study: OR and (95% CI) of 1.10 (0.78-1.55), 0.87 (0.64-1.19), 0.83 (0.61-1.14) and 0.91 (0.68-1.22) for interleukin-1β, interleukin-6, TNF-α and CRP respectively (P > 0.05). Finally, no effect of ARBs was found when comparing participants who received ARBs throughout the 5.4-year follow-up with participants on other antihypertensive drugs: OR and (95% CI) of 0.93 (0.61-1.42), 0.80 (0.54-1.17), 0.86 (0.59-1.25) and 0.95 (0.67-1.35) for interleukin-1β, interleukin-6, TNF-α and CRP respectively (P > 0.05).

CONCLUSION

ARBs are not associated with reduced levels of inflammatory markers in the general population.

Toward a noncytotoxic glioblastoma therapy: blocking MCP-1 with the MTZ Regimen

To improve the prognosis of glioblastoma, we developed an adjuvant treatment directed to a neglected aspect of glioblastoma growth, the contribution of nonmalignant monocyte lineage cells (MLCs) (monocyte, macrophage, microglia, dendritic cells) that infiltrated a main tumor mass. These nonmalignant cells contribute to glioblastoma growth and tumor homeostasis. MLCs comprise of approximately 10%-30% of glioblastoma by volume. After integration into the tumor mass, these become polarized toward an M2 immunosuppressive, pro-angiogenic phenotype that promotes continued tumor growth. Glioblastoma cells initiate and promote this process by synthesizing 13 kDa MCP-1 that attracts circulating monocytes to the tumor. Infiltrating monocytes, after polarizing toward an M2 phenotype, synthesize more MCP-1, forming an amplification loop. Three noncytotoxic drugs, an antibiotic - minocycline, an antihypertensive drug - telmisartan, and a bisphosphonate - zoledronic acid, have ancillary attributes of MCP-1 synthesis inhibition and could be re-purposed, singly or in combination, to inhibit or reverse MLC-mediated immunosuppression, angiogenesis, and other growth-enhancing aspects. Minocycline, telmisartan, and zoledronic acid - the MTZ Regimen - have low-toxicity profiles and could be added to standard radiotherapy and temozolomide. Re-purposing older drugs has advantages of established safety and low drug cost. Four core observations support this approach: 1) malignant glioblastoma cells require a reciprocal trophic relationship with nonmalignant macrophages or microglia to thrive; 2) glioblastoma cells secrete MCP-1 to start the cycle, attracting MLCs, which subsequently also secrete MCP-1 perpetuating the recruitment cycle; 3) increasing cytokine levels in the tumor environment generate further immunosuppression and tumor growth; and 4) MTZ regimen may impede MCP-1-driven processes, thereby interfering with glioblastoma growth.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Combination of Telmisartan and Linagliptin Preserves Pancreatic Islet Cell Function and Morphology in db/db Mice

OBJECTIVES

The present study aimed to investigate the synergistic action of telmisartan and linagliptin in ameliorating pancreatic islet functions and morphology in type 2 diabetes mellitus and to delineate the molecular signaling pathway involved.

METHODS

db/db mice were given telmisartan (3 mg/kg) or linagliptin (3 mg/kg) alone or in combination, daily for 8 weeks, and were studied in vivo by fasting and random blood glucose tests, oral glucose tolerance tests, and intraperitoneal insulin tolerance tests, as well as ex vivo by glucose-stimulated insulin secretion and morphology of pancreatic islets. The underlying signaling pathways were examined by Western blot, real-time quantitative polymerase chain reaction, and dihydroethidium staining analyses using mouse pancreatic islets and rat β-insulinoma cells.

RESULTS

Telmisartan/linagliptin combination induced significantly better glucose homeostasis than the monotherapies. Posttreatment reactive oxygen species level was suppressed most significantly after the telmisartan/linagliptin combined therapy, whereas no significant change in peroxisome proliferator-activated receptor γ expressions was observed after treatments.

CONCLUSIONS

The telmisartan/linagliptin combination preserved pancreatic islet cell functions and morphology via reduction of oxidative stress but independent of the peroxisome proliferator-activated receptor γ pathway. Our data shed light on the therapeutic potential of using the telmisartan/linagliptin combination in the treatment of human type 2 diabetes mellitus and its related complications.

CD97/ADGRE5 Inhibits LPS Induced NF-κB Activation through PPAR-γ Upregulation in Macrophages

CD97/ADGRE5 protein is predominantly expressed on leukocytes and belongs to the EGF-TM7 receptors family. It mediates granulocytes accumulation in the inflammatory tissues and is involved in firm adhesion of PMNC on activated endothelial cells. There have not been any studies exploring the role of CD97 in LPS induced NF-κB activation in macrophages. Therefore, we first measured the CD97 expression in LPS treated human primary macrophages and subsequently analyzed the levels of inflammatory factor TNF-α and transcription factor NF-κB in these macrophages that have been manipulated with either CD97 knockdown or overexpression. We found that a reported anti-inflammatory transcription factor, PPAR-γ, was involved in the CD97 mediated NF-κB suppression. Furthermore, by immunofluorescence staining, we established that CD97 overexpression not only inhibited LPS induced p65 expression in the nucleus but also promoted the PPAR-γ expression. Moreover, using CD97 knockout THP-1 cells, we further demonstrated that CD97 promoted PPAR-γ expression and decreased LPS induced NF-κB activation. In conclusion, CD97 plays a negative role in LPS induced NF-κB activation and TNF-α secretion, partly through PPAR-γ upregulation.

An integrative genome-wide transcriptome reveals that candesartan is neuroprotective and a candidate therapeutic for Alzheimer's disease

BACKGROUND

Alzheimer's disease is the most frequent age-related dementia, and is currently without treatment. To identify possible targets for early therapeutic intervention we focused on glutamate excitotoxicity, a major early pathogenic factor, and the effects of candesartan, an angiotensin receptor blocker of neuroprotective efficacy in cell cultures and rodent models of Alzheimer's disease. The overall goal of the study was to determine whether gene analysis of drug effects in a primary neuronal culture correlate with alterations in gene expression in Alzheimer's disease, thus providing further preclinical evidence of beneficial therapeutic effects.

METHODS

Primary neuronal cultures were treated with candesartan at neuroprotective concentrations followed by excitotoxic glutamate amounts. We performed genome-wide expression profile analysis and data evaluation by ingenuity pathway analysis and gene set enrichment analysis, compared with alterations in gene expression from two independent published datasets identified by microarray analysis of postmortem hippocampus from Alzheimer's disease patients. Preferential expression in cerebrovascular endothelial cells or neurons was analyzed by comparison to published gene expression in these cells isolated from human cortex by laser capture microdissection.

RESULTS

Candesartan prevented glutamate upregulation or downregulation of several hundred genes in our cultures. Ingenuity pathway analysis and gene set enrichment analysis revealed that inflammation, cardiovascular disease and diabetes signal transduction pathways and amyloid β metabolism were major components of the neuronal response to glutamate excitotoxicity. Further analysis showed associations of glutamate-induced changes in the expression of several hundred genes, normalized by candesartan, with similar alterations observed in hippocampus from Alzheimer's disease patients. Gene analysis of neurons and cerebrovascular endothelial cells obtained by laser capture microdissection revealed that genes up- and downregulated by glutamate were preferentially expressed in endothelial cells and neurons, respectively.

CONCLUSIONS

Our data may be interpreted as evidence of direct candesartan neuroprotection beyond its effects on blood pressure, revealing common and novel disease mechanisms that may underlie the in vitro gene alterations reported here and glutamate-induced cell injury in Alzheimer's disease. Our observations provide novel evidence for candesartan neuroprotection through early molecular mechanisms of injury in Alzheimer's disease, supporting testing this compound in controlled clinical studies in the early stages of the illness.

Telmisartan prevention of LPS-induced microglia activation involves M2 microglia polarization via CaMKKβ-dependent AMPK activation

Brain inflammation plays an important role in the pathophysiology of many psychiatric and neurological diseases. During brain inflammation, microglia cells are activated, producing neurotoxic molecules and neurotrophic factors depending on their pro-inflammatory M1 and anti-inflammatory M2 phenotypes. It has been demonstrated that Angiotensin II type 1 receptor blockers (ARBs) ameliorate brain inflammation and reduce M1 microglia activation. The ARB telmisartan suppresses glutamate-induced upregulation of inflammatory genes in cultured primary neurons. We wished to clarify whether telmisartan, in addition, prevents microglia activation through polarization to an anti-inflammatory M2 phenotype. We found that telmisartan promoted M2 polarization and reduced M1 polarization in LPS-stimulated BV2 and primary microglia cells, effects partially dependent on PPARγ activation. The promoting effects of telmisartan on M2 polarization, were attenuated by an AMP-activated protein kinase (AMPK) inhibitor or AMPK knockdown, indicating that AMPK activation participates on telmisartan effects. Moreover, in LPS-stimulated BV2 cells, telmisartan enhancement of M2 gene expression was prevented by the inhibitor STO-609 and siRNA of calmodulin-dependent protein kinase kinase β (CaMKKβ), an upstream kinase of AMPK. Furthermore, telmisartan enhanced brain AMPK activation and M2 gene expression in a mouse model of LPS-induced neuroinflammation. In addition, telmisartan reduced the LPS-induced sickness behavior in this in vivo model, and this effect was prevented by prior administration of an AMPK inhibitor. Our results indicate that telmisartan can be considered as a novel AMPK activator, suppressing microglia activation by promoting M2 polarization. Telmisartan may provide a novel, safe therapeutic approach to treat brain disorders associated with enhanced inflammation.

Telmisartan inhibits hyperalgesia and inflammatory progression in a diabetic neuropathic pain model of Wistar rats

Objective:

To evaluate the potential therapeutic value of telmisartan (TMT) against diabetic neuropathy (DN) and associated pain in Wistar rats.

Methods:

Peripheral DN was induced by a single intraperitoneal streptozotocin injection (55 mg/kg), and 3 weeks later TMT treatment was started (5 and 10 mg/kg/day), and continued for 4 weeks. Mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold tests were performed before and after TMT treatment. In serum, glucose, pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-1β, and interleukin-6 were assessed. Nerve growth factor (NGF) levels and histopathological changes were estimated in the sciatic nerve. This study was conducted at the Experimental Animal Care Center, Department of Pharmacology, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia between January 2013 and May 2014.

Results:

We observed a significant reduction in mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold in diabetic animals. The TMT treatment significantly enhanced the reduced mechanical nociceptive threshold. The untreated diabetic animals revealed a significant decrease in sciatic NGF, which was markedly attenuated by TMT. The elevated serum levels of cytokines in diabetic animals were inhibited by the TMT treatments. Histopathological evaluation showed obvious nerve degeneration in the diabetic group that was eliminated in the TMT treated diabetic groups.

Conclusion:

Telmisartan has a potential neuro-protective effect on peripheral DN; this is mediated through its anti-inflammatory effects and its dual properties as an angiotensin receptor blocker, and a partial peroxisome proliferator activator receptor-g ligand.

Telmisartan attenuated LPS-induced neuroinflammation in human IMR-32 neuronal cell line via SARM in AT1R independent mechanism

AIM

The aim of this study was to find the protective role of Telmisartan (TS) in LPS intoxicated neuronal cells and elucidate the possible neuroprotective mechanism of action.

MAIN METHODS

TLR4 and AT1R specific primers were designed and used in rtPCR to confirm the receptor expression in IMR-32 and Neuro2A cell lines. The protective effect of TS was assayed by MTT assay. The mechanism of action of TS was elucidated by assessing the expression and activation of TLR4 specific adaptor proteins SARM and MyD88, phosphorylated NFκB, PPARγ, MAPK p38, c-JNK, ERK by Western blotting. Selective PPARγ antagonist GW9662 was used to confirm the link between PPARγ activation and TLR4 mediated NFκB inflammatory mechanisms. The pro-inflammatory cytokines TNFα, IL1β, and IL-6 and anti-inflammatory cytokine IL10 release were measured by ELISA.

KEY FINDINGS

IMR-32 cells expressed TLR4 receptor and Neuro2A cells expressed both AT1R and TLR4 receptors. TS significantly protected both the cell lines from LPS intoxication. TS significantly suppressed the TLR4 mediated inflammatory response by PPARγ and SARM protein activation and the effect was reversed significantly by selective PPARγ antagonist GW9662, confirming the existence of link between PPARγ activation and TLR4 mediated inflammation via SARM.

SIGNIFICANCE

LPS intoxicated human neuronal IMR-32 cells can be a good in vitro model to study inflammatory mediated neurodegeneration due to TLR4 receptor expression. Our study strongly recommends that the PPARγ activating pleiotropic effect of TS is responsible for the protective effect in LPS induced TLR4 mediated inflammation via SARM adaptor protein in the IMR-32 cell line.

Neuroprotective effects of angiotensin receptor blockers

Angiotensin II receptor blockers (ARBs, collectively called sartans) are widely used compounds therapeutically effective in cardiovascular disorders, renal disease, the metabolic syndrome, and diabetes. It has been more recently recognized that ARBs are neuroprotective and have potential therapeutic use in many brain disorders. ARBs ameliorate inflammatory and apoptotic responses to glutamate, interleukin 1β and bacterial endotoxin in cultured neurons, astrocytes, microglial, and endothelial cerebrovascular cells. When administered systemically, ARBs enter the brain, protecting cerebral blood flow, maintaining blood brain barrier function and decreasing cerebral hemorrhage, excessive brain inflammation and neuronal injury in animal models of stroke, traumatic brain injury, Alzheimer's and Parkinson's disease and other brain conditions. Epidemiological analyses reported that ARBs reduced the progression of Alzheimer's disease, and clinical studies suggested amelioration of cognitive loss following stroke and aging. ARBs are pharmacologically heterogeneous; their effects are not only the result of Ang II type 1(AT1) receptor blockade but also of additional mechanisms selective for only some compounds of the class. These include peroxisome proliferator-activated receptor gamma activation and other still poorly defined mechanisms. However, the complete pharmacological spectrum and therapeutic efficacy of individual ARBs have never been systematically compared, and the neuroprotective efficacy of these compounds has not been rigorously determined in controlled clinical studies. The accumulation of pre-clinical evidence should promote further epidemiological and controlled clinical studies. Repurposing ARBs for the treatment of brain disorders, currently without effective therapy, may be of immediate and major translational value.

Losartan protects liver against ischaemia/reperfusion injury through PPAR-γ activation and receptor for advanced glycation end-products down-regulation

BACKGROUND AND PURPOSE

PPAR-γ has been reported to be a protective regulator in ischaemia/reperfusion (I/R) injury. The receptor for advanced glycation end-products (RAGE) plays a major role in the innate immune response, and its expression is associated with PPAR-γ activation. Several angiotensin receptor blockers possess partial agonist activities towards PPAR-γ. Therefore, this study investigated the action of losartan, particularly with regard to PPAR-γ activation and RAGE signalling pathways during hepatic I/R.

EXPERIMENTAL APPROACH

Mice were subjected to 60 min of ischaemia followed by 6 h of reperfusion. Losartan (0.1, 1, 3 and 10 mg · kg⁻¹) was administered 1 h prior to ischaemia and immediately before reperfusion. GW9662, a PPAR-γ antagonist, was administered 30 min prior to first pretreatment with losartan.

KEY RESULTS

Losartan enhanced the DNA-binding activity of PPAR-γ in I/R. Losartan attenuated the increased serum alanine aminotransferase activity, TNF-α and IL-6 levels, and nuclear concentrations of NF-κB in I/R. GW9662 reversed these beneficial effects. Losartan caused a decrease in apoptosis as assessed by TUNEL assay, in release of cytochrome c and in cleavage of caspase-3, and these effects were abolished by GW9662 administration. Losartan attenuated not only I/R-induced RAGE overexpression, but also its downstream early growth response protein-1-dependent macrophage inflammatory protein 2 level; phosphorylation of p38, ERK and JNK; and subsequent c-Jun phosphorylation. GW9662 reversed these effects of losartan administration.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that losartan ameliorates I/R-induced liver damage through PPAR-γ activation and down-regulation of the RAGE signalling pathway.

Telmisartan protects central neurons against nutrient deprivation-induced apoptosis in vitro through activation of PPARγ and the Akt/GSK-3β pathway

AIM

To determine whether angiotensin II receptor blockers (ARBs) could protect central neurons against nutrient deprivation-induced apoptosis in vitro and to elucidate the underlying mechanisms.

METHODS

Primary rat cerebellar granule cells (CGCs) underwent B27 (a serum substitute) deprivation for 24 h to induce neurotoxicity, and cell viability was analyzed using LDH assay and WST-1 assay. DNA laddering assay and TUNEL assay were used to detect cell apoptosis. The expression of caspase-3 and Bcl-2, and the phosphorylation of Akt and GSK-3β were detected using Western blot analysis. AT1a mRNA expression was determined using RT-PCR analysis.

RESULTS

B27 deprivation significantly increased the apoptosis of CGCs, as demonstrated by LDH release, DNA laddering, caspase-3 activation and positive TUNEL staining. Pretreatment with 10 μmol/L ARBs (telmisartan, candesartan or losartan) partially blocked B27 deprivation-induced apoptosis of CGCs with telmisartan being the most effective one. B27 deprivation markedly increased the expression of AT1a receptor in CGCs, inhibited Akt and GSK-3β activation, decreased Bcl-2 level, and activated caspase-3, which were reversed by pretreatment with 1 μmol/L telmisartan. In addition, pretreatment with 10 μmol/L PPARγ agonist pioglitazone was more effective in protecting CGCs against B27 deprivation-induced apoptosis, whereas pretreatment with 20 μmol/L PPARγ antagonist GW9662 abolished all the effects of telmisartan in CGCs deprived of B27.

CONCLUSION

ARBs, in particular telmisartan, can protect the nutrient deprivation-induced apoptosis of CGCs in vitro through activation of PPARγ and the Akt/GSK-3β pathway.

KDT501, a derivative from hops, normalizes glucose metabolism and body weight in rodent models of diabetes

Aims/Hypothesis

We developed KDT501, a novel substituted 1,3-cyclopentadione chemically derived from hop extracts, and evaluated it in various in vitro and in vivo models of diabetes and insulin sensitivity.

Methods

KDT501 was evaluated for anti-inflammatory effects in monocyte/macrophage cells; agonistic activity for peroxisome proliferator-activated receptors (PPAR); lipogenesis and gene expression profile in human subcutaneous adipocytes. Body composition, glucose, insulin sensitivity, and lipids were assessed in diet-induced obesity (DIO) mice and Zucker Diabetic Fatty (ZDF) rats after oral administration.

Results

KDT501 mediated lipogenesis in 3T3L1 and human subcutaneous adipocytes; however, the gene expression profile of KDT501 differed from that of the full PPARγ agonist rosiglitazone, suggesting that KDT501 has pleiotropic biological activities. In addition, KDT501 showed only modest, partial PPARγ agonist activity and exhibited anti-inflammatory effects in monocytes/macrophages that were not observed with rosiglitazone. In a DIO mouse model, oral administration of KDT501 significantly reduced fed blood glucose, glucose/insulin AUC following an oral glucose bolus, and body fat. In ZDF rats, oral administration of KDT501 significantly reduced fed glucose, fasting plasma glucose, and glucose AUC after an oral glucose bolus. Significant, dose-dependent reductions of plasma hemoglobin A1c, weight gain, total cholesterol, and triglycerides were also observed in animals receiving KDT501.

Conclusion

These results indicate that KDT501 produces a unique anti-diabetic profile that is distinct in its spectrum of pharmacological effects and biological mechanism from both metformin and pioglitazone. KDT501 may thus constitute a novel therapeutic agent for the treatment of Type 2 diabetes and associated conditions.

Telmisartan ameliorates glutamate-induced neurotoxicity: roles of AT(1) receptor blockade and PPARγ activation

Sartans (Angiotensin II AT(1) Receptor Blockers, ARBs) are powerful neuroprotective agents in vivo and protect against IL-1β neurotoxicity in vitro. The purpose of this research was to determine the extent of sartan neuroprotection against glutamate excitotoxicity, a common cause of neuronal injury and apoptosis. The results show that sartans are neuroprotective, significantly reducing glutamate-induced neuronal injury and apoptosis in cultured rat primary cerebellar granule cells (CGCs). Telmisartan was the most potent sartan studied, with an order of potency telmisartan > candesartan > losartan > valsartan. Mechanisms involved reduction of pro-apoptotic caspase-3 activation, protection of the survival PI3K/Akt/GSK-3β pathway and prevention of glutamate-induced ERK1/2 activation. NMDA receptor stimulation was essential for glutamate-induced cell injury and apoptosis. Participation of AT(1A) receptor was supported by glutamate-induced upregulation of AT(1A) gene expression and AT(1) receptor binding. Conversely, AT(1B) or AT(2) receptors played no role. Glutamate-induced neuronal injury and the neuroprotective effect of telmisartan were decreased, but not abolished, in CGCs obtained from AT(1A) knock-out mice. This indicates that although AT(1) receptors are necessary for glutamate to exert its full neurotoxic potential, part of the neuroprotective effect of telmisartan is independent of AT(1) receptor blockade. PPARγ activation was also involved in the neuroprotective effects of telmisartan, as telmisartan enhanced PPARγ nuclear translocation and the PPARγ antagonist GW9662 partially reversed the neuroprotective effects of telmisartan. The present results substantiate the therapeutic use of sartans, in particular telmisartan, in neurodegenerative diseases and traumatic brain disorders where glutamate neurotoxicity plays a significant role.

Angiotensin converting enzyme-inhibitor reduces colitis severity in an IL-10 knockout model

BACKGROUND

We previously demonstrated angiotensin converting enzymes (ACE) over-expression in a dextran-sodium sulfate colitis model; ACE inhibitor (ACE-I) treatment reduced colitis severity in this model. However, ACE-I has not been tested in more immunologically relevant colitis models.

AIM

We hypothesized that ACE-I would decrease disease severity in an IL-10 knockout (-/-) colitis model.

METHODS

Colitis was induced by giving 10-week old IL-10-/- mice piroxicam (P.O.) for 14 days. The ACE-I enalaprilat was given transanally at a dose of 6.25 mg/kg for 21 days. Prednisolone (PSL) with or without enalaprilat were used as therapeutic, comparative groups. All groups were compared to a placebo treated group. Outcome measures were clinical course, histology, abundance of pro-inflammatory cytokines/chemokines, and epithelial barrier function.

RESULTS

Enalaprilat exhibited better survival (91 %) versus other treatment groups (PSL: 85.7 %, PSL + ACE-I: 71.4 %, placebo: 66.6 %). The ACE-I and PSL + ACE-I groups showed significantly better histological scores versus placebo mice. ACE-I and the PSL groups significantly reduced several pro-inflammatory cytokines versus placebo mice. FITC-dextran permeability was reduced in the ACE-I and PSL + ACE-I groups. Blood pressure was not affected in ACE-I treated mice compared to placebo mice.

CONCLUSIONS

ACE-I was effective in reducing severity of colitis in an IL-10-/- model. The addition of prednisolone minimally augmented this effect. The findings suggest that appropriately dosed ACE-I with or without steroids may be a new therapeutic agent for colitis.

Fimasartan, anti-hypertension drug, suppressed inducible nitric oxide synthase expressions via nuclear factor-kappa B and activator protein-1 inactivation

Since inhibition of angiotensin II type 1 (AT1) receptor reduces chronic inflammation associated with hypertension, we evaluated the anti-inflammatory potential and the underlying mechanism of fimasartan, a Korean Food and Drug Administration approved anti-hypertension drug, in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Fimasartan suppressed the expressions of inducible nitric oxide synthase (iNOS) by down-regulating its transcription, and subsequently inhibited the productions of nitric oxide (NO). In addition, fimasartan attenuated LPS-induced transcriptional and DNA-binding activities of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1). These reductions were accompanied by parallel reductions in the nuclear translocation of NF-κB and AP-1. Taken together, our data suggest that fimasartan down-regulates the expression of the iNOS in macrophages via NF-κB and AP-1 inactivation.

A systematic comparison of the properties of clinically used angiotensin II type 1 receptor antagonists

Angiotensin II type 1 receptor antagonists (ARBs) have become an important drug class in the treatment of hypertension and heart failure and the protection from diabetic nephropathy. Eight ARBs are clinically available [azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan]. Azilsartan (in some countries), candesartan, and olmesartan are orally administered as prodrugs, whereas the blocking action of some is mediated through active metabolites. On the basis of their chemical structures, ARBs use different binding pockets in the receptor, which are associated with differences in dissociation times and, in most cases, apparently insurmountable antagonism. The physicochemical differences between ARBs also manifest in different tissue penetration, including passage through the blood-brain barrier. Differences in binding mode and tissue penetration are also associated with differences in pharmacokinetic profile, particularly duration of action. Although generally highly specific for angiotensin II type 1 receptors, some ARBs, particularly telmisartan, are partial agonists at peroxisome proliferator-activated receptor-γ. All of these properties are comprehensively reviewed in this article. Although there is general consensus that a continuous receptor blockade over a 24-hour period is desirable, the clinical relevance of other pharmacological differences between individual ARBs remains to be assessed.

AT1-receptor-deficiency induced atheroprotection in diabetic mice is partially mediated via PPARγ

Objective

Peroxisome-proliferator–activated-receptor-γ (PPARγ) acts as a transcriptional regulator of multiple genes involved in glucose and lipid metabolism. In vitro studies showed that activated PPARγ suppresses AT1R-gene expression and vice versa. However, it has not yet been determined in vivo, whether AT1R-PPARγ-interactions play a relevant role in the pathogenesis of diabetic complications and specifically in accelerated atherosclerosis.

Methods and results

ApoE^−/− and ApoE^−/−/AT1R^−/−-mice were rendered diabetic by intraperitoneal injections of streptozotocin. Diabetic and non-diabetic ApoE^−/−-mice were further randomized to receive the AT1R antagonist telmisartan, the selective PPARγ antagonist GW9662, telmisartan and GW9662 or vehicle for 18 weeks. Diabetic and non-diabetic ApoE^−/−/AT1R^−/−-mice were randomized to receive either GW9662 or vehicle. GW9662 treatment in diabetic ApoE^−/− and diabetic ApoE^−/−/AT1^−/−-mice resulted in the highest elevation of fasting blood glucose levels, whereas telmisartan treatment and AT1 deficiency in ApoE^−/−-mice showed the lowest fasting blood glucose levels. Diabetic ApoE^−/−-mice displayed severe impairment of endothelial function, enhanced oxidative stress and increased atherosclerotic lesion formation. ApoE^−/−/AT1R^−/− and telmisartan-treated ApoE^−/−-mice showed a significantly better endothelial function, decreased oxidative stress and reduced atherosclerotic lesion formation. Treatment of diabetic ApoE^−/− and ApoE^−/−/AT1R^−/−-mice with the selective PPARγ antagonist GW9662 omitted the atheroprotective effects of AT1R deficiency or AT1 antagonism.

Conclusion

Genetic disruption or pharmacological inhibition of the AT1R attenuates atherosclerosis and improves endothelial function in diabetic ApoE^−/−-mice via the PPARγ pathway.

Candesartan, an angiotensin II AT₁-receptor blocker and PPAR-γ agonist, reduces lesion volume and improves motor and memory function after traumatic brain injury in mice

Traumatic brain injury (TBI) results in complex pathological reactions, the initial lesion worsened by secondary inflammation and edema. Angiotensin II (Ang II) is produced in the brain and Ang II receptor type 1 (AT₁R) overstimulation produces vasoconstriction and inflammation. Ang II receptor blockers (ARBs) are neuroprotective in models of stroke but little is known of their effect when administered in TBI models. We therefore performed controlled cortical impact (CCI) injury on mice to investigate whether the ARB candesartan would mitigate any effects of TBI. We administered candesartan or vehicle to mice 5 h before CCI injury. Candesartan treatment reduced the lesion volume after CCI injury by approximately 50%, decreased the number of dying neurons, lessened the number of activated microglial cells, protected cerebral blood flow (CBF), and reduced the expression of the cytokine TGFβ1 while increasing expression of TGFβ3. Candesartan-treated mice also showed better motor skills on the rotarod 3 days after injury, and improved performance in the Morris water maze 4 weeks after injury. These results indicate that candesartan is neuroprotective, reducing neuronal injury, decreasing lesion volume and microglial activation, protecting CBF and improving functional behavior in a mouse model of TBI. Co-treatment with a peroxisome proliferator-activated receptor-gamma (PPARγ) antagonist significantly reduced some of the beneficial effects of candesartan after CCI, suggesting that PPARγ activation may contribute to part or to all of the neuroprotective effect of candesartan. Overall, our data suggest that ARBs with dual AT₁R-blocking and PPARγ activation properties may have therapeutic value in treating TBI.