Role of renin angiotensin system inhibitors and metformin in Glioblastoma Therapy: a review.

Glioblastoma multiforme (GBM) is a highly aggressive and incurable disease accounting for about 10,000 deaths in the USA each year. Despite the current treatment approach which includes surgery with chemotherapy and radiation therapy, there remains a high prevalence of recurrence. Notable improvements have been observed in persons receiving concurrent antihypertensive drugs such as renin angiotensin inhibitors (RAS) or the antidiabetic drug metformin with standard therapy. Anti-tumoral effects of RAS inhibitors and metformin have been observed in in vitro and in vivo studies. Although clinical trials have shown mixed results, the potential for the use of RAS inhibitors and metformin as adjuvant GBM therapy remains promising. Nevertheless, evidence suggest that these drugs exert multimodal antitumor actions; by particularly targeting several cancer hallmarks. In this review, we highlight the results of clinical studies using multidrug cocktails containing RAS inhibitors and or metformin added to standard therapy for GBM. In addition, we highlight the possible molecular mechanisms by which these repurposed drugs with an excellent safety profile might elicit their anti-tumoral effects. RAS inhibition elicits anti-inflammatory, anti-angiogenic, and immune sensitivity effects in GBM. However, metformin promotes anti-migratory, anti-proliferative and pro-apoptotic effects mainly through the activation of AMP-activated protein kinase. Also, we discussed metformin's potential in targeting both GBM cells as well as GBM associated-stem cells. Finally, we summarize a few drug interactions that may cause an additive or antagonistic effect that may lead to adverse effects and influence treatment outcome.

Gender equity perceptions among social and administrative science faculty: A qualitative evaluation.

BACKGROUND: Anecdotal evidence suggests that gender inequity persists in academic pharmacy. To date, there are limited published data about the perception of gender inequity in academic pharmacy. OBJECTIVE: The objective of this project was to determine themes associated with gender inequity perceptions in social and administrative science faculty from 2 national pharmacy organizations. METHODS: A gender equity task force comprising 13 members from Social and Administrative Sciences (SAS) sections of the American Pharmacists Association and the American Association of Colleges of Pharmacy was formed. The task force designed a semistructured interview guide comprising questions about demographics and core areas where inequities likely exist. When the survey invitation was sent to faculty members of the SAS sections via Qualtrics, faculty indicated whether they were willing to be interviewed. Interviews were conducted by 2 members of the task force via video conferencing application. The interviews were transcribed. Topic coding involving general categorization by theme followed by refinement to delineate subcategories was used. Coding was conducted independently by 3 coders followed by consensus when discrepancies were identified. RESULTS: A total of 21 faculty participated in the interviews. Respondents were primarily female (71%), were white (90%), had Doctor of Philosophy as their terminal degree (71%), and were in nontenure track positions (57%). Most respondents (90%) experienced gender inequity. A total of 52% reported experiencing gender inequity at all ranks from graduate student to full professor. Four major themes were identified: microaggression (57%), workload (86%), respect (76%), and opportunities (38%). Workload, respect, and opportunities included multiple subthemes. CONCLUSION: Faculty respondents perceive gender inequities in multiple areas of their work. Greater inequity perceptions were present in areas of workload and respect. The task force offers multiple recommendations to address these inequities.

Reliability and Validity Evidence for an Academic Gender Equity Questionnaire.

Objective. The majority of practicing pharmacists and student pharmacists are women. However, instruments to assess perceptions of gender equity within pharmacy academia are not available. The objective of this research was to describe the psychometric analysis of a questionnaire developed to assess gender equity by a Gender Equity Task Force and to report reliability and validity evidence.Methods. A questionnaire with 21 items addressing the teaching, research, service, advancement, mentoring, recruitment, and gender of college leaders was created. The survey was distributed via email in December 2020 to all social and administrative science section members of two professional associations. Rasch analysis was performed to evaluate the reliability and validity evidence for the questionnaire.Results. After reverse coding, all items met parameters for unidimensionality necessary for Rasch analysis. Once adjacent categories were merged to create a 3-point scale, the scale and items met parameters for appropriate functionality. Items were ordered hierarchically in order of difficulty. The modified instrument and scale can be treated as interval level data for future use.Conclusion. This analysis provides reliability and validity evidence supporting use of the gender equity questionnaire in the social and administrative academic pharmacy population if recommended edits such as the 3-point scale are used. Future research on gender equity can benefit from use of a psychometrically sound questionnaire for data collection.

Roles of Angiotensin III in the brain and periphery.

Angiotensin (Ang) III, a biologically active peptide of the renin angiotensin system (RAS) is predominantly known for its central effects on blood pressure. Our understanding of the RAS has evolved from the simplified, classical RAS, a hormonal system regulating blood pressure to a complex system affecting numerous biological processes. Ang II, the main RAS peptide has been widely studied, and its deleterious effects when overexpressed is well-documented. However, other components of the RAS such as Ang III are not well studied. This review examines the molecular and biological actions of Ang III and provides insight into Ang III's potential role in metabolic diseases.

15-Deoxy-Δ-12,14-prostaglandin J2 effects in vascular smooth muscle cells: Implications in vascular smooth muscle cell proliferation and contractility.

15-Deoxy-Δ-12,14-prostaglandin J2 (15d-PGJ2) is an endogenous agonist of the ligand dependent transcriptional factor, peroxisome proliferator-activated receptor -gamma (PPAR-γ). Although PPAR-γ mediates some actions of 15d-PGJ2, many actions of 15d-PGJ2 are independent of PPAR-γ. The PPAR-γ signaling pathway has beneficial effects on tumor progression, inflammation, oxidative stress, and angiogenesis in numerous studies. In this review, various studies were analyzed to understand the effects of 15d-PGJ2 in vascular smooth muscle cells (VSMC)s. 15d-PGJ2 inhibits proliferation of VSMCs during vascular remodeling and it alters the expression of contractile proteins and inflammatory components within these cells as well. However, the effects of 15d-PGJ2 as well as its ability to induce PPAR-γ activation remains controversial as contradictory effects of this prostaglandin in VSMCs exist. Understanding the mechanisms by which 15d-PGJ2 elicit beneficial actions whether by PPAR-γ activation or independently, will aid in developing new therapeutic strategies for diseases such as hypertension with an inflammatory component. Although great advances are being made, more research is needed to reach definitive conclusions.

Contrasting Roles of Ang II and ACEA in the Regulation of IL10 and IL1ß Gene Expression in Primary SHR Astroglial Cultures.

Angiotensin (Ang) II is well-known to have potent pro-oxidant and pro-inflammatory effects in the brain. Extensive crosstalk between the primary Ang II receptor, Ang type 1 receptor (AT1R), and the cannabinoid type 1 receptor (CB1R) has been demonstrated by various groups in the last decade. Since activation of glial CB1R has been demonstrated to play a key role in the resolution of inflammatory states, we investigated the role of Ang II (100 nM) and/or ACEA (10 nM), a potent CB1R-specific agonist in the regulation of inflammatory markers in astrocytes from spontaneously hypertensive rats (SHR) and Wistar rats. Astrocytes were cultured from brainstems and cerebellums of SHR and Wistar rats and assayed for IL1ß and IL10 gene expression and secreted fraction, in treated and non-treated cells, by employing qPCR and ELISA, respectively. mRNA expression of both IL10 and IL1ß were significantly elevated in untreated brainstem and cerebellar astrocytes isolated from SHR when compared to Wistar astrocytes. No changes were observed in the secreted fraction. While ACEA-treatment resulted in a significant increase in IL10 gene expression in Wistar brainstem astrocytes (Log2FC ≥ 1, p < 0.05), its effect in SHR brainstem astrocytes was diminished. Ang II treatment resulted in a strong inhibitory effect on IL10 gene expression in astrocytes from both brain regions of SHR and Wistar rats (Log2FC ≤ -1, p < 0.05), and an increase in IL1ß gene expression in brainstem astrocytes from both strains (Log2FC ≥ 1, p < 0.05). Co-treatment of Ang II and ACEA resulted in neutralization of Ang II-mediated effect in Wistar brainstem and cerebellar astrocytes, but not SHR astrocytes. Neither Ang II nor ACEA resulted in any significant changes in IL10 or IL1ß secreted proteins. These data suggest that Ang II and ACEA have opposing roles in the regulation of inflammatory gene signature in astrocytes isolated from SHR and Wistar rats. This however does not translate into changes in their secreted fractions.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases.

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Angiotensin III induces p38 Mitogen-activated protein kinase leading to proliferation of vascular smooth muscle cells.

BACKGROUND: Mitogen-activated protein kinases (MAPKs) are essential molecular transducers of extracellular stimuli into intracellular responses. MAPKs are crucial in mediating actions of the renin-angiotensin-aldosterone system (RAAS), in particular, functions mediated by Angiotensin (Ang) II, the main biological peptide produced by this system. We have shown that another biologically active heptapeptide Ang III also induces MAPKs in the central nervous system. The ability of Ang III to induce MAPKs in the periphery is unknown and was the focus of this study. METHODS: We determined whether Ang III induced p38 MAPK in vascular smooth cells (VSMCs) isolated from Wistar and spontaneously hypertensive rats (SHRs) and compared these actions to those of Ang II. Further, the role of this MAPK in Ang III-mediated VSMC proliferation was also determined. RESULTS: Both Ang peptides similarly induced p38 MAPK phosphorylation in VSMCs of Wistar VSMCs in a concentration- and time-dependent manner. SHR VSMCs were less sensitive to Ang III, which caused less of an effect on p38 MAPK phosphorylation in these cells. The Ang III effect was specific and occurred by activation of the Ang type 1 (AT1) receptor. The p38 MAPK pathway was also involved in Ang III-induced VSMC growth, as measured by DNA synthesis. CONCLUSIONS: These findings suggest that the p38 MAPK signaling pathway is an important cascade in regulating the actions of Ang III in VSMCs. Most importantly, dysregulation of Ang III actions in these cells are apparent and may contribute to pathological conditions associated with dysfunctions in VSMCS.

Effects of angiotensin III on c-Jun N terminal kinase in Wistar and hypertensive rat vascular smooth muscle cells.

Proliferation of vascular smooth muscle cells (VSMCs) and inflammation are well known actions associated with hypertension. Angiotensin (Ang) II mediates these physiological actions through the c-Jun N terminal Kinase (JNK), mitogen-activated proteins kinase (MAPK) pathway. Ang III effects on this pathway in VSMCs are unknown. The aim of this study was to determine whether Ang III activates JNK MAPK in Wistar VSMCs and determined whether the response was different in spontaneously hypertensive rat (SHR) VSMCs. We also ascertained whether this effect leads to VSMC proliferation. Western blots were used to determine the time and concentration effects of Ang II on JNK MAPK phosphorylation in Wistar VSMCs. Similar studies were conducted for Ang III in Wistar and SHR VSMCs. Both peptides induced JNK phosphorylation in a concentration- and time-dependent manner in Wistar VSMCs. Ang III also increased JNK phosphorylation in a concentration- and time-dependent fashion in SHR VSMCs as well. However, the ability of Ang III to induce JNK MAPK was different in SHR VSMCs as the phosphorylation levels of JNK were significantly higher in Wistar VSMCs as compared to SHR VSMCs at several time points and concentrations. Further, Ang III-mediated DNA synthesis, a measure of VSMC proliferation, occurred through activation of JNK MAPK. This study is the first to show Ang III effects on the JNK MAPK pathway in VSMCs and the role of JNK in Ang III-mediated cellular proliferation. These findings impart key information for the understanding of Ang III functions, especially in VSMCs and possible cardiovascular diseases.

Angiotensin III Induces JAK2/STAT3 Leading to IL-6 Production in Rat Vascular Smooth Muscle Cells.

The Janus kinase-2/ signal transducer and activators of transcription-3 (JAK2/STAT3) pathway and interleukin-6 (IL-6) are pleiotropic signal transduction systems that are responsible for induction of many cytokines and growth factors. It is unknown whether the renin angiotensin aldosterone system (RAAS) peptide, angiotensin (Ang) III induces JAK2/STAT3 and IL-6 in vascular smooth muscle cells (VSMCs). Thus, the purpose of this study was to investigate whether Ang III induces the JAK2/STAT3 pathway leading to IL-6 production in cultured VSMCs isolated from Wistar rats and determine whether differences exist in spontaneously hypertensive rat (SHR) VSMCs. We gauged Ang III's effects on this pathway by measuring its action on STAT3 as well as IL-6 production. Ang III behaved similarly as Ang II in stimulation of STAT3 phosphorylation in Wistar and SHR VSMCs. Moreover, there were no differences in this Ang III effect in SHR versus Wistar VSMCs. In Wistar VSMCs, Ang II and Ang III significantly induced IL-6 protein secretion and mRNA expression. However, IL-6 protein secretions mediated by these peptides were significantly greater in SHR VSMCs. Ang III induced the JAK2/STAT3 pathway, leading to IL-6 protein secretion and IL-6 mRNA expression via actions on AT1Rs. Moreover, the actions of Ang III to induce IL-6 production was dysregulated in SHR VSMCs. These findings suggest that Ang III acts on AT1Rs to induce JAK2/STAT3, leading to an increase in IL-6 in cultured VSMCs. These findings are important in establishing Ang III as an important physiologically relevant peptide in VSMCs.

Angiotensin II induces cyclooxygenase 2 expression in rat astrocytes via the angiotensin type 1 receptor.

We previously showed that Angiotensin (Ang) II stimulated pro-inflammatory and mitogenic actions in astrocytes suggesting that astrocytes are emerging as key players in neuroinflammation. Evidence suggests that neuroinflammation may contribute to central sympathetic overactivity and elevated blood pressure. Further, cyclooxygenase (Cox)-derived prostanoids were implicated in Ang II-dependent hypertension. Cox2 is one of two Cox isoenzymes that is responsible for the formation of prostanoids from arachidonic acid. Constitutively expressed Cox2 has a protective and homeostatic role in the cardiovascular and renal systems. Inducible Cox2 has been associated with pathogenic stimuli resulting in inflammatory conditions and cancers. In this study, we investigated the effect of Ang II on Cox2 protein and mRNA expression in brainstem and cerebellum astrocytes, and determined whether any differences in Cox2 expression exist in spontaneously hypertensive rat (SHR) astrocytes compared to their normotensive control Wistar rats. We demonstrated that Ang II increased Cox2 protein and mRNA levels relative to untreated controls in a time-dependent manner, in Wistar and SHR brainstem and cerebellum astrocytes. Increases in Cox2 protein expression were evident within 4 h, with subsequent sustained elevation for several hours followed by a decline at 48 h. Ang II-induced Cox2 protein levels were higher in Wistar compared to SHRs in both brainstem and cerebellum astrocytes for the majority of time points examined. The Ang II-induced Cox2 mRNA levels increased within 8 h followed by a rapid decline to almost basal levels at later time points. At the earlier time points, Cox2 mRNA elevation were higher in SHR compared to Wistar rat astrocytes. These Ang II actions were mediated by the Ang type I receptor. Our results corroborate previous reports of Ang II's ability to stimulate neuroinflammatory mediators in astrocytes. Cox2-derived prostaglandins might play a role in brain-renin angiotensin system associated hypertension, and astrocytes could be significant players.

Role of ßarrestin1 in AT1 R-mediated mitogen-activated protein kinase activation in Wistar and SHR brainstem astrocytes.

ßarrestin (ßarr)-1 and -2 are ubiquitously (outside the retina) expressed G-protein-coupled receptor adapter proteins. They uncouple G-protein-coupled receptors from G proteins, internalize the receptor, and subsequently initiate their own wave of signaling independently of G proteins. Angiotensin (Ang) II type 1 receptor (AT1 R) is a well-established example of a receptor signaling through ßarrs. Despite the pivotal role of brain AT1 Rs in the regulation of blood pressure, the involvement of ßarr-dependent signaling, mediated by AT1 Rs is not well studied. Particularly, in brain astrocytes very little is known about the effects of ßarrs in AT1 R signaling. Herein, we utilized a combination of pharmacological and gene manipulation approaches to investigate the role of ßarrs in AT1 R-mediated signaling in isolated brainstem astrocytes from spontaneously hypertensive rats (SHRs) and Wistar rats. We observed that ßarr1 is the predominant arrestin isoform at the protein level in these cells. Its expression was down-regulated in SHR astrocytes compared to Wistar rat astrocytes. Ang II, contrary to observations in SHR astrocytes where it had no effect, up-regulates ßarr1 protein in Wistar rat astrocytes. We observed differential involvement of ßarr1 in MAPK activation in brainstem astrocytes of SHR versus Wistar rats. The ßarr-biased agonist peptide [Sar1 , Il4 , Il8] Ang-II (SII), induced AT1 R-mediated ERK and p38 activation in Wistar rat astrocytes. SII had no effect on ERK and p38 activation in SHRs brainstem astrocytes. Our results indicate, reduced involvement of ßarr1 in dampening Ang II-induced MAPKs activation and diminished ßarr1-mediated ERK and p38 activation in SHR brainstem astrocytes. These findings might be mechanistically related to the development of the brain renin-angiotensin-aldosterone system hyperactivity, which leads to pathogenesis of the hypertensive state of the SHR model.

Astrocytes and the Renin Angiotensin System: Relevance in Disease Pathogenesis.

The presence of a brain renin angiotensin system (RAS) is well documented. An overactive brain RAS contributes to the development and progression of cardiovascular and renal disorders among other conditions. In hypertension, an augmented brain RAS leads to an increase in sympathetic nervous system activity. In addition, impaired baroreceptor reflex function, increased vasopressin activity and neuroinflammation are important contributors as well. The relevance of angiotensins in central and peripheral systems, such as neurons and vascular smooth muscle cells, in cardiovascular disease pathogenesis is fairly understood. However, the role of astrocytes is less well studied. Astrocytes are a major contributor to neuroinflammation by increased synthesis and secretion of inflammatory mediators, dysregulated astrogliosis and impaired astrocyte proliferation. Astrocytes may also contribute to impaired neuromodulation. The precise molecular mechanisms by which astrocytes mediate these effects are still not fully understood. Here, we summarize the role of astrocytes in RAS -mediated pathogenesis of hypertension and other cardiovascular diseases.

Molecular Basis of the Brain Renin Angiotensin System in Cardiovascular and Neurologic Disorders: Uncovering a Key Role for the Astroglial Angiotensin Type 1 Receptor AT1R.

The central renin angiotensin system (RAS) is one of the most widely investigated cardiovascular systems in the brain. It is implicated in a myriad of cardiovascular diseases. However, studies from the last decade have identified its involvement in several neurologic abnormalities. Understanding the molecular functionality of the various RAS components can thus provide considerable insight into the phenotypic differences and mechanistic drivers of not just cardiovascular but also neurologic disorders. Since activation of one of its primary receptors, the angiotensin type 1 receptor (AT1R), results in an augmentation of oxidative stress and inflammatory cytokines, it becomes essential to investigate not just neuronal RAS but glial RAS as well. Glial cells are key homeostatic regulators in the brain and are critical players in the resolution of overt oxidative stress and neuroinflammation. Designing better and effective therapeutic strategies that target the brain RAS could well hinge on understanding the molecular basis of both neuronal and glial RAS. This review provides a comprehensive overview of the major studies that have investigated the mechanisms and regulation of the brain RAS, and it also provides insight into the potential role of glial AT1Rs in the pathophysiology of cardiovascular and neurologic disorders.

Neuroinflammation and sympathetic overactivity: Mechanisms and implications in hypertension.

Essential hypertension is a multifactorial disorder with a strong genetic predisposition. Although anti-hypertensive medications have drastically reduced cardiovascular diseases mortality and morbidity rates, a significant percentage of hypertensive individuals currently on anti-hypertensive therapy, remain hypertensive. In spite of the emergence of transgenic animals and sophisticated tools to study the pathophysiology of hypertension, unraveling the causal mechanisms remains a challenge. Research on borderline hypertensive humans and/or prehypertensive rat models revealed an elevation in centrally-mediated sympathetic activity and a heightened neuroinflammatory state. Hyperactive brain renin angiotensin system (RAS), oxidative stress and neuroinflammation in brainstem cardiovascular centers and other brain regions are implicated as key factors in augmenting sympathetic activity in hypertension and other cardiovascular abnormalities. Angiotensin (Ang) II, the main RAS effector peptide, has been shown to trigger significant upsurges in pro-inflammatory cytokines and reactive oxygen species (ROS). Both microglial and astroglial cells, via a host of different mechanisms, contribute to pro-inflammatory states and ROS generation in the brain. Hence, it becomes essential to understand the impact of Ang II and neuroinflammatory mediators on the impairment of cardioregulatory centers in the brain, and to investigate the role of glia in Ang II-mediated sympathoexcitation. Understanding the mechanisms leading to an elevation in neuroinflammatory states, and the possible ways of counteracting it, could aid in devising better therapeutic strategies for the treatment of cardiovascular diseases and hypertension. This review primarily focuses on the molecular aspects of hypertension from a neuroinflammatory standpoint within brainstem cardiovascular centers.

MAPK activation patterns of AT1R and CB1R in SHR versus Wistar astrocytes: Evidence of CB1R hypofunction and crosstalk between AT1R and CB1R.

BACKGROUND: Angiotensin (Ang) II and cannabinoids regulate physiologically relevant astroglial functions via receptor-mediated activation of Mitogen-activated protein kinases (MAPKs). In this study, we investigated the consequences of astroglial Ang II type 1 receptor (AT1R) and Cannabinoid type 1 receptor (CB1R) activation, alone and in combination, on MAPK activation in the presence and absence of hypertensive states. In addition, we also investigated a novel unidirectional crosstalk mechanism between AT1R and CB1R, that involves PKC-mediated phosphorylation of CB1R. METHODS: Astrocytes were isolated from the brainstem and cerebellum of Spontaneously hypertensive rats (SHRs) and normotensive Wistar rats. The cells were treated with either 100nM Ang II or 10nM Arachidonyl-2'-chloroethylamide (ACEA), both alone and in combination, for varying time periods, and the extent of phosphorylation of MAPKs, ERK and p38, and the phosphorylated forms of CB1R (p-CB1R), were measured using western blotting. RESULTS: Ang II treatment resulted in a greater activation of MAPKs in SHR brainstem astrocytes, but not SHR cerebellar astrocytes when compared to Wistar rats. ACEA-mediated MAPK activation was significantly lower in brainstem astrocytes of SHRs when compared to Wistar rats. ACEA negatively modulates AT1R-mediated MAPK activation in both cerebellar and brainstem astrocytes of both models. The effect however was diminished in brainstem astrocytes. Ang II caused a significant increase in phosphorylation of CB1R in cerebellar astrocytes, while its effect was diminished in brainstem astrocytes of both models. CONCLUSION: Both Ang II and ACEA-induced MAPK activation were significantly altered in SHR astrocytes when compared to Wistar astrocytes. A possible reduction in CB1R functionality, coupled with a hyperfunctional AT1R in the brainstem, could well be significant factors in the development of hypertensive states. AT1R-mediated phosphorylation of CB1R could be critical for impaired cerebellar development characterized by a hyperactive RAS.

Biased agonism/antagonism at the AngII-AT1 receptor: Implications for adrenal aldosterone production and cardiovascular therapy.

Many of the effects of angiotensin II (AngII), including adrenocortical aldosterone release, are mediated by the AngII type 1 receptor (AT1R), a receptor with essential roles in cardiovascular homeostasis. AT1R belongs to the G protein-coupled receptor (GPCR) superfamily, mainly coupling to the Gq/11 type of G proteins. However, it also signals through ßarrestins, oftentimes in parallel to eliciting G protein-dependent signaling. This has spurred infinite possibilities for cardiovascular pharmacology, since various beneficial effects are purportedly exerted by AT1R via ßarrestins, unlike AT1R-induced G protein-mediated pathways that usually result in damaging cardiovascular effects, including hypertension and aldosterone elevation. Over the past decade however, a number of studies from our group and others have suggested that AT1R-induced ßarrestin signaling can also be damaging for the heart, similarly to the G protein-dependent one, with regard to aldosterone regulation. Additionally, AT1R-induced ßarrestin signaling in astrocytes from certain areas of the brain may also play a significant role in central regulation of blood pressure and hypertension pathogenesis. These findings have provided the impetus for testing available angiotensin receptor blockers (ARBs) in their efficacy towards blocking both routes (i.e. both G protein- and ßarrestin-dependent) of AT1R signaling in vitro and in vivo and also have promoted structure-activity relationship (SAR) studies for the AngII molecule in terms of ßarrestin signaling to certain cellular effects, e.g. adrenal aldosterone production. In the present review, we will recount all of these recent studies on adrenal and astrocyte AT1R-dependent ßarrestin signaling while underlining their implications for cardiovascular pathophysiology and therapy.

Angiotensin II induces interleukin-6 expression in astrocytes: Role of reactive oxygen species and NF-κB.

Previously, we showed that the bio-peptide angiotensin (Ang) II induces interleukin-6 (IL-6) in cultured astrocytes; however, the mechanism(s) involved in this effect were unknown. In the current study, we determined in brainstem and cerebellum astrocytes from the spontaneously hypertensive rat (SHR), the effect of Ang II to induce IL-6 as well as reactive oxygen species (ROS) generation. Results from this study showed that Ang II significantly induced the differential expression of IL-6 mRNA and protein levels in astrocytes from both regions of Wistar and SHRs. There were differences in the ability of Ang II to induce IL-6 mRNA and protein levels, but these differences were not apparent at all time points examined. Ang II also induced ROS generation, but there were no significant differences between ROS generation in SHR samples as compared to the Wistar samples. Ang II-induced IL-6 levels were mediated via the AT1/Nuclear Factor Kappa beta/ROS pathway. Overall, our findings suggest that there may be dysregulation in IL-6 production from astrocytes, contributing to differences observed in SHRs versus its normotensive control. Elucidating the mechanisms involved in Ang II pro-inflammatory effects in the central nervous system may lead to the development of novel therapeutic strategies that can be harnessed not just to treat hypertension, but other Ang II-mediated diseases as well.

Heterologous regulation of the cannabinoid type 1 receptor by angiotensin II in astrocytes of spontaneously hypertensive rats.

Brainstem and cerebellar astrocytes have critical roles to play in hypertension and attention-deficit hyperactivity disorder, respectively. Angiotensin (Ang) II, via the astroglial Ang type 1 receptor (AT1R), has been demonstrated to elevate pro-inflammatory mediators in the brainstem and the cerebellum. The activation of astroglial cannabinoid type 1 receptor (CB1R), a master regulator of homeostasis, has been shown to neutralize inflammatory states. Factors that drive disease progression are known to alter the expression of CB1Rs. In this study, we investigated the role of Ang II in regulating CB1R protein and mRNA expression in astrocytes isolated from the brainstem and the cerebellum of spontaneously hypertensive rats (SHRs). The results were then compared with their normotensive counterpart, Wistar rats. Not only was the basal expression of CB1R protein and mRNA significantly lower in SHR brainstem astrocytes, but treatment with Ang II resulted in lowering it further in the initial 12 h. In the case of cerebellum, Ang II up-regulated the CB1R protein and mRNA in SHR astrocytes. While the effect of Ang II on CB1R protein was predominantly mediated via the AT1R in SHR brainstem; both AT1R- and AT2R-mediated Ang II's effect in the SHR cerebellum. These data are strongly indicative of a potential new mode of cross-talk between components of the renin angiotensin system and the endocannabinoid system in astrocytes. The consequence of such a cross-talk could be a potential reduced endocannabinoid tone in brainstem in hypertensive states, but not in the cerebellum under the same conditions.

Regulation of angiotensinogen expression by angiotensin II in spontaneously hypertensive rat primary astrocyte cultures.

BACKGROUND: Angiotensin (Ang) II, a bio-peptide of the renin-angiotensin system (RAS), plays a pivotal role in biological systems. It has been well established that in the brain, astrocytes are the predominant source for angiotensinogen (AGT), which is the precursor molecule for Ang II. The primary objective of this study was to determine the effect of Ang II on AGT mRNA and protein expression levels in primary cultures of astrocytes isolated from the brainstem and cerebellum regions of spontaneously hypertensive rats (SHRs) and normotensive Wistar rats. METHODS: Astrocytes were treated with 100nM Ang II and the effect of time and the receptors involved in AGT mRNA and protein expression were measured using qPCR, and western blotting techniques, respectively. RESULTS: Ang II significantly downregulated AGT mRNA levels and upregulated AGT protein levels in both SHR and Wistar rat astrocytes. Basal AGT mRNA levels in SHR samples were significantly lower as compared to Wistar astrocytes isolated from brainstem and cerebellum. There was no difference in the basal AGT protein levels when SHR and Wistar samples were compared. There was a tendency for higher Ang II-induced AGT protein levels in SHR samples compared to normotensive controls, but the difference was not significant. Ang II tended to decrease AGT mRNA levels of Wistar samples to a greater degree than SHR samples. The Ang AT1 receptor mediated the actions of Ang II on AGT protein and mRNA levels. CONCLUSION: These findings highlight the complexity of AGT regulation and show that AGT protein and mRNA levels are responsive to Ang II in both SHR and Wistar astrocytes. Most importantly, our findings suggest that this peptide can induce its own synthesis by positively regulating AGT protein synthesis, an effect that was more robust in SHR astrocytes. Thus, dysregulation of this system may be important in preserving the hypertensive phenotype in this model.