Macrophages in neuroinflammation: role of the renin-angiotensin-system

The potential role of brain renin-angiotensin system in the neuropathology of Parkinson disease: Friend, foe or turncoat?

Parkinson disease (PD) is one of the most common neurodegenerative diseases of the brain. Of note, brain renin-angiotensin system (RAS) is intricate in the PD neuropathology through modulation of oxidative stress, mitochondrial dysfunction and neuroinflammation. Therefore, modulation of brain RAS by angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) may be effective in reducing the risk and PD neuropathology. It has been shown that all components including the peptides and enzymes of the RAS are present in the different brain areas. Brain RAS plays a critical role in the regulation of memory and cognitive function, and in the controlling of central blood pressure. However, exaggerated brain RAS is implicated in the pathogenesis of different neurodegenerative diseases including PD. Two well-known pathways of brain RAS are recognized including; the classical pathway which is mainly mediated by AngII/AT1R has detrimental effects. Conversely, the non-classical pathway which is mostly mediated by ACE2/Ang1-7/MASR and AngII/AT2R has beneficial effects against PD neuropathology. Exaggerated brain RAS affects the viability of dopaminergic neurons. However, the fundamental mechanism of brain RAS in PD neuropathology was not fully elucidated. Consequently, the purpose of this review is to disclose the mechanistic role of RAS in in the pathogenesis of PD. In addition, we try to revise how the ACEIs and ARBs can be developed for therapeutics in PD.

Modulator Effect of AT1 Receptor Knockdown on THP-1 Macrophage Proinflammatory Activity

Currently, it is known that angiotensin II (AngII) induces inflammation, and an AT1R blockade has anti-inflammatory effects. The use of an AT1 receptor antagonist promotes the inhibition of the secretion of multiple proinflammatory cytokines in macrophages, as well as a decrease in the concentration of reactive oxygen species. The aim of this study was to determine the effect of AT1 receptor gene silencing on the modulation of cytokines (e.g., IL-1β, TNF-α, and IL-10) in THP-1 macrophages and the relation to the gene expression of NF-κB.

MATERIALS AND METHODS

We evaluated the gene expression of PPAR-γ in THP-1 macrophages using PMA (60 ng/mL). For the silencing, cells were incubated with the siRNA for 72 h and telmisartan (10 µM) was added to the medium for 24 h. After that, cells were incubated during 1 and 24 h, respectively, with Ang II (1 µM). The gene expression levels of AT1R, NF-κB, and cytokines (IL-1β, TNF-α, and IL-10) were measured by RT-qPCR.

RESULTS

We observed that silencing of the AT1 receptor causes a decrease in the expression of mRNA of proinflammatory cytokines (IL-1β and TNF-α), NF-κB, and PPAR-γ.

CONCLUSIONS

We conclude that AT1R gene silencing is an alternative to modulating the production of proinflammatory cytokines such as TNF-α and IL-1β via NF-κB in macrophages and having high blood pressure decrease.

Role of brain renin-angiotensin system in depression: A new perspective

Depression is a mood disorder characterized by abnormal thoughts. The pathophysiology of depression is related to the deficiency of serotonin (5HT), which is derived from tryptophan (Trp). Mitochondrial dysfunction, oxidative stress, and neuroinflammation are involved in the pathogenesis of depression. Notably, the renin-angiotensin system (RAS) is involved in the pathogenesis of depression, and different findings revealed that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) may be effective in depression. However, the underlying mechanism for the role of dysregulated brain RAS-induced depression remains speculative. Therefore, this review aimed to revise the conceivable role of ACEIs and ARBs and how these agents ameliorate the pathophysiology of depression. Dysregulation of brain RAS triggers the development and progression of depression through the reduction of brain 5HT and expression of brain-derived neurotrophic factor (BDNF) and the induction of mitochondrial dysfunction, oxidative stress, and neuroinflammation. Therefore, inhibition of central classical RAS by ARBS and ACEIs and activation of non-classical RAS prevent the development of depression by regulating 5HT, BDNF, mitochondrial dysfunction, oxidative stress, and neuroinflammation.

Targeting the Renin-Angiotensin System (RAS) for Neuropsychiatric Disorders

BACKGROUND

Neuropsychiatric disorders, such as mood disorders, schizophrenia, and Alzheimer's disease (AD) and related dementias, are associated to significant morbidity and mortality worldwide. The pathophysiological mechanisms of neuropsychiatric disorders remain to be fully elucidated, which has hampered the development of effective therapies. The Renin Angiotensin System (RAS) is classically viewed as a key regulator of cardiovascular and renal homeostasis. The discovery that RAS components are expressed in the brain pointed out a potential role for this system in central nervous system (CNS) pathologies. The understanding of RAS involvement in the pathogenesis of neuropsychiatric disorders may contribute to identifying novel therapeutic targets.

AIMS

We aim to report current experimental and clinical evidence on the role of RAS in physiology and pathophysiology of mood disorders, schizophrenia, AD and related dementias. We also aim to discuss bottlenecks and future perspectives that can foster the development of new related therapeutic strategies.

CONCLUSION

The available evidence supports positive therapeutic effects for neuropsychiatric disorders with the inhibition/antagonism of the ACE/Ang II/AT1 receptor axis or the activation of the ACE2/Ang-(1-7)/Mas receptor axis. Most of this evidence comes from pre-clinical studies and clinical studies lag much behind, hampering a potential translation into clinical practice.

Intrarenal renin-angiotensin system activation and macrophage infiltrations in pediatric chronic glomerulonephritis

BACKGROUND

The current study tested the hypothesis that urinary angiotensinogen (UAGT) and urinary monocyte chemoattractant protein-1 (UMCP-1) levels provide a specific index of intrarenal renin-angiotensin system (RAS) status and the degree of infiltration of macrophages associated with RAS blockade and immunosuppressant treatment in pediatric patients with chronic glomerulonephritis.

METHODS

We measured baseline UAGT and UMCP-1 levels to examine the correlation between glomerular injury in 48 pediatric chronic glomerulonephritis patients before treatment. Furthermore, we performed immunohistochemical analysis of angiotensinogen (AGT) and CD68 in 27 pediatric chronic glomerulonephritis patients treated with RAS blockades and immunosuppressants for 2 years. Finally, we examined the effects of angiotensin II (Ang II) on monocyte chemoattractant protein-1 (MCP-1) expression in cultured human mesangial cells (MCs).

RESULTS

Baseline UAGT and UMCP-1 levels positively correlated with urinary protein levels, scores for mesangial hypercellularity, rate of crescentic formation, and expression levels of AGT and CD68 in renal tissues (p < 0.05). UAGT and UMCP-1 levels were significantly decreased after RAS blockade and immunosuppressant treatment (p < 0.01), which was accompanied by AGT and CD68 (p < 0.01), as well as the magnitude of glomerular injury. Cultured human MCs showed increased MCP-1 messenger ribonucleic acid and protein levels after Ang II treatment (p < 0.01).

CONCLUSIONS

The data indicates that UAGT and UMCP-1 are useful biomarkers of the degree of glomerular injury during RAS blockade and immunosuppressant treatment in pediatric patients with chronic glomerulonephritis.

Skin regulation of salt and blood pressure and potential clinical implications

Sodium chloride, as salt, gives rise to hypertension. Nevertheless, individual susceptibility to the ramifications of sodium chloride is heterogeneous. The conventional nephron-centric regulation of sodium with neurohormonal inputs and responses is now expanded to include an intricate extrarenal pathway including the endothelium, skin, lymphatics, and immune cells. An overabundance of sodium is buffered and regulated by the skin interstitium. Excess sodium passes through (and damages) the vascular endothelium and can be dynamically stored in the skin, modulated by skin immune cells and lymphatics. This excess interstitially stored sodium is implicated in hypertension, cardiovascular dysfunction, metabolic disruption, and inflammatory dysregulation. This extrarenal pathway of regulating sodium represents a novel target for better blood pressure management, rebalancing disturbed inflammation, and hence addressing cardiovascular and metabolic disease.

Captopril alleviates epilepsy and cognitive impairment by attenuation of C3-mediated inflammation and synaptic phagocytosis

Evidence from experimental and clinical studies implicates immuno-inflammatory responses as playing an important role in epilepsy-induced brain injury. Captopril, an angiotensin-converting enzyme inhibitor (ACEi), has previously been shown to suppress immuno-inflammatory responses in a variety of neurological diseases. However, the therapeutic potential of captopril on epilepsy remains unclear. In the present study, Sprague Dawley (SD) rats were intraperitoneally subjected to kainic acid (KA) to establish a status epilepticus. Captopril (50 mg/kg, i.p.) was administered daily following the KA administration from day 3 to 49. We found that captopril efficiently suppressed the KA-induced epilepsy, as measured by electroencephalography. Moreover, captopril ameliorated the epilepsy-induced cognitive deficits, with improved performance in the Morris water maze, Y-maze and novel objective test. RNA sequencing (RNA-seq) analysis indicated that captopril reversed a wide range of epilepsy-related biological processes, particularly the glial activation, complement system-mediated phagocytosis and the production of inflammatory factors. Interestingly, captopril suppressed the epilepsy-induced activation and abnormal contact between astrocytes and microglia. Immunohistochemical experiments demonstrated that captopril attenuated microglia-dependent synaptic remodeling presumably through C3–C3ar-mediated phagocytosis in the hippocampus. Finally, the above effects of captopril were partially blocked by an intranasal application of recombinant C3a (1.3 μg/kg/day). Our findings demonstrated that captopril reduced the occurrence of epilepsy and cognitive impairment by attenuation of inflammation and C3-mediated synaptic phagocytosis. This approach can easily be adapted to long-term efficacy and safety in clinical practice.

Graphical Abstract

Bioinformatics analysis of pathways of renal infiltrating macrophages in different renal disease models

Background

Recent studies have suggested that macrophages are significantly involved in different renal diseases. However, the role of these renal infiltrating macrophages has not been entirely uncovered. To further clarify the underlying mechanism and identify therapeutic targets, a bioinformatic analysis based on transcriptome profiles was performed.

Methods

Three transcription profiling datasets, GSE27045, GSE51466 and GSE75808, were obtained from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were assessed by Gene Ontology (GO) functional annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and gene set enrichment analysis (GSEA).

Results

The classic signaling pathways and metabolic pathways of macrophages infiltrating the kidney in different pathophysiological processes, including lupus nephritis (LN), renal crystal formation and renal ischemia-reperfusion injury (IRI), were analysed. Furthermore, the common classical pathways significantly altered in the three renal disorders were the oxidative phosphorylation, VEGF signaling and JAK/STAT signaling pathways, while the renin-angiotensin system was uniquely altered in LN, the glycolysis and gluconeogenesis pathways were uniquely altered in models of renal crystal formation, and the calcium signaling pathway was specific to renal IRI.

Conclusions

Via bioinformatics analysis, this study revealed the transcriptional features of macrophages in murine LN, renal crystal formation and IRI models, which may serve as promising targets for mechanistic research and the clinical treatment of multiple renal diseases.

Mitochondria-Endoplasmic Reticulum Crosstalk in Parkinson's Disease: The Role of Brain Renin Angiotensin System Components

The past few decades have seen an increased emphasis on the involvement of the mitochondrial-associated membrane (MAM) in various neurodegenerative diseases, particularly in Parkinson’s disease (PD) and Alzheimer’s disease (AD). In PD, alterations in mitochondria, endoplasmic reticulum (ER), and MAM functions affect the secretion and metabolism of proteins, causing an imbalance in calcium homeostasis and oxidative stress. These changes lead to alterations in the translocation of the MAM components, such as IP3R, VDAC, and MFN1 and 2, and consequently disrupt calcium homeostasis and cause misfolded proteins with impaired autophagy, distorted mitochondrial dynamics, and cell death. Various reports indicate the detrimental involvement of the brain renin–angiotensin system (RAS) in oxidative stress, neuroinflammation, and apoptosis in various neurodegenerative diseases. In this review, we attempted to update the reports (using various search engines, such as PubMed, SCOPUS, Elsevier, and Springer Nature) demonstrating the pathogenic interactions between the various proteins present in mitochondria, ER, and MAM with respect to Parkinson’s disease. We also made an attempt to speculate the possible involvement of RAS and its components, i.e., AT1 and AT2 receptors, angiotensinogen, in this crosstalk and PD pathology. The review also collates and provides updated information on the role of MAM in calcium signaling, oxidative stress, neuroinflammation, and apoptosis in PD.

The renin-angiotensin system, mood, and suicide: Are there associations?

Available evidence points to a possible role of the renin-angiotensin system (RAS) in the pathophysiology of mood disorders and suicide. We carried out a critical analysis of literature data regarding this role, with a focus on the proposed association between RAS dysfunction and suicidal behavior. Epidemiological, genetic, and biochemical findings are described, and the pathophysiological hypothesis aiming at explaining the possible relationship between RAS and suicide are discussed. Available findings do support the involvement of the RAS in the neurobiology of suicide, although the exact mechanisms underlying this involvement are still unknown.

Microglial TREM2 Mitigates Inflammatory Responses and Neuronal Apoptosis in Angiotensin II-Induced Hypertension in Middle-Aged Mice

Growing evidence suggests that hypertension and aging are prominent risk factors for the development of late-onset Alzheimer's disease (LOAD) by inducement of neuroinflammation. Recent study showed that neuroinflammation via activated microglia induces reactive astrocytes, termed A1 astrocytes, that highly upregulate numerous classical complement cascade genes that are destructive to neurons in neurodegeneration diseases. Moreover, triggering receptor expressed on myeloid cells 2 (TREM2) is considered as one of the strongest single-allele genetic risk factors and plays important roles in neuroinflammation for LOAD. However, the mechanisms of microglia in the regulation of A1 astrocytic activation are still not clear. We introduced angiotensin II-induced hypertension in middle-aged mice and found that hypertension-upregulated TREM2 expression and A1 astrocytic activation were involved in neuroinflammation in the animal models used in this study. The in vitro results revealed that overexpression of microglial TREM2 not only mitigated microglial inflammatory response but also had salutary effects on reverse A1 astrocytic activation and neuronal toxicity.

Regulation of Monocytes/Macrophages by the Renin-Angiotensin System in Diabetic Nephropathy: State of the Art and Results of a Pilot Study

Diabetic nephropathy (DN) is characterized by albuminuria, loss of renal function, renal fibrosis and infiltration of macrophages originating from peripheral monocytes inside kidneys. DN is also associated with intrarenal overactivation of the renin-angiotensin system (RAS), an enzymatic cascade which is expressed and controlled at the cell and/or tissue levels. All members of the RAS are present in the kidneys and most of them are also expressed in monocytes/macrophages. This review focuses on the control of monocyte recruitment and the modulation of macrophage polarization by the RAS in the context of DN. The local RAS favors the adhesion of monocytes on renal endothelial cells and increases the production of monocyte chemotactic protein-1 and of osteopontin in tubular cells, driving monocytes into the kidneys. There, proinflammatory cytokines and the RAS promote the differentiation of macrophages into the M1 proinflammatory phenotype, largely contributing to renal lesions of DN. Finally, resolution of the inflammatory process is associated with a phenotype switch of macrophages into the M2 anti-inflammatory subset, which protects against DN. The pharmacologic interruption of the RAS reduces albuminuria, improves the trajectory of the renal function, decreases macrophage infiltration in the kidneys and promotes the switch of the macrophage phenotype from M1 to M2.

Angiotensin receptors and neuropathic pain

Growing evidence implicates the renin-angiotensin system (RAS) in multiple facets of neuropathic pain (NP). This narrative review focuses primarily on the major bioactive RAS peptide, Angiotensin II (Ang II), and its receptors, namely type 1 (AT1R) and type 2 (AT2R). Both receptors are involved in the development of NP and represent potential therapeutic targets. We first discuss the potential role of Ang II receptors in modulation of NP in the central nervous system. Ang II receptor expression is widespread in circuits associated with the perception and modulation of pain, but more studies are required to fully characterize receptor distribution, downstream signaling, and therapeutic potential of targeting the central nervous system RAS in NP. We then describe the peripheral neuronal and nonneuronal distribution of the RAS, and its contribution to NP. Other RAS modulators (such as Ang (1-7)) are briefly reviewed as well. AT1R antagonists are analgesic across different pain models, including NP. Several studies show neuronal protection and outgrowth downstream of AT2R activation, which may lead to the use of AT2R agonists in NP. However, blockade of AT2R results in analgesia. Furthermore, expression of the RAS in the immune system and a growing appreciation of neuroimmune crosstalk in NP add another layer of complexity and therapeutic potential of targeting this pathway. A growing number of human studies also hint at the analgesic potential of targeting Ang II signaling. Altogether, Ang II receptor signaling represents a promising, far-reaching, and novel strategy to treat NP.

Interaction Between the Angiotensin-(1-7) Mas Receptor and the Dopamine D2 Receptor: Implications in Inflammation

[Figure: see text].

Renin-Angiotensin System and Alzheimer's Disease Pathophysiology: From the Potential Interactions to Therapeutic Perspectives

New roles of the Renin-Angiotensin System (RAS), apart from fluid homeostasis and Blood Pressure (BP) regulation, are being progressively unveiled, since the discoveries of RAS alternative axes and local RAS in different tissues, including the brain. Brain RAS is reported to interact with pathophysiological mechanisms of many neurological and psychiatric diseases, including Alzheimer's Disease (AD). Even though AD is the most common cause of dementia worldwide, its pathophysiology is far from elucidated. Currently, no treatment can halt the disease course. Successive failures of amyloid-targeting drugs have challenged the amyloid hypothesis and increased the interest in the inflammatory and vascular aspects of AD. RAS compounds, both centrally and peripherally, potentially interact with neuroinflammation and cerebrovascular regulation. This narrative review discusses the AD pathophysiology and its possible interaction with RAS, looking forward to potential therapeutic approaches. RAS molecules affect BP, cerebral blood flow, neuroinflammation, and oxidative stress. Angiotensin (Ang) II, via angiotensin type 1 receptors may promote brain tissue damage, while Ang-(1-7) seems to elicit neuroprotection. Several studies dosed RAS molecules in AD patients' biological material, with heterogeneous results. The link between AD and clinical conditions related to classical RAS axis overactivation (hypertension, heart failure, and chronic kidney disease) supports the hypothesized role of this system in AD. Additionally, RAStargeting drugs as Angiotensin Converting Enzyme inhibitors (ACEis) and Angiotensin Receptor Blockers (ARBs) seem to exert beneficial effects on AD. Results of randomized controlled trials testing ACEi or ARBs in AD are awaited to elucidate whether AD-RAS interaction has implications on AD therapeutics.

Role of Peripheral Immune Cells-Mediated Inflammation on the Process of Neurodegenerative Diseases

Neurodegenerative diseases are characterized by progressive loss of selectively vulnerable neuronal populations, which contrasts with selectively static loss of neurons due to toxic or metabolic disorders. The mechanisms underlying their progressive nature remain unknown. To date, a timely and well-controlled peripheral inflammatory reaction is verified to be essential for neurodegenerative diseases remission. The influence of peripheral inflammation on the central nervous system is closely related to immune cells activation in peripheral blood. The immune cells activation participated in the uncontrolled and prolonged inflammation that drives the chronic progression of neurodegenerative diseases. Thus, the dynamic modulation of this peripheral inflammatory reaction by interrupting the vicious cycle might become a disease-modifying therapeutic strategy for neurodegenerative diseases. This review focused on the role of peripheral immune cells on the pathological progression of neurodegenerative diseases.

The intracellular renin-angiotensin system: Friend or foe. Some light from the dopaminergic neurons

The renin-angiotensin system (RAS) is one of the oldest hormone systems in vertebrate phylogeny. RAS was initially related to regulation of blood pressure and sodium and water homeostasis. However, local or paracrine RAS were later identified in many tissues, including brain, and play a major role in their physiology and pathophysiology. In addition, a major component, ACE2, is the entry receptor for SARS-CoV-2. Overactivation of tissue RAS leads several oxidative stress and inflammatory processes involved in aging-related degenerative changes. In addition, a third level of RAS, the intracellular or intracrine RAS (iRAS), with still unclear functions, has been observed. The possible interaction between the intracellular and extracellular RAS, and particularly the possible deleterious or beneficial effects of the iRAS activation are controversial. The dopaminergic system is particularly interesting to investigate the RAS as important functional interactions between dopamine and RAS have been observed in the brain and several peripheral tissues. Our recent observations in mitochondria and nucleus of dopaminergic neurons may clarify the role of the iRAS. This may be important for the developing of new therapeutic strategies, since the effects on both extracellular and intracellular RAS must be taken into account, and perhaps better understanding of COVID-19 cell mechanisms.

Involvement of dopaminergic signaling in the cross talk between the renin-angiotensin system and inflammation

The renin-angiotensin system (RAS) is a fundamental regulator of blood pressure and has emerged as an important player in the control of inflammatory processes. Accordingly, imbalance on RAS components either systemically or locally might trigger the development of inflammatory disorders by affecting immune cells. At the same time, alterations in the dopaminergic system have been consistently involved in the physiopathology of inflammatory disorders. Accordingly, the interaction between the RAS and the dopaminergic system has been studied in the context of inflammation of the central nervous system (CNS), kidney, and intestine, where they exert antagonistic actions in the regulation of the immune system. In this review, we summarized, integrated, and discussed the cross talk of the dopaminergic system and the RAS in the regulation of inflammatory pathologies, including neurodegenerative disorders, such as Parkinson’s disease. We analyzed the molecular mechanisms underlying the interaction between both systems in the CNS and in systemic pathologies. Moreover, we also analyzed the impact of the commensal microbiota in the regulation of RAS and dopaminergic system and how it is involved in inflammatory disorders. Furthermore, we summarized the therapeutic approaches that have yielded positive results in preclinical or clinical studies regarding the use of drugs targeting the RAS and dopaminergic system for the treatment of inflammatory conditions. Further understanding of the molecular and cellular regulation of the RAS-dopaminergic cross talk should allow the formulation of new therapies consisting of novel drugs and/or repurposing already existing drugs, alone or in combination, for the treatment of inflammatory disorders.

The role of the brain renin-angiotensin system (RAS) in mild traumatic brain injury (TBI)

There is considerable interest in traumatic brain injury (TBI) induced by repeated concussions suffered by athletes in sports, military personnel from combat-and non-combat related activities, and civilian populations who suffer head injuries from accidents and domestic violence. Although the renin-angiotensin system (RAS) is primarily a systemic cardiovascular regulatory system that, when dysregulated, causes hypertension and cardiovascular pathology, the brain contains a local RAS that plays a critical role in the pathophysiology of several neurodegenerative diseases. This local RAS includes receptors for angiotensin (Ang) II within the brain parenchyma, as well as on circumventricular organs outside the blood-brain-barrier. The brain RAS acts primarily via the type 1 Ang II receptor (AT₁R), exacerbating insults and pathology. With TBI, the brain RAS may contribute to permanent brain damage, especially when a second TBI occurs before the brain recovers from an initial injury. Agents are needed that minimize the extent of injury from an acute TBI, reducing TBI-mediated permanent brain damage. This review discusses how activation of the brain RAS following TBI contributes to this damage, and how drugs that counteract activation of the AT₁R including AT₁R blockers (ARBs), renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, and agonists at type 2 Ang II receptors (AT₂) and at Ang (1-7) receptors (Mas) can potentially ameliorate TBI-induced brain damage.

Neuroimmune crosstalk in the pathophysiology of hypertension

Hypertension is an important risk factor for cardiovascular morbidity and mortality and for events such as myocardial infarction, stroke, heart failure and chronic kidney disease and is a major determinant of disability-adjusted life-years. Despite the importance of hypertension, the pathogenesis of essential hypertension, which involves the complex interaction of several mechanisms, is still poorly understood. Evidence suggests that interplay between bone marrow, microglia and immune mediators underlies the development of arterial hypertension, in particular through mechanisms involving cytokines and peptides, such as neuropeptide Y, substance P, angiotensin II and angiotensin-(1-7). Chronic psychological stress also seems to have a role in increasing the risk of hypertension, probably through the activation of neuroimmune pathways. In this Review, we summarize the available data on the possible role of neuroimmune crosstalk in the origin and maintenance of arterial hypertension and discuss the implications of this crosstalk for recovery and rehabilitation after cardiac and cerebral injuries.

Attenuated inflammatory response of monocyte-derived macrophage from patients with BD: a preliminary report

BACKGROUND

Innate immune system dysfunction has been recognized as an important element in the pathophysiology of bipolar disorder (BD). We aimed to investigate whether there are differences in the response of macrophages derived from patients in the early stages and late stages of BD and healthy subjects.

METHODS

Human monocytes purified from peripheral blood mononuclear cells (PBMCs) of patients with BD type I (n = 18)-further classified into early- and late stage BD patients according to their functioning- and from healthy individuals (n = 10) were differentiated into macrophages in vitro. Monocyte-derived macrophages (M) were exposed to IFNγ plus LPS-M(IFNγ + LPS)- or IL-4-M(IL-4)-to induce their polarization into the classical (also called M1) or alternative (also called M2) activation phenotypes, respectively; or either Mψ were not exposed to any stimuli characterizing the resting state (denominated M0). In vitro secretion of cytokines, such as IL-1β, IL-6, IL-10, and TNF-α, was used as an index of macrophage activity.

RESULTS

M(IFNγ + LPS) from late-stage BD patients produced less amount of IL-1β, IL-6, and IL-10 when compared to early-stage BD patients and healthy controls. Following alternative activation, M(IL-4) derived from late-stage patients secreted less IL-6 compared to the other groups. TNFα was less secreted by all macrophage phenotypes derived from late-stage patients when compared to healthy controls only (p < 0.005). Mψ from late-stage patients exhibited lower production of IL-1β and IL-10 compared to macrophages from healthy subjects and early-stage patients respectively. Interestingly, cytokines secretion from M(IFNγ + LPS), M(IL-4) and Mψ were similar between early-stage patients and healthy controls.

CONCLUSION

Our results suggest a progressive dysfunction in the response of peripheral innate immune cells of BD patients in the late stages of the illness. This failure in the regulation of the immune system function may be implicated in the multisystemic progression of BD.

Neuroinflammation in hypertension: the renin-angiotensin system versus pro-resolution pathways

Overstimulation of the pro-inflammatory pathways within brain areas responsible for sympathetic outflow is well evidenced as a primary contributing factor to the establishment and maintenance of neurogenic hypertension. However, the precise mechanisms and stimuli responsible for promoting a pro-inflammatory state are not fully elucidated. Recent work has unveiled novel compounds derived from omega-3 polyunsaturated fatty acids (ω-3 PUFAs), termed specialized pro-resolving mediators (SPMs), which actively regulate the resolution of inflammation. Failure or dysregulation of the resolution process has been linked to a variety of chronic inflammatory and neurodegenerative diseases. Given the pathologic role of neuroinflammation in the hypertensive state, SPMs and their associated pathways may provide a link between hypertension and the long-standing association of dietary ω-3 PUFAs with cardioprotection. Herein, we review recent progress in understanding the RAS-driven pathophysiology of neurogenic hypertension, particularly in regards to the chronic low-grade neuroinflammatory response. In addition, we examine the potential for an impaired resolution of inflammation process in the context of hypertension.

Cross-Talk between Neurohormonal Pathways and the Immune System in Heart Failure: A Review of the Literature

Heart failure is a complex clinical syndrome involving a multitude of neurohormonal pathways including the renin-angiotensin-aldosterone system, sympathetic nervous system, and natriuretic peptides system. It is now emerging that neurohumoral mechanisms activated during heart failure, with both preserved and reduced ejection fraction, modulate cells of the immune system. Indeed, these cells express angiotensin I receptors, adrenoceptors, and natriuretic peptides receptors. Ang II modulates macrophage polarization, promoting M2 macrophages phenotype, and this stimulation can influence lymphocytes Th1/Th2 balance. β-AR activation in monocytes is responsible for inhibition of free oxygen radicals production, and together with α2-AR can modulate TNF-α receptor expression and TNF-α release. In dendritic cells, activation of β2-AR inhibits IL-12 production, resulting in the inhibition of Th1 and promotion of Th2 differentiation. ANP induces the activation of secretion of superoxide anion in polymorphonucleated cells; reduces TNF-α and nitric oxide secretion in macrophages; and attenuates the exacerbated TH1 responses. BNP in macrophages can stimulate ROS production, up-regulates IL-10, and inhibits IL-12 and TNF-α release by dendritic cells, suggesting an anti-inflammatory cytokines profile induction. Therefore, different neurohormonal-immune cross-talks can determine the phenotype of cardiac remodeling, promoting either favorable or maladaptive responses. This review aims to summarize the available knowledge on neurohormonal modulation of immune responses, providing supportive rational background for further research.

Aliskiren: Preclinical evidence for the treatment of hyperproliferative skin disorders

Psoriasis is a complex inflammatory and hyperproliferative skin disease. The pathogenesis and mechanisms involved are not completely understood, which makes treatment a difficult issue. Angiotensin II, the most active peptide of the renin-angiotensin system, seems to be involved in processes related to psoriasis pathogenesis, such as inflammation and cell proliferation. The aim of this study was to investigate the influence of renin inhibition on inflammation parameters and keratinocyte proliferation in a mouse model of chronic skin inflammation induced by croton oil. Aliskiren had anti-inflammatory effects by reducing levels of tumor necrosis factor-α and interleukin -6, and by inhibiting myeloperoxidase activity. Aliskiren also showed antiproliferative activity by reducing epidermal hyperplasia and proliferating cell nuclear antigen levels. Aliskiren treatment did not induce alterations in the cardiovascular system, normal skin thickness, and organ weight. These results suggest that aliskiren could be a valuable tool to be incorporated in the treatment of hyperproliferative and inflammatory skin disorders such as psoriasis.

Angiotensin receptor blocker irbesartan reduces stress-induced intestinal inflammation via AT1a signaling and ACE2-dependent mechanism in mice

Stress is associated with pathophysiology of both irritable bowel syndrome (IBS) and hypertension. Angiotensin receptor blockers (ARB) have anti-inflammatory properties via inhibition of angiotensin II (Ang II)/Ang II type I receptor axis (AT1). Inhibition of the classical RAS pathway is also involved in upregulation of angiotensin converting enzyme-2 (ACE2), which activates the Ang-(1-7)/Mas pathway to counteract inflammatory signaling and acts as a partner of the amino acid transporter, B⁰AT-1, to absorb tryptophan for regulation of microbiota-gut-brain axis. In this study, we determined the effects of ARB irbesartan on stress-induced intestinal inflammation. C57BL/6J mice were subjected to 2-week intermittent restraint stress. They were orally treated during the stress with either vehicle, 3 or 10 mg/kg/day irbesartan. Restraint stress resulted in colon inflammation with higher histological damage scores, increased expression of Nox4, TLR-4 and IL1-β, accumulation of reactive oxygen species (ROS), and activation of the ACE-angiotensin II-AT1 receptor axis. Stress also downregulated intestinal amino acid transporter, ACE2/B⁰AT-1, and activity of intestinal mammalian target of rapamycin (mTOR) and p70 S6 kinase (p70S6K), resulting in decrease in α-defensins, changes in intestinal microbial contents, and perturbation of tryptophan metabolism with activation of the kynurenine pathway. Administration of irbesartan inhibited activation of stress-induced AT1 pathway to reduce intestinal ROS accumulation and inflammation, restored expression of ACE2/B⁰AT-1, activity of mTOR and p70S6K, dysbiosis and tryptophan metabolism. Our results suggest that AT1 is a potentially suitable therapeutic target in stress-induced intestinal inflammation, and that irbesartan could be beneficially suitable for the treatment of stressed patients with IBS.

Cell biological mechanisms in regulation of the post-infarction inflammatory response

Inflammation plays a crucial role in cardiac repair, but may also extend ischemic injury and contribute to post-infarction remodeling. This review manuscript discusses recent advances in our understanding of the cell biology of the post-infarction inflammatory response. Recently published studies demonstrated that the functional repertoire of inflammatory and reparative cells may extend beyond the roles suggested by traditional teachings. Neutrophils may play an important role in cardiac repair by driving macrophages toward a reparative phenotype. Subsets of activated fibroblasts have been implicated in protection of ischemic cardiomyocytes, in phagocytosis of apoptotic cells, and in regulation of inflammation. Dissection of the cellular effectors of cardiac repair is critical in order to develop new therapeutic strategies for patients with acute myocardial infarction.

Pattern of Mas expression in acute and post-acute stage of nerve injury in mice

Angiotensin-(1-7) (Ang [1-7]) and its receptor Mas are involved in a number of physiological processes, including control of arterial pressure and modulation of nervous system actions. However, the involvement of the Ang-(1-7)/Mas axis in peripheral nerve injury has not been investigated. Using a model of sciatic nerve injury in mice, we demonstrated opposing changes in Mas receptor expression at days 2 and 14 post-injury. Mas receptor expression was more intense 2days after the nerve lesion, compared with the intensity of the intact nerve. At this time point, the sciatic nerve functional index was -20. At day 14 after the lesion, the intensity of the immunostaining labeling in longitudinal sections of the nerve was reduced (∼30%) and the functional index increased +36 (gait improvement). In the axotomized group treated with A779 (a Mas receptor antagonist), the functional recovery index decreased in relation to the untreated axotomized group. The Mas receptor inhibitor also altered the intensity of labeling of S-100, GAP43, and IBA-1 (morphological features compatible with delayed axon growth). This study demonstrated that Ang-(1-7)/Mas axis activity was differentially modulated in the acute and post-acute stages of nerve injury.

Ginsenoside Rb1 improves cardiac function and remodeling in heart failure

We investigated the effect of ginsenoside Rb1 on cardiac function and remodeling in heart failure (HF). Four weeks after HF induction, the rats were administrated with ginsenoside Rb1 (35 and 70 mg/kg) and losartan (4.5 mg/kg) for 8 weeks. Losartan was used as a positive control. Cardiac function was assessed by measuring hemodynamic parameters. Histological changes were analyzed by HE and Masson’s trichrome staining. Cardiac hypertrophy, fibrosis, mitochondrial membrane potential and glucose transporter type 4 (GLUT4) levels were evaluated. In the present study, high dose of (H−) ginsenoside Rb1 decreased heart rate, improved cardiac function and alleviated histological changes induced by HF. H-ginsenoside Rb1 attenuated cardiac hypertrophy and myocardial fibrosis by decreasing left ventricular (LV) weight/heart weight ratio and cardiomyocyte cross-sectional area and reducing the levels of atrial natriuretic factor (ANF), β-myosin heavy chain (β-MHC), periostin, collagen I, Angiotensin II (Ang II), Angiotensin converting enzyme (ACE) and Ang II type 1 (AT1) receptor. Moreover, H-ginsenoside Rb1 decreased mitochondrial membrane potential and enhanced the translocation of GLUT4 to plasma membrane. The TGF-β1/Smad and ERK signaling pathways were inhibited and the Akt pathway was activated. These findings suggest that ginsenoside Rb1 might restore cardiac/mitochondrial function, increase glucose uptake and protect against cardiac remodeling via the TGF-β1/Smad, ERK and Akt signaling pathways.