Angiotensin II AT1 blockade reduces the lipopolysaccharide-induced innate immune response in rat spleen

Targeting the renin angiotensin system for the treatment of anxiety and depression

Emotional disorders like anxiety and depression are responsible for considerable morbidity and mortality all over the world. Several antidepressant and anxiolytic medications are available for the treatment of anxiety and depression. However, a significant number of patients either do not respond to these medications or respond inadequately. Hence, there is a need to identify novel targets for the treatment of anxiety and depression. In this review we focus on the renin angiotensin system (RAS) as a potential target for the treatment of these disorders. We review work that has evaluated the effects of various compounds targeting the RAS on anxiety- and depression-like behaviors. Further, we suggest future work that must be carried out to fully exploit the RAS for the treatment of anxiety and depression. The RAS provides an attractive target for both the identification of novel anxiolytic and antidepressant medications and/or for enhancing the efficacy of currently available medications used for the treatment of anxiety and depression.

The therapeutic potential of losartan in lung metastasis of colorectal cancer

Colorectal cancer (CRC) is a common cancer with a high incidence rate. Components of the renin-angiotensin system (RAS) have been reported to be dysregulated in several malignancies including CRC. Here, we have explored the potential anti-metastatic effects of a RAS inhibitor, losartan, in an experimental model of lung metastasis in CRC. A murine model of lung metastasis of CRC was used, which involved the intravenous injection of CT26 cells via a tail vein. Four experimental groups comprised: an untreated group; a group that received 5-FU which was administered intraperitoneally; a losartan group that received a combination group that received 5-FU plus losartan . We evaluated the anti-inflammatory effects of losartan by histopathological method, and the measurement of oxidative or antioxidant markers including malondialdehyde (MDA) and total-thiols (T-SH) tissue levels, superoxide-dismutase (SOD) and catalase activity. We found that losartan inhibited lung metastasis of CRC and there was a reduction of the IL-6 expression level in the tissue sample. It was also associated with reduced levels of the anti-angiogenic factor Vascular endothelial growth factor (VEGF). Furthermore, we found that losartan induced oxidative stress as assessed by an elevation of MDA level, reduction of T-SH, SOD and catalase activities in lung tissue. Our findings demonstrated that losartan ameliorates angiogenesis, inflammation and the induction of oxidative stress via Angiotensin II type I receptor (AT1R). This may shine some lights on targeting the RAS pathway as a potential therapeutic approach in the treatment of metastatic CRC patients.

Fimasartan reduces neointimal formation and inflammation after carotid arterial injury in apolipoprotein E knockout mice

BACKGROUND

The beneficial effects of angiotensin II type 1 receptor blockers (ARBs) on atherosclerosis have been demonstrated in numerous studies. We investigated the effects of fimasartan on reducing neointimal formation and systemic inflammation after carotid artery (CA) injury in Apolipoprotein E knockout (ApoE KO) mice.

METHODS

ApoE KO mice were randomly allocated to Group I (without CA injury), Group II (without CA injury + Fimasartan), Group III (CA injury), and Group IV (CA injury + Fimasartan). Fimasartan was orally administered everyday starting 3 days before iatrogenic left CA injury.

RESULTS

At 28 days, neointimal hyperplasia and the inflammatory cytokines including TNFα, IL-6, ICAM, and MMP-9 in the peripheral blood were significantly reduced in Groups II and IV compared to Groups I and III, respectively. All fimasartan-administered groups revealed significant increases of CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells with increased plasma levels of IL-10 and TGFβ. In addition, increased CD8⁺ T cells by fimasartan were correlated with reduced smooth muscle cell (SMC) proliferation in the neointima in Groups II and IV. Furthermore, the populations of Treg and CD8⁺ T cells in total splenocytes were increased in Groups II and IV compared to Groups I and III, respectively. The enlargement of spleens due to CA injury in the Group III was attenuated by fimasartan, as shown in the Group IV. These data indicate that fimasartan significantly reduced SMC proliferation in neointima and increased Treg cells in ApoE KO CA injury mice.

CONCLUSIONS

This study suggests fimasartan could be an efficient strategy for reduction of atherosclerotic progression, with a decrease in immune response and systemic inflammation.

SGK1-FoxO1 Signaling Pathway Mediates Th17/Treg Imbalance and Target Organ Inflammation in Angiotensin II-Induced Hypertension

It has been demonstrated that serum/glucocorticoid regulated kinase 1 (SGK1) and the downstream transcription factor forkhead box O1 (FoxO1) plays a critical role in the differentiation of T helper 17 cells/regulatory T cells (Th17/Treg). In the present study, we hypothesized that this SGK1-FoxO1 signaling pathway is involved in Th17/Treg imbalance and target organ damage in angiotensin II (AngII)-induced hypertensive mice. Results show that SGK1 inhibitor EMD638683 significantly reversed renal dysfunction and cardiac dysfunction in echocardiography as indicated by decreased blood urine nitrogen and serum creatinine in AngII-infused mice. Flow cytometric assay shows that there was significant Th17/Treg imbalance in spleen and in renal/cardiac infiltrating lymphocytes as indicated by the increased Th17 cells (CD4⁺-IL17A⁺ cells) and decreased Treg cells (CD4⁺-Foxp3⁺). Consistently, real-time PCR shows that Th17-related cytokines including IL-17A, IL-23, and tumor necrosis factor α (TNF-α) was increased and Treg-related cytokine IL-10 was decreased in renal and cardiac infiltrating lymphocytes in AngII-infused mice. Meanwhile, SGK1 protein level, as well as its phosphorylation and activity, was significantly increased in spleen in AngII-infused rats. Furthermore, it was found that splenic phosphorylated FoxO1 was significantly increased, whereas total FoxO1 in nuclear preparation was significantly decreased in AngII-infused mice, suggesting that increased FoxO1 phosphorylation initiate its translocation from cytoplasm to nucleus. Notably, all changes were significantly inhibited by the treatment of EMD638683. These results suggest that SGK1 was involved in Th17/Treg imbalance and target organ damage in AngII-induced hypertension.

Repeated Stress Exaggerates Lipopolysaccharide-Induced Inflammatory Response in the Rat Spleen

Spleen is an immune organ innervated with sympathetic nerves which together with adrenomedullary system control splenic immune functions. However, the mechanism by which prior stress exposure modulates the immune response induced by immunogenic challenge is not sufficiently clarified. Thus, the aim of this study was to investigate the effect of a single (2 h) and repeated (2 h daily for 7 days) immobilization stress (IMO) on the innate immune response in the spleen induced by lipopolysaccharide (LPS, 100 µg/kg). LPS elevated splenic levels of norepinephrine and epinephrine, while prior IMO prevented this response. LPS did not alter de novo production of catecholamines, however, prior IMO attenuated phenylethanolamine N-methyltransferase gene expression. Particularly repeated IMO exacerbated LPS-induced down-regulation of α1B- and β1-adrenergic receptors (ARs), while enhanced α2A- and β2-AR mRNAs. Elevated expression of inflammatory mediators (iNOS2, IL-1β, IL-6, TNF-α, IL-10) was observed following LPS and repeated IMO again potentiated this effect. These changes were associated with enhanced Ly6C gene expression, a monocyte marker, and elevated MCP-1, GM-CSF, and CXCL1 mRNAs suggesting an increased recruitment of monocytes and neutrophils into the spleen. Additionally, we observed increased Bax/Bcl-1 mRNA ratio together with reduced B cell numbers in rats exposed to repeated IMO and treated with LPS but not in acutely stressed rats. Altogether, these data indicate that repeated stress via changes in CA levels and specific α- and β-AR subtypes exaggerates the inflammatory response likely by recruiting peripheral monocytes and neutrophils to the spleen, resulting in the induction of apoptosis within this tissue, particularly in B cells. These changes may alter the splenic immune functions with potentially pathological consequences.

The angiotensin receptor blocker, Losartan, inhibits mammary tumor development and progression to invasive carcinoma

Drugs that target the Renin-Angiotensin System (RAS) have recently come into focus for their potential utility as cancer treatments. The use of Angiotensin Receptor Blockers (ARBs) and Angiotensin-Converting Enzyme (ACE) Inhibitors (ACEIs) to manage hypertension in cancer patients is correlated with improved survival outcomes for renal, prostate, breast and small cell lung cancer. Previous studies demonstrate that the Angiotensin Receptor Type I (AT₁R) is linked to breast cancer pathogenesis, with unbiased analysis of gene-expression studies identifying significant up-regulation of AGTR1, the gene encoding AT₁R in ER^+ve/HER2^−ve tumors correlating with poor prognosis. However, there is no evidence, so far, of the functional contribution of AT₁R to breast tumorigenesis. We explored the potential therapeutic benefit of ARB in a carcinogen-induced mouse model of breast cancer and clarified the mechanisms associated with its success.

Mammary tumors were induced with 7,12-dimethylbenz[α]antracene (DMBA) and medroxyprogesterone acetate (MPA) in female wild type mice and the effects of the ARB, Losartan treatment assessed in a preventative setting (n = 15 per group). Tumor histopathology was characterised by immunohistochemistry, real-time qPCR to detect gene expression signatures, and tumor cytokine levels measured with quantitative bioplex assays. AT₁R was detected with radiolabelled ligand binding assays in fresh frozen tumor samples.

We showed that therapeutic inhibition of AT₁R, with Losartan, resulted in a significant reduction in tumor burden; and no mammary tumor incidence in 20% of animals. We observed a significant reduction in tumor progression from DCIS to invasive cancer with Losartan treatment. This was associated with reduced tumor cell proliferation and a significant reduction in IL-6, pSTAT3 and TNFα levels. Analysis of tumor immune cell infiltrates, however, demonstrated no significant differences in the recruitment of lymphocytes or tumour-associated macrophages in Losartan or vehicle-treated mammary tumors.

Analysis of AT₁R expression with radiolabelled ligand binding assays in human breast cancer biopsies showed high AT₁R levels in 30% of invasive ductal carcinomas analysed. Furthermore, analysis of the TCGA database identified that high AT₁R expression to be associated with luminal breast cancer subtype.

Our in vivo data and analysis of human invasive ductal carcinoma samples identify the AT₁R is a potential therapeutic target in breast cancer, with the availability of a range of well-tolerated inhibitors currently used in clinics. We describe a novel signalling pathway critical in breast tumorigenesis, that may provide new therapeutic avenues to complement current treatments.

The renin-angiotensin system: a possible new target for depression

Depression remains a debilitating condition with an uncertain aetiology. Recently, attention has been given to the renin-angiotensin system. In the central nervous system, angiotensin II may be important in multiple pathways related to neurodevelopment and regulation of the stress response. Studies of drugs targeting the renin-angiotensin system have yielded promising results. Here, we review the potential beneficial effects of angiotensin blockers in depression and their mechanisms of action. Drugs blocking the angiotensin system have efficacy in several animal models of depression. While no randomised clinical trials were found, case reports and observational studies showed that angiotensin-converting enzyme inhibitors or angiotensin receptor blockers had positive effects on depression, whereas other antihypertensive agents did not. Drugs targeting the renin-angiotensin system act on inflammatory pathways implicated in depression. Both preclinical and clinical data suggest that these drugs possess antidepressant properties. In light of these results, angiotensin system-blocking agents offer new horizons in mood disorder treatment.

The weakening effect of soluble epoxide hydrolase inhibitor AUDA on febrile response to lipopolysaccharide and turpentine in rat

A still growing body of evidence suggests the importance of epoxyeicosatrienoic acids (EETs) in the regulation of inflammatory response; therefore, drugs that stabilize their levels by targeting the soluble epoxide hydrolase (sEH), an enzyme responsible for their metabolism, are currently under investigation. The effect of sEH inhibitors on molecular components of fever mechanism, i.e., on synthesis of pro-inflammatory cytokines or prostaglandins, has been repeatedly proven; however, the hypothesis that sEH inhibitors affect febrile response has never been tested. The aim of this study was to examine if sEH inhibition affects core body temperature (Tb) as well as Tb changes during febrile response to infectious (lipopolysaccharide; LPS) or non-infectious (turpentine; TRP) stimuli. Male Wistar rats were implanted intra-abdominally with miniature biotelemeters to monitor Tb. A potent sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) was suspended in olive oil and administrated into animals in the intraperitoneal (i.p.) dose of 15 mg/kg, which, as we showed, has no significant influence on normal Tb. We have found that AUDA injected 3 h after LPS (50 μg/kg i.p.) significantly weakened febrile rise of Tb. Moreover, injection of sEH inhibitor 7 h after turpentine (administrated subcutaneously in a dose of 100 μL/rat) markedly reduced the peak period of aseptic fever. Obtained results provide first experimental evidence that sEH inhibitors possess anti-pyretic properties. Therefore, medicines targeting sEH enzymatic activity should be considered as a complement to the arsenal of topical medications used to treat fever especially in clinical situations when non-steroidal anti-inflammatory drugs are ineffective.

Angiotensin II type-1 receptor (AT1R) regulates expansion, differentiation, and functional capacity of antigen-specific CD8+ T cells

Angiotensin II (Ang II) and its receptor AT₁ (AT₁R), an important effector axis of renin-angiotensin system (RAS), have been demonstrated to regulate T-cell responses. However, these studies characterized Ang II and AT₁R effects using pharmacological tools, which do not target only Ang II/AT₁R axis. The specific role of AT₁R expressed by antigen-specific CD8⁺ T cells is unknown. Then we immunized transgenic mice expressing a T-cell receptor specific for SIINFEKL epitope (OT-I mice) with sporozoites of the rodent malaria parasite Plasmodium berghei expressing the cytotoxic epitope SIINFEKL. Early priming events after immunization were not affected but the expansion and contraction of AT₁R-deficient (AT₁R^-/-) OT-I cells was decreased. Moreover, they seemed more activated, express higher levels of CTLA-4, PD-1, LAG-3, and have decreased functional capacity during the effector phase. Memory AT₁R^-/- OT-I cells exhibited higher IL-7Rα expression, activation, and exhaustion phenotypes but less cytotoxic capacity. Importantly, AT₁R^-/- OT-I cells show better control of blood parasitemia burden and ameliorate mice survival during lethal disease induced by blood-stage malaria. Our study reveals that AT₁R in antigen-specific CD8⁺ T cells regulates expansion, differentiation, and function during effector and memory phases of the response against Plasmodium, which could apply to different infectious agents.

Buthionine sulfoximine, a glutathione depletor, attenuates endotoxic fever and reduces IL-1β and IL-6 level in rats

PURPOSE

The aim of our study was to investigate the effect of buthionine sulfoximine (BSO) - a glutathione depletor - on a course of endotoxic fever and IL-1β and IL-6 production.

MATERIAL AND METHODS

Male Wistar rats were subjected to intraperitoneal injection of lipopolysaccharide (LPS) from E. coli (50μg/kg, ip) to provoke fever. The level of spleen glutathione, plasma interleukin (IL)-1β, IL-6, and deep body temperature (Tb) were measured.

RESULTS

The LPS administration provoked fever (the average Tb was 38.14±0.05°C in NaCl/LPS-treated rats vs 37.10±0.03°C in control, not-treated rats; p<0.001). We observed that LPS injection induced a decrease in spleen glutathione level (7.67±0.92nM/g vs 13.27±0.47nM/g in not-treated rats; p<0.001). Furthermore, the injection of LPS provoked an elevation of plasma IL-1β and IL-6 concentration (from values below the lowest detectable standard in not-treated animals to 199.99±34.89pg/mL and 7500±542.21pg/mL, respectively; p<0.001). Pretreatment with BSO enhanced glutathione decrease in LPS-treated rats (5.05±0.49nM/g), and significantly affected fever (maximal Tb was 37.81±0.07°C in BSO/LPS-treated rats vs 38.76±0.11°C in NaCl/LPS-treated rats). BSO 4h after LPS injection decreased IL-1β and IL-6 gene expression (about 1.5 fold, and 2 fold, respectively). In a consequence we observed a decrease in plasma IL-6 concentration (4h after LPS injection plasma IL-6 was 4167.17±956.54pg/mL in BSO/LPS-treated rats vs 7500±542.21pg/mL in NaCl/LPS-treated rats; p<0.001), and later IL-1β (7h after LPS injection the IL-1β concentration was not detected).

CONCLUSION

Based on these data, we conclude that BSO, in addition to well-known application as an inhibitor of glutathione synthesis, is an antipyretic agent which reduces both IL-1β and IL-6 concentration.

Compound 21, a selective angiotensin II type 2 receptor agonist, downregulates lipopolysaccharide-stimulated tissue factor expression in human peripheral blood mononuclear cells

Intricate interrelationships connect tissue factor (TF), the principal initiator of the clotting cascade, to inflammation, a cross-talk amplified by locally active angiotensin II, a proinflammatory agent with direct TF-stimulating properties mediated by the angiotensin II type 1 receptor (AT1R)s. However, angiotensin II also stimulates angiotensin II type 2 receptor (AT2R)s and they may as well contribute to TF expression, a possibility in need of further evaluation. We investigated the effect of C21, a highly specific AT2R agonist, on TF antigen (ELISA), procoagulant activity (PCA, one-stage clotting assay) and TF-mRNA (real-time PCR) in peripheral blood mononuclear cell (PBMC)s activated by lipopolysaccharide (LPS), a pro-inflammatory and procoagulant stimulus. C21 downregulated LPS-stimulated TF antigen, PCA and TF mRNA, an effect abolished by PD123 319, a selective AT2R antagonist, and left unchanged by omesartan, a selective AT1R antagonist. PD123 319 per se did not affect LPS-induced TF expression while omesartan inhibited and BAY 11-7082, a specific NFκB inhibitor, abolished endotoxin-activated procoagulant activity (PCA). C21, a selective AT2R agonist, downregulates the transcriptional expression of TF in LPS-activated PBMCs, a finding consistent with the existence in PBMCs of AT2Rs whose stimulation attenuates inflammation-mediated procoagulant responses. The data open insofar unexplored and potentially relevant facets to our understanding of the complex links connecting angiotensin II to inflammation and coagulation.

Zearalenone mycotoxin affects immune mediators, MAPK signalling molecules, nuclear receptors and genome-wide gene expression in pig spleen

The toxicity of zearalenone (ZEA) was evaluated in swine spleen, a key organ for the innate and adaptative immune response. Weaned pigs were fed for 18 days with a control or a ZEA contaminated diet. The effect of ZEA was assessed on wide genome expression, pro- (TNF-α, IL-8, IL-6, IL-1β, IFN-γ) and anti-inflammatory (IL-10, IL-4) cytokines, other molecules involved in inflammatory processes (MMPs/TIMPs), as well as signaling molecules, (p38/JNK1/JNK2-MAPKs) and nuclear receptors (PPARγ/NFkB/AP-1/STAT3/c-JUN). Microarray analysis showed that 46% of total number of differentially expressed genes was involved in cellular signaling pathway, 13% in cytokine network and 10% in the inflammatory response. ZEA increased expression and synthesis of pro- inflammatory (TNF-α, IL-8, IL-6, IL-1β) and had no effect on IFN-γ, IL-4 and IL-10 cytokines in spleen. The inflammatory stimulation might be a consequence of JNK pathway activation rather than of p-38MAPK and NF-kB involvement whose gene and protein expression were suppressed by ZEA action. In summary, our findings indicated the role of ZEA as an immune disruptor at spleen level.

The immune system and hypertension

A powerful interaction between the autonomic and the immune systems plays a prominent role in the initiation and maintenance of hypertension and significantly contributes to cardiovascular pathology, end-organ damage and mortality. Studies have shown consistent association between hypertension, proinflammatory cytokines and the cells of the innate and adaptive immune systems. The sympathetic nervous system, a major determinant of hypertension, innervates the bone marrow, spleen and peripheral lymphatic system and is proinflammatory, whereas the parasympathetic nerve activity dampens the inflammatory response through α7-nicotinic acetylcholine receptors. The neuro-immune synapse is bidirectional as cytokines may enhance the sympathetic activity through their central nervous system action that in turn increases the mobilization, migration and infiltration of immune cells in the end organs. Kidneys may be infiltrated by immune cells and mesangial cells that may originate in the bone marrow and release inflammatory cytokines that cause renal damage. Hypertension is also accompanied by infiltration of the adventitia and perivascular adipose tissue by inflammatory immune cells including macrophages. Increased cytokine production induces myogenic and structural changes in the resistance vessels, causing elevated blood pressure. Cardiac hypertrophy in hypertension may result from the mechanical afterload and the inflammatory response to resident or migratory immune cells. Toll-like receptors on innate immune cells function as sterile injury detectors and initiate the inflammatory pathway. Finally, abnormalities of innate immune cells and the molecular determinants of their activation that include toll-like receptor, adrenergic, cholinergic and AT1 receptors can define the severity of inflammation in hypertension. These receptors are putative therapeutic targets.

Renin-angiotensin system contributes to naive T-cell migration in vivo

Angiotensin II (Ang II) plays an important role in the regulation of the T-cell response during inflammation. However, the cellular mechanisms underlying the regulation of lymphocytes under physiologic conditions have not yet been studied. Here, we tested the influence of Ang II on T-cell migration using T cells from BALB/c mice. The results obtained in vivo showed that when Ang II production or the AT1 receptor were blocked, T-cell counts were enhanced in blood but decreased in the spleen. The significance of these effects was confirmed by observing that these cells migrate, through fibronectin to Ang II via the AT1 receptor. We also observed a gradient of Ang II from peripheral blood to the spleen, which explains its chemotactic effect on this organ. The following cellular mechanisms were identified to mediate the Ang II effect: upregulation of the chemokine receptor CCR9; upregulation of the adhesion molecule CD62L; increased production of the chemokines CCL19 and CCL25 in the spleen. These results indicate that the higher levels of Ang II in the spleen and AT1 receptor activation contribute to migration of naive T cells to the spleen, which expands our understanding on how the Ang II/AT1 receptor axis contributes to adaptive immunity.

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.

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

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

The immune system in hypertension

While hypertension has predominantly been attributed to perturbations of the vasculature, kidney, and central nervous system, research for almost 50 yr has shown that the immune system also contributes to this disease. Inflammatory cells accumulate in the kidneys and vasculature of humans and experimental animals with hypertension and likely contribute to end-organ damage. We and others have shown that mice lacking adaptive immune cells, including recombinase-activating gene-deficient mice and rats and mice with severe combined immunodeficiency have blunted hypertension to stimuli such as ANG II, high salt, and norepinephrine. Adoptive transfer of T cells restores the blood pressure response to these stimuli. Agonistic antibodies to the ANG II receptor, produced by B cells, contribute to hypertension in experimental models of preeclampsia. The central nervous system seems important in immune cell activation, because lesions in the anteroventral third ventricle block hypertension and T cell activation in response to ANG II. Likewise, genetic manipulation of reactive oxygen species in the subfornical organ modulates both hypertension and immune cell activation. Current evidence indicates that the production of cytokines, including tumor necrosis factor-α, interleukin-17, and interleukin-6, contribute to hypertension, likely via effects on both the kidney and vasculature. In addition, the innate immune system also appears to contribute to hypertension. We propose a working hypothesis linking the sympathetic nervous system, immune cells, production of cytokines, and, ultimately, vascular and renal dysfunction, leading to the augmentation of hypertension. Studies of immune cell activation will clearly be useful in understanding this common yet complex disease.

Septic shock: desperately seeking treatment

Septic shock results from the dysregulation of the innate immune response following infection. Despite major advances in fundamental and clinical research, patients diagnosed with septic shock still have a poor prognostic outcome, with a mortality rate of up to 50%. Indeed, the reasons leading to septic shock are still poorly understood. First postulated 30 years ago, the general view of septic shock as an acute and overwhelming inflammatory response still prevails today. Recently, the fact that numerous clinical trials have failed to demonstrate any positive medical outcomes has caused us to question our fundamental understanding of this condition. New and sophisticated technologies now allow us to accurately profile the various stages and contributory components of the inflammatory response defining septic shock, and many studies now report a more complex inflammatory response, particularly during the early phase of sepsis. In addition, novel experimental approaches, using more clinically relevant animal models, to standardize and stratify research outcomes are now being argued for. In the present review, we discuss the most recent findings in relation to our understanding of the underlying mechanisms involved in septic shock, and highlight the attempts made to improve animal experimental models. We also review recent studies reporting promising results with two vastly different therapeutic approaches influencing the renin-angiotensin system and applying mesenchymal stem cells for clinical intervention.

Angiotensin II AT(1) receptor blockers as treatments for inflammatory brain disorders

The effects of brain AngII (angiotensin II) depend on AT(1) receptor (AngII type 1 receptor) stimulation and include regulation of cerebrovascular flow, autonomic and hormonal systems, stress, innate immune response and behaviour. Excessive brain AT(1) receptor activity associates with hypertension and heart failure, brain ischaemia, abnormal stress responses, blood-brain barrier breakdown and inflammation. These are risk factors leading to neuronal injury, the incidence and progression of neurodegerative, mood and traumatic brain disorders, and cognitive decline. In rodents, ARBs (AT(1) receptor blockers) ameliorate stress-induced disorders, anxiety and depression, protect cerebral blood flow during stroke, decrease brain inflammation and amyloid-β neurotoxicity and reduce traumatic brain injury. Direct anti-inflammatory protective effects, demonstrated in cultured microglia, cerebrovascular endothelial cells, neurons and human circulating monocytes, may result not only in AT(1) receptor blockade, but also from PPARγ (peroxisome-proliferator-activated receptor γ) stimulation. Controlled clinical studies indicate that ARBs protect cognition after stroke and during aging, and cohort analyses reveal that these compounds significantly reduce the incidence and progression of Alzheimer's disease. ARBs are commonly used for the therapy of hypertension, diabetes and stroke, but have not been studied in the context of neurodegenerative, mood or traumatic brain disorders, conditions lacking effective therapy. These compounds are well-tolerated pleiotropic neuroprotective agents with additional beneficial cardiovascular and metabolic profiles, and their use in central nervous system disorders offers a novel therapeutic approach of immediate translational value. ARBs should be tested for the prevention and therapy of neurodegenerative disorders, in particular Alzheimer's disease, affective disorders, such as co-morbid cardiovascular disease and depression, and traumatic brain injury.

Neurohormonal modulation of the innate immune system is proinflammatory in the prehypertensive spontaneously hypertensive rat, a genetic model of essential hypertension

RATIONALE

Inflammation and autonomic dysfunction contribute to the pathophysiology of hypertension. Cholinergic stimulation suppresses innate immune responses. Angiotensin II (Ang II) induces hypertension and is associated with proinflammatory immune responses.

OBJECTIVE

Our goal was to define the innate immune response in a model of genetic hypertension and the influences of cholinergic stimulation and Ang II.

METHODS AND RESULTS

Studies were conducted on 4- to 5-week-old prehypertensive spontaneously hypertensive rats (SHRs) and age-matched normotensive control, Wistar Kyoto (WKY) rats. Isolated splenocytes were preexposed to nicotine or Ang II before Toll-like receptor (TLR) activation. Culture supernatants were tested for cytokines (tumor necrosis factor-α, interleukin [IL]-10, and IL-6). TLR-mediated cytokine responses were most pronounced with TLR7/8 and TLR9 activation and similar between WKY rats and SHRs. Nicotine and Ang II enhanced this TLR-mediated IL-6 response in prehypertensive SHR splenocytes. In contrast, nicotine suppressed the TLR-mediated IL-6 response in WKY rats, whereas Ang II had no effect. In vivo, nicotine enhanced plasma levels of TLR7/8-mediated IL-6 and IL-1β responses in prehypertensive SHRs but suppressed these responses in WKY rats. Flow cytometry revealed an increase in a CD161+ innate immune cell population, which was enhanced by nicotine in the prehypertensive SHR spleen but not in WKY.

CONCLUSIONS

There is a pronounced anti-inflammatory nicotinic/cholinergic modulation of the innate immune system in WKY rats, which is reversed in prehypertensive SHRs. The results support the novel concept that neurohormonal regulation of the innate immune system plays a role in the pathogenesis of genetic hypertension and provide putative molecular targets for treatment of hypertension.

Green tea polyphenols and 1-α-OH-vitamin D₃ attenuate chronic inflammation-induced myocardial fibrosis in female rats

Studies have suggested that 1-α-OH-vitamin D₃ and green tea polyphenols (GTPs) are promising dietary supplements for mitigating chronic inflammation-induced fibrosis of vessels because of their anti-inflammatory properties. This study evaluated (1) the impact of 1-α-OH-vitamin D₃ on myocardial fibrosis in female rats with chronic inflammation and (2) if 1-α-OH-vitamin D₃ and GTPs have an additive or synergistic effect to attenuate myocardial fibrosis in these female rats. A 3-month study of a 2 (no 1-α-OH-vitamin D₃ vs. 0.05 μg/kg 1-α-OH-vitamin D₃, five times per week) ×2 (no GTPs vs. 0.5% GTPs in drinking water) factorial design in lipopolysaccharide (LPS)-administered female rats was performed. Additionally, a group receiving placebo administration was used to compare with a group receiving LPS administration only to evaluate the effect of LPS. Masson's Trichrome staining evaluated myocardial fibrosis in coronary vessels and surrounding myocardium. Spleen cyclooxygenase-2 mRNA expression was determined by real-time polymerase chain reaction. Total lipid profiles were also determined. Whole blood was used for differential cell counts. Data were analyzed by two-way analysis of variance followed by mean separation procedures. At 3 months LPS administration induced myocardial fibrosis in vessels and surrounding myocardium, spleen cyclooxygenase-2 mRNA expression, and elevated leukocyte counts, whereas both 1-α-OH-vitamin D₃ administration and GTPs supplementation significantly attenuated these pro-inflammatory events. The inhibitory effects of 1-α-OH-vitamin D₃ and GTPs seem to be an individual effect, instead of an additive or synergistic effect. 1-α-OH-vitamin D₃ and GTPs lowered red blood cell counts, hematocrit, and hemoglobin. Neither 1-α-OH-vitamin D₃ nor GTPs affected lipid profiles. In summary, both 1-α-OH-vitamin D₃ administration and GTPs supplementation mitigate myocardial fibrosis through suppression of a chronic inflammation innate immune response.

Adiponectin and plant-derived mammalian adiponectin homolog exert a protective effect in murine colitis

BACKGROUND

Hypoadiponectinemia has been associated with states of chronic inflammation in humans. Mesenteric fat hypertrophy and low adiponectin have been described in patients with Crohn's disease. We investigated whether adiponectin and the plant-derived homolog, osmotin, are beneficial in a murine model of colitis.

METHODS

C57BL/6 mice were injected (i.v.) with an adenoviral construct encoding the full-length murine adiponectin gene (AN+DSS) or a reporter-LacZ (Ctr and V+DSS groups) prior to DSS colitis protocol. In another experiment, mice with DSS colitis received either osmotin (Osm+DSS) or saline (DSS) via osmotic pumps. Disease progression and severity were evaluated using body weight, stool consistency, rectal bleeding, colon lengths, and histology. In vitro experiments were carried out in bone marrow-derived dendritic cells.

RESULTS

Mice overexpressing adiponectin had lower expression of proinflammatory cytokines (TNF, IL-1β), adipokines (angiotensin, osteopontin), and cellular stress and apoptosis markers. These mice had higher levels of IL-10, alternative macrophage marker, arginase 1, and leukoprotease inhibitor. The plant adiponectin homolog osmotin similarly improved colitis outcome and induced robust IL-10 secretion. LPS induced a state of adiponectin resistance in dendritic cells that was reversed by treatment with PPARγ agonist and retinoic acid.

CONCLUSION

Adiponectin exerted protective effects during murine DSS colitis. It had a broad activity that encompassed cytokines, chemotactic factors as well as processes that assure cell viability during stressful conditions. Reducing adiponectin resistance or using plant-derived adiponectin homologs may become therapeutic options in inflammatory bowel disease.

Angiotensin II AT(1) receptor blockers ameliorate inflammatory stress: a beneficial effect for the treatment of brain disorders

Excessive allostatic load as a consequence of deregulated brain inflammation participates in the development and progression of multiple brain diseases, including but not limited to mood and neurodegenerative disorders. Inhibition of the peripheral and brain Renin-Angiotensin System by systemic administration of Angiotensin II AT(1) receptor blockers (ARBs) ameliorates inflammatory stress associated with hypertension, cold-restraint, and bacterial endotoxin administration. The mechanisms involved include: (a) decreased inflammatory factor production in peripheral organs and their release to the circulation; (b) reduced progression of peripherally induced inflammatory cascades in the cerebral vasculature and brain parenchyma; and (c) direct anti-inflammatory effects in cerebrovascular endothelial cells, microglia, and neurons. In addition, ARBs reduce bacterial endotoxin-induced anxiety and depression. Further pre-clinical experiments reveal that ARBs reduce brain inflammation, protect cognition in rodent models of Alzheimer's disease, and diminish brain inflammation associated with genetic hypertension, ischemia, and stroke. The anti-inflammatory effects of ARBs have also been reported in circulating human monocytes. Clinical studies demonstrate that ARBs improve mood, significantly reduce cognitive decline after stroke, and ameliorate the progression of Alzheimer's disease. ARBs are well-tolerated and extensively used to treat cardiovascular and metabolic disorders such as hypertension and diabetes, where inflammation is an integral pathogenic mechanism. We propose that including ARBs in a novel integrated approach for the treatment of brain disorders such as depression and Alzheimer's disease may be of immediate translational relevance.

Epigallocatechin-3-gallate Regulates Inducible Nitric Oxide Synthase Expression in Human Umbilical Vein Endothelial Cells

Inducible nitric oxide synthase (iNOS) is a main enzyme producing nitric oxide during inflammation and thus contributes to the initiation and development of inflammatory cardiovascular diseases such as atherosclerosis. Epigallocatechin-3-gallate (EGCG), the major catechin derived from green tea, has multiple beneficial effects for treating cardiovascular disease, but the effect of EGCG on the expression of vascular iNOS remains unknown. In this study, we investigated (i) whether EGCG inhibits the expression of vascular iNOS induced by angiotensin II in human umbilical vein endothelial cells and, if it does inhibit, (ii) mechanisms underlying the inhibition. Angiotensin II increased expression levels of vascular iNOS; EGCG counteracted this effect. EGCG increased the production of reactive oxygen species. Moreover, EGCG did not affect the production of reactive oxygen species induced by angiotensin II. These data suggest a novel mechanism whereby EGCG provides direct vascular benefits for treating inflammatory cardiovascular diseases.

Angiotensin II AT1 receptor blockade ameliorates brain inflammation

Brain inflammation has a critical role in the pathophysiology of brain diseases of high prevalence and economic impact, such as major depression, schizophrenia, post-traumatic stress disorder, Parkinson's and Alzheimer's disease, and traumatic brain injury. Our results demonstrate that systemic administration of the centrally acting angiotensin II AT(1) receptor blocker (ARB) candesartan to normotensive rats decreases the acute brain inflammatory response to administration of the bacterial endotoxin lipopolysaccharide (LPS), a model of brain inflammation. The broad anti-inflammatory effects of candesartan were seen across the entire inflammatory cascade, including decreased production and release to the circulation of centrally acting proinflammatory cytokines, repression of nuclear transcription factors activation in the brain, reduction of gene expression of brain proinflammatory cytokines, cytokine and prostanoid receptors, adhesion molecules, proinflammatory inducible enzymes, and reduced microglia activation. These effects are widespread, occurring not only in well-known brain target areas for circulating proinflammatory factors and LPS, that is, hypothalamic paraventricular nucleus and the subfornical organ, but also in the prefrontal cortex, hippocampus, and amygdala. Candesartan reduced the associated anorexic effects, and ameliorated associated body weight loss and anxiety. Direct anti-inflammatory effects of candesartan were also documented in cultured rat microglia, cerebellar granule cells, and cerebral microvascular endothelial cells. ARBs are widely used in the treatment of hypertension and stroke, and their anti-inflammatory effects contribute to reduce renal and cardiac failure. Our results indicate that these compounds may offer a novel and safe therapeutic approach for the treatment of brain disorders.

Blockade of brain angiotensin II AT1 receptors ameliorates stress, anxiety, brain inflammation and ischemia: Therapeutic implications

Poor adaptation to stress, alterations in cerebrovascular function and excessive brain inflammation play critical roles in the pathophysiology of many psychiatric and neurological disorders such as major depression, schizophrenia, post traumatic stress disorder, Parkinson's and Alzheimer's diseases and traumatic brain injury. Treatment for these highly prevalent and devastating conditions is at present very limited and many times inefficient, and the search for novel therapeutic options is of major importance. Recently, attention has been focused on the role of a brain regulatory peptide, Angiotensin II, and in the translational value of the blockade of its physiological AT(1) receptors. In addition to its well-known cardiovascular effects, Angiotensin II, through AT(1) receptor stimulation, is a pleiotropic brain modulatory factor involved in the control of the reaction to stress, in the regulation of cerebrovascular flow and the response to inflammation. Excessive brain AT(1) receptor activity is associated with exaggerated sympathetic and hormonal response to stress, vulnerability to cerebrovascular ischemia and brain inflammation, processes leading to neuronal injury. In animal models, inhibition of brain AT(1) receptor activity with systemically administered Angiotensin II receptor blockers is neuroprotective; it reduces exaggerated stress responses and anxiety, prevents stress-induced gastric ulcerations, decreases vulnerability to ischemia and stroke, reverses chronic cerebrovascular inflammation, and reduces acute inflammatory responses produced by bacterial endotoxin. These effects protect neurons from injury and contribute to increase the lifespan. Angiotensin II receptor blockers are compounds with a good margin of safety widely used in the treatment of hypertension and their anti-inflammatory and vascular protective effects contribute to reduce renal and cardiovascular failure. Inhibition of brain AT(1) receptors in humans is also neuroprotective, reducing the incidence of stroke, improving cognition and decreasing the progression of Alzheimer's disease. Blockade of AT(1) receptors offers a novel and safe therapeutic approach for the treatment of illnesses of increasing prevalence and socioeconomic impact, such as mood disorders and neurodegenerative diseases of the brain.

Synergistic effects of green tea polyphenols and alphacalcidol on chronic inflammation-induced bone loss in female rats

Studies suggest that green tea polyphenols (GTP) or alphacalcidol is promising agent for preventing bone loss. Findings that GTP supplementation plus alphacalcidol administration increased bone mass via a decrease of oxidative stress and inflammation suggest a significant role of GTP plus alphacalcidol in bone health of patients with chronic inflammation.

INTRODUCTION

Studies have suggested that green tea polyphenols (GTP) or alphacalcidol are promising dietary supplements for preventing bone loss in women. However, the mechanism(s) related to the possible osteo-protective role of GTP plus D(3) in chronic inflammation-induced bone loss is not well understood.

METHODS

This study evaluated bioavailability, efficacy, and related mechanisms of GTP in combination with alphacalcidol in conserving bone loss in rats with chronic inflammation. A 12-week study of 2 (no GTP vs. 0.5% GTP in drinking water) × 2 (no alphacalcidol vs. 0.05 μg/kg alphacalcidol, 5×/week) factorial design in lipopolysaccharide-administered female rats was performed. In addition, a group receiving placebo administration was used to compare with a group receiving lipopolysaccharide administration only to evaluate the effect of lipopolysaccharide.

RESULTS

Lipopolysaccharide administration resulted in lower values for bone mass, but higher values for serum tartrate-resistant acid phosphatase (TRAP), urinary 8-hydroxy-2'-deoxyguanosine, and mRNA expression of tumor necrosis factor-α and cyclooxygenase-2 in spleen. GTP supplementation increased urinary epigallocatechin and epicatechin concentrations. Both GTP supplementation and alphacalcidol administration resulted in a significant increase in bone mass, but a significant decrease in serum TRAP levels, urinary 8-hydroxydeoxyguanosine levels, and mRNA expression of tumor necrosis factor-α and cyclooxygenase-2 in spleen. A synergistic effect of GTP and alphacalcidol was observed in these parameters. Neither GTP nor alphacalcidol affected femoral bone area or serum osteocalcin.

CONCLUSION

We conclude that a bone-protective role of GTP plus alphacalcidol during chronic inflammation bone loss may be due to a reduction of oxidative stress damage and inflammation.

Impaired function of dendritic cells deficient in angiotensin II type 1 receptors

Dendritic cells (DC) are highly specialized antigen-presenting cells with a unique ability to activate resting T lymphocytes and initiate primary immune responses. Angiotensin II (AII) is involved in key events of the inflammatory response. Because our previous work implicated an effect of AII on differentiation and function of murine and human DC, we investigated the impact of AII type 1 receptor (AT(1)) deficiency on the phenotypical and functional properties of mouse DC in vitro and in vivo. Bone marrow (BM) cells isolated from mice lacking AII subtype 1a receptor (AT(1a)), AII subtype 1b receptor (AT(1b)), or both receptor isoforms and control littermates [wild type (WT)] were cultured for 7 days in the presence of recombinant mouse granulocyte/macrophage colony-stimulating factor to generate myeloid DC in vitro. Generation of CD11c(+) cells was less efficient in both AT(1a)- and AT(1b)-deficient BM cells than in WT BM cell cultures. Moreover, DC generated from AT(1)-deficient progenitors showed lower levels of expression of major histocompatibility complex II (MHC-II) and CD11c (p < 0.01) and a marked reduction in their allostimulatory activity (p < 0.01 or 0.001). Although AT(1)-deficient DC released comparable levels of interleukin (IL)-10 and IL-12p70 to WT DC, they produced significantly lower levels of tumor necrosis factor alpha (TNF-alpha) (p < 0.05). Remarkably, CD11c(+) cells isolated from the spleen of AT(1) knockout mice challenged with lipopolysaccharide in vivo up-regulated MHC-II, CD40, and CD80 as did WT, but released significantly lower levels of TNF-alpha (p < 0.01). These data provide clear evidence that AT(1) controls differentiation and functionality of DC and thus may have a crucial impact on inflammatory processes where local angiotensinergic systems are known to be activated.

In vivo Angiotensin II AT1 receptor blockade selectively inhibits LPS-induced innate immune response and ACTH release in rat pituitary gland

Systemic lipopolysaccharide (LPS) administration induces an innate immune response and stimulates the hypothalamic-pituitary-adrenal axis. We studied Angiotensin II AT(1) receptor participation in the LPS effects with focus on the pituitary gland. LPS (50 microg/kg, i.p.) enhanced, 3h after administration, gene expression of pituitary CD14 and that of Angiotensin II AT(1A) receptors in pituitary and hypothalamic paraventricular nucleus (PVN); stimulated ACTH and corticosterone release; decreased pituitary CRF(1) receptor mRNA and increased all plasma and pituitary pro-inflammatory factors studied. The AT(1) receptor blocker (ARB) candesartan (1mg/kg/day, s.c. daily for 3 days before LPS) blocked pituitary and PVN AT(1) receptors, inhibited LPS-induced ACTH but not corticosterone secretion and decreased LPS-induced release of TNF-alpha, IL-1beta and IL-6 to the circulation. The ARB reduced LPS-induced pituitary gene expression of IL-6, LIF, iNOS, COX-2 and IkappaB-alpha; and prevented LPS-induced increase of nNOS/eNOS activity. The ARB did not affect LPS-induced TNF-alpha and IL-1beta gene expression, IL-6 or IL-1beta protein content or LPS-induced decrease of CRF(1) receptors. When administered alone, the ARB increased basal plasma corticosterone levels and basal PGE(2) mRNA in pituitary. Our results demonstrate that the pituitary gland is a target for systemically administered LPS. AT(1) receptor activity is necessary for the complete pituitary response to LPS and is limited to specific pro-inflammatory pathways. There is a complementary and complex influence of the PVN and circulating cytokines on the initial pituitary response to LPS. Our findings support the proposal that ARBs may be considered for the treatment of inflammatory conditions.

Increased angiotensin II AT1 receptor mRNA and binding in spleen and lung of AT2 receptor gene disrupted mice

To clarify the relationship between Angiotensin II AT(1) and AT(2) receptors, we studied AT(1) receptor mRNA and binding expression in tissues from AT(2) receptor gene disrupted (AT(2)(-/-)) female mice, where AT(2) receptors are not expressed in vivo, using in situ hybridization and quantitative autoradiography. Wild type mice expressed AT(1A) receptor mRNA and AT(1) receptor binding in lung parenchyma, the spleen, predominantly in the red pulp, and in liver parenchyma. In wild type mice, lung AT(2) receptors were expressed in lung bronchial epithelium and smooth muscle, and were not present in the lung parenchyma, the spleen or the liver. This indicates that AT(1) and AT(2) receptors were not expressed in the same cells. In AT(2)(-/-) mice, we found higher AT(1A) receptor mRNA and AT(1) receptor binding in lung parenchyma and in the red pulp of the spleen, but not in the liver, when compared to littermate wild type controls. Our results suggest that impaired AT(2) receptor function upregulates AT(1) receptor transcription and expression in a tissue-specific manner and in cells not expressing AT(2) receptors. AT(1) upregulation explains the increased sensitivity to Angiotensin II characteristic of the AT(2)(-/-) phenotype, consistent with enhanced AT(1) receptor activation in a number of tissues.