Kinin B2 receptor regulates chemokines CCL2 and CCL5 expression and modulates leukocyte recruitment and pathology in experimental autoimmune encephalomyelitis (EAE) in mice

Cannabidiol Attenuates In Vivo Leukocyte Recruitment to the Spinal Cord Microvasculature at Peak Disease of Experimental Autoimmune Encephalomyelitis

Introduction: Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system characterized by neuroinflammation leading to demyelination. The associated symptoms lead to a devastating decrease in quality of life. The cannabinoids and their derivatives have emerged as an encouraging alternative due to their management of symptom in MS. Objective: The aim of the study was to investigate the mechanism of action of cannabidiol (CBD), a nonpsychoactive cannabinoid, on molecular and cellular events associated with leukocyte recruitment induced by experimental autoimmune encephalomyelitis (EAE). Materials and Methods: C57BL/6 female mice were randomly assigned to the four experimental groups: C (control group), CBD (cannabidiol-treated group, 5 mg/kg i.p.; 14 days), EAE (experimental autoimmune encephalomyelitis-induced group), and EAE+CBD (experimental autoimmune encephalomyelitis-induced plus cannabidiol-treated group). Results: The results indicated that 5 mg/kg of CBD injected intraperitoneally between the 1st and 14th days of EAE could reduce the leukocyte rolling and adhesion into the spinal cord microvasculature as well cellular tissue infiltration. These results were supported by a decreased mRNA expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the spinal cord. Conclusion: Purified CBD reduces in vivo VCAM and ICAM-mediated leukocyte recruitment to the spinal cord microvasculature at EAE peak disease.

Low sulfated heparan sulfate mimetic differentially affects repair in immune-mediated and toxin-induced experimental models of demyelination

There is an urgent need for therapies that target the multicellular pathology of central nervous system (CNS) disease. Modified, nonanticoagulant heparins mimic the heparan sulfate glycan family and are known regulators of multiple cellular processes. In vitro studies have demonstrated that low sulfated modified heparin mimetics (LS-mHeps) drive repair after CNS demyelination. Herein, we test LS-mHep7 (an in vitro lead compound) in experimental autoimmune encephalomyelitis (EAE) and cuprizone-induced demyelination. In EAE, LS-mHep7 treatment resulted in faster recovery and rapidly reduced inflammation which was accompanied by restoration of animal weight. LS-mHep7 treatment had no effect on remyelination or on OLIG2 positive oligodendrocyte numbers within the corpus callosum in the cuprizone model. Further in vitro investigation confirmed that LS-mHep7 likely mediates its pro-repair effect in the EAE model by sequestering inflammatory cytokines, such as CCL5 which are upregulated during immune-mediated inflammatory attacks. These data support the future clinical translation of this next generation modified heparin as a treatment for CNS diseases with active immune system involvement.

Multiple Sclerosis: Inflammatory and Neuroglial Aspects

Multiple sclerosis (MS) represents the most common acquired demyelinating disorder of the central nervous system (CNS). Its pathogenesis, in parallel with the well-established role of mechanisms pertaining to autoimmunity, involves several key functions of immune, glial and nerve cells. The disease's natural history is complex, heterogeneous and may evolve over a relapsing-remitting (RRMS) or progressive (PPMS/SPMS) course. Acute inflammation, driven by infiltration of peripheral cells in the CNS, is thought to be the most relevant process during the earliest phases and in RRMS, while disruption in glial and neural cells of pathways pertaining to energy metabolism, survival cascades, synaptic and ionic homeostasis are thought to be mostly relevant in long-standing disease, such as in progressive forms. In this complex scenario, many mechanisms originally thought to be distinctive of neurodegenerative disorders are being increasingly recognized as crucial from the beginning of the disease. The present review aims at highlighting mechanisms in common between MS, autoimmune diseases and biology of neurodegenerative disorders. In fact, there is an unmet need to explore new targets that might be involved as master regulators of autoimmunity, inflammation and survival of nerve cells.

Hsp65-producing Lactococcus lactis inhibits experimental autoimmune encephalomyelitis by preventing cell migration into spinal cord

Multiple sclerosis is an autoimmune disease that affects the central nervous system. Because of its complexity and the difficulty to treat, searching for immunoregulatory responses that reduce the clinical signs of disease by non-aggressive mechanisms and without adverse effects is a scientific challenge. Herein we propose a protocol of oral tolerance induction that prevented and controlled MOG-induced experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice. The genetically modified strain HSP65-producing Lactococcus lactis was orally administered for 5 consecutive days either before or during disease development in mice. Both protocols of feeding HSP65 resulted in significant reduction in the clinical score of EAE. Frequencies of LAP+CD4+Foxp3- regulatory T cells were higher in spleens and inguinal lymph nodes of fed mice. In addition, intravital microscopy showed that adherence of leukocytes to venules in the spinal cord was reduced in orally treated mice. Oral treatment with HSP65-producing L.lactis prevented leukocytes to leave the secondary lymphoid organs, therefore they could not reach the central nervous system. Despite the inhibition of pathological immune response that drive EAE development, activated T cells were at normal frequencies suggesting that oral tolerance did not induce general immunosuppression, but it led to specific control of pathogenic T cells. Our results indicate a novel therapeutic strategy to prevent and control autoimmune diseases such as multiple sclerosis.

RGMa regulates CCL5 expression via the BMP receptor in experimental autoimmune encephalomyelitis mice and endothelial cells

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS). Repulsive guidance molecule a (RGMa) has been indicated to act as a bone morphogenetic protein (BMP) co-receptor, enhancing BMP signalling activity. However, the role and downstream pathways of the BMP signalling pathway mediated by RGMa have yet to be fully elucidated. A recent study revealed that C-C motif chemokine ligand 5 (CCL5) has a major role in the pathogenesis of MS via the recruitment of macrophages and T-lymphocytes into the CNS. The present study aimed to evaluate whether RGMa regulates CCL5 via the BMP pathway in MS. The results demonstrated that RGMa regulated CCL5 expression in a BMP ligand-dependent manner in experimental autoimmune encephalomyelitis (EAE) mice in vivo and in endothelial cells in vitro. First, specific inhibition of the expression of RGMa via RNA interference led to a significant reduction of the expression of RGMa and this was associated with a significant delay of EAE, an alleviated disease course and downregulation of CCL5 expression at both the protein and mRNA levels. Furthermore, exogenous noggin, an extracellular antagonist of BMP ligand, abolished the induction effect of RGMa on CCL5 in endothelial cells. Taken together, these results suggested that RGMa is an important regulator of MS and inflammatory mediators such as CCL5, and the present results should prove to be useful in terms of further elucidating the RGMa-BMP receptor signalling pathway and the pathogenesis of RGMa on MS as far as the involvement of blood-brain barrier permeability is concerned.

Detecting cells in intravital video microscopy using a deep convolutional neural network

The analysis of leukocyte recruitment in intravital video microscopy (IVM) is essential to the understanding of inflammatory processes. However, because IVM images often present a large variety of visual characteristics, it is hard for an expert human or even conventional machine learning techniques to detect and count the massive amount of cells and extract statistical measures precisely. Convolutional neural networks are a promising approach to overcome this problem, but due to the difficulty of labeling cells, large data sets with ground truth are rare. The present work explores an adaptation of the RetinaNet model with a suite of augmentation techniques and transfer learning for detecting leukocytes in IVM data. The augmentation techniques include simulating the Airy pattern and motion artifacts present in microscopy imaging, followed by traditional photometric, geometric and smooth elastic transformations to reproduce color and shape changes in cells. In addition, we analyzed the use of different network backbones, feature pyramid levels, and image input scales. We have found that even with limited data, our strategy not only enables training without overfitting but also boosts generalization performance. Among several experiments, the model reached a value of 94.84 for the average precision (AP) metric as our best outcome when using data from different image modalities. We also compared our results with conventional image processing techniques and open-source tools. The results showed an outstanding precision of the method compared with other approaches, presenting low error rates for cell counting and centroid distances. Code is available at: https://github.com/brunoggregorio/retinanet-cell-detection.

B1 and B2 kinin receptor blockade improves psoriasis-like disease

BACKGROUND AND PURPOSE

The entire kallikrein-kinin system is present in the skin, and it is thought to exert a relevant role in cutaneous diseases, including psoriasis. The present study was designed to evaluate the relevance of kinin receptors in the development and progression of a model of psoriasis in mice.

EXPERIMENTAL APPROACH

The effects of kinin B₁ and B₂ receptor knockout and of kinin receptor antagonists (SSR240612C or FR173657) were assessed in a model of psoriasis induced by imiquimod in C57BL/6 mice. Severity of psoriasis was assessed by histological and immunohistochemical assays of skin, along with objective scores based on the clinical psoriasis area and severity index.

KEY RESULTS

Both kinin receptors were up-regulated following 6 days of imiquimod treatment. Kinin B₁ and B₂ receptor deficiency and the use of selective antagonists show morphological and histological improvement of the psoriasis hallmarks. This protective effect was associated with a decrease in undifferentiated and proliferating keratinocytes, decreased cellularity (neutrophils, macrophages, and CD4⁺ T lymphocytes), reduced γδ T cells, and lower accumulation of IL-17. The lack of B₂ receptors resulted in reduced CD8⁺ T cells in the psoriatic skin. Relevantly, blocking kinin receptors reflected the improvement of psoriasis disease in the well-being behaviour of the mice.

CONCLUSIONS AND IMPLICATIONS

Kinins exerted critical roles in imiquimod-induced psoriasis. Both B₁ and B₂ kinin receptors exacerbated the disease, influencing keratinocyte proliferation and immunopathology. Antagonists of one or even both kinin receptors might constitute a new strategy for the clinical treatment of psoriasis.

Functional interrelationships between the kallikrein-related peptidases family and the classical kinin system in the human neutrophil

In the human neutrophil, kallikrein-related peptidases (KLKs) have a significant functional relationship with the classical kinin system as a kinin B1 receptor agonist induces secretion of KLK1, KLK6, KLK10, KLK13 and KLK14 into the medium. Secretion of KLK1, the kinin-forming enzyme, may perpetuate formation of kinin in the inflammatory milieu by hydrolyzing extravasated kininogens present in tissue edema. Secretion of KLKs into the inflammatory milieu, induced by kinins or other proinflammatory mediators, provides the human neutrophil with a wide range of molecular interactions to hydrolyze different cellular and extracellular matrix components, which may be of critical relevance in different mechanisms involving inflammation.

The Coagulation Factors Fibrinogen, Thrombin, and Factor XII in Inflammatory Disorders-A Systematic Review

Background

The interaction of coagulation factors has been shown to go beyond their traditional roles in hemostasis and to affect the development of inflammatory diseases. Key molecular players, such as fibrinogen, thrombin, or factor XII have been mechanistically and epidemiologically linked to inflammatory disorders like multiple sclerosis (MS), rheumatoid arthritis (RA), and colitis.

Objectives

To systematically review the evidence for a role of coagulation factors, especially factor XII, fibrinogen, and thrombin in inflammatory disorders like MS, RA, and bowel disorders.

Methods

A systematic literature search was done in the PubMed database to identify studies about coagulation factors in inflammatory diseases. Original articles and reviews investigating the role of the kallikrein–kinin and the coagulation system in mouse and humans were included.

Results

We identified 43 animal studies dealing with inflammatory disorders and factors of the kallikrein–kinin or the coagulation system. Different immunological influences are described and novel molecular mechanisms linking coagulation and inflammation are reported.

Conclusion

A number of studies have highlighted coagulation factors to tip the balance between hemostasis and thrombosis and between protection from infection and extensive inflammation. To optimize the treatment of chronic inflammatory disorders by these factors, further studies are necessary.

Implication of the Kallikrein-Kinin system in neurological disorders: Quest for potential biomarkers and mechanisms

Neurological disorders represent major health concerns in terms of comorbidity and mortality worldwide. Despite a tremendous increase in our understanding of the pathophysiological processes involved in disease progression and prevention, the accumulated knowledge so far resulted in relatively moderate translational benefits in terms of therapeutic interventions and enhanced clinical outcomes. Aiming at specific neural molecular pathways, different strategies have been geared to target the development and progression of such disorders. The kallikrein-kinin system (KKS) is among the most delineated candidate systems due to its ubiquitous roles mediating several of the pathophysiological features of these neurological disorders as well as being implicated in regulating various brain functions. Several experimental KKS models revealed that the inhibition or stimulation of the two receptors of the KKS system (B1R and B2R) can exhibit neuroprotective and/or adverse pathological outcomes. This updated review provides background details of the KKS components and their functions in different neurological disorders including temporal lobe epilepsy, traumatic brain injury, stroke, spinal cord injury, Alzheimer's disease, multiple sclerosis and glioma. Finally, this work will highlight the putative roles of the KKS components as potential neurotherapeutic targets and provide future perspectives on the possibility of translating these findings into potential clinical biomarkers in neurological disease.

Disorders of Astrocytes: Alexander Disease as a Model

Astrocytes undergo important phenotypic changes in many neurological disorders, including strokes, trauma, inflammatory diseases, infectious diseases, and neurodegenerative diseases. We have been studying the astrocytes of Alexander disease (AxD), which is caused by heterozygous mutations in the GFAP gene, which is the gene that encodes the major astrocyte intermediate filament protein. AxD is a primary astrocyte disease because GFAP expression is specific to astrocytes in the central nervous system (CNS). The accumulation of extremely large amounts of GFAP causes many molecular changes in astrocytes, including proteasome inhibition, stress kinase activation, mechanistic target of rapamycin (mTOR) activation, loss of glutamate and potassium buffering capacity, loss of astrocyte coupling, and changes in cell morphology. Many of these changes appear to be common to astrocyte reactions in other neurological disorders. Using AxD to illuminate common mechanisms, we discuss the molecular pathology of AxD astrocytes and compare that to astrocyte pathology in other disorders.

Misbalanced CXCL12 and CCL5 Chemotactic Signals in Vitiligo Onset and Progression

Generalized nonsegmental vitiligo is often associated with the activation of melanocyte-specific autoimmunity. Because chemokines play an important role in the maintenance of immune responses, we examined chemotactic signatures in cultured vitiligo melanocytes and skin samples of early (≤2 months) and advanced (≥6 months) vitiligo. Analysis showed that melanocytes in early lesions have altered expression of several chemotaxis-associated molecules, including elevated secretion of CXCL12 and CCL5. Higher levels of these chemokines coincided with prominent infiltration of the skin with antigen presenting cells (APCs) and T cells. Most of the intralesional APCs expressed the CD86 maturation marker and co-localized with T cells, particularly in early vitiligo lesions. These observations were confirmed by in vivo animal studies showing preferential recruitment of APCs and T cells to CXCL12- and CCL5-expressing transplanted melanocytes, immunotargeting of the chemokine-positive cells, continuous loss of the pigment-producing cells from the epidermis, and development of vitiligo-like lesions. Taken together, our studies show that melanocyte-derived CXCL12 and CCL5 support APC and T-cell recruitment, antigen acquisition, and T-cell activation in early vitiligo and reinforce the role of melanocyte-derived CXCL12 and CCL5 in activation of melanocyte-specific immunity and suggest inhibition of these chemotactic axes as a strategy for vitiligo stabilization.

Modulation of Kinin B2 Receptor Signaling Controls Aortic Dilatation and Rupture in the Angiotensin II-Infused Apolipoprotein E-Deficient Mouse

OBJECTIVE

Abdominal aortic aneurysm (AAA) is an important cause of mortality in older adults. Activity of the local kallikrein-kinin system may be important in cardiovascular disease. The effect of kinin B2 receptor (B2R) agonist and antagonist peptides on experimental AAA was investigated.

APPROACH AND RESULTS

AAA was induced in apolipoprotein E-deficient mice via infusion of angiotensin II (1.0 μg/kg per minute SC). B2R agonists or antagonists were given via injection (2 mg/kg IP) every other day. The B2R agonist (B9772) promoted aortic rupture in response to angiotensin II associated with an increase in neutrophil infiltration of the aorta in comparison to controls. Mice receiving a B2R/kinin B1 receptor antagonist (B9430) were relatively protected from aortic rupture. Neutrophil depletion abrogated the ability of the B2R agonist to promote aortic rupture. Progression of angiotensin II-induced aortic dilatation was inhibited in mice receiving a B2R antagonist (B9330). Secretion of metalloproteinase-2 and -9, osteoprotegerin, and osteopontin by human AAA explant was reduced in the presence of the B2R antagonist (B9330). B2R agonist and antagonist peptides enhanced and inhibited, respectively, angiotensin II-induced neutrophil activation and aortic smooth muscle cell inflammatory phenotype. The B2R antagonist (B9330; 5 μg) delivered directly to the aortic wall 1 week post-AAA induction with calcium phosphate in a rat model reduced aneurysm growth associated with downregulation of aortic metalloproteinase-9.

CONCLUSIONS

B2R signaling promotes aortic rupture within a mouse model associated with the ability to stimulate inflammatory phenotypes of neutrophils and vascular smooth muscle cells. B2R antagonism could be a potential therapy for AAA.

IL-1β Is Involved with the Generation of Pain in Experimental Autoimmune Encephalomyelitis

Pain is one of the main symptoms of multiple sclerosis, a demyelinating disease of the central nervous system that affects millions of people worldwide. The experimental autoimmune encephalomyelitis (EAE) is considered an experimental model of multiple sclerosis, and besides motor weakness, hypernociception is one of the clinical signs of animals with EAE. In this study, we investigated the influence of some cytokines in the generation of the hypernociceptive response in a mouse model of EAE using MOG_35-55. We measured some cytokines in the dorsal root ganglia (DRG), an important anatomical structure involved in pain. We found increased levels of the cytokines TNF-α, IL-1β, and Kc in DRGs of animals with EAE. We used the antibody IL-1ra to antagonize the effects of IL-1β, and animals presented a decrease in the hypernociceptive response. Thus, our results suggest that hypernociception in this experimental model of EAE may be a consequence of the increase in some cytokines in DRGs, especially IL-1β.

Astrocyte pathology in Alexander disease causes a marked inflammatory environment

Astrocytes and microglia are commonly involved in a wide variety of CNS pathologies. However, they are typically involved in a secondary response in which many cell types are affected simultaneously and therefore it is difficult to know their contributions to the pathology. Here, we show that pathological astrocytes in a mouse model of Alexander disease (AxD; GFAP (Tg);Gfap (+/R236H)) cause a pronounced immune response. We have studied the inflammatory response in the hippocampus and spinal cord of these mice and have found marked microglial activation, which follows that of astrocytes in a spatial pathological progression, as shown by increased levels of Iba1 and microglial cell (Iba1+) density. RNA sequencing and subsequent gene ontology (GO) analysis revealed that a majority of the most upregulated genes in GFAP (Tg);Gfap (+/R236H) mice are directly associated with immune function and that cytokine and chemokine GO attributes represent nearly a third of the total immune attributes. Cytokine and chemokine analysis showed CXCL10 and CCL2 to be the most and earliest increased molecules, showing concentrations as high as EAE or stroke models. CXCL10 was localized exclusively to astrocytes while CCL2 was also present in microglia. Despite the high levels of CXCL10 and CCL2, T cell infiltration was mild and no B cells were found. Thus, mutations in GFAP are sufficient to trigger a profound inflammatory response. The cellular stress caused by the accumulation of GFAP likely leads to the production of inflammatory molecules and microglial activation. Examination of human AxD CNS tissues also revealed microglial activation and T cell infiltrates. Therefore, the inflammatory environment may play an important role in producing the neuronal dysfunction and seizures of AxD.

High CD6 and low chemokine receptor expression on peripheral blood lymphocytes correlates with MRI gadolinium enhancement in MS

Correlation between gadolinium-enhancing [Gd(+)] lesions on MRI and expression of CD6 molecules and a group of chemokine receptors on peripheral blood (PB) and cerebrospinal fluid (CSF) immune cells was measured in multiple sclerosis (MS) patients. Twenty remitting-relapsing MS patients with (n=10) and without (n=10) Gd(+) lesions entered the study. mRNA and surface expression of CD6 and CCR1, CCR2, CCR3 and CCR5 was measured by immunostaining and flow cytometry. Expression of mRNA and surface staining for CD6 in PB T lymphocytes was increased in Gd(+) compared to Gd(-) patients (p<0.01; p<0.05, respectively). CD6 mRNA correlated with the number and size of Gd(+) lesions (r=0.67, and r=0.65 respectively). mRNA and surface expression for CCR1, CCR2, and CCR3 in PB cells was lower in Gd(+) compared to Gd(-) MS patients (p<0.05, p<0.05). The frequency of cells co-expressing CD6 with CCR1 and CCR5 was low in PB T lymphocytes and high in CSF (p<0.05, p<0.05). These results suggest that Gd(+) correlates with increased expression of CD6 and decreased expression of chemokine receptors on PB T lymphocytes. Co-expression of CD6 with CCR1 and CCR5 predisposes cells for transmigration into CSF.

Chemokine-mediated redirection of T cells constitutes a critical mechanism of glucocorticoid therapy in autoimmune CNS responses

Glucocorticoids (GCs) are the standard therapy for treating multiple sclerosis (MS) patients suffering from an acute relapse. One of the main mechanisms of GC action is held to be the induction of T cell apoptosis leading to reduced lymphocyte infiltration into the CNS, yet our analysis of experimental autoimmune encephalomyelitis (EAE) in three different strains of genetically manipulated mice has revealed that the induction of T cell apoptosis is not essential for the therapeutic efficacy of GCs. Instead, we identified the redirection of T cell migration in response to chemokines as a new therapeutic principle of GC action. GCs inhibited the migration of T cells towards CCL19 while they enhanced their responsiveness towards CXCL12. Importantly, blocking CXCR4 signaling in vivo by applying Plerixafor(®) strongly impaired the capacity of GCs to interfere with EAE, as revealed by an aggravated disease course, more pronounced CNS infiltration and a more dispersed distribution of the infiltrating T cells throughout the parenchyma. Our observation that T cells lacking the GC receptor were refractory to CXCL12 further underscores the importance of this pathway for the treatment of EAE by GCs. Importantly, methylprednisolone pulse therapy strongly increased the capacity of peripheral blood T cells from MS patients of different subtypes to migrate towards CXCL12. This indicates that modulation of T cell migration is an important mechanistic principle responsible for the efficacy of high-dose GC therapy not only of EAE but also of MS.

Balance between the two kinin receptors in the progression of experimental focal and segmental glomerulosclerosis in mice

Focal and segmental glomerulosclerosis (FSGS) is one of the most important renal diseases related to end-stage renal failure. Bradykinin has been implicated in the pathogenesis of renal inflammation, whereas the role of its receptor 2 (B2RBK; also known as BDKRB2) in FSGS has not been studied. FSGS was induced in wild-type and B2RBK-knockout mice by a single intravenous injection of Adriamycin (ADM). In order to further modulate the kinin receptors, the animals were also treated with the B2RBK antagonist HOE-140 and the B1RBK antagonist DALBK. Here, we show that the blockage of B2RBK with HOE-140 protects mice from the development of FSGS, including podocyte foot process effacement and the re-establishment of slit-diaphragm-related proteins. However, B2RBK-knockout mice were not protected from FSGS. These opposite results were due to B1RBK expression. B1RBK was upregulated after the injection of ADM and this upregulation was exacerbated in B2RBK-knockout animals. Furthermore, treatment with HOE-140 downregulated the B1RBK receptor. The blockage of B1RBK in B2RBK-knockout animals promoted FSGS regression, with a less-inflammatory phenotype. These results indicate a deleterious role of both kinin receptors in an FSGS model and suggest a possible cross-talk between them in the progression of disease.

Differential gene expression of bradykinin receptors 1 and 2 in peripheral monocytes from patients with essential hypertension

Bradykinin participates in various hypertensive processes, exerted via its type 1 and type 2 receptors (BKR1 and BKR2). The aim of the study was to investigate BKR1 and BK2R gene expression in peripheral monocytes in patients with essential hypertension compared with healthy individuals. Seventeen hypertensive patients (9 males, age 56 ± 7 years) and 12 healthy individuals (7 males, age 55 ± 6) participated. Mononuclear cells isolated using anti-CD14+ antibodies and mRNAs of BKR1 and BKR2 were estimated by real-time quantitative reverse transcription-PCR. Both BKR1 and BKR2 showed significantly upregulated gene expression in the group of hypertensive patients. Specifically, BKR1 gene expression was 142.1 ± 42.2 in hypertensives versus 20.2 ± 8 in controls (P = 0.024) and BKR2 was 1222.2 ± 361.6 in hypertensives versus 259.5 ± 99.1 in controls (P = 0.038). Antihypertensive treatment resulted in a decrease in BKR1 (from 142.1 ± 42.2 to 55.2 ± 17.1, P = 0.065) and in BKR2 (from 1222.2 ± 361.6 to 256.8 ± 81.8, P = 0.014) gene expression. BKR1 and BKR2 gene expression on peripheral monocytes is upregulated in essential hypertension. This may lead to functional changes in monocytes and contribute to the development of target organ damage in hypertensive patients.

Spatial reference memory deficits precede motor dysfunction in an experimental autoimmune encephalomyelitis model: the role of kallikrein-kinin system

Multiple sclerosis (MS) is a progressive T cell-mediated autoimmune demyelinating inflammatory disease of the central nervous system (CNS). Although it is recognized that cognitive deficits represent a manifestation of the disease, the underlying pathogenic mechanisms remain unknown. Here we provide evidence of spatial reference memory impairments during the pre-motor phase of experimental autoimmune encephalomyelitis (EAE) in mice. Specifically, these cognitive deficits were accompanied by down-regulation of choline acetyltransferase (ChAT) mRNA expression on day 5 and 11 post-immunization, and up-regulation of inflammatory cytokines in the hippocampus and prefrontal cortex. Moreover, a marked increase in B1R mRNA expression occurred selectively in the hippocampus, whereas protein level was up-regulated in both brain areas. Genetic deletion of kinin B1R attenuated cognitive deficits and cholinergic dysfunction, and blocked mRNA expression of both IL-17 and IFN-γ in the prefrontal cortex, lymph node and spleen of mice subjected to EAE. The discovery of kinin receptors, mainly B1R, as a target for controlling neuroinflammatory response, as well as the cognitive deficits induced by EAE may foster the therapeutic exploitation of the kallikrein-kinin system (KKS), in particular for the treatment of autoimmune disorders, such as MS, mainly during pre-symptomatic phase.

Ischemic stroke and traumatic brain injury: the role of the kallikrein-kinin system

Acute ischemic stroke and traumatic brain injury are a major cause of mortality and morbidity. Due to the paucity of therapies, there is a pressing clinical demand for new treatment options. Successful therapeutic strategies for these conditions must target multiple pathophysiological mechanisms occurring at different stages of brain injury. In this respect, the kallikrein-kinin system is an ideal target linking key pathological hallmarks of ischemic and traumatic brain damage such as edema formation, inflammation, and thrombosis. In particular, the kinin receptors, plasma kallikrein, and coagulation factor XIIa are highly attractive candidates for pharmacological development, as kinin receptor antagonists or inhibitors of plasma kallikrein and coagulation factor XIIa are neuroprotective in animal models of stroke and traumatic brain injury. Nevertheless, conflicting preclinical evaluation as well as limited and inconclusive data from clinical trials suggest caution when transferring observations made in animals into the human situation. This review summarizes current evidence on the pathological significance of the kallikrein-kinin system during ischemic and traumatic brain damage, with a particular focus on experimental data derived from animal models. Experimental findings are also compared with human data if available, and potential therapeutic implications are discussed.

G protein-coupled receptors as therapeutic targets for multiple sclerosis

G protein-coupled receptors (GPCRs) mediate most of our physiological responses to hormones, neurotransmitters and environmental stimulants. They are considered as the most successful therapeutic targets for a broad spectrum of diseases. Multiple sclerosis (MS) is an inflammatory disease that is characterized by immune-mediated demyelination and degeneration of the central nervous system (CNS). It is the leading cause of non-traumatic disability in young adults. Great progress has been made over the past few decades in understanding the pathogenesis of MS. Numerous data from animal and clinical studies indicate that many GPCRs are critically involved in various aspects of MS pathogenesis, including antigen presentation, cytokine production, T-cell differentiation, T-cell proliferation, T-cell invasion, etc. In this review, we summarize the recent findings regarding the expression or functional changes of GPCRs in MS patients or animal models, and the influences of GPCRs on disease severity upon genetic or pharmacological manipulations. Hopefully some of these findings will lead to the development of novel therapies for MS in the near future.

Characterization of dual agonists for kinin B1 and B2 receptors and their biased activation of B2 receptors

Kinin B1 and B2 receptors (kB1R and kB2R) play important roles in many physiological and pathological processes. In some cases, kB1R or kB2R activation can have overlapping or complementary beneficial effects, thus an activator of both receptors might be advantageous. We found that replacement of the C-terminal Arg in the natural kB2R activators bradykinin (BK) or kallidin (KD) with Lys (K(9)-BK or K(10)-KD) resulted in agonists that effectively stimulate the downstream signaling of both the kB1R and kB2R as measured by increased inositol turnover, intracellular calcium, ERK1/2 phosphorylation, arachidonic acid release and NO production. However, K(9)-BK and K(10)-KD displayed some characteristics of biased agonism for kB2Rs as indicated by the rapid kinetics of ERK1/2 phosphorylation induced by K(9)-BK or K(10)-KD compared with the prolonged response mediated by BK or KD. In contrast, kinetics of ERK phosphorylation stimulated by K(10)-KD activation of the kB1R was the same as that induced by known kB1R agonist des-Arg(10)-KD. Furthermore, the endocytosis of kB2Rs mediated by K(9)-BK and K(10)-KD was remarkably less than that induced by BK and KD respectively. K(10)-KD stimulated kB1R and kB2R-dependent calcium responses and ERK1/2 phosphorylation in bovine endothelial cells. In cytokine-treated human endothelial cells, K(10)-KD stimulated ERK1/2 phosphorylation and a transient peak of NO production that was primarily kB2R-dependent. K(10)-KD also stimulated prolonged NO production that was both kB1R and kB2R-dependent. These data provide the first examples of dual agonists of kB1R and kB2R, and a biased agonist of kB2R and may provide useful clues for developing dual modulators of kB1Rs and kB2Rs for potential therapeutic use.

Mechanisms of dendritic cell trafficking across the blood-brain barrier

Although the central nervous system (CNS) is considered to be an immunoprivileged site, it is susceptible to a host of autoimmune as well as neuroinflammatory disorders owing to recruitment of immune cells across the blood-brain barrier into perivascular and parenchymal spaces. Dendritic cells (DCs), which are involved in both primary and secondary immune responses, are the most potent immune cells in terms of antigen uptake and processing as well as presentation to T cells. In light of the emerging importance of DC traficking into the CNS, these cells represent good candidates for targeted immunotherapy against various neuroinflammatory diseases. This review focuses on potential physiological events and receptor interactions between DCs and the microvascular endothelial cells of the brain as they transmigrate into the CNS during degeneration and injury. A clear understanding of the underlying mechanisms involved in DC migration may advance the development of new therapies that manipulate these mechanistic properties via pharmacologic intervention. Furthermore, therapeutic validation should be in concurrence with the molecular imaging techniques that can detect migration of these cells in vivo. Since the use of noninvasive methods to image migration of DCs into CNS has barely been explored, we highlighted potential molecular imaging techniques to achieve this goal. Overall, information provided will bring this important leukocyte population to the forefront as key players in the immune cascade in the light of the emerging contribution of DCs to CNS health and disease.

The role of kinin receptors in preventing neuroinflammation and its clinical severity during experimental autoimmune encephalomyelitis in mice

Background

Multiple sclerosis (MS) is a demyelinating and neuroinflammatory disease of the human central nervous system (CNS). The expression of kinins is increased in MS patients, but the underlying mechanisms by which the kinin receptor regulates MS development have not been elucidated.

Methodology/Principal Findings

Experimental autoimmune encephalomyelitis (EAE) was induced in female C57BL/6 mice by immunization with MOG_35–55 peptide emulsified in complete Freund's adjuvant and injected with pertussis toxin on day 0 and day 2. Here, we report that blockade of the B₁R in the induction phase of EAE markedly suppressed its progression by interfering with the onset of the immune response. Furthermore, B₁R antagonist suppressed the production/expression of antigen-specific T_H1 and T_H17 cytokines and transcription factors, both in the periphery and in the CNS. In the chronic phase of EAE, the blockade of B₁R consistently impaired the clinical progression of EAE. Conversely, administration of the B₁R agonist in the acute phase of EAE suppressed disease progression and inhibited the increase in permeability of the blood-brain barrier (BBB) and any further CNS inflammation. Of note, blockade of the B₂R only showed a moderate impact on all of the studied parameters of EAE progression.

Conclusions/Significance

Our results strongly suggest that kinin receptors, mainly the B₁R subtype, play a dual role in EAE progression depending on the phase of treatment through the lymphocytes and glial cell-dependent pathways.

Bradykinin receptor 2 extends inflammatory cell recruitment in a model of acute gouty arthritis

The aim of this study was determine the effect of bradykinin receptor antagonism on MSU crystal-induced chemokine production and leukocyte recruitment. Mice were injected intraperitoneally with monosodium urate (MSU) crystals ± bradykinin B1- or B2 receptor antagonists, Des-Arg-HOE-140 and HOE-140, respectively. MSU crystal-induced chemokine production and leukocyte recruitment in the peritoneum were measured over 24h and B1 and B2 receptor expression on leukocytes and peritoneal membrane was determined by flow cytometry and fluorescence microscopy. Data analysis showed that only B2 receptor antagonism decreased monocyte and neutrophil infiltration 24 h post MSU crystal administration. Decreased leukocyte infiltration was associated with reduced monocyte (CCL2) chemokine levels. MSU crystal-induced damage to the surrounding visceral membrane was also attenuated in the presence of B2 receptor antagonism. Together, these data show that bradykinin receptor 2 plays a role in maintaining MSU crystal-induced leukocyte infiltration and membrane permeability and identify the B2 receptor as a potential therapeutic target for managing inflammation in gout.

Plasmodium berghei NK65 induces cerebral leukocyte recruitment in vivo: an intravital microscopic study

Malaria is second only to tuberculosis as the leading cause of morbidity and mortality as a consequence of a single infectious agent. Much of the pathology of malaria arises from the inappropriate or excessive immune response mounted by the host in an attempt to eliminate the parasite. We here report the inflammatory changes observed in the cerebral microvasculature of C57BL/6 and BALB/c mice that had been inoculated with Plasmodium berghei NK65, a lethal strain of rodent malaria. Although no neurological signs were observed in experimentally infected mice, inflammation of the cerebral microvasculature was clearly evident. Histopathological analysis demonstrated that alterations in cerebral tissue were more intense in infected C57Bl/6 mice than in infected BALB/c animals. Intravital microscopic examination of the cerebral microvasculature revealed increased leukocyte rolling and adhesion in pial venules of infected mice compared with non-infected animals. The extravasation of Evans blue dye into the cerebral parenchyma was also elevated in infected mice in comparison with their non-infected counterparts. Additionally, protein levels of TNF-α, MIG/CXCL9, MCP-1/CCL2, MIP-1α/CCL3 and RANTES/CCL5 were up-regulated in brain samples derived from infected C57Bl/6 mice. Taken together, the data reported here illustrate the complex strain-dependent relationships between leukocyte recruitment, blood brain barrier permeability and chemokine production.

Role of CCR5 and its ligands in the control of vascular inflammation and leukocyte recruitment required for acute excitotoxic seizure induction and neural damage

Chemokines may play a role in leukocyte migration across the blood-brain barrier (BBB) during neuroinflammation and other neuropathological processes, such as epilepsy. We investigated the role of the chemokine receptor CCR5 in seizures. We used a rat model based on intraperitoneal kainic acid (KA) administration. Four months before KA injection, adult rats were given femoral intramarrow inoculations of SV (RNAiR5-RevM10.AU1), which carries an interfering RNA (RNAi) against CCR5, plus a marker epitope (AU1), or its monofunctional RNAi-carrying homologue, SV(RNAiR5). This treatment lowered expression of CCR5 in circulating cells. In control rats, seizures induced elevated expression of CCR5 ligands MIP-1α and RANTES in the microvasculature, increased BBB leakage and CCR5(+) cells, as well as neuronal loss, inflammation, and gliosis in the hippocampi. Animals given either the bifunctional or the monofunctional vector were largely protected from KA-induced seizures, neuroinflammation, BBB damage, and neuron loss. Brain CCR5 mRNA was reduced. Rats receiving RNAiR5-bearing vectors showed far greater repair responses: increased neuronal proliferation, and decreased production of MIP-1α and RANTES. Controls received unrelated SV(BUGT) vectors. Decrease in CCR5 in circulating cells strongly protected from excitotoxin-induced seizures, BBB leakage, CNS injury, and inflammation, and facilitated neurogenic repair.

Distribution and expression of B2-kinin receptor on human leukocyte subsets in young adults and elderly using flow cytometry

The kallikrein-kinin system has been investigated in many experimental models. Dysregulations of the KKS are likely to be involved in pathologies such as inflammation, cancer and cardiovascular diseases. Previous works on the human KKS mostly rely on gene polymorphism and mRNA expression. In order to assess the KKS in human at the protein level, we have developed an approach based on flow cytometric analysis of leukocytes. Whole blood samples were collected and erythrocytes were lysed. Permeabilised leukocytes were incubated with anti-B2R (IgG2b), anti-IgG2b-PE, anti-CD3-PerCP (lymphocytes) and anti-CD14-APC (monocytes) antibodies. FACScalibur analyzed fluorescence intensities. Results were expressed as per cent of B2R-positive cells in each leukocyte subset and as B2R fluorescence intensity per positive cell. Detection of the B2R protein by this methodology was validated by (i) correlation with Western blotting using two different B2R antibodies, (ii) BK-induced Erk activation, (iii) B2R mRNA expression. The methodology was then applied to evaluate variations of B2R expression in a population including young healthy, elderly healthy, and elderly treated hypertensive men and women. In the young healthy subjects, B2R distribution was: monocytes>polymorphonuclear neutrophils (PMN)>lymphocytes and no difference with gender was observed. Moreover, no difference was observed on PMN B2R expression. B2R expression remained unchanged in the elderly healthy or hypertensive men. By contrast, monocytes and lymphocytes B2R expressions were decreased in the elderly healthy women. Finally, FACS analysis of B2R expression on leukocytes subsets provides single cell quantification of B2R expression allowing comparison of cellular sub-populations. This approach provides a new efficient tool to investigate B2R profiling of immune system in pathological states.

Kinins in cardiac inflammation and regeneration: insights from ischemic and diabetic cardiomyopathy

The kallikrein-kinin system (KKS) is a system of vasoactive peptides, the kinins, involved in different aspects of remodeling, inflammation and angiogenesis. Kinins mediate their actions through two receptors, B1R and B2R. It is increasingly recognized that the KKS is involved in the inflammatory processes of the heart. Evidence shows that the B2R is beneficial in myocardial diseases, protecting from inflammation, fibrosis and apoptosis, while B1R shows a proinflammatory character contributing to the disease progression by increasing the production of cytokines and stimulating the migration of immune cells. Furthermore, novel important actions of the KKS and its receptors contribute to neovascularization and recruitment of endothelial progenitor cells in ischemic areas and endothelial dysfunction. The kinin receptors could therefore constitute potential therapeutic targets in the treatment of myocardial ischemia and diabetic cardiomyopathy.

Kinin B1 receptors contributes to acute pain following minor surgery in humans

Background

Kinins play an important role in regulation of pain and hyperalgesia after tissue injury and inflammation by activating two types of G-protein-coupled receptors, the kinin B₁ and B₂ receptors. It is generally accepted that the B₂ receptor is constitutively expressed, whereas the B₁ receptor is induced in response to inflammation. However, little is known about the regulatory effects of kinin receptors on the onset of acute inflammation and inflammatory pain in humans. The present study investigated the changes in gene expression of kinin receptors and the levels of their endogenous ligands at an early time point following tissue injury and their relation to clinical pain, as well as the effect of COX-inhibition on their expression levels.

Results

Tissue injury resulted in a significant up-regulation in the gene expression of B₁ and B₂ receptors at 3 hours post-surgery, the onset of acute inflammatory pain. Interestingly, the up-regulation in the gene expression of B₁ and B₂ receptors was positively correlated to pain intensity only after ketorolac treatment, signifying an interaction between prostaglandins and kinins in the inflammatory pain process. Further, the gene expression of both B₁ and B₂ receptors were correlated. Following tissue injury, B₁ ligands des-Arg⁹-BK and des-Arg¹⁰-KD were significantly lower at the third hour compared to the first 2 hours in both the placebo and the ketorolac treatment groups but did not differ significantly between groups. Tissue injury also resulted in the down-regulation of TRPV1 gene expression at 3 hours post-surgery with no significant effect by ketorolac treatment. Interestingly, the change in gene expression of TRPV1 was correlated to the change in gene expression of B₁ receptor but not B₂ receptor.

Conclusions

These results provide evidence at the transcriptional level in a clinical model of tissue injury that up-regulation of kinin receptors are involved in the development of the early phase of inflammation and inflammatory pain. The up-regulation of B₁ receptors may contribute to acute inflammatory pain through TRPV1 activation.

Small but powerful: short peptide hormones and their role in autoimmune inflammation

In the recent years, it has become increasingly clear that the immune response is also influenced by mediators which were first discovered as regulators in the nervous or also cardiovascular system. Here, small peptide hormones may play an important role. Kinins like bradykinins act on the endothelium and play a role for trafficking of lymphocytes over the blood-brain barrier. Neuropeptides like vasoactive intestinal peptide or neuropeptide Y also directly act on T cells and favour the differentiation of Th2 cells or regulatory T cell populations. Recently, the renin-angiotensin system (RAS) came into the focus of interest. Inhibition of the RAS at different levels may influence autoimmune responses and involve T cells as well as antigen-presenting cells, probably via different signalling pathways. Inhibitors of angiotensin converting enzyme and antagonists of the angiotensin 1 receptors are used in the treatment of hypertension, kidney disease or stroke by millions of people worldwide. These inexpensive and safe pharmaceuticals may also represent an interesting and innovative approach for the (combination) treatment of autoimmune diseases like multiple sclerosis.

Activation of kinin receptor B1 limits encephalitogenic T lymphocyte recruitment to the central nervous system

Previous proteomic and transcriptional analyses of multiple sclerosis lesions revealed modulation of the renin-angiotensin and the opposing kallikrein-kinin pathways. Here we identify kinin receptor B1 (Bdkrb1) as a specific modulator of immune cell entry into the central nervous system (CNS). We demonstrate that the Bdkrb1 agonist R838 (Sar-[D-Phe]des-Arg(9)-bradykinin) markedly decreases the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) in SJL mice, whereas the Bdkrb1 antagonist R715 (Ac-Lys-[D-betaNal(7), Ile(8)]des-Arg(9)-bradykinin) resulted in earlier onset and greater severity of the disease. Bdkrb1-deficient (Bdkrb1(-/-)) C57BL/6 mice immunized with a myelin oligodendrocyte glycoprotein fragment, MOG(35-55), showed more severe disease with enhanced CNS-immune cell infiltration. The same held true for mixed bone marrow-chimeric mice reconstituted with Bdkrb1(-/-) T lymphocytes, which showed enhanced T helper type 17 (T(H)17) cell invasion into the CNS. Pharmacological modulation of Bdkrb1 revealed that in vitro migration of human T(H)17 lymphocytes across blood-brain barrier endothelium is regulated by this receptor. Taken together, these results suggest that the kallikrein-kinin system is involved in the regulation of CNS inflammation, limiting encephalitogenic T lymphocyte infiltration into the CNS, and provide evidence that Bdkrb1 could be a new target for the treatment of chronic inflammatory diseases such as multiple sclerosis.