Inflammatory cytokines TNF-α and IL-17 enhance the efficacy of cystic fibrosis transmembrane conductance regulator modulators.

Without cystic fibrosis transmembrane conductance regulator-mediated (CFTR-mediated) HCO3- secretion, airway epithelia of newborns with cystic fibrosis (CF) produce an abnormally acidic airway surface liquid (ASL), and the decreased pH impairs respiratory host defenses. However, within a few months of birth, ASL pH increases to match that in non-CF airways. Although the physiological basis for the increase is unknown, this time course matches the development of inflammation in CF airways. To learn whether inflammation alters CF ASL pH, we treated CF epithelia with TNF-α and IL-17 (TNF-α+IL-17), 2 inflammatory cytokines that are elevated in CF airways. TNF-α+IL-17 markedly increased ASL pH by upregulating pendrin, an apical Cl-/HCO3- exchanger. Moreover, when CF epithelia were exposed to TNF-α+IL-17, clinically approved CFTR modulators further alkalinized ASL pH. As predicted by these results, in vivo data revealed a positive correlation between airway inflammation and CFTR modulator-induced improvement in lung function. These findings suggest that inflammation is a key regulator of HCO3- secretion in CF airways. Thus, they explain earlier observations that ASL pH increases after birth and indicate that, for similar levels of inflammation, the pH of CF ASL is abnormally acidic. These results also suggest that a non-cell-autonomous mechanism, airway inflammation, is an important determinant of the response to CFTR modulators.

IL-17A Secreted by Th17 Cells Is Essential for the Host against Streptococcus agalactiae Infections.

Streptococcus agalactiae is an important bacterial pathogen and causative agent of diseases including neonatal sepsis and meningitis, as well as infections in healthy adults and pregnant women. Although antibiotic treatments effectively relieve symptoms, the emergence and transmission of multidrug-resistant strains indicate the need for an effective immunotherapy. Effector T helper (Th) 17 cells are a relatively newly discovered subpopulation of helper CD4+ T lymphocytes, and which, by expressing interleukin (IL)-17A, play crucial roles in host defenses against a variety of pathogens, including bacteria and viruses. However, whether S. agalactiae infection can induce the differentiation of CD4+ T cells into Th17 cells, and whether IL-17A can play an effective role against S. agalactiae infections, are still unclear. In this study, we analyzed the responses of CD4+ T cells and their defensive effects after S. agalactiae infection. The results showed that S. agalactiae infection induces not only the formation of Th1 cells expressing interferon (IFN)-γ, but also the differentiation of mouse splenic CD4+ T cells into Th17 cells, which highly express IL-17A. In addition, the bacterial load of S. agalactiae was significantly increased and decreased in organs as determined by antibody neutralization and IL-17A addition experiments, respectively. The results confirmed that IL-17A is required by the host to defend against S. agalactiae and that it plays an important role in effectively eliminating S. agalactiae. Our findings therefore prompt us to adopt effective methods to regulate the expression of IL-17A as a potent strategy for the prevention and treatment of S. agalactiae infection.

Background to new treatments for COVID-19, including its chronicity, through altering elements of the cytokine storm.

Anti-tumour necrosis factor (TNF) biologicals, Dexamethasone and rIL-7 are of considerable interest in treating COVID-19 patients who are in danger of, or have become, seriously ill. Yet reducing sepsis mortality by lowering circulating levels of TNF lost favour when positive endpoints in earlier simplistic models could not be reproduced in well-conducted human trials. Newer information with anti-TNF biologicals has encouraged reintroducing this concept for treating COVID-19. Viral models have had encouraging outcomes, as have the effects of anti-TNF biologicals on community-acquired COVID-19 during their long-term use to treat chronic inflammatory states. The positive outcome of a large scale trial of dexamethasone, and its higher potency late in the disease, harmonises well with its capacity to enhance levels of IL-7Rα, the receptor for IL-7, a cytokine that enhances lymphocyte development and is increased during the cytokine storm. Lymphoid germinal centres required for antibody-based immunity can be harmed by TNF, and restored by reducing TNF. Thus the IL-7- enhancing activity of dexamethasone may explain its higher potency when lymphocytes are depleted later in the infection, while employing anti-TNF, for several reasons, is much more logical earlier in the infection. This implies dexamethasone could prove to be synergistic with rIL-7, currently being trialed as a COVID-19 therapeutic. The principles behind these COVID-19 therapies are consistent with the observed chronic hypoxia through reduced mitochondrial function, and also the increased severity of this disease in ApoE4-positive individuals. Many of the debilitating persistent aspects of this disease are predictably susceptible to treatment with perispinal etanercept, since they have cerebral origins.

ACT1 Is Required for Murine IL-23-Induced Psoriasiform Inflammation Potentially Independent of E3 Ligase Activity.

Psoriasis is a debilitating skin disease characterized by epidermal thickening, abnormal keratinocyte differentiation, and proinflammatory immune cell infiltrate into the affected skin. IL-17A plays a critical role in the etiology of psoriasis. ACT1, an intracellular adaptor protein and a putative ubiquitin E3 ligase, is essential for signal transduction downstream of the IL-17A receptor. Thus, IL-17A signaling in general, and ACT1 specifically, represent attractive targets for the treatment of psoriasis. We generated Act1 knockout and Act1 L286G knockin (ligase domain) mice to investigate the potential therapeutic effects of targeting ACT1 and its U-box domain, respectively. Act1 knockout, but not Act1 L286G knockin, mice were resistant to increases in CXCL1 plasma levels induced by subcutaneous injection of recombinant IL-17A. Moreover, in a mouse model of psoriasiform dermatitis induced by intradermal IL-23 injection, Act1 knockout, but not Act1 L286G knockin, was protective against increases in ear thickness, keratinocyte hyperproliferation, expression of genes for antimicrobial peptides and chemokines, and infiltration of monocytes and macrophages. Our studies highlight the critical contribution of ACT1 to proinflammatory skin changes mediated by the IL-23/IL-17 signaling axis and illustrate the need for further insight into ACT1 E3 ligase activity.

Intraventricular IL-17A administration activates microglia and alters their localization in the mouse embryo cerebral cortex.

Viral infection during pregnancy has been suggested to increase the probability of autism spectrum disorder (ASD) in offspring via the phenomenon of maternal immune activation (MIA). This has been modeled in rodents. Maternal T helper 17 cells and the effector cytokine, interleukin 17A (IL-17A), play a central role in MIA-induced behavioral abnormalities and cortical dysgenesis, termed cortical patch. However, it is unclear how IL-17A acts on fetal brain cells to cause ASD pathologies. To assess the effect of IL-17A on cortical development, we directly administered IL-17A into the lateral ventricles of the fetal mouse brain. We analyzed injected brains focusing on microglia, which express IL-17A receptors. We found that IL-17A activated microglia and altered their localization in the cerebral cortex. Our data indicate that IL-17A activates cortical microglia, which leads to a cascade of ASD-related brain pathologies, including excessive phagocytosis of neural progenitor cells in the ventricular zone.

CD8+ T Cell Immunity Is Compromised by Anti-CD20 Treatment and Rescued by Interleukin-17A.

Treatment with anti-CD20, used in many diseases in which B cells play a pathogenic role, has been associated with susceptibility to intracellular infections. Here, we studied the effect of anti-CD20 injection on CD8+ T cell immunity using an experimental model of Trypanosoma cruzi infection, in which CD8+ T cells play a pivotal role. C57BL/6 mice were treated with anti-CD20 for B cell depletion prior to T. cruzi infection. Infected anti-CD20-treated mice exhibited a CD8+ T cell response with a conserved expansion phase followed by an early contraction, resulting in a strong reduction in total and parasite-specific CD8+ T cell numbers at 20 days postinfection. Anti-CD20 injection increased the frequency of apoptotic CD8+ T cells, decreased the number of effector and memory CD8+ T cells, and reduced the frequency of proliferating and cytokine-producing CD8+ T cells. Accordingly, infected anti-CD20-treated mice presented lower cytotoxicity of T. cruzi peptide-pulsed target cells in vivo All of these alterations in CD8+ T cell immunity were associated with increased tissue parasitism. Anti-CD20 injection also dampened the CD8+ T cell response, when this had already been generated, indicating that B cells were involved in the maintenance rather than the induction of CD8+ T cell immunity. Anti-CD20 injection also resulted in a marked reduction in the frequency of interleukin-6 (IL-6)- and IL-17A-producing cells, and recombinant IL-17A (rIL-17A) injection partially restored the CD8+ T cell response in infected anti-CD20-treated mice. Thus, anti-CD20 reduced CD8+ T cell immunity, and IL-17A is a candidate for rescuing deficient responses either directly or indirectly.IMPORTANCE Monoclonal antibody targeting the CD20 antigen on B cells is used to treat the majority of non-Hodgkin lymphoma patients and some autoimmune disorders. This therapy generates adverse effects, notably opportunistic infections and activation of viruses from latency. Here, using the infection murine model with the intracellular parasite Trypanosoma cruzi, we report that anti-CD20 treatment affects not only B cell responses but also CD8+ T cell responses, representing the most important immune effectors involved in control of intracellular pathogens. Anti-CD20 treatment, directly or indirectly, affects cytotoxic T cell number and function, and this deficient response was rescued by the cytokine IL-17A. The identification of IL-17A as the cytokine capable of reversing the poor response of CD8+ T cells provides information about a potential therapeutic treatment aimed at enhancing defective immunity induced by B cell depletion.

Interleukin-17A induces vascular remodeling of small arteries and blood pressure elevation.

An important link exists between hypertension and inflammation. Hypertensive patients present elevated circulating levels of proinflammatory cytokines, including interleukin-17A (IL-17A). This cytokine participates in host defense, autoimmune and chronic inflammatory pathologies, and cardiovascular diseases, mainly through the regulation of proinflammatory factors. Emerging evidence also suggests that IL-17A could play a role in regulating blood pressure and end-organ damage. Here, our preclinical studies in a murine model of systemic IL-17A administration showed that increased levels of circulating IL-17A raised blood pressure induced inward remodeling of small mesenteric arteries (SMAs) and arterial stiffness. In IL-17A-infused mice, treatment with hydralazine and hydrochlorothiazide diminished blood pressure elevation, without modifying mechanical and structural properties of SMA, suggesting a direct vascular effect of IL-17A. The mechanisms of IL-17A seem to involve an induction of vascular smooth muscle cell (VSMC) hypertrophy and phenotype changes, in the absence of extracellular matrix (ECM) proteins accumulation. Accordingly, treatment with an IL-17A neutralizing antibody diminished SMA remodeling in a model of angiotensin II (Ang II) infusion. Moreover, in vitro studies in VSMCs reported here, provide further evidence of the direct effects of IL-17A on cell growth responses. Our experimental data suggest that IL-17A is a key mediator of vascular remodeling of the small arteries, which might contribute, at least in part, to blood pressure elevation.

Interleukine-17 Administration Modulates Adult Hippocampal Neurogenesis and Improves Spatial Learning in Mice.

Adult hippocampal neurogenesis plays an important role in health and disease. Regulating neurogenesis may be a key mechanism in the pathophysiology and treatment of several neurobehavioral disorders such as schizophrenia, depression, autism spectrum disorders and Alzheimer's disease. Cytokines are known to affect adult neurogenesis, but conflicting studies have been reported with regard to their actual role. Interleukine-17 (IL-17), a potent pro-inflammatory cytokine, has been shown to inhibit proliferation of neuroprogenitors and thus reduce hippocampal neurogenesis, while other studies suggested it can promote neurite outgrowth. In the present study we sought to explore the possible effect of a single dose administration of IL-17 on neurogenesis related behavior, i.e. spatial learning. Surprisingly, ICR mice injected with IL-17 (8 µg) had a significant slight improvement in spatial learning in the Morris water maze paradigm, without any changes in general locomotion compared with control mice. Indeed, the expression of neurogenesis related genes was down regulated following IL-17 treatment. However, we detected an upregulation in the expression of FGF-13, a gene promoting microtubule polymerization and neurite outgrowth, thus supporting neuronal maturation. We thus suggest that IL-17 has a complex role in regulating adult neurogenesis: inhibiting neuroprogenitors proliferation on one hand, while promoting maturation of already formed neuroblasts on the other hand. Our findings suggest that these roles can potentially affect neurogenesis related behavior. Its actual role in health and disease is yet to be determined.

Chronic infusion of interleukin-17 promotes hypertension, activation of cytolytic natural killer cells, and vascular dysfunction in pregnant rats.

Previous studies by our lab have established that placental-ischemia stimulated T-helper 17 cells (TH 17s) cause increased cytolytic natural killer (cNK) cell proliferation and activation during pregnancy; however, the exact mechanism is unknown. The objective of this study was to investigate the role of interlukin 17 (IL-17) in inducing cNK cell activation in pregnancy. We infused 150 pg/day of recombinant IL-17 into a subset of normal pregnant (NP) Sprague Dawley rats from gestation day (GD) 12-19 (NP+IL-17). On GD 19, mean arterial pressure (MAP), fetal and placental weights, cytokines, cNK cell activation, cytotoxic enzymes, and vascular reactivity were assessed. MAP significantly increased from 99 ± 3 mmHg in NP to 120 ± 1 mmHg in NP+IL-17 (P < 0.05). Fetal weight significantly decreased from 2.52 ± 0.04 g in NP to 2.32 ± 0.03 g in NP+IL-17 as did placental weight (NP: 0.65 ± 0.03 g; NP+IL-17: 0.54 ± 0.01 g, P < 0.05). Plasma levels of TNF-α increased to 281.4 ± 55.07 pg/mL in NP+IL-17 from 145.3 ± 16.03 pg/mL in NP (P < 0.05) while placental levels of VEGF decreased from 74.2 ± 6.48 pg/mg in NP to 54.2 ± 3.19 pg/mg in NP+IL-17. Total NK cells were increased in the placenta (NP: 14.3 ± 3.49%; NP+IL-17: 29.33 ± 2.76%, P < 0.05) as were cytolytic NK cells (NP: 3.31 ± 1.25%; NP+IL-17: 13.41 ± 1.81%, P < 0.05). A similar trend was observed in circulating NK cells. Plasma granzyme K increased from 3.55 ± 2.29 pg/mL in NP to 20.9 ± 7.76 pg/mL in NP+IL-17 (P < 0.05), and plasma granzyme B increased from 10.95 ± 0.64 pg/mL in NP to 14.9 ± 0.98 pg/mL in NP+IL-17(P < 0.05). In the placenta, both granzyme A (NP: 246.1 ± 16.7 pg/mg; NP+IL-17: 324.3 ± 15.07 pg/mg, P < 0.05) and granzyme B (NP: 15.18 ± 3.79 pg/mg; NP+IL-17: 27.25 ± 2.34 pg/mg, P < 0.05) increased in response to IL-17 infusion. Finally, vascular reactivity of uterine arteries was significantly impaired in response to IL-17 infusion. The results of this study suggest that IL-17 plays a significant role in the activation of cNK cells during pregnancy.

The effects of interleukin 17A on left stellate ganglion remodeling are mediated by neuroimmune communication in normal structural hearts.

BACKGROUND: It is reported interleukin (IL)-17A, a classical proinflammatory cytokine, is implicated in neuroimmune-associated remodeling in neural plasticity and pathological conditions. However, the effect of IL-17A on left stellate ganglion (LSG) remodeling remains unclear. OBJECTIVE: This study was performed to determine whether exogenous IL-17A promotes LSG remodeling and destabilize ventricular electrophysiological properties (EPs) in normal canines. METHODS: 24 beagles were randomly allocated into three groups. In the first group, animals were subjected to 0.1 ml phosphate buffer saline (PBS) microinjection of into LSG (n = 8), an equivalent IL-17A was administrated in the second group (n = 8), and an equivalent anti-IL-17A mAb plus IL-17A was administrated in the third group (n = 8). The ventricular EPs, neural function and activity of the LSG were determined at baseline and 30 min after administration. In the end, LSG tissues were collected. RESULTS: Compared with the control group, the experimental group had a significantly shorter effective refractory period (ERP) and action potential duration (APD)90, an increased ERP, APD90, Smax dispersion, and APD alternans cycle length; and steepened APD restitution curves. In addition, IL-17A enhanced the neural function and activity of the LSG, upregulated the expressions of neuropeptides and proinflammatory cytokines and cells. And all these effects were attenuated by anti-IL-17A mAb. Importantly, IL-17 receptor A (IL-17R-A) was detected in sympathetic neurons in the LSG. CONCLUSION: IL-17A promoted LSG remodeling by regulating the neural inflammation response. It did so by binding to IL-17R-A, resulting in unstable ventricular electrophysiology in normal structural hearts.

IL-17A-mediated ERK1/2/p65 signaling pathway is associated with cell apoptosis after non-alcoholic steatohepatitis.

Interleukin (IL)-17A is pro-inflammatory cytokine which has been identified as a noninvasive marker of the pathogenesis of non-alcoholic steatohepatitis (NASH). However, the underlying role of IL-17A in NASH progression remains unclear. This study was designed to investigate the biological function and molecular mechanism of IL-17A in the induction of NASH. The results showed that IL-17A was highly expressed in high-fat diet (HFD)-induced NASH mouse model. Intravenous injection of IL-17A exacerbated steatohepatitis process via promoting hepatocyte apoptosis. Furthermore, IL-17A-induced apoptosis was mediated by ERK1/2/p65 signaling pathway. In conclusion, we demonstrated that IL-17A-mediated ERK1/2/p65 signaling pathway was a promising target for the treatment of NASH. © 2018 IUBMB Life, 71(3):302-309, 2019.

Activations of group 2 innate lymphoid cells depend on endotypes of chronic rhinosinusitis.

OBJECTIVE: Chronic rhinosinusitis (CRS) is a complicated disease with several variants caused by different cellular and molecular mechanisms. The characterization of this heterogeneity supports the definition that the disease consists of many endotypes, such as eosinophilic and neutrophilic CRS, and so on. This study aimed to explore group 2 innate lymphoid cells (ILC2s) in neutrophilic CRS without nasal polyps (CRSsNP) and with nasal polyps (CRSwNP), and evaluate ILC2s across characteristics of the disease. METHODS: Nasal biopsy samples were obtained from normal subjects or subjects with CRSsNP or CRSwNP during surgery. ILC2s were sorted and purified as CD45+Lin-CD127+CD4-CD8-CRTH2+CD161+ cells through flow cytometry, and were compared among three groups of subjects. Then, these samples were cultured in vitro, and inflammatory factors were assessed in tissue cultures. After that, human recombinant (rm) interleukin (IL)-33 or IL-17 were administered into the cultures, and we again examined relevant inflammatory substances. RESULTS: ILC2s were upregulated in neutrophilic CRSsNP and CRSwNP patients, and there were no statistical differences between them. Eosinophil cation protein (ECP), myeloperoxidase (MPO), IL-25, IL-33, IL-5, IL-13, interferon (IFN)-γ and IL-17 were increased in the cultures, however, only concentrations of MPO, IFN-γ and IL-17 were enhanced in CRSwNP tissues compared to CRSsNP ones. After administration of rmIL-33, ECP, IL-5 and IL-13 were all increased in tissues from CRSsNP and CRSwNP patients, however, there were no significant differences between them. Finally, we evaluated concentrations of several above inflammatory factors after the treatment of rmIL-17, and found that MPO and IFN-γ were enhanced in these two phenotypes of patients, and were elevated significantly in CRSwNP tissue cultures. CONCLUSION: These findings show that ILC2s might be inactivated in neutrophilic CRSsNP and CRSwNP based on this pilot study.

IL-17A-induced neutrophilic airway inflammation is mediated by oxidant-antioxidant imbalance and inflammatory cytokines in mice.

IL-17 A is produced by several innate and adaptive immune cells which include Th17, and innate lymphoid 3 cells in the lung. IL-17 A can activate airway epithelial cells (AECs), through IL-17 receptor (IL-17R) leading to production of chemokines/cytokines. Inflammatory nature of IL-17 A and its signaling has been assessed by several studies using IL-17 A/IL-17R knockout mice which show attenuated inflammation in different disease models. IL-17 A/IL-17R signaling also plays an important role in pulmonary inflammation through recruitment of neutrophils. However, effect of IL-17 A on oxidant-antioxidant balance in the lung and its association with pulmonary inflammation has not been evaluated earlier. Our study evaluated the effect of intranasal administration of IL-17 A on oxidant-antioxidant balance [inducible nitric oxide synthase (iNOS), nitrotyrosine, lipid peroxides, glutathione peroxidase, and total glutathione levels] and chemokines/cytokines expression (IL-6, MCP-1, and MIP-2) in the lung/AECs and their modulation by an antioxidant, N-acetyl cysteine (NAC). Our study shows that IL-17 A administration leads to increased neutrophilic inflammation along with concomitant increase in iNOS and nitrotyrosine/lipid peroxides. On the other hand, there was a reduction in GPx activity and total thiol levels after IL-17 A administration. IL-17 A administration also led to increased IL-6/MCP-1/MIP-2. IL-17A-induced oxidative stress/IL-6 expression and neutrophilic inflammation was attenuated by NAC treatment, whereas there was no effect on chemokines. This suggests that antioxidant NAC attenuates IL-17A-induced pulmonary inflammation by restoring oxidant-antioxidant balance and attenuation of IL-6 in the lung. Further, our study suggests that inflammatory pulmonary disorders which involve increase in IL-17 A may be ameliorated by NAC treatment.

Interleukin-17 enhances cardiac ventricular remodeling via activating MAPK pathway in ischemic heart failure.

BACKGROUND: We aimed to investigate the impact of interleukin (IL)-17 on ventricular remodeling and the genesis of ventricular arrhythmia (VA) in an ischemic heart failure (HF) model. The expression of the proinflammatory cytokine IL-17 is upregulated during myocardial ischemia and plays a fundamental role in post-infarct inflammation. However, the influence of IL-17 on the genesis of VA has not yet been studied. METHODS AND RESULTS: The level of inflammation and Th17 cell (CD4+IL-17+) expression in the rabbit model of ischemic HF were studied by flow cytometry, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). The effect of IL-17 on VA induction following acute and chronic administration of IL-17 was determined using electrophysiological techniques and optical mapping. The expression of IL-17 target genes and related cytokines and chemokines in vivo and in vitro were measured using qPCR, ELISA, and immunoblotting. Th17 cells were markedly increased in the ischemic HF rabbit model. IL-17 directly induced VA in vivo and in vitro in a dose-dependent manner. IL-17 decreased conduction velocity, lengthened action potential duration, and increased the slope of the left ventricle (LV) restitution curve. IL-17 treatment led to fibrosis, collagen production and apoptosis in the LV. Furthermore, increased IL-17 signaling activated mitogen-activated protein kinase and increased the expression of downstream target genes, IL-6, TNF, CCL20, and CXCL1. An anti-IL-17 neutralizing antibody abolished the effects of IL-17. CONCLUSIONS: The expression of IL-17 and its downstream target genes may play fundamental roles in inducing VA in ischemic HF.

Effect of active immunization with IL-17A on B cell function and infection risk in pristane-induced lupus model.

PURPOSE: The aim of this study was to determine the effect of active immunization of interleukin (IL)-17A to inhibit B cell functions and monitor the risk of infection in a pristane-induced lupus mice model. METHODS: Female Balb/c mice were given a single intraperitoneal injection of 0.5 mL pristane. IL-17A was coupled to keyhole limpet hemocyanin (KLH) and given to mice in three different doses: D0 (0 µg/mL), D1 (1 µg/mL), and D2 (10 µg/mL). The vaccine was given three times with 3-week intervals. At day 42, mice were injected intraperitoneally with methicillin-resistant Staphylococcus aureus (MRSA) and monitored for 3 weeks. Plasma cells proliferation, Th17 and plasma cell percentages were measured by flow cytometry; anti-IL-17A antibody titers, IL-17A, and anti-double-stranded DNA (anti-dsDNA) levels were measured by enzyme-linked immunosorbent assay; and MRSA colonization was measured by bacterial counter. RESULTS: Anti-IL-17A antibody titers were significantly higher in D2 compared to D0 (P = 0.012). Serum IL-17A levels were also significantly lower in D2 compared to D0 (P = 0.000) while Th17 percentages were not significantly different between groups. D2 was also had significantly lower anti-dsDNA (P = 0.021), lower plasma cell percentages (P = 0.000) and lower B cell proliferation rate (P = 0.001) compared to D0. Analysis for the risk of infection also revealed that D2 did not increase the risk of infection compared to D0 (P = 0.504). CONCLUSION: Active immunization with IL-17A coupled to KLH was able to induce a high titer of neutralizing antibodies against IL-17A and inhibit B cell functions without increasing the risk of infection in a pristane-induced lupus mice model.

The synergistic effects of IL-6/IL-17A promote osteogenic differentiation by improving OPG/RANKL ratio and adhesion of MC3T3-E1 cells on hydroxyapatite.

OBJECTIVE: In this study, we evaluated the potential role of IL-6 and/or IL-17A in regulating the OPG/RANKL (osteoprotegerin/receptor activator of nuclear factor kappa b ligand) system of murine osteoblast cell line (MC3T3-E1) cultured on hydroxyapatite (HA). METHODS: MC3T3-E1 cells were seeded on HA and treated with recombinant IL-6 or rIL-17A or combination of the two cytokines. Cell proliferation and differentiation activity were measured by MTS and alkaline phosphatase assays respectively. Observation of cell adhesion and proliferation was examined by scanning electron microscopy. Gene and protein expressions were performed on RANKL and OPG using qPCR, Western blot and ELISA. RESULTS: We demonstrated that treatment with recombinant IL-17A (rIL-17A) and the combination rIL-6/rIL-17A promoted better adhesion and higher proliferation of cells on HA. Cells treated with rIL-17A and the combination cytokines showed a significant increase in differentiation activity on day 7, 10 and 14 as indicated by ALP activity (p < 0.001). Gene and protein expressions showed significant up-regulation of OPG and ALP (p < 0.001) and down-regulation of RANKL (p < 0.001) expression by all the treated groups. Interestingly, the combination of the two cytokines resulted in a significant increase of OPG/RANKL ratio (p < 0.001). CONCLUSION: These findings indicated that treatment with the combination of the two cytokines (IL-6/IL-17A) has synergistic effects to promote osteoblastic differentiation but suppress osteoclastogenesis by altering the OPG/RANKL ratio.

Dietary salt promotes neurovascular and cognitive dysfunction through a gut-initiated TH17 response.

A diet rich in salt is linked to an increased risk of cerebrovascular diseases and dementia, but it remains unclear how dietary salt harms the brain. We report that, in mice, excess dietary salt suppresses resting cerebral blood flow and endothelial function, leading to cognitive impairment. The effect depends on expansion of TH17 cells in the small intestine, resulting in a marked increase in plasma interleukin-17 (IL-17). Circulating IL-17, in turn, promotes endothelial dysfunction and cognitive impairment by the Rho kinase-dependent inhibitory phosphorylation of endothelial nitric oxide synthase and reduced nitric oxide production in cerebral endothelial cells. The findings reveal a new gut-brain axis linking dietary habits to cognitive impairment through a gut-initiated adaptive immune response compromising brain function via circulating IL-17. Thus, the TH17 cell-IL-17 pathway is a putative target to counter the deleterious brain effects induced by dietary salt and other diseases associated with TH17 polarization.

Activation of IL-17 receptor leads to increased oxidative inflammation in peripheral monocytes of autistic children.

Millions of children are affected by different neurodevelopmental disorders, out of which autism spectrum disorder (ASD) poses a major hurdle to normal life style due to associated behavioral abnormalities. Several studies have shown an increased expression/release of Th17 related cytokine, IL-17A in ASD. IL-17A may enhance neuroinflammation via its IL-17A receptor, i.e. IL-17RA expressed in immune cells (such as monocytes) of autistic children. Increased oxidative stress has been implicated in a number of neuropsychiatric disorders including ASD. However, whether IL-17A/IL-17RA signaling contributes to oxidative inflammation in monocytes of autistic children has not been explored previously. With this background, we performed this study in peripheral monocytes of ASD patients and age-matched typically developing children. Our study shows that ASD individuals have increased IL-17RA expression in monocytes which is associated with increased nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) pathway and inducible nitric oxide synthase (iNOS)/nitrotyrosine expression as compared to typically developing children. Moreover, in vitro activation of IL-17 receptor by IL-17A in monocytes isolated from ASD individuals leads to enhanced iNOS expression via NFκB pathway. IL-17RA antibody treatment in vitro reversed IL-17A-induced increase in NFκB and iNOS/nitrotyrosine expression in monocytes isolated from ASD subjects. These data connect increased IL-17A/IL-17RA signaling in ASD patients with enhanced oxidative inflammation in monocytes. Therefore, IL-17 receptor signaling in monocytes may potentiate the effects of IL-17A released by other immune cells and may aggravate neuroinflammation in ASD. Our study further suggests that blockade of IL-17A/IL-17 receptor signaling may be beneficial in the children with ASD.