Abstract WP239: Intestinal Alkaline Phosphatase: A Novel Regulator Of The Gut-brain Axis In Acute Ischemic Stroke

While strokes are typically associated with the brain, it is widely known that stroke outcomes are influenced by communication between the brain and peripheral organs. The gastrointestinal (GI) tract comprises a critical organ system that is affected during and after stroke, and the interaction between the GI tract and the brain in stroke is attributed to the modulation of the gut-brain axis. Intestinal alkaline phosphatase (IAP; gene: Akp3 ) is a brush border enzyme localized in the intestinal epithelium that regulates intestinal homeostasis by modulating inflammation and intestinal integrity. We hypothesized that IAP regulates the early post-stroke changes within the gut-brain axis, and that loss of IAP disrupts the gut-brain axis to worsen post-stroke outcomes and disrupt immune responses. We utilized 4-6 month-old male and female mice with a genomic deletion of Akp3 and their wild type (WT) littermate controls. Following the induction of photothrombotic stroke (PTS), stroke-injured mice and their sham controls were for evaluated for bacterial load, intestinal permeability, intestinal motility, neurological deficits, cerebral blood flow, and immune responses over the next 24 hours. Statistical analysis of Clark’s neurological score, laser speckle flowmetry, and 2,3,5-Triphenyltetrazolium chloride (TTC) staining at day 1 post stroke showed a main effect of stroke but no differences between genotypes. While no differences in intestinal motility were observed due to stroke or genotype, gut permeability to 3kD-FITC dextran quantified at 3.5 hours post-stroke was higher in Akp3-/- mice compared to WT mice. Further analysis of bacterial burden showed that anaerobic bacteria in the ileum were diminished in Akp3-/- mice post-stroke compared to WT counterparts. Quantification of immune cell populations in cervical lymph nodes and spleen showed that Akp3-/- mice displayed baseline decreases in monocyte and dendritic cell populations that were either maintained or further decreased at 24-hours post-stroke, suggesting that Akp3-/- mice are unable to mount an appropriate innate immune response in acute stroke. Taken together, the current results support the hypothesis that IAP shapes early outcomes and modulates the gut-brain axis in ischemic stroke.

A potential monocyte-regulatory T cell axis in neurorestoration following ischemic stroke

Neurorestoration following ischemic stroke is regulated by a complex interaction between the resident glial cells and the immune cells infiltrated to the brain. Using transient middle cerebral artery occlusion (tMCAO), it was shown that both monocytes and regulatory T cells (Tregs) play a critical role in facilitating neurorestoration following ischemic injury of the brain. However, the underlying mechanisms are not well-understood. Importantly, it is unclear whether the neurorestorative effect of monocytes and Tregs require their cognate interaction. The goal of this study is to investigate the interplay between monocytes and Tregs in facilitating brain recovery following ischemic injury. Using mouse tMCAO model, we found that 1) Monocytes were present in the brain both at the sub-acute (day 3) and chronic phases (day 14) following tMCAO, whereas Tregs were significantly increased in the brain only at the chronic phase. 2) During the chronic phase, monocytes and Tregs interacted within the glial scar. 3) CCR2, which controls monocyte trafficking, was expressed in monocytes but not in Tregs, but the number of both monocytes and Tregs were substantially reduced following tMCAO when CCR2 was deleted. 4) CCR2-deficient mice had a reduced survival rate and a larger area of glia scar during the chronic phase post-stroke compared to CCR2-sufficient mice. 5) Tregs in the cervical lymph nodes expressed CCR4 following tMCAO, which is known to control Treg trafficking. 6) Monocytes express CCR4 ligands, CCL17 and CCL22, during differentiation into monocyte-derived cells (MDCs) in vitro. Thus, our data demonstrate that monocytes may exert their neuroprotective via the regulation of Treg trafficking and/or expansion following ischemic stroke.

This work was supported by NIH grants P20GM109098 and R21NS125056 to Edwin Wan. Kelly Monaghan was supported through The American Association of Immunologists Careers in Immunology Fellowship Program.

Tetramerization of STAT5 promotes autoimmune-mediated neuroinflammation

Signal transducers and activators of transcription 5 A and B (STAT5A & B) play a critical role in mediating cellular responses following cytokine stimulation. STAT5 proteins critically signal via the formation of dimers through SH2 domain interactions. However, tetramerization of STAT5 through dimer interactions in the N-domain, has key biological roles. STAT5 tetramers control the suppressive function of regulatory T cells (Tregs), the expansion of CD8+ T cells, and the terminal differentiation of NK cells. However, the role of STAT5 tetramerization in autoimmune-mediated neuroinflammation has not been investigated. Using the STAT5 tetramer-deficient Stat5a-Stat5b N-domain double knock-in (DKI) mouse strain, in which dimer function is preserved, we found that STAT5 tetramers promote the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. The mild EAE phenotype observed in DKI mice correlates with impaired extravasation of pathogenic Th17 cells and interactions between Th17 cells and monocyte-derived cells (MDCs) in the meninges. We further demonstrated that STAT5 tetramerization mediated by GM-CSF signaling, a key EAE-associated cytokine, regulates the production of the chemokine CCL17 by MDCs. Importantly, CCL17 can partially restore the pathogenicity of DKI Th17 cells, and this is dependent on the activity of the integrin VLA-4. Thus, our study reveals a novel GM-CSF-STAT5 tetramer-CCL17 pathway in MDCs that promotes autoimmune-mediated neuroinflammation.

This work was supported by NIH grant P20 GM109098 and WVU Institutional Funds to E.C.K.W.; Praespero Innovation Award Program to E.C.K.W. and V.L.; NIH grants P20 GM103434 and U54 GM104942 to G.H.; the Intramural Research Program of the National Heart, Lung, and Blood Institute, NIH to W.J.L.; the Intramural Research Program of the National Cancer Institute, NIH to V.L. NIH grants S10 OD016165, U57 GM104942, P30 GM103488, and P20 GM103434 to the WVU Flow Cytometry & Single Cell Core Facility. NIH grants U54 GM104942, P20 GM103434 and P20 GM121299 to the WVU and Marshall University Genomics Cores. Funds from WVU Cancer Institute, WVU HSC Office of Research and Graduate Education, and NIH grants P20 RR016440, P30 GM103488, P20 GM121322, U54 GM104942, and P20 GM103434 to the WVU Microscope Imaging Facility. K.L.M. was supported through The American Association of Immunologists Careers in Immunology Fellowship Program.

Tetramerization of STAT5 promotes autoimmune-mediated neuroinflammation

Signal tranducer and activator of transcription 5 (STAT5) plays a critical role in mediating cellular responses following cytokine stimulation. STAT proteins critically signal via the formation of dimers, but additionally, STAT tetramers serve key biological roles, and we previously reported their importance in T and natural killer (NK) cell biology. However, the role of STAT5 tetramerization in autoimmune-mediated neuroinflammation has not been investigated. Using the STAT5 tetramer-deficient Stat5a-Stat5b N-domain double knockin (DKI) mouse strain, we report here that STAT5 tetramers promote the pathogenesis of experimental autoimmune encephalomyelitis (EAE). The mild EAE phenotype observed in DKI mice correlates with the impaired extravasation of pathogenic T-helper 17 (Th17) cells and interactions between Th17 cells and monocyte-derived cells (MDCs) in the meninges. We further demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF)-mediated STAT5 tetramerization regulates the production of CCL17 by MDCs. Importantly, CCL17 can partially restore the pathogenicity of DKI Th17 cells, and this is dependent on the activity of the integrin VLA-4. Thus, our study reveals a GM-CSF-STAT5 tetramer-CCL17 pathway in MDCs that promotes autoimmune neuroinflammation.

Role of vitamin D in flare ups of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is one of the most prevalent autoimmune diseases worldwide. Some researchers have suggested that the serum vitamin D (Vit D) level may relate to disease activity. The current study was designed to identify the correlation between vitamin D prescription and prevention of relapses in rheumatoid arthritis.

PATIENTS AND METHOD

A double blinded, randomized controlled trial study was performed using 80 RA patients. RA was controlled and patients were in remission during the past 2 months. Serum level of Vit D in the studied patients was below 30 ng/dl. Patients were randomly allocated to receive Vit D or placebo. In the 6-month follow-up period, the Disease Activity Score 28 (DAS28) was used in case of relapses as an index of RA activity to compare the two groups.

RESULTS

The flare rate was not different between two groups (p > 0.05). The odds ratio of the rate of decline in patients of the trial group compared with the control group was 1.17 (not significant; p > 0.05). The mean DAS28 between the two patient groups was not significant (p > 0.05).

CONCLUSION

A low Vit D level was not identified to be a risk factor for RA severity or flare ups; however, although not statistically significant, Vit D treatment might be clinically effective. Further studies are needed with more emphasis on the issue of cost effectiveness and clinical importance to provide more information.