Roxana del Rio

Activation of p38 MAPK in CD4 T cells controls IL-17 production and autoimmune encephalomyelitis

Although several transcription factors have been shown to be critical for the induction and maintenance of IL-17 expression by CD4 Th cells, less is known about the role of nontranscriptional mechanisms. Here we show that the p38 MAPK signaling pathway is essential for in vitro and in vivo IL-17 production by regulating IL-17 synthesis in CD4 T cells through the activation of the eukaryotic translation initiation factor 4E/MAPK-interacting kinase (eIF-4E/MNK) pathway. We also show that p38 MAPK activation is required for the development and progression of both chronic and relapsing-remitting forms of experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis. Furthermore, we show that regulation of p38 MAPK activity specifically in T cells is sufficient to modulate EAE severity. Thus, mechanisms other than the regulation of gene expression also contribute to Th17 cell effector functions and, potentially, to the pathogenesis of other Th17 cell-mediated diseases.

Regulatory T cells control tolerogenic versus autoimmune response to sperm in vasectomy

Vasectomy is a well accepted global contraceptive approach frequently associated with epididymal granuloma and sperm autoantibody formation. To understand the long-term sequelae of vasectomy, we investigated the early immune response in vasectomized mice. Vasectomy leads to rapid epithelial cell apoptosis and necrosis, persistent inflammation, and sperm granuloma formation in the epididymis. Vasectomized B6AF1 mice did not mount autoimmune response but instead developed sperm antigen-specific tolerance, documented as resistance to immunization-induced experimental autoimmune orchitis (EAO) but not experimental autoimmune encephalomyelitis. Strikingly, tolerance switches over to pathologic autoimmune state following concomitant CD4+CD25+Foxp3+ regulatory T cell (Treg) depletion: unilaterally vasectomized mice produce dominant autoantibodies to an orchitogenic antigen (zonadhesin), and develop CD4 T-cell– and antibody-dependent bilateral autoimmune orchitis. Therefore, (i) Treg normally prevents spontaneous organ-specific autoimmunity induction by persistent endogenous danger signal, and (ii) autoantigenic stimulation with sterile autoinflammation can lead to tolerance. Finally, postvasectomy tolerance occurs in B6AF1, C57BL/6, and A/J strains. However, C57BL/6 mice resisted EAO after 60% Treg depletion, but developed EAO after 97% Treg reduction. Therefore, variance in intrinsic Treg function—a possible genetic trait—can influence the divergent tolerogenic versus autoimmune response to vasectomy.

Histamine H4 Receptor Optimizes T Regulatory Cell Frequency and Facilitates Anti-Inflammatory Responses within the Central Nervous System

Histamine is a biogenic amine that mediates multiple physiological processes, including immunomodulatory effects in allergic and inflammatory reactions, and also plays a key regulatory role in experimental allergic encephalomyelitis, the autoimmune model of multiple sclerosis. The pleiotropic effects of histamine are mediated by four G protein-coupled receptors, as follows: Hrh1/H1R, Hrh2/H2R, Hrh3/H3R, and Hrh4/H4R. H4R expression is primarily restricted to hematopoietic cells, and its role in autoimmune inflammatory demyelinating disease of the CNS has not been studied. In this study, we show that, compared with wild-type mice, animals with a disrupted Hrh4 (H4RKO) develop more severe myelin oligodendrocyte glycoprotein (MOG)35\x{2013}55-induced experimental allergic encephalomyelitis. Mechanistically, we also show that H4R plays a role in determining the frequency of T regulatory (TR) cells in secondary lymphoid tissues, and regulates TR cell chemotaxis and suppressor activity. Moreover, the lack of H4R leads to an impairment of an anti-inflammatory response due to fewer TR cells in the CNS during the acute phase of the disease and an increase in the proportion of Th17 cells.

Resistance to Lipopolysaccharide-Induced Preterm Delivery Mediated by Regulatory T Cell Function in Mice

Abstract Intrauterine or intraperitoneal administration of lipopolysaccharide (LPS) into normal mice at midgestation induces preterm delivery (PTD) within 24 h through a mechanism dependent on Toll-like receptor signaling and expression of inflammatory cytokines. The exact participants in the cellular network involved in PTD are not known. Although the activities of innate immune cells are thought to be important, the extent to which this process depends on T and B cells has yet to be examined. Mice deficient in T and B cells due to genetic deficiency in the recombination activating gene 1 (Rag1−/−) were given LPS intraperitoneally on Day 15 of gestation and found to be susceptible to LPS-induced PTD. This was found to involve many of the inflammatory mediators reported as important in normal mice. Moreover, at a low dose (3 μg), pregnant Rag1−/− mice were found to be more susceptible to PTD than a cohort of normal mice on the same genetic background. This increased susceptibility was partially reversed by transfer, on Day 10 of gestation, of whole lymphocytes or purified CD4+ T cells. Transfer of purified CD4+ T cells to Rag1−/− mice resulted in a uterine draining node population of FOXP3+ cells, suggesting that these cells may contribute to resistance to LPS-induced PTD. Overall, the data suggest that, although T and B lymphocytes are not critical positive regulators of LPS-induced PTD, CD4+ T cells play a protective and regulatory role, and thus could be a target for preventive or therapeutic manipulation.

Von-Willebrand factor influences blood brain barrier permeability and brain inflammation in experimental allergic encephalomyelitis

Weibel-Palade bodies within endothelial cells are secretory granules known to release von Willebrand Factor (VWF), P-selectin, chemokines, and other stored molecules following histamine exposure. Mice with a disrupted VWF gene (VWFKO) have endothelial cells that are deficient in Weibel-Palade bodies. These mice were used to evaluate the role of VWF and/or Weibel-Palade bodies in Bordetella pertussis toxin-induced hypersensitivity to histamine, a subphenotype of experimental allergic encephalomyelitis, the principal autoimmune model of multiple sclerosis. No significant differences in susceptibility to histamine between wild-type and VWFKO mice were detected after 3 days; however, histamine sensitivity persisted significantly longer in VWFKO mice. Correspondingly, encephalomyelitis onset was earlier, disease was more severe, and blood brain barrier (BBB) permeability was significantly increased in VWFKO mice, as compared with wild-type mice. Moreover, inflammation was selectively increased in the brains, but not spinal cords, of VWFKO mice as compared with wild-type mice. Early increases in BBB permeability in VWFKO mice were not due to increased encephalitogenic T-cell activity since BBB permeability did not differ in adjuvant-treated VWFKO mice as compared with littermates immunized with encephalitogenic peptide plus adjuvant. Taken together, these data indicate that VWF and/or Weibel-Palade bodies negatively regulate BBB permeability changes and autoimmune inflammatory lesion formation within the brain elicited by peripheral inflammatory stimuli.

Combinatorial roles for histamine H1-H2 and H3-H4 receptors in autoimmune inflammatory disease of the central nervous system

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system in which histamine (HA) and its receptors have been implicated in disease pathogenesis. HA exerts its effects through four different G protein‐coupled receptors designated H1‐H4. We previously examined the effects of traditional single HA receptor (HR) knockouts (KOs) in experimental allergic encephalomyelitis (EAE), the autoimmune model of MS. Our results revealed that H1R and H2R are propathogenic, while H3R and H4R are antipathogenic. This suggests that combinatorial targeting of HRs may be an effective disease‐modifying therapy (DMT) in MS. To test this hypothesis, we generated H1H2RKO and H3H4RKO mice and studied them for susceptibility to EAE. Compared with wild‐type (WT) mice, H1H2RKO mice developed a less severe clinical disease course, whereas the disease course of H3H4RKO mice was more severe. H1H2RKO mice also developed less neuropathology and disrupted blood brain barrier permeability compared with WT and H3H4RKO mice. Additionally, splenocytes from immunized H1H2RKO mice produced less interferon(IFN)‐γ and interleukin(IL)‐17. These findings support the concept that combined pharmacological targeting of HRs may be an appropriate ancillary DMT in MS and other immunopathologic diseases.

Systemic Lack of Canonical Histamine Receptor Signaling Results in Increased Resistance to Autoimmune Encephalomyelitis

Histamine (HA) is a key regulator of experimental allergic encephalomyelitis (EAE), the autoimmune model of multiple sclerosis. HA exerts its effects through four known G-protein–coupled receptors: H1, H2, H3, and H4 (histamine receptors; H1–4R). Using HR-deficient mice, our laboratory has demonstrated that H1R, H2R, H3R, and H4R play important roles in EAE pathogenesis, by regulating encephalitogenic T cell responses, cytokine production by APCs, blood–brain barrier permeability, and T regulatory cell activity, respectively. Histidine decarboxylase–deficient mice (HDCKO), which lack systemic HA, exhibit more severe EAE and increased Th1 effector cytokine production by splenocytes in response to myelin oligodendrocyte gp35–55. In an inverse approach, we tested the effect of depleting systemic canonical HA signaling on susceptibility to EAE by generating mice lacking all four known G-protein–coupled-HRs (H1–4RKO mice). In this article, we report that in contrast to HDCKO mice, H1–4RKO mice develop less severe EAE compared with wild-type animals. Furthermore, splenocytes from immunized H1–4RKO mice, compared with wild-type mice, produce a lower amount of Th1/Th17 effector cytokines. The opposing results seen between HDCKO and H1–4RKO mice suggest that HA may signal independently of H1–4R and support the existence of an alternative HAergic pathway in regulating EAE resistance. Understanding and exploiting this pathway has the potential to lead to new disease-modifying therapies in multiple sclerosis and other autoimmune and allergic diseases.

Genetics of experimental allergic encephalomyelitis supports the role of T helper cells in multiple sclerosis pathogenesis.

The major histocompatibility complex (MHC) is the primary genetic contributor to multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), but multiple additional interacting loci are required for genetic susceptibility. The identity of most of these non‐MHC genes is unknown. In this report, we identify genes within evolutionarily conserved genetic pathways leading to MS and EAE.

Genetic control of estrogen-regulated transcriptional and cellular responses in mouse uterus

The uterotropic response of the uterus to 17β‐estradiol (E2) is genetically controlled, with marked variation observed depending on the mouse strain studied. Previous genetic studies from our laboratory using inbred mice that are high [C57BL/6J (B6)] or low [C3H/HeJ (C3H)] responders to E2 led to the identification of quantitative trait (QT) loci associated with phenotypic variation in uterine growth and leukocyte infiltration. The mechanisms underlying differential responsiveness to E2, and the genes involved, are unknown. Therefore, we used a microarray approach to show association of distinct E2‐regulated transcriptional signatures with genetically controlled high and low responses to E2 and their segregation in (C57BL/6J×C3H/HeJ) F1 hybrids. Among the 6664 E2‐regulated transcripts, analysis of cellular functions of those that were strain specific indicated C3H‐selective enrichment of apoptosis, consistent with a 7‐fold increase in the apoptosis indicator CASP3, and a 2.4‐fold decrease in the apoptosis inhibitor Naip1 (Birc1a) in C3H vs. B6 following treatment with E2. In addition, several differentially expressed transcripts reside within our previously identified QT loci, including the ERα‐tethering factor Runx1, demonstrated to enhance E2‐mediated transcript regulation. The level of RUNX1 in uterine epithelial cells was shown to be 3.5‐fold greater in B6 compared to C3H. Our novel insights into the mechanisms underlying the genetic control of tissue sensitivity to estrogen have great potential to advance understanding of individualized effects in physiological and disease states.—Wall, E. H., Hewitt, S. C., Liu, L., del Rio, R., Case, L. K., Lin, C.‐Y., Korach, K. S., Teuscher, C. Genetic control of estrogen‐regulated transcriptional and cellular responses in mouse uterus. FASEB J. 27, 1874–1886 (2013). www.fasebj.org

H2 Control of Natural T Regulatory Cell Frequency in the Lymph Node Correlates with Susceptibility to Day 3 Thymectomy-Induced Autoimmune Disease

Day 3 thymectomy (D3Tx) results in a loss of peripheral tolerance mediated by natural regulatory T cells (nTregs) and development of autoimmune ovarian dysgenesis (AOD) and autoimmune dacryoadenitis (ADA) in A/J and (C57BL/6J × A/J) F1 hybrids (B6A), but not in C57BL/6J (B6) mice. Previously, using quantitative trait locus (QTL) linkage analysis, we showed that D3Tx-AOD is controlled by five unlinked QTL (Aod1-Aod5) and H2. In this study, using D3Tx B6-ChrA/J/NaJ chromosome (Chr) substitution strains, we confirm that QTL on Chr16 (Aod1a/Aod1b), Chr3 (Aod2), Chr1 (Aod3), Chr2 (Aod4), Chr7 (Aod5), and Chr17 (H2) control D3Tx-AOD susceptibility. In addition, we also present data mapping QTL controlling D3Tx-ADA to Chr17 (Ada1/H2), Chr1 (Ada2), and Chr3 (Ada3). Importantly, B6-ChrXA/J mice were as resistant to D3Tx-AOD and D3Tx-ADA as B6 mice, thereby excluding Foxp3 as a susceptibility gene in these models. Moreover, we report quantitative differences in the frequency of nTregs in the lymph nodes (LNs), but not spleen or thymus, of AOD/ADA-resistant B6 and AOD/ADA-susceptible A/J, B6A, and B6-Chr17A/J mice. Similar results correlating with experimental allergic encephalomyelitis and orchitis susceptibility were seen with B10.S and SJL/J mice. Using H2-congenic mice, we show that the observed difference in frequency of LN nTregs is controlled by Ada1/H2. These data support the existence of an LN-specific, H2-controlled mechanism regulating the prevalence of nTregs in autoimmune disease susceptibility.