The enteric nervous system relays psychological stress to intestinal inflammation.

Mental health profoundly impacts inflammatory responses in the body. This is particularly apparent in inflammatory bowel disease (IBD), in which psychological stress is associated with exacerbated disease flares. Here, we discover a critical role for the enteric nervous system (ENS) in mediating the aggravating effect of chronic stress on intestinal inflammation. We find that chronically elevated levels of glucocorticoids drive the generation of an inflammatory subset of enteric glia that promotes monocyte- and TNF-mediated inflammation via CSF1. Additionally, glucocorticoids cause transcriptional immaturity in enteric neurons, acetylcholine deficiency, and dysmotility via TGF-ß2. We verify the connection between the psychological state, intestinal inflammation, and dysmotility in three cohorts of IBD patients. Together, these findings offer a mechanistic explanation for the impact of the brain on peripheral inflammation, define the ENS as a relay between psychological stress and gut inflammation, and suggest that stress management could serve as a valuable component of IBD care.

Preferential HIV infection of CCR6+ Th17 cells is associated with higher levels of virus receptor expression and lack of CCR5 ligands.

Th17 cells are enriched in the gut mucosa and play a critical role in maintenance of the mucosal barrier and host defense against extracellular bacteria and fungal infections. During chronic human immunodeficiency virus (HIV) infection, Th17 cells were more depleted compared to Th1 cells, even when the patients had low or undetectable viremia. To investigate the differential effects of HIV infection on Th17 and Th1 cells, a culture system was used in which CCR6(+) CD4(+) T cells were sorted from healthy human peripheral blood and activated in the presence of interleukin 1ß (IL-1ß) and IL-23 to drive expansion of Th17 cells while maintaining Th1 cells. HIV infection of these cultures had minimal effects on Th1 cells but caused depletion of Th17 cells. Th17 loss correlated with greater levels of virus-infected cells and cell death. In identifying cellular factors contributing to higher susceptibility of Th17 cells to HIV, we compared Th17-enriched CCR6(+) and Th17-depleted CCR6(-) CD4 T cell cultures and noted that Th17-enriched CCR6(+) cells expressed higher levels of α4ß7 and bound HIV envelope in an α4ß7-dependent manner. The cells also had greater expression of CD4 and CXCR4, but not CCR5, than CCR6(-) cells. Moreover, unlike Th1 cells, Th17 cells produced little CCR5 ligand, and transfection with one of the CCR5 ligands, MIP-1ß (CCL4), increased their resistance against HIV. These results indicate that features unique to Th17 cells, including higher expression of HIV receptors and lack of autocrine CCR5 ligands, are associated with enhanced permissiveness of these cells to HIV.

Gut bacteria-derived succinate induces enteric nervous system regeneration.

Enteric neurons control gut physiology by regulating peristalsis, nutrient absorption, and secretion 1 . Disruptions in microbial communities caused by antibiotics or enteric infections result in the loss of enteric neurons and long-term motility disorders 2-5 . However, the signals and underlying mechanisms of this microbiota-neuron communication are unknown. We studied the effects of microbiota on the recovery of the enteric nervous system after microbial dysbiosis caused by antibiotics. We found that both enteric neurons and glia are lost after antibiotic exposure, but recover when the pre-treatment microbiota is restored. Using murine gnotobiotic models and fecal metabolomics, we identified neurogenic bacterial species and their derived metabolite succinate as sufficient to rescue enteric neurons and glia. Unbiased single-nuclei RNA-seq analysis uncovered a novel neural precursor-like population marked by the expression of the neuronal gene Nav2. Genetic fate-mapping showed that Plp1+ enteric glia differentiate into neurons following antibiotic exposure. In contrast, Nav2+ neurons expand upon succinate treatment and indicate an alternative mode of neuronal regeneration under recovery conditions. Our findings highlight specific microbial species, metabolites, and the underlying cellular mechanisms involved in neuronal regeneration, with potential therapeutic implications for peripheral neuropathies.

TCR-Vγδ usage distinguishes protumor from antitumor intestinal γδ T cell subsets.

γδ T cells represent a substantial fraction of intestinal lymphocytes at homeostasis, but they also constitute a major lymphocyte population infiltrating colorectal cancers (CRCs); however, their temporal contribution to CRC development or progression remains unclear. Using human CRC samples and murine CRC models, we found that most γδ T cells in premalignant or nontumor colons exhibit cytotoxic markers, whereas tumor-infiltrating γδ T cells express a protumorigenic profile. These contrasting T cell profiles were associated with distinct T cell receptor (TCR)-Vγδ gene usage in both humans and mice. Longitudinal intersectional genetics and antibody-dependent strategies targeting murine γδ T cells enriched in the epithelium at steady state led to heightened tumor development, whereas targeting γδ subsets that accumulate during CRC resulted in reduced tumor growth. Our results uncover temporal pro- and antitumor roles for γδ T cell subsets.

The Microbiome as a Circadian Coordinator of Metabolism.

The microbiome is critically involved in the regulation of systemic metabolism. An important but poorly understood facet of this regulation is the diurnal activity of the microbiome. Herein, we summarize recent developments in our understanding of the diurnal properties of the microbiome and their integration into the circadian regulation of organismal metabolism. The microbiome may be involved in the detrimental consequences of circadian disruption for host metabolism and the development of metabolic disease. At the same time, the mechanisms by which microbiome diurnal activity is integrated into host physiology reveal several translational opportunities by which the time of day can be harnessed to optimize microbiome-based therapies. The study of circadian microbiome properties may thus provide a new avenue for treating disorders associated with circadian disruption from the gut.

The CD300a (IRp60) inhibitory receptor is rapidly up-regulated on human neutrophils in response to inflammatory stimuli and modulates CD32a (FcgammaRIIa) mediated signaling.

To achieve an adequate response, cells of the immune system must be tightly regulated to avoid hypo or hyper responsiveness. One of the mechanisms used by the immune system to avoid excessive inflammation is the modulation of the response through inhibitory receptors containing immunoreceptor tyrosine based inhibitory motifs (ITIM). Here, we show that human neutrophils from peripheral blood express the ITIM containing CD300a (also known as IRp60 and CMRF-35H) receptor. By using the HL-60 differentiation model, we show that the expression of CD300a receptor is developmentally regulated. Stimulation of human neutrophils with LPS and GM-CSF increased the cell surface expression of CD300a as a result of the rapid translocation of an intracellular pool of the receptor to the cell surface. Co-ligation of CD300a with the immunoreceptor tyrosine based activating motif (ITAM) containing CD32a (FcgammaRIIa) activation receptor inhibited CD32a mediated signalling; whereas, it did not inhibit toll-like receptor (TLR)-4 mediated reactive oxygen species (ROS) production. Therefore, at least for human neutrophils, the inhibitory signals mediated by the CD300a receptor may be selective in their action.

Acute Pancreatitis after Colonoscopy: A Case Presentation and Literature Review.

We report a case of acute pancreatitis after an elective screening colonoscopy. A 51-year-old male with a left ventricular assist device for end-stage nonischemic cardiomyopathy and a family history of colorectal cancer was admitted for an expedited heart transplant evaluation. He underwent screening colonoscopy during this admission which was technically uncomplicated apart from requiring slight maneuvering at the splenic flexure. The following day, the patient developed acute epigastric pain and one episode of emesis. Subsequent laboratory evaluation revealed a significantly elevated lipase level and cross-sectional imaging consistent with acute pancreatitis. With no evidence of gallstones, alcohol use, and hypertriglyceridemia, the acute pancreatitis was deemed to be a complication of colonoscopy. The presumed mechanism of the pancreatitis was due to mechanical trauma from insufflation and abdominal pressure, applied to at the splenic flexure, which is in close proximity to the pancreatic tail. The patient was treated with supportive care (intravenous fluid, analgesia, and pancreatic rest) and improved significantly over a three-day period.

Intergenerational transfer of antibiotic-perturbed microbiota enhances colitis in susceptible mice.

Antibiotic exposure in children has been associated with the risk of inflammatory bowel disease (IBD). Antibiotic use in children or in their pregnant mother can affect how the intestinal microbiome develops, so we asked whether the transfer of an antibiotic-perturbed microbiota from mothers to their children could affect their risk of developing IBD. Here we demonstrate that germ-free adult pregnant mice inoculated with a gut microbial community shaped by antibiotic exposure transmitted their perturbed microbiota to their offspring with high fidelity. Without any direct or continued exposure to antibiotics, this dysbiotic microbiota in the offspring remained distinct from controls for at least 21 weeks. By using both IL-10-deficient and wild-type mothers, we showed that both inoculum and genotype shape microbiota populations in the offspring. Because IL10-/- mice are genetically susceptible to colitis, we could assess the risk due to maternal transmission of an antibiotic-perturbed microbiota. We found that the IL10-/- offspring that had received the perturbed gut microbiota developed markedly increased colitis. Taken together, our findings indicate that antibiotic exposure shaping the maternal gut microbiota has effects that extend to the offspring, with both ecological and long-term disease consequences.

Induction of intestinal immunity by mucosal vaccines as a means of controlling HIV infection.

CD4(+) T cells in the mucosa of the gastrointestinal (GI) tract are preferentially targeted and depleted by HIV. As such, the induction of an effective anti-HIV immune response in the mucosa of the GI tract-through vaccination-could protect this vulnerable population of cells. Mucosal vaccination provides a promising means of inducing robust humoral and cellular responses in the GI tract. Here we review data from the literature about the effectiveness of various mucosal vaccination routes--oral (intraintestinal/tonsilar/sublingual), intranasal, and intrarectal--with regard to the induction of immune responses mediated by cytotoxic T cells and antibodies in the GI mucosa, as well as protective efficacy in challenge models. We present data from the literature indicating that mucosal routes have the potential to effectively elicit GI mucosal immunity and protect against challenge. Given their capacity for the induction of anti-HIV immune responses in the GI mucosa, we propose that mucosal routes, including the nonconventional sublingual, tonsilar, and intrarectal routes, be considered for the delivery of the next generation HIV vaccines. However, further studies are necessary to determine the ideal vectors and vaccination regimens for these routes of immunization and to validate their efficacy in controlling HIV infection.

In vitro restoration of Th17 response during HIV infection with an antiretroviral drug and Th17 differentiation cytokines.

The Th17 subset is preferentially depleted as compared to the Th1 subset in chronically HIV-infected patients, even after successful antiretroviral therapy. In this study, we have established an in vitro system utilizing primary human CD4 T cell cultures that recapitulates the dramatic loss of Th17 response upon HIV-1 infection that is accompanied with a less profound Th1 decrease. With this experimental system, we showed that blocking viral entry with CCR5 ligands or TAK779 reduced the infection and enhanced Th17 response but not Th1 response. Antiretroviral drug 3TC (lamivudine), given at the time of infection, completely prevented the loss of Th17 and Th1 responses but was ineffective when given after infection was already established. Only when Th17 differentiation cytokines were given along with 3TC to the cultures with established HIV infection was Th17 response fully restored and virus replication kept suppressed. Finally, a significant increase of Th17 response was achieved in peripheral lymphocytes of HIV-infected patients on antiretroviral therapy after treatment with Th17 differentiation cytokines. These data demonstrate the presence of CD4 T cells remaining capable of mounting Th17 response during HIV infection and indicate the potential use of immunotherapeutic modalities to supplement antiretroviral drugs for restoring Th17 response in chronically HIV-infected patients.

HIV envelope gp120 activates LFA-1 on CD4 T-lymphocytes and increases cell susceptibility to LFA-1-targeting leukotoxin (LtxA).

The cellular adhesion molecule LFA-1 and its ICAM-1 ligand play an important role in promoting HIV-1 infectivity and transmission. These molecules are present on the envelope of HIV-1 virions and are integral components of the HIV virological synapse. However, cellular activation is required to convert LFA-1 to the active conformation that has high affinity binding for ICAM-1. This study evaluates whether such activation can be induced by HIV itself. The data show that HIV-1 gp120 was sufficient to trigger LFA-1 activation in fully quiescent naïve CD4 T cells in a CD4-dependent manner, and these CD4 T cells became more susceptible to killing by LtxA, a bacterial leukotoxin that preferentially targets leukocytes expressing high levels of the active LFA-1. Moreover, virus p24-expressing CD4 T cells in the peripheral blood of HIV-infected subjects were found to have higher levels of surface LFA-1, and LtxA treatment led to significant reduction of the viral DNA burden. These results demonstrate for the first time the ability of HIV to directly induce LFA-1 activation on CD4 T cells. Although LFA-1 activation may enhance HIV infectivity and transmission, it also renders the cells more susceptible to an LFA-1-targeting bacterial toxin, which may be harnessed as a novel therapeutic strategy to deplete virus reservoir in HIV-infected individuals.

Human Th1 cells that express CD300a are polyfunctional and after stimulation up-regulate the T-box transcription factor eomesodermin.

Human naïve CD4 T cells express low levels of the immunomodulatory receptor CD300a, whereas effector/memory CD4 cells can be either CD300a(+) or CD300a(-). This suggested that CD300a expression could define a specific subset within the effector/memory CD4 T cell subpopulations. In fact, ex vivo analysis of the IFN-gamma producing CD4 T cells showed that they are enriched in the CD300a(+) subset. Moreover, stimulated CD4 T cells producing TNF-alpha and IL-2 besides IFN-gamma (polyfunctional) are predominantly CD300a(+). In addition to producing markedly higher levels of Th1-associated cytokines, the stimulated CD300a(+) CD4 T cells are distinguished by a striking up-regulation of the T-box transcription factor eomesodermin (Eomes), whereas T-bet is up-regulated in both CD300a(+) and CD300a(-) activated CD4 T cells to similar levels. The pleiotropic cytokine TGF-beta1 has a determinant role in dictating the development of this Th1 subset, as its presence inhibits the expression of CD300a and down-regulates the expression of Eomes and IFN-gamma. We conclude that CD300a(+) human Th1 cells tend to be polyfunctional and after stimulation up-regulate Eomes.