Activated Prothrombin Complex Concentrates for the Treatment of Factor Xa Inhibitor-Associated Spontaneous Intracerebral Hemorrhage.

Background: Anticoagulant-associated intracerebral hemorrhage (ICH) is a significant cause of morbidity and mortality. Despite approval of a specific reversal agent for factor Xa inhibitors, there is still much interest in nonspecific reversal agents, such as activated prothrombin complex concentrates (aPCCs). Objective: The objective of this study was to describe ICH expansion in a cohort of patients with factor Xa inhibitor-associated ICH who were treated with aPCC. Methods: This was a retrospective cohort study conducted at an academic medical center designated as a comprehensive stroke center. Consecutive patients admitted for ICH who reported use of apixaban or rivaroxaban prior to admission were considered for inclusion in the study. Patients were treated with 25 to 50 units/kg of aPCC. Intracerebral hemorrhage volume was measured before administration of aPCC and then again within 36 hours of aPCC administration. Results: A total of 40 patients were included in the final analysis. Overall, the cohort was predominantly male (24 [60%]), white (27 [67.5%]), and the mean age was 75.3 ± 10.5 years. Most patients reported taking apixaban prior to admission (31 [77.5%]) and a large proportion were also taking aspirin (13 [32.5%]). The mean change in ICH volume was 1.12 ± 6.03 mL (P = 0.2475). Conclusions and Relevance: There was a nonsignificant change in mean ICH volume and no reported cases of thromboembolism. Due to the relatively high proportion of patients with significant hematoma expansion, more studies are needed on which patient population would best benefit from treatment with aPCC.

The aryl hydrocarbon receptor regulates expression of mucosal trafficking receptor GPR15.

GPR15 is a chemoattractant receptor that facilitates colon homing of regulatory and effector CD4+ T cells in health and colitis. The molecular mechanisms that control GPR15 expression are not fully known. Here we report the presence of two highly conserved aryl hydrocarbon receptor (AHR) binding sequences in a 3' enhancer of GPR15, leading us to investigate AHR function in regulating GPR15 expression. Using luciferase reporter assays, we show that AHR activation increased GPR15 expression and requires both the AHR binding sites. Consistent with a transcriptional regulatory role, treatment with AHR agonists induce GPR15 expression on human CD4+ T cells. Using AHR-deficient mice, we demonstrate that the lack of AHR signaling drastically reduces GPR15 expression on effector/memory and Foxp3+ CD4+ T cells. In mixed bone marrow chimeras of AHR-deficient and wildtype cells, GPR15 expression was similarly diminished on AHR-deficient CD4+ effector/memory and regulatory T cells in the colon and small intestine. Furthermore, administration of AHR agonists upregulated GPR15 expression on CD4+ effector/memory T cells and increased their homing capability, especially to the colon. Collectively, our studies reveal a novel function of the AHR in regulation of GPR15 expression and increased colon trafficking of CD4+ T cells expressing GPR15.

A Mucosal and Cutaneous Chemokine Ligand for the Lymphocyte Chemoattractant Receptor GPR15.

Chemoattractants control lymphocyte recruitment from the blood, contributing to the systemic organization of the immune system. The G protein-linked receptor GPR15 mediates lymphocyte homing to the large intestines and skin. Here we show that the 9 kDa CC-motif containing cationic polypeptide AP57/colon-derived sushi containing domain-2 binding factor (CSBF), encoded by C10orf99 in the human and 2610528A11Rik in the mouse, functions as a chemokine ligand for GPR15 (GPR15L). GPR15L binds GPR15 and attracts GPR15-expressing T cells including lymphocytes in colon-draining lymph nodes and Vγ3+ thymic precursors of dermal epithelial T cells. Patterns of GPR15L expression by epithelial cells in adult mice and humans suggest a homeostatic role for the chemokine in lymphocyte localization to the large intestines, as well as a role in homing to the epidermis during wound healing or inflammation. GPR15L is also significantly expressed in squamous mucosa of the oral cavity and esophagus with still poorly defined regulation. Identification of the chemotactic activity of GPR15L adds to its reported antibacterial and tumor cell growth regulatory functions and suggests the potential of targeting GPR15L-GPR15 interactions for modulation of mucosal and cutaneous inflammation.

Role and species-specific expression of colon T cell homing receptor GPR15 in colitis.

Lymphocyte recruitment maintains intestinal immune homeostasis but also contributes to inflammation. The orphan chemoattractant receptor GPR15 mediates regulatory T cell homing and immunosuppression in the mouse colon. We show that GPR15 is also expressed by mouse TH17 and TH1 effector cells and is required for colitis in a model that depends on the trafficking of these cells to the colon. In humans GPR15 is expressed by effector cells, including pathogenic TH2 cells in ulcerative colitis, but is expressed poorly or not at all by colon regulatory T (Treg) cells. The TH2 transcriptional activator GATA-3 and the Treg-associated transcriptional repressor FOXP3 robustly bind human, but not mouse, GPR15 enhancer sequences, correlating with receptor expression. Our results highlight species differences in GPR15 regulation and suggest it as a potential therapeutic target for colitis.

miR172 regulates stem cell fate and defines the inner boundary of APETALA3 and PISTILLATA expression domain in Arabidopsis floral meristems.

In Arabidopsis, two floral homeotic genes APETALA2 (AP2) and AGAMOUS (AG) specify the identities of perianth and reproductive organs, respectively, in flower development. The two genes act antagonistically to restrict each other to their proper domains of action within the floral meristem. In addition to AG, which antagonizes AP2, miR172, a microRNA, serves as a negative regulator of AP2. In this study, we showed that AG and miR172 have distinct functions in flower development and that they largely act independently in the negative regulation of AP2. We uncovered functions of miR172-mediated repression of AP2 in the regulation of floral stem cells and in the delineation of the expression domain of another class of floral homeotic genes. Given the antiquity of miR172 in land plants, our findings have implications for the recruitment of a microRNA in the building of a flower in evolution.