Regulation Of A1 Research Articles

β-catenin negatively regulates IL-6 and IL-8 expression at transcriptional level and induces reactivity in human astrocytes

Abstract HIV invades the brain during acute infection, setting the stage for persistent neuroinflammation despite combined antiretroviral therapy (cART) and leads to HIV-Associated Neurocognitive Disorders (HAND), which occurs in ~50% of HIV-infected individuals. Our lab is focused on understanding the role of Wnt/β-catenin signaling in HAND. Here, we evaluated the impact of β-catenin on inflammatory mediators associated with neuroinflammation, chemotactic molecules, and regulation of A1 (proinflammatory)/A2 (protective/repair) phenotypes of astrocytes. We demonstrate that knockdown (KD) of β-catenin in normal human astrocytes (NHAs) significantly induced IL-6 and IL-8 at the transcription and protein levels and conversely, induction of β-catenin significantly downregulated these two molecules. These findings are intriguing given that no role for β-catenin to date is associated with IL-6 and IL-8 regulation. Further, KD of β-catenin induced three genes associated with A1 phenotype by 2.4–6.4 fold. These findings indicate that β-catenin expression in astrocytes is a critical regulator of anti-inflammatory responses and its disruption can potentially mediate persistent neuroinflammation.

Hyperthermia-induced seizures alter adenosine A1 and A2A receptors and 5'-nucleotidase activity in rat cerebral cortex.

Febrile seizure is one of the most common convulsive disorders in children. The neuromodulator adenosine exerts anticonvulsant actions through binding adenosine receptors. Here, the impact of hyperthermia-induced seizures on adenosine A1 and A2A receptors and 5'-nucleotidase activity has been studied at different periods in the cerebral cortical area by using radioligand binding, real-time PCR, and 5'-nucleotidase activity assays. Hyperthermic seizures were induced in 13-day-old rats using a warmed air stream from a hair dryer. Neonates exhibited rearing and falling over associated with hindlimb clonus seizures (stage 5 on Racine scale criteria) after hyperthermic induction. A significant increase in A1 receptor density was observed using [(3) H]DPCPX as radioligand, and mRNA coding A1 was observed 48h after hyperthermia-induced seizures. In contrast, a significant decrease in A2A receptor density was detected, using [(3) H]ZM241385 as radioligand, 48h after hyperthermia-evoked convulsions. These short-term changes in A1 and A2A receptors were also accompanied by a loss of 5'-nucleotidase activity. No significant variations either in A1 or A2A receptor density or 5'-nucleotidase were observed 5 and 20days after hyperthermic seizures. Taken together, both regulation of A1 and A2A receptors and loss of 5'-nucleotidase in the cerebral cortex suggest the existence of a neuroprotective mechanism against seizures. Febrile seizure is one of the most common convulsive disorders in children. The consequences of hyperthermia-induced seizures (animal model of febrile seizures) on adenosine A1 and A2A receptors and 5'-nucleotidase activity have been studied at different periods in cerebral cortical area. A significant increase in A1 receptor density and mRNA coding A1 was observed 48h after hyperthermia-induced seizures. In contrast, a significant decrease in A2A receptor density and 5'-nucleotidase activity was detected 48h after convulsions evoked by hyperthermia. These changes suggest the possible existence of a neuroprotective mechanism against seizures.

Regulation of A1 by OX40 Contributes to CD8+ T Cell Survival and Anti-Tumor Activity

The TNFR family member OX40 (CD134) is critical for optimal clonal expansion and survival of T cells. However, the intracellular targets of OX40 in CD8 T cells are not fully understood. Here we show that A1, a Bcl-2 family protein, is regulated by OX40 in effector CD8 T cells. In contrast to wild-type T cells, OX40-deficient CD8 T cells failed to maintain A1 expression driven by antigen. Conversely, enforced OX40 stimulation promoted A1 expression. In both situations, the expression of A1 directly correlated with CD8 T cell survival. In addition, exogenous expression of A1 in OX40-deficient CD8 T cells reversed their survival defect in vitro and in vivo. Moreover, forced expression of A1 in CD8 T cells from OX40-deficient mice restored the ability of these T cells to suppress tumor growth in a murine model. These results indicate that OX40 signals regulate CD8 T cell survival at least in part through maintaining expression of the anti-apoptotic molecule A1, and provide new insight into the mechanism by which OX40 may impact anti-tumor immunity.

Regulated expression of anti-apoptotic MCL-1 and A1 controls the population structure of myeloid derived suppressor cells (P1070)

Abstract Myeloid-derived suppressor cells (MDSCs) are an immunosuppressive population of immature monocytic and granulocytic cells. MDSCs emerge from the bone marrow as inactive precursors and upon migration to sites of inflammation become activated regulatory cells. However, both the fate and key immunosuppressive subsets within the MDSC pool at inflammatory sites remain unclear. Here we show MDSCs express high amounts of anti-apoptotic MCL-1 and A1. We reasoned if MCL-1 was ablated in MDSC populations, MDSCs would be less suppressive and more prone to apoptotic death. However, MCL-1 deficient MDSCs were more suppressive than wild type (WT) MDSCs because MCL-1 deficient MDSCs were predominately monocytic in lineage. In the absence of MCL-1, granulocytic MDSCs are apoptotic and are not functional suppressor cells. These data define monocytic MDSCs as the key immunosuppressive population. When we sorted purified monocytic MDSCs from MCL-1 deficient mice we found they had reduced suppressive activity and higher apoptosis than sorted WT monocytic MDSCs. Further investigation demonstrated in the absence of MCL-1, regulated A1 expression in monocytic MDSCs is necessary for their full suppressive capacity and survival. Furthermore, we show GM-CSF is a key player in the survival of monocytic MDSCs via A1 regulation. These data have implications for the engineering of MDSCs as suppressors for autoimmune diseases and therapies to selectively ablate monocytic MDSCs in the treatment of cancer.

Regulation of A1 and Mcl-1 from costimulatory signals affects T cell survival (47.2)

Abstract Costimulation is critical for T cell activation. In recent years, advances have been made in studies of costimulation as potential therapies in the treatment of diseases. However, the intracellular signals by which costimulation affects the function of T cells are not fully understood. A1 and Mcl-1, two bcl-2 family proteins are up regulated in effector T cells by ligation with an agonist antibody to the costimulatory molecule OX40 (CD134), which is essential for long-term T cell survival. To determine whether A1 and Mcl-1 are intracellular molecules of OX40, we examined A1 and Mcl-1 expression in primary T cells from wild-type and OX40-deficient mice, and found A1 and Mcl-1 were up-regulated after early T cell activation, but not be maintained in T cells from OX40-deficient mice. In addition, we used retrovirus-mediated transduction to introduce A1 or Mcl-1 into antigen (Ag)-responding T cells from OX40-deficent mice. We found that exogenous expression of A1 or Mcl-1 reversed the survival defect of OX40-deficient T cells both in vitro and in vivo. Moreover, sustained expression of A1 or Mcl-1 in CD8+ T cells from OX40-deficient mice reversed their defect in preventing tumor growth in a murine model. These results indicate that A1 and Mcl-1 are intracellular molecules of OX40, which regulate T cell survival. The data provide new insights into the mechanisms by which costimualtion regulates T cell survival.

Regulation of A1/Bfl-1 expression in peripheral splenic B cells

We analyzed here the expression of the prosurvival Bcl-2 homologue A1 in peripheral B cell compartment. We observed that A1 mRNA are highly expressed in peripheral B cells as compared with other anti-apoptotic genes of the Bcl-2 family such as bcl-xl and bcl-2 itself. The expression of A1 is up-regulated in immature B cells at the transition between transitional type 1 (T1) and type 2 (T2) cells, and remained highly expressed in mature (M) B cells. We, therefore, analyzed the effect of B cell antigen receptor (BCR) and BAFF receptor (BAFF-R) engagement on the regulation of A1 in total B220 + cells but also FACS-sorted immature T1, T2 and M B cells. We demonstrated that only BCR engagement up-regulated the expression of A1 mRNA and protein. These results suggest that A1 may play a key role in antigen-dependent signals that are required for survival and/or proliferation of peripheral B cells.

Homospecific regulation of A1 and A2 adenosine receptors

Homospecific regulation of A1 and A2 adenosine receptors