Functional association of NR4A3 downregulation with impaired differentiation in myeloid leukemogenesis.

The coincident downregulation of NR4A1 and NR4A3 has been implicated in myeloid leukemogenesis, but it remains unknown how these two genes function in myeloid cells and how their combined downregulation promotes myeloid leukemogenesis. Since NR4A1 abrogation is thought to confer a survival and proliferation advantage to myeloid cells, we hypothesized that downregulation of NR4A3 may have a complementary effect on myeloid cell differentiation. First, we tested the association between differentiation status of leukemic cells and NR4A3 expression using two large clinical datasets from patients with different acute myeloid leukemia (AML) subtypes. The analysis revealed a close association between differentiation status and different subtypes of AML Then, we probed the effects of differentiation-inducing treatments on NR4A3 expression and NR4A3 knockdown on cell differentiation using two myeloid leukemia cell lines. Differentiation-inducing treatments caused upregulation of NR4A3, while NR4A3 knockdown prevented differentiation in both cell lines. The cell culture findings were validated using samples from chronic myeloid leukemia (CML) patients at chronic, accelerated and blastic phases, and in acute promyelocytic leukemia (APL) patients before and after all trans-retinoic acid (ATRA)-based differentiation therapy. Progressive NR4A3 downregulation was coincident with impairments in differentiation in patients during progression to blastic phase of CML, and NR4A3 expression was increased in APL patients treated with ATRA-based differentiating therapy. Together, our findings demonstrate a tight association between impaired differentiation status and NR4A3 downregulation in myeloid leukemias, providing a plausible mechanistic explanation of how myeloid leukemogenesis might occur upon concurrent downregulation of NR4A1 and NR4A3.

Polymorphism of PXR gene associated with the increased risk of drug-induced liver injury in Indonesian pulmonary tuberculosis patients.

WHAT IS KNOWN AND OBJECTIVE: Tuberculosis is still a major infectious disease in Indonesia. Patients are treated mostly using fixed-dose combination treatment in primary public health facilities. The incidence of antituberculosis drug-induced liver injury (AT-DILI) is approximately 10% among Indonesian tuberculosis patients who used standard fixed combination regimens during the intensive phase of treatment. However, information regarding genetic polymorphism associated with the increase risk of drug-induced liver injury is still limited. The aim of this study was to investigate pregnane X receptor (PXR) gene polymorphisms as one of the risk factors of AT-DILI. METHODS: In this prospective cohort study, we recruited 106 adult patients diagnosed with pulmonary tuberculosis and treated with category I FDC (fixed-dose combination). The identification of SNP -25385C>T (rs3814055) was conducted by ARMS (amplification refractory mutation system). Hepatotoxicity was defined as ALT and/or AST levels above the normal threshold on the second, fourth and sixth months of monitoring during tuberculosis treatment. RESULTS AND DISCUSSION: The logistic regression analysis showed that patients with the TT genotype of PXR gene (rs3814055) significantly had a greater risk of AT-DILI (OR 8·89; 95% CI 1·36-57·93, P < 0·05), compared with those of wild-type CC genotype. WHAT IS NEW AND CONCLUSION: The result suggests that in Indonesian patients with tuberculosis, the risk of having AT-DILI was associated with TT genotype of the PXR gene.

A mechanism for the anti-fibrogenic effects of the pregnane X receptor (PXR) in the liver: inhibition of NF-kappaB?

The liver is susceptible to chronic damage through exposure to a variety of toxins (e.g. alcohol) and viruses (e.g. hepatitis C). Obesity, autoimmune diseases (e.g. autoimmune hepatitis) and a variety of genetic diseases (e.g. Wilson's disease) also lead to chronic liver damage. This damage results in scarring fibrogenesis, structural disruption and functional impairment of the organ. Recent work suggests that there is cross-talk between the PXR and NF-kappaB pathways. This cross-talk may explain the observation that PXR activators inhibit liver fibrosis in in vitro and in vivo animal models of the disease. This reveiw will focus on the two transcription factors and their potential interaction.

Adaptive and maladaptive psychobiological responses to severe psychological stress: implications for the discovery of novel pharmacotherapy.

Post-traumatic stress disorder (PTSD) is one of the few DSM-IV diagnoses contingent upon a psychosocial stressor. In this context, there is an urgent need to acquire a better understanding of both the adaptive and maladaptive psychobiological responses to traumatic stress. Preclinical investigators have utilized a variety of animal models to identify the behavioral and neurobiological features of the organism's response to stress. However, given the complexity of the healthy and pathological human response to physiological and psychological stress, the extent to which the animal data is immediately transferable to human remains to be fully determined. This review draws upon preclinical and clinical literature to examine the transformation of an adaptive human stress response into a maladaptive and debilitating mental disorder. An integrative psychobiological model for PTSD is presented, linking psychological processes and behavioral patterns with current findings in neurocircuitry, neurochemistry and psychophysiology. The implications of this model for the discovery of novel pharmacological approaches to the treatment of severe psychological distress are discussed.