Antigen-presenting cells (APCs) are critical in T-cell activation and in the induction of T-cell tolerance. Epigenetic modifications of specific genes in the APC play a key role in this process, and among them, histone deacetylases (HDACs) have emerged as key participants. HDAC6, one of the members of this family of enzymes, has been shown to be involved in regulation of inflammatory and immune responses. Here we show for the first time, that genetic or pharmacologic disruption of HDAC6 in macrophages and dendritic cells resulted in diminished production of the immunosuppressive cytokine IL-10, and induction of inflammatory APCs that effectively activate antigen-specific naïve T-cells and restore the responsiveness of anergic CD4+ T-cells. Mechanistically, we have found that HDAC6 forms a previously unknown molecular complex with STAT3, association that was detected in both the cytoplasmic and nuclear compartments of the APC. By using HDAC6 recombinant mutants we identified the domain comprising aminoacids 503-840 as being required for HDAC6 interaction with STAT3. Furthermore, by re-chromatin immunoprecipitation we confirmed that HDAC6 and STAT3 are both recruited to the same DNA sequence within the Il10 gene promoter. Of note, disruption of this complex by knocking down HDAC6 resulted in decreased STAT3 phosphorylation -but no changes in STAT3 acetylation- as well as diminished recruitment of STAT3 to the Il10 gene promoter region. The additional demonstration that a selective HDAC6 inhibitor disrupts this STAT3/IL-10 tolerogenic axis points to HDAC6 as a novel molecular target in APCs to overcome immune tolerance and tips the balance towards T-cell immunity.

Myeloid-derived suppressor cells (MDSC's), a heterogeneous population of cells capable of suppressing anti-tumor T cell function in the tumor microenvironment, represent an imposing obstacle in the development of cancer immunotherapeutics. Thus, identifying elements essential to the development and perpetuation of these cells will undoubtedly improve our ability to circumvent their suppressive impact. HDAC11 has emerged as a key regulator of IL-10 gene expression in myeloid cells, suggesting that this may represent an important targetable axis through which to dampen MDSC formation. Using a murine transgenic reporter model system where eGFP expression is controlled by the HDAC11 promoter (Tg-HDAC11-eGFP), we provide evidence that HDAC11 appears to function as a negative regulator of MDSC expansion/function in vivo. MDSCs isolated from EL4 tumor-bearing Tg-HDAC11-eGFP display high expression of eGFP, indicative of HDAC11 transcriptional activation at steady state. In striking contrast, immature myeloid cells in tumor-bearing mice display a diminished eGFP expression, implying that the transition of IMC to MDSC's require a decrease in the expression of HDAC11, where we postulate that it acts as a gate-keeper of myeloid differentiation. Indeed, tumor-bearing HDAC11-knockout mice (HDAC11-KO) demonstrate a more suppressive MDSC population as compared to wild-type (WT) tumor-bearing control. Notably, the HDAC11-KO tumor-bearing mice exhibit enhanced tumor growth kinetics when compare to the WT control mice. Thus, through a better understanding of this previously unknown role of HDAC11 in MDSC expansion and function, rational development of targeted epigenetic modifiers may allow us to thwart a powerful barrier to efficacious immunotherapies.

BACKGROUND: A gender-based compensation gap among physicians is well documented. Even after adjusting for age, experience, work hours, productivity, and academic rank, the gender gap remained and widened over the course of a physician’s career. This study aimed to examine if a significant gender pay gap still existed for anesthesiologists in the United States. METHODS: In 2018, we surveyed 28,812 physician members of the American Society of Anesthesiologists to assess the association of compensation with gender and to identify possible causes of wage disparities. Gender was the primary variable examined in the model, and compensation by gender was the primary outcome. Compensation was defined as the amount reported as direct compensation on a W-2, 1099, or K-1, plus all voluntary salary reductions (eg, 401[k], health insurance). The survey directed respondents to include salary, bonuses, incentive payments, research stipends, honoraria, and distribution of profits to employees. Respondents had the option of providing a point estimate of their compensation or selecting a range in $50,000 increments. Potential confounding variables that could affect compensation were identified based on a scoping literature review and the consensus expertise of the authors. We fitted a generalized ordinal logistic regression with 7 ranges of compensation. For the sensitivity analyses, we used linear regressions of log-transformed compensation based on respondent point estimates and imputed values. RESULTS: The final analytic sample consisted of 2081 observations (response rate, 7.2%). This sample represented a higher percentage of women and younger physicians compared to the demographic makeup of anesthesiologists in the United States. The adjusted odds ratio associated with gender equal to woman was an estimated 0.44 (95% confidence interval, 0.37–0.53), indicating that for a given compensation range, women had a 56% lower odds than men of being in a higher compensation range. Sensitivity analyses found the relative percentage difference in compensation for women compared to men ranged from −8.3 to −8.9. In the sensitivity analysis based on the subset of respondents (n = 1036) who provided a point estimate of compensation, the relative percentage difference (−8.3%; 95% confidence interval, −4.7 to −11.7) reflected a $32,617 lower compensation for women than men, holding other covariates at their means. CONCLUSIONS: Compensation for anesthesiologists showed a significant pay gap that was associated with gender even after adjusting for potential confounding factors, including age, hours worked, geographic practice region, practice type, position, and job selection criteria.

Antigen-presenting cells (APCs) are important in the initiation of productive antigen-specific T-cell responses and in the induction of T-cell anergy. The inflammatory status of the APC at the time of encounter with antigen specific T-cells plays a central role in determining such divergent T-cell outcomes. A better understanding of the regulation of pro-inflammatory and anti-inflammatory genes in its natural setting, the chromatin substrate, might provide novel insights to overcome anergic mechanisms mediated by APCs. Here we show for the first time that treatment of BALB/c murine macrophages with the histone deacetylase inhibitor (HDI) LAQ824, induces chromatin changes at the level of the IL-10 gene promoter that leads to enhanced recruitment of the transcriptional repressors HDAC11 and PU.1. Such an effect is associated with diminished IL-10 production and induction of inflammatory cells able of priming naïve antigen-specific T-cells, but more importantly, capable of restoring the responsiveness of anergized antigen-specific CD4+ T-cells.

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