Description: PU.1 is an ETS family transcription factor that is important for the development of multiple hematopoietic cell lineages. Previous work demonstrated a critical role for PU.1 in promoting Th9 development and in limiting Th2 cytokine production. Whether PU.1 has functions in other Th lineages is not clear. In this study, we examined the effects of ectopic expression of PU.1 in CD4 + T cells and observed decreased expression of genes involved with the function of T follicular helper (Tfh) cells, including Il21 and Tnfsf5 (encoding CD40L). T cells from conditional mutant mice that lack expression of PU.1 in T cells ( Sfpi1 lck–/– ) demonstrated increased production of CD40L and IL-21 in vitro. Following adjuvant-dependent or adjuvant-independent immunization, we observed that Sfpi1 lck–/– mice had increased numbers of Tfh cells, increased germinal center B cells (GCB cells), and increased Ab production in vivo. This correlated with increased expression of IL-21 and CD40L in Tfh cells from Sfpi1 lck–/– mice compared with control mice. Finally, although blockade of IL-21 did not affect GCB cells in Sfpi1 lck–/– mice, anti-CD40L treatment of immunized Sfpi1 lck–/– mice decreased GCB cell numbers and Ag-specific Ig concentrations. Together, these data indicate an inhibitory role for PU.1 in the function of Tfh cells, germinal centers, and Tfh-dependent humoral immunity.

Description: PGC-1α is a transcriptional coactivator promoting oxidative metabolism in many tissues. Its expression in skeletal muscle (SKM) is induced by hypoxia and reactive oxidative species (ROS) generated during exercise, suggesting that PGC-1α might mediate the cross talk between oxidative metabolism and cellular responses to hypoxia and ROS. Here we found that PGC-1α directly interacted with Bhlhe40, a basic helix-loop-helix (bHLH) transcriptional repressor induced by hypoxia, and protects SKM from ROS damage, and they cooccupied PGC-1α-targeted gene promoters/enhancers, which in turn repressed PGC-1α transactivational activity. Bhlhe40 repressed PGC-1α activity through recruiting histone deacetylases (HDACs) and preventing the relief of PGC-1α intramolecular repression caused by its own intrinsic suppressor domain. Knockdown of Bhlhe40 mRNA increased levels of ROS, fatty acid oxidation, mitochondrial DNA, and expression of PGC-1α target genes. Similar effects were also observed when the Bhlhe40-mediated repression was rescued by a dominantly active form of the PGC-1α-interacting domain (PID) from Bhlhe40. We further found that Bhlhe40-mediated repression can be largely relieved by exercise, in which its recruitment to PGC-1α-targeted cis elements was significantly reduced. These observations suggest that Bhlhe40 is a novel regulator of PGC-1α activity repressing oxidative metabolism gene expression and mitochondrion biogenesis in sedentary SKM.

Description: Background Heme is an essential iron-containing molecule for cardiovascular physiology, but in excess it may increase oxidative stress. Failing human hearts have increased heme levels, with upregulation of the rate-limiting enzyme in heme synthesis, -aminolevulinic acid synthase 2 (ALAS2), which is normally not expressed in cardiomyocytes. We hypothesized that increased heme accumulation (through cardiac overexpression of ALAS2) leads to increased oxidative stress and cell death in the heart. Methods and Results We first showed that ALAS2 and heme levels are increased in the hearts of mice subjected to coronary ligation. To determine the causative role of increased heme in the development of heart failure, we generated transgenic mice with cardiac-specific overexpression of ALAS2. While ALAS2 transgenic mice have normal cardiac function at baseline, their hearts display increased heme content, higher oxidative stress, exacerbated cell death, and worsened cardiac function after coronary ligation compared to nontransgenic littermates. We confirmed in cultured cardiomyoblasts that the increased oxidative stress and cell death observed with ALAS2 overexpression is mediated by increased heme accumulation. Furthermore, knockdown of ALAS2 in cultured cardiomyoblasts exposed to hypoxia reversed the increases in heme content and cell death. Administration of the mitochondrial antioxidant MitoTempo to ALAS2-overexpressing cardiomyoblasts normalized the elevated oxidative stress and cell death levels to baseline, indicating that the effects of increased ALAS2 and heme are through elevated mitochondrial oxidative stress. The clinical relevance of these findings was supported by the finding of increased ALAS2 induction and heme accumulation in failing human hearts from patients with ischemic cardiomyopathy compared to nonischemic cardiomyopathy. Conclusions Heme accumulation is detrimental to cardiac function under ischemic conditions, and reducing heme in the heart may be a novel approach for protection against the development of heart failure.

Description: Objectives This study investigated the prevalence and correlates of electronic cigarettes (e-cigarettes) use in Taiwan. Design and setting We studied a nationally representative random sample in the 2015 Taiwan Adult Smoking Behavior Survey. Participants This study included 26 021 participants aged 15 years or older (51% women, 79% non-smokers, 16% aged 15–24 years), after excluding 31 persons (0.1%) who had missing information on e-cigarette use. Primary outcome measures The prevalence of ever having used e-cigarettes was calculated in the overall sample and by smoking status (current, former and never) or age (15–24, 25–44 and ≥45 years). We performed multivariable log-binomial regression to assess correlates of ever having used e-cigarettes among all participants and separately for subgroups by smoking status and age. Results Approximately 3% of all participants had ever used e-cigarettes. The prevalence of ever having used e-cigarettes was high in current smokers (14%) and people aged 18–24 years (7%). E-cigarette use was particularly common in people aged 15–24 years who were current (49–52%) or former (22–39%) smokers. Ever having used e-cigarettes was positively associated with tobacco smoking (adjusted prevalence ratio (aPR): 21.5, 95% CI 15.4 to 29.8, current smokers; aPR: 8.3, 95% CI 15.2 to 13.1, former smokers), younger age and high socioeconomic status. Age remained a significant factor of ever having used e-cigarettes across smoking status groups. Among non-smokers, men had a 2.4-fold (95% CI 1.5 to 3.8) greater prevalence of e-cigarette use than women. Conclusions E-cigarette use was uncommon in the general population in Taiwan, but prevalence was high among smokers and young people. This study highlights challenges that e-cigarettes pose to tobacco control, which warrant high priority action by policymakers and public health professionals. E-cigarette regulations should focus on young people.

Description: Objective Fibroblast growth factor 15/19 (FGF15/19), an enterokine that regulates synthesis of hepatic bile acids (BA), has been proposed to influence fat metabolism. Without FGF15/19, mouse liver regeneration after partial hepatectomy (PH) is severely impaired. We studied the role of FGF15/19 in response to a high fat diet (HFD) and its regulation by saturated fatty acids. We developed a fusion molecule encompassing FGF19 and apolipoprotein A-I, termed Fibapo, and evaluated its pharmacological properties in fatty liver regeneration. Design Fgf15 –/– mice were fed a HFD. Liver fat and the expression of fat metabolism and endoplasmic reticulum (ER) stress-related genes were measured. Influence of palmitic acid (PA) on FGF15/19 expression was determined in mice and in human liver cell lines. In vivo half-life and biological activity of Fibapo and FGF19 were compared. Hepatoprotective and proregenerative activities of Fibapo were evaluated in obese db/db mice undergoing PH. Results Hepatosteatosis and ER stress were exacerbated in HFD-fed Fgf15 –/– mice. Hepatic expression of Ppar2 was elevated in Fgf15 –/– mice, being reversed by FGF19 treatment. PA induced FGF15/19 expression in mouse ileum and human liver cells, and FGF19 protected from PA-mediated ER stress and cytotoxicity. Fibapo reduced liver BA and lipid accumulation, inhibited ER stress and showed enhanced half-life. Fibapo provided increased db/db mice survival and improved regeneration upon PH. Conclusions FGF15/19 is essential for hepatic metabolic adaptation to dietary fat being a physiological regulator of Ppar2 expression . Perioperative administration of Fibapo improves fatty liver regeneration.