Antigen uptake receptors on dendritic cells (DCs) provide efficient entry for the initiation of antigen-specific adaptive immunity. Here we show that targeting of antigen to Fc receptors on DCs accomplishes combined activation of Th1 CD4 and CD8 effector responses in vivo, namely delayed-type hypersensitivity and tumor immunity. Tumor immunity specific for ovalbumin-expressing tumors was provided by immunization with wild-type but not FcgammaRgamma(-/-) DCs loaded with ovalbumin-containing immune complexes. Tumor protection was eliminated when immune complex-loaded DCs lacked beta(2) microglobulin, TAP, or MHC class II, demonstrating that Fc receptor-targeted antigenic uptake led to both MHC class I- and class II-restricted responses, which together are required for effector tumor immunity. Thus the cross-presentation pathway accessed by antigens acquired endocytically through Fc receptors links humoral and cellular immunity. These data suggest that administration of antitumor antibodies may enhance tumor-specific T cell responses in vivo and provide the rationale for Fc receptor targeting in vaccine development.

Antigen uptake receptors on dendritic cells (DCs) provide efficient entry for the initiation of antigen-specific adaptive immunity. Here we show that targeting of antigen to Fc receptors on DCs accomplishes combined activation of Th1 CD4 and CD8 effector responses in vivo, namely delayedtype hypersensitivity and tumor immunity. Tumor immunity specific for ovalbumin-expressing tumors was provided by immunization with wild-type but not FcγRγ -/-DCs loaded with ovalbumincontaining immune complexes. Tumor protection was eliminated when immune complex-loaded DCs lacked β 2 microglobulin, TAP, or MHC class II, demonstrating that Fc receptor-targeted antigenic uptake led to both MHC class I-and class II-restricted responses, which together are required for effector tumor immunity. Thus the cross-presentation pathway accessed by antigens acquired endocytically through Fc receptors links humoral and cellular immunity. These data suggest that administration of antitumor antibodies may enhance tumor-specific T cell responses in vivo and provide the rationale for Fc receptor targeting in vaccine development.This article was published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.

Background/Aims: Systemic hyperlipidemia and intracellular lipid accumulation induced by chronic high fat diet (HFD) leads to enhanced fatty acid oxidation (FAO) and ketogenesis. The present study was aimed to determine whether activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) by surplus free fatty acids (FA) in hyperlipidemic condition, has a positive feedback regulation over FAO and ketogenic enzymes controlling lipotoxicity and cardiac apoptosis. Methods: 8 weeks old C57BL/6 wild type (WT) or PPAR-γ^-/- mice were challenged with 16 weeks 60% HFD to induce obesity mediated type 2 diabetes mellitus (T2DM) and diabetic cardiomyopathy. Treatment course was followed by echocardiographic measurements, glycemic and lipid profiling, immunoblot, qPCR and immunohistochemistry (IHC) analysis of PPAR-γ and following mitochondrial metabolic enzymes 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2), mitochondrial β- hydroxy butyrate dehydrogenase (BDH1) and pyruvate dehydrogenase kinase isoform 4 (PDK4). In vivo model was translated in vitro, with neonatal rat cardiomyocytes (NRCM) treated with PPAR-γ agonist/antagonist and PPAR-γ overexpression adenovirus in presence of palmitic acid (PA). Apoptosis was determined in vivo from left ventricular heart by TUNEL assay and immunoblot analysis. Results: We found exaggerated circulating ketone bodies production and expressions of the related mitochondrial enzymes HMGCS2, BDH1 and PDK4 in HFD-induced diabetic hearts and in PA-treated NRCM. As a mechanistic approach we found HFD mediated activation of PPAR-γ is associated with the above-mentioned mitochondrial enzymes. HFD-fed PPAR-γ^-/-mice display decreased hyperglycemia, hyperlipidemia associated with increased insulin responsiveness as compared to HFD-fed WT mice PPAR-γ^-/–HFD mice demonstrated a more robust functional recovery after diabetes induction, as well as significantly reduced myocyte apoptosis and improved cardiac function. Conclusions: PPAR-γ has been described previously to regulate lipid metabolism and adipogenesis. The present study suggests for the first time that increased PPAR-γ expression by HFD is responsible for cardiac dysfunction via upregulation of mitochondrial enzymes HMGCS2, BDH1 and PDK4. Targeting PPAR-γ and its downstream mitochondrial enzymes will provide novel strategies in preventing metabolic and myocardial dysfunction in diabetes mellitus.

Inflammatory cells and their proteases contribute to tissue reparation at site of inflammation. Although beneficial at early stages, excessive inflammatory reaction leads to cell death and tissue damage. Cathepsin G (Cat.G), a neutrophil-derived serine protease, has been shown to induce neonatal rat cardiomyocyte detachment and apoptosis by anoikis through caspase-3 dependent pathway. However the early mechanisms that trigger Cat.G-induced caspase-3 activation are not known. This study identifies focal adhesion kinase (FAK) tyrosine dephosphorylation as an early mechanism that regulates Cat.G-induced anoikis in cardiomyocytes. Both FAK tyrosine phosphorylation at Tyr-397 and kinase activity decrease rapidly upon Cat.G treatment and was associated with a decrease of FAK association with adapter and cytoskeletal proteins, p130Cas and paxillin, respectively. FAK-decreased tyrosine phosphorylation is required for Cat.G-induced myocyte anoikis as concurrent expression of phosphorylation-deficient FAK mutated at Tyr-397 or pretreatment with a protein-tyrosine phosphatase (PTP) inhibitor, pervanadate, blocks Cat.G-induced FAK tyrosine dephosphorylation, caspase-3 activation and DNA fragmentation. Analysis of PTPs activation shows that Cat.G treatment induces an increase of SHP 2 and PTEN phosphorylation; however, only SHP 2 forms a complex with FAK in response to Cat.G. Expression of dominant negative SHP 2 mutant markedly attenuates FAK tyrosine dephosphorylation induced by Cat.G and protects myocytes to undergo apoptosis. In contrast, increased SHP 2 expression exacerbates Cat.G-induced FAK tyrosine dephosphorylation and myocyte apoptosis. Taken together, these results show that Cat.G induces SHP 2 activation that leads to FAK tyrosine dephosphorylation and promotes cardiomyocyte anoikis.

.-We investigated how exercise training superimposed on chronic hypertension impacted left ventricular remodeling. Cardiomyocyte hypertrophy, apoptosis, and proliferation in hearts from female spontaneously hypertensive rats (SHRs) were examined. Four-month-old SHR animals were placed into a sedentary group (SHR-SED; n ϭ 18) or a treadmill running group (SHR-TRD, 20 m/min, 1 h/day, 5 days/wk, 12 wk; n ϭ 18). Age-matched, sedentary Wistar Kyoto (WKY) rats were controls (n ϭ 18). Heart weight was greater in SHR-TRD vs. both WKY (P Ͻ 0.01) and SHR-SED (P Ͻ 0.05). Morphometricderived left ventricular anterior, posterior, and septal wall thickness were increased in SHR-SED relative to WKY and augmented in SHR-TRD. Cardiomyocyte surface area, length, and width were increased in SHR-SED relative to WKY and further increased in SHR-TRD. Calcineurin abundance was increased in SHR-SED vs. WKY (P Ͻ 0.001) and attenuated in SHR-TRD relative to SHR-SED (P Ͻ 0.05). Protein abundance and mRNA of Akt was not different among groups. The rate of apoptosis was increased in SHR-SED relative to WKY and mitigated in SHR-TRD. The abundance of Ki-67 ϩ cells across groups was not statistically different across groups. The abundance of cardiac progenitor cells (c-Kit ϩ cells) was increased in SHR-TRD relative to WKY. These data suggest that exercise training superimposed on hypertension augmented cardiomyocyte hypertrophy, despite attenuating calcineurin abundance. Exercise training also mitigated apoptosis in hypertension and showed a tendency to enhance the abundance of cardiac progenitor cells, resulting in a more favorable cardiomyocyte number in the exercise-trained hypertensive heart. hypertrophy; myocytes; apoptosis; proliferation CHRONIC HYPERTENSION INDUCES overall cardiac enlargement, which is, in part, due to cardiomyocyte hypertrophy. This is a significant health issue, since pathological cardiac enlargement increases the risk for the development of congestive heart failure (4). Increased apoptosis has also been noted in the hypertensive heart, which may be an integral substrate in overall remodeling and progression to heart failure (33).Several studies have reported that cardiac myocytes are capable of mitotic division and proliferation (13,14). While the control mechanisms for the induction of cardiomyocyte proliferation remain unclear, one theory purports the involvement of a resident population of cardiac progenitor cells (1, 30), which have been shown to increase their activity in stress-induced pathological conditions (1,28,31). In the hypertensive heart, cardiomyocyte proliferation may counteract apoptosis, thus reducing the progressive loss of cardiomyocytes.Recent studies from our laboratory, as well as others, have shown an overall phenotypical improvement for the myocardium with exercise training in hypertension (3,17,24,34,35,42). However, the precise putative mechanisms associated with the observed adaptations with exercise training remain unclear. Our present hypothesis is that exercise training in hypertension ...