Signal regulatory protein alpha initiates cachexia through muscle to adipose tissue crosstalk

BACKGROUND: Muscle wasting from chronic kidney disease (CKD) or from defective insulin signalling results in morbidity and, ultimately, mortality. We have identified an endogenous mediator of insulin resistance, signal regulatory protein alpha (SIRPα), which leads to cachexia in mice and is associated with cachexia in patients with CKD. METHODS: We assessed insulin signalling and mechanisms causing muscle atrophy plus white adipose tissue (WAT) metabolism in mouse models of CKD or acute diabetes (streptozotocin treatment). We then examined these factors in mice with global knockout (KO) of SIRPα and sought mediators of metabolic responses in muscle and adipose tissues of mice with either muscle-specific or adipose tissue-specific KO of SIRPα. Metabolic responses were confirmed in primary cultures of adipose cells. RESULTS: In mice with CKD, SIRPα expression was increased in WAT (three-fold, P \u3c 0.05), and this was associated with precursors of cachexia: \u27pathologic browning\u27, thermogenesis, and a two-fold activation of protein kinase A (P \u3c 0.05 vs. control mice) plus loss of adipose tissue mass. In contrast, mice with SIRPα global KO and CKD or acute diabetes experienced improved insulin signalling and activation of pAkt plus \u27physiologic browning\u27 of WAT. These mice avoided losses of muscle and adipose tissues and experienced a 31% improvement in survival (P \u3c 0.05) than did wild-type mice with CKD. In muscle-specific SIRPα KO mice with CKD, we uncovered that serum SIRPα levels (P \u3c 0.05) were suppressed and were associated with improved insulin signalling both in skeletal muscles and in WAT. These changes were accompanied by physiologic WAT browning. However, in adipose-specific SIRPα KO mice with CKD, levels of serum SIRPα were increased over two-fold (P \u3c 0.05), while muscle losses were minimally inhibited. Clinical implications of SIRPα signalling are suggested by our findings that include increased SIRPα expression in muscle and adipose tissues (P \u3c 0.05 vs. healthy controls) plus higher SIRPα levels in the serum of patients with CKD (2.4-fold, P=0.000017 vs. healthy controls). CONCLUSIONS: Our results show that SIRPα plays an important role as an anti-insulin mediator regulating pathways to cachexia. In muscle-specific SIRPα KO, changes in SIRPα serum levels seem to improve insulin signalling in muscle and WAT, suggesting crosstalk between muscle and adipose tissue. Therefore, targeting SIRPα may prevent cachexia in patients with CKD or acute diabetes

Interactions between p-Akt and Smad3 in injured muscles initiate myogenesis or fibrogenesis

In catabolic conditions such as aging and diabetes, IGF signaling is impaired and fibrosis develops in skeletal muscles. To examine whether impaired IGF signaling initiates muscle fibrosis, we generated IGF-IR+/- heterozygous mice by crossing loxP-floxed IGF-IR (exon 3) mice with MyoD-cre mice. IGF-IR+/- mice were studied because we were unable to obtain homozygous IGF-IR-KO mice. in IGF-IR+/- mice, both growth and expression of myogenic genes (MyoD and myogenin; markers of satellite cell proliferation and differentiation, respectively) were depressed. Likewise, in injured muscles of IGF-IR+/- mice, there was impaired regeneration, depressed expression of MyoD and myogenin, and increased expression of TGF-beta 1, alpha-SMA, collagen I, and fibrosis. To uncover mechanisms stimulating fibrosis, we isolated satellite cells from muscles of IGF-IR+/- mice and found reduced proliferation and differentiation plus increased TGF-beta 1 production. in C2C12 myoblasts (a model of satellite cells), IGF-I treatment inhibited TGF-beta 1-stimulated Smad3 phosphorylation, its nuclear translocation, and expression of fibronectin. Using immunoprecipitation assay, we found an interaction between p-Akt or Akt with Smad3 in wild-type mouse muscles and in C2C12 myoblasts; importantly, IGF-I increased p-Akt and Smad3 interaction, whereas TGF-beta 1 decreased it. Therefore, in muscles of IGF-IR+/- mice, the reduction in IGF-IR reduces p-Akt, allowing for dissociation and nuclear translocation of Smad3 to enhance the TGF-beta 1 signaling pathway, leading to fibrosis. Thus, strategies to improve IGF signaling could prevent fibrosis in catabolic conditions with impaired IGF signaling.Satellite HealthAmerican Diabetes AssociationNational Institute of Diabetes and Digestive and Kidney DiseasesBaylor Coll Med, Div Nephrol, Dept Med, Houston, TX 77030 USAEmory Univ, Dept Med, Div Renal, Atlanta, GA 30322 USACapital Med Univ, Beijing An Zhen Hosp, Beijing Inst Heart Lung & Blood Vessel Dis, Beijing, Peoples R ChinaUniversidade Federal de São Paulo, Div Nephrol, Dept Med, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nephrol, Dept Med, São Paulo, BrazilAmerican Diabetes Association: 1-11-BS-194National Institute of Diabetes and Digestive and Kidney Diseases: R37-DK-37175National Institute of Diabetes and Digestive and Kidney Diseases: T32-DK-62706Web of Scienc

The nuclear phosphatase SCP4 regulates FoxO transcription factors during muscle wasting in chronic kidney disease

Chronic kidney disease (CKD) and related inflammatory responses stimulate protein-energy wasting, a complication causing loss of muscle mass. Primarily, muscle wasting results from accelerated protein degradation via autophagic/lysosomal and proteasomal pathways, but mechanisms regulating these proteolysis pathways remain unclear. Since dephosphorylation of FoxOs regulates ubiquitin/proteasome protein metabolism, we tested whether a novel nuclear phosphatase, the small C-terminal domain phosphatase (SCP) 4, regulates FoxOs signaling and, in turn, muscle wasting. In cultured mouse myoblast cells, SCP4 overexpression stimulated proteolysis, while knockdown of SCP4 prevented the proteolysis stimulated by inflammatory cytokines. SCP4 overexpression led to nuclear accumulation of FoxO1/3a followed by increased expression of catabolic factors including myostatin, Atrogin-1, and MuRF-1, and induction of lysosomal-mediated proteolysis. Treatment of C2C12 myotubes with proinflammatory cytokines stimulated SCP4 expression in an NF-\u3baB-dependent manner. In skeletal muscle of mice with CKD, SCP4 expression was up-regulated. Similarly, in skeletal muscle of patients with CKD, SCP4 expression was significantly increased. Knockdown of SCP4 significantly suppressed FoxO1/3a-mediated expression of Atrogin-1 and MuRF-1 and prevented muscle wasting in mice with CKD. Thus, SCP4 is a novel regulator of FoxO transcription factors and promotes cellular proteolysis. Hence, targeting SCP4 may prevent muscle wasting in CKD and possibly other catabolic conditions

SIRPα Mediates IGF1 Receptor in Cardiomyopathy Induced by Chronic Kidney Disease

BACKGROUND: Chronic kidney disease (CKD) is characterized by increased myocardial mass despite near-normal blood pressure, suggesting the presence of a separate trigger. A potential driver is SIRPα (signal regulatory protein alpha)-a mediator impairing insulin signaling. The objective of this study is to assess the role of circulating SIRPα in CKD-induced adverse cardiac remodeling. METHODS: SIRPα expression was evaluated in mouse models and patients with CKD. Specifically, mutant, muscle-specific, or cardiac muscle-specific SIRPα KO (knockout) mice were examined after subtotal nephrectomy. Cardiac function was assessed by echocardiography. Metabolic responses were confirmed in cultured muscle cells or cardiomyocytes. RESULTS: We demonstrate that SIRPα regulates myocardial insulin/IGF1R (insulin growth factor-1 receptor) signaling in CKD. First, in the serum of both mice and patients, SIRPα was robustly secreted in response to CKD. Second, cardiac muscle upregulation of SIRPα was associated with impaired insulin/IGF1R signaling, myocardial dysfunction, and fibrosis. However, both global and cardiac muscle-specific SIRPα KO mice displayed improved cardiac function when compared with control mice with CKD. Third, both muscle-specific or cardiac muscle-specific SIRPα KO mice did not significantly activate fetal genes and maintained insulin/IGF1R signaling with suppressed fibrosis despite the presence of CKD. Importantly, SIRPα directly interacted with IGF1R. Next, rSIRPα (recombinant SIRPα) protein was introduced into muscle-specific SIRPα KO mice reestablishing the insulin/IGF1R signaling activity. Additionally, overexpression of SIRPα in myoblasts and cardiomyocytes impaired pAKT (phosphorylation of AKT) and insulin/IGF1R signaling. Furthermore, myotubes and cardiomyocytes, but not adipocytes treated with high glucose or cardiomyocytes treated with uremic toxins, stimulated secretion of SIRPα in culture media, suggesting these cells are the origin of circulating SIRPα in CKD. Both intracellular and extracellular SIRPα exert biologically synergistic effects impairing intracellular myocardial insulin/IGF1R signaling. CONCLUSIONS: Myokine SIRPα expression impairs insulin/IGF1R functions in cardiac muscle, affecting cardiometabolic signaling pathways. Circulating SIRPα constitutes an important readout of insulin resistance in CKD-induced cardiomyopathy

Soft Corals and Seafans of India

Soft Corals and Seafans of Indi

Surfactant protein D inhibits HIV-1 infection of target cells via interference with gp120-CD4 interaction and modulates pro-inflammatory cytokine production

© 2014 Pandit et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Surfactant Protein SP-D, a member of the collectin family, is a pattern recognition protein, secreted by mucosal epithelial cells and has an important role in innate immunity against various pathogens. In this study, we confirm that native human SP-D and a recombinant fragment of human SP-D (rhSP-D) bind to gp120 of HIV-1 and significantly inhibit viral replication in vitro in a calcium and dose-dependent manner. We show, for the first time, that SP-D and rhSP-D act as potent inhibitors of HIV-1 entry in to target cells and block the interaction between CD4 and gp120 in a dose-dependent manner. The rhSP-D-mediated inhibition of viral replication was examined using three clinical isolates of HIV-1 and three target cells: Jurkat T cells, U937 monocytic cells and PBMCs. HIV-1 induced cytokine storm in the three target cells was significantly suppressed by rhSP-D. Phosphorylation of key kinases p38, Erk1/2 and AKT, which contribute to HIV-1 induced immune activation, was significantly reduced in vitro in the presence of rhSP-D. Notably, anti-HIV-1 activity of rhSP-D was retained in the presence of biological fluids such as cervico-vaginal lavage and seminal plasma. Our study illustrates the multi-faceted role of human SPD against HIV-1 and potential of rhSP-D for immunotherapy to inhibit viral entry and immune activation in acute HIV infection. © 2014 Pandit et al.The work (Project no. 2011-16850) was supported by Medical Innovation Fund of Indian Council of Medical Research, New Delhi, India (www.icmr.nic.in/)

Nivolumab versus Everolimus in Advanced Renal-Cell Carcinoma

This randomised phase III trial compared standard of care Everolimus with the anti-PD1 monoclonal antibody Nivolumab in previously treated patients with locally advanced inoperable or metastatic clear cell renal cancer. 810 patients were randomised to receive either Everolimus 10 mg orally daily or 3 mg/kg of Nivolumab intravenously every two weeks. Patients were treated until unacceptable toxicity or disease progression. Patients could be treated beyond progression if the investigator believed that the patient was gaining clinical benefit. The primary endpoint was overall survival. The median survival was 25 months for Nivolumab and 19.8 months for Everolimus (p=0.002). The objective response rate was higher for Nivolumab (25 versus 5%; p=<0.001).The median progression free survivals were 4.6 & 4.4 months (p=0.11). Grade 3 & 4 treatment related toxicities were observed in 19 & 37% of patients on Nivolumab or Everolimus respectively. In patients with previously treated renal cell carcinoma Nivolumab produced superior survival and more tolerable treatment than Everolimus

Structural Insight into How Bacteria Prevent Interference between Multiple Divergent Type IV Secretion Systems

Prokaryotes use type IV secretion systems (T4SSs) to translocate substrates (e.g., nucleoprotein, DNA, and protein) and/or elaborate surface structures (i.e., pili or adhesins). Bacterial genomes may encode multiple T4SSs, e.g., there are three functionally divergent T4SSs in some Bartonella species (vir, vbh, and trw). In a unique case, most rickettsial species encode a T4SS (rvh) enriched with gene duplication. Within single genomes, the evolutionary and functional implications of cross-system interchangeability of analogous T4SS protein components remains poorly understood. To lend insight into cross-system interchangeability, we analyzed the VirB8 family of T4SS channel proteins. Crystal structures of three VirB8 and two TrwG Bartonella proteins revealed highly conserved C-terminal periplasmic domain folds and dimerization interfaces, despite tremendous sequence divergence. This implies remarkable structural constraints for VirB8 components in the assembly of a functional T4SS. VirB8/TrwG heterodimers, determined via bacterial two-hybrid assays and molecular modeling, indicate that differential expression of trw and vir systems is the likely barrier to VirB8-TrwG interchangeability. We also determined the crystal structure of Rickettsia typhi RvhB8-II and modeled its coexpressed divergent paralog RvhB8-I. Remarkably, while RvhB8-I dimerizes and is structurally similar to other VirB8 proteins, the RvhB8-II dimer interface deviates substantially from other VirB8 structures, potentially preventing RvhB8-I/RvhB8-II heterodimerization. For the rvh T4SS, the evolution of divergent VirB8 paralogs implies a functional diversification that is unknown in other T4SSs. Collectively, our data identify two different constraints (spatio-temporal for Bartonella trw and vir T4SSs and structural for rvh T4SSs) that mediate the functionality of multiple divergent T4SSs within a single bacterium. IMPORTANCE Assembly of multiprotein complexes at the right time and at the right cellular location is a fundamentally important task for any organism. In this respect, bacteria that express multiple analogous type IV secretion systems (T4SSs), each composed of around 12 different components, face an overwhelming complexity. Our work here presents the first structural investigation on factors regulating the maintenance of multiple T4SSs within a single bacterium. The structural data imply that the T4SS-expressing bacteria rely on two strategies to prevent cross-system interchangeability: (i) tight temporal regulation of expression or (ii) rapid diversification of the T4SS components. T4SSs are ideal drug targets provided that no analogous counterparts are known from eukaryotes. Drugs targeting the barriers to cross-system interchangeability (i.e., regulators) could dysregulate the structural and functional independence of discrete systems, potentially creating interference that prevents their efficient coordination throughout bacterial infection.Peer reviewe

Nucleic acid-based fluorescent probes and their analytical potential

It is well known that nucleic acids play an essential role in living organisms because they store and transmit genetic information and use that information to direct the synthesis of proteins. However, less is known about the ability of nucleic acids to bind specific ligands and the application of oligonucleotides as molecular probes or biosensors. Oligonucleotide probes are single-stranded nucleic acid fragments that can be tailored to have high specificity and affinity for different targets including nucleic acids, proteins, small molecules, and ions. One can divide oligonucleotide-based probes into two main categories: hybridization probes that are based on the formation of complementary base-pairs, and aptamer probes that exploit selective recognition of nonnucleic acid analytes and may be compared with immunosensors. Design and construction of hybridization and aptamer probes are similar. Typically, oligonucleotide (DNA, RNA) with predefined base sequence and length is modified by covalent attachment of reporter groups (one or more fluorophores in fluorescence-based probes). The fluorescent labels act as transducers that transform biorecognition (hybridization, ligand binding) into a fluorescence signal. Fluorescent labels have several advantages, for example high sensitivity and multiple transduction approaches (fluorescence quenching or enhancement, fluorescence anisotropy, fluorescence lifetime, fluorescence resonance energy transfer (FRET), and excimer-monomer light switching). These multiple signaling options combined with the design flexibility of the recognition element (DNA, RNA, PNA, LNA) and various labeling strategies contribute to development of numerous selective and sensitive bioassays. This review covers fundamentals of the design and engineering of oligonucleotide probes, describes typical construction approaches, and discusses examples of probes used both in hybridization studies and in aptamer-based assays

Mammographic density, breast cancer risk and risk prediction

In this review, we examine the evidence for mammographic density as an independent risk factor for breast cancer, describe the risk prediction models that have incorporated density, and discuss the current and future implications of using mammographic density in clinical practice. Mammographic density is a consistent and strong risk factor for breast cancer in several populations and across age at mammogram. Recently, this risk factor has been added to existing breast cancer risk prediction models, increasing the discriminatory accuracy with its inclusion, albeit slightly. With validation, these models may replace the existing Gail model for clinical risk assessment. However, absolute risk estimates resulting from these improved models are still limited in their ability to characterize an individual's probability of developing cancer. Promising new measures of mammographic density, including volumetric density, which can be standardized using full-field digital mammography, will likely result in a stronger risk factor and improve accuracy of risk prediction models