Search

© 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)., The decision whether endosomes enter the degradative or recycling pathway in mammalian cells is of fundamental importance for pathogen killing, and its malfunctioning has pathological consequences. We discovered that human p11 is a critical factor for this decision. The HscA protein present on the conidial surface of the human-pathogenic fungus Aspergillus fumigatus anchors p11 on conidia-containing phagosomes (PSs), excludes the PS maturation mediator Rab7, and triggers binding of exocytosis mediators Rab11 and Sec15. This reprogramming redirects PSs to the non-degradative pathway, allowing A. fumigatus to escape cells by outgrowth and expulsion as well as transfer of conidia between cells. The clinical relevance is supported by the identification of a single nucleotide polymorphism in the non-coding region of the S100A10 (p11) gene that affects mRNA and protein expression in response to A. fumigatus and is associated with protection against invasive pulmonary aspergillosis. These findings reveal the role of p11 in mediating fungal PS evasion., This work was funded by the Deutsche Forschungsgemeinschaft (DFG) cluster of excellence Balance of the Microverse (Project-ID 390713860, Gepris 2051), the DFG-ANR project “AfuInf (316898429),” DFG CRC/Transregio 124 “FungiNet” (A1, Z2; 210879364), DFG CRC 1278 “PolyTarget” (Z01; 316213987), Leibniz project (K217/2016), Fundação para a Ciência e a Tecnologia (FCT) (PTDC/MED-OUT/1112/2021, UIDB/50026/2020, UIDP/50026/2020, NORTE-01-0145-FEDER-000039), EU’s Horizon 2020 (847507), “la Caixa” Foundation (ID 100010434) and FCT (LCF/PR/HR17/52190003), Gilead Research Scholars Program - Anti-Fungals, and EU-funded Horizon 2020 project HDM-FUN (ID 847507). M.R. and F.S. were supported by the DFG excellence graduate school Jena School for Microbial Communication, and C.C. by FCT (CEECIND/04058/2018).

Metabolic pathways and cycles are reaction chains where chemical products become the substrate for the next step. All substrates are chemically transformed in reactions that belong to either pathways (if the reactions are aligned in linear fashion) or metabolic cycles (if the moieties of the reactions are preserved). The term substrate oxidation is used for substrate degradation ultimately leading to CO2 production. However, such an oxidative pathway may be interrupted for several reasons, such as in the case of glucose oxidation, where limited oxygen results in the production of lactate rather than water and CO2. Some but not all substrates can also be converted to building blocks for biosynthetic processes. This chapter will describe the main metabolic pathways and cycles of cardiac substrate metabolism. It will also address their interactions and their contributions to meet cardiac-energy requirements.

In order for the heart to sustain its regular heartbeat, it needs a constant supply of energy for contraction. Cardiac metabolism comprises all processes involved in the biochemical conversion of molecules within the cell utilizing energy substrates. These substrates are mainly fatty acids, glucose, and lactate, but as a true metabolic omnivore the heart is able to utilize them all for energy production. In addition, cardiac metabolism comprises all biochemical processes of the cell aimed at the generation of building blocks for cell maintenance, biosynthesis, and cellular growth. This chapter provides orientation for optimal use of and navigation through this book.

The heart constantly requires high-energy turnover and has the highest oxygen consumption rate per weight of all organs. Cardiac cell homeostasis, and with this, contractility and cardiac output, relies on constant substrate availability. It is well established, that heart failure is associated with profound derangements of cardiomyocyte energy homeostasis. Hence, the understanding of cardiac metabolism is pivotal for new therapeutic approaches for heart disease. Here, we discuss current noninvasive imaging techniques of cardiac metabolism with scientific and clinical implications as well as established and possible new therapeutic strategies for the treatment of heart failure utilizing the current knowledge of the mechanisms of cardiac metabolism.

Cardiac metabolism encompasses all biochemical processes that result in the conversion of substrates or intermediates of metabolic pathways and cycles for the purpose of cell function, growth, and contraction. Methods investigating metabolism must therefore address the moieties of metabolic pathways and cycles, flux through them and the activity and regulation of their enzymes. Such investigations can be performed in vivo, in vitro , or ex vivo ; in humans, in animals, or in cell culture. In this chapter, we will describe the principles of the main methods used to examine cardiac metabolism in health and disease. As mitochondria have moved into the focus of attention in recent years, we will put a focus on the assessment of mitochondrial function. We will start with the methods of assessing moieties of pathways and cycles, that is, the amounts of RNA, proteins, and metabolites, then continue with the description of methods to assess enzyme activities in vitro , and move on to methods of addressing fluxes and imaging of metabolic activity in intact organs or in vivo . This chapter is not meant to describe individual techniques in detail and is not meant to be complete but to provide an overview and to illustrate principles of the currently available methodology.

BACKGROUND: Pulmonary dysfunction presumably linked to an inflammatory response is frequent after cardiac operations using cardiopulmonary bypass (CPB) and pulmonary hypoperfusion. We previously demonstrated that active perfusion of the lungs during CPB reduces ischemic lung injury. We now hypothesized that avoiding ischemia of the lungs during CPB by active pulmonary perfusion would decrease pulmonary inflammatory response. METHODS: Pigs were randomized to a control group with CPB for 120 minutes, followed by 120 minutes of postbypass reperfusion, or to the study groups where animals underwent active pulmonary perfusion with pulsatile or nonpulsatile perfusion during CPB (n = 7 in each group). Activation of transcription factor activity (nuclear factor [NF]-kappaB and activating protein [AP]-1) was determined by electrophoretic mobility shift assay. Levels of proinflammatory protein expression (interleukin [IL]-1, IL-6, and tumor necrosis factor [TNF]-alpha) were quantified by enzyme-linked immunoabsorbent assay. Caspase-3 activity was measured using a fluorogenic assay. RESULTS: The activation of transcription factor AP-1 and NF-kappaB was reduced in the pulsatile pulmonary perfusion group. The caspase-3 activity and the expression of IL-1, IL-6, and TNF-alpha revealed a significant decrease in the pulsatile and nonpulsatile pulmonary perfusion groups. Animals of the pulsatile pulmonary perfusion group showed significantly reduced IL-6 expression and caspase-3 activity compared with the nonpulsatile pulmonary perfusion group. CONCLUSIONS: Active pulmonary perfusion reduces the inflammatory response and apoptosis in the lungs observed during conventional CPB. This effect is greatest when pulmonary perfusion is performed with pulsatility. The reduction in cytokine expression by pulsatile pulmonary perfusion might be mediated by AP-1 and NF-kappaB.