The 'injury hypothesis' in organ transplantation suggests that ischemia-reperfusion injury is involved in the adaptative alloimmune response. We previously found that a strong immune/inflammatory response was induced by ischemia during kidney transplantation in rats. We show here that immature dendritic cells (DCs) undergo hypoxia-mediated differentiation comparable to allogeneic stimulation. Hypoxia-differentiated DCs overexpress hypoxia inducible factor-1alpha (HIF-1alpha) and its downstream target genes, such as vascular endothelial growth factor or glucose transporter-1. Rapamycin attenuated DC differentiation, HIF-1alpha expression, and its target gene expression in a dose-dependent manner along with downregulated interleukin-10 secretion. Coculture of hypoxia-differentiated DCs with CD3 lymphocytes induced proliferation of lymphocytes, a process also neutralized by rapamycin. Furthermore, in vivo examination of ischemia-reperfusion-injured mouse kidneys showed a clear maturation of resident DCs that was blunted by rapamycin pretreatment. Our results suggest that hypoxia is a central part of the 'injury hypothesis' triggering DC differentiation under hypoxic conditions. Rapamycin attenuates the hypoxic immune-inflammatory response through inhibition of the HIF-1alpha pathway.

Summary This study reviews the current understanding of ischemic preconditioning (IP) in experimental and clinical setting, and the mechanisms that mediate the complex processes involved as a tool to protect against ischemia and reperfusion (I/R) injury, but is not intended as a complete literature review of preconditioning. IP has been mainly elucidated in cardiac ischemia. Recent reports confirm the efficacy of pre‐ and postconditioning in cardiac surgery and percutaneous coronary interventions in humans. IP utilizes endogenous as well as distant mechanisms in skeletal muscle, liver, lung, kidney, intestine and brain in animal models to convey varying degrees of protection from I/R injury. Specifically, preconditioned tissues exhibit altered energy metabolism, better electrolyte homeostasis and genetic reorganization, as well as less oxygen‐free radicals and activated neutrophils release, reduced apoptosis and better microcirculatory perfusion. To date, there are few human studies, but recent trials suggest that human liver, lung and skeletal muscle acquire protection after IP. Present data address the potential therapeutic application of IP in the prevention of I/R damage specially aimed at clinical transplantation. IP is ubiquitous but more research is required to fully translate these findings to the clinical arena.

A biocompatible fluorescent nanoprobe for singlet oxygen ( 1 O2) detection in biological systems has been designed, synthesised and characterized, that circumvents many of the limitations of the molecular probe Singlet Oxygen Sensor Green® (SOSG). This widely used commercial singlet oxygen probe has been covalently linked to a polyacrylamide nanoparticle core using different architectures to optimize the response to 1 O2. In contrast with its molecular counterpart, the optimum SOSG-based nanoprobe, which we call NanoSOSG, is readily internalised by E. coli cells, does not interact with BSA, does not change its spectrum inside cells and responds to intracellularly-generated 1 O2 by increasing its fluorescence.Singlet oxygen ( 1 O2) is the lowest excited electronic state of molecular oxygen and is endowed with atypical but appealing physico-chemical properties and behavior that puts it at the forefront of research in many different disciplines.[1] Great efforts have been made in developing techniques and/or methods able not only to detect, but also to quantify the generation of O2 produced inside a cell is rapidly quenched, resulting in a very short lifetime [6] and hence reducing the probability of it being captured by the probe.There is an emerging trend of using nanoparticles (NPs) for drug delivery, [7] sensing [8] and imaging. [9] However, only a few reports exist on the use of 1 O2 traps associated with NPs. Among the emerging nanomaterials for biomedical applications, polyacrylamide is attracting much interest owing to its biocompatibility and chemical versatility. Successful examples of its use have recently been published in several fields.[10] Synthesis of polyacrylamide NPs is straightforward and it allows tailoring both the size and the functionalization of the nanospecies to suit the needs of specific applications. The porosity of polyacrylamide allows analytes (e.g., ions, small molecules, etc.) to diffuse within the NP and interact with the sensing moiety making it an ideal support for nanosensors.