Preparation of Chiral Photosensitive Organocatalysts and Their Application for the Enantioselective Synthesis of 1,2-Diamines

International audienceChiral phosphoric acid based organocatalysis and visible-light photocatalysis have both emerged as promising technologies for the sustainable production of fine chemicals. In this context, we have envisioned the design and the synthesis of a new class of chimeric catalytic entities that would feature both catalytic capabilities. Given their multitask nature, such catalysts would reveal 2 particularly attractive for the development of new catalytic transformations, tandem processes in particular. To this aim, several BINOL-based chiral phosphoric acids backbone presenting one or two visible-light sensitive thioxanthone moieties have been prepared and studied. The utility of these new photoactive chiral organocatalysts is then demonstrated in the enantioselective tandem three-component electrophilic amination of enecarbamates. Of note, the C1-symmetric organo/photo catalyst has given a better catalytic activity than those presenting a C2 symmetry

A straightforward synthesis of a new family of molecules: 2,5,8-trialkoxyheptazines. Application to photoredox catalyzed transformations

International audienceThe combined Lewis acid catalytic system, generated from molecular iodine and tritylium tetrafluoroborate effectively catalyzed the Friedel-Crafts (FC) arylation of diarylmethyl sulfides providing an efficient access to various unsymmetrical triarylmethanes. The addition of tritylium and iodine created a more active catalytic system to promote the cleavage of sulfidic C-S bonds

Visible-Light-Triggered C–C and C–N Bond Formation by C–S Bond Cleavage of Benzylic Thioethers

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Benefits of active oxygenation during hypothermic machine perfusion of kidneys in a preclinical model of deceased after cardiac death donors

<p>Background: Deceased after cardiac death donors (DCDs) represent a valuable source of organs; however, preventing poor outcome is difficult, even with the use of machine perfusion (MP). It is of paramount importance to improve this method. We proposed to evaluate the benefits of active oxygenation during kidney graft hypothermic MP using a novel perfusion machine: Kidney Assist (KA).</p><p>Methods: We used a pig model of DCD transplantation in Large White pigs. Cold preservation was performed by conventional non-oxygenated MP (KAnoO(2)) or oxygenated MP (KA).</p><p>Results: In the first 2 wk post-transplant, KA grafts displayed a lower serum creatinine peak and a faster return to normal levels compared with KAnoO(2) animals, translating into a smaller area under the curve. Urinary neutrophil gelatinase-associated lipocalin levels and serum aspartate amino transferase levels were lower in KA animals compared with the non-oxygenated group. These correlated with better chronic function. Longer follow-up of the animals (3 mo) permitted evaluation of chronic outcome lesions. Interstitial fibrosis was reduced in the KA group, and these kidneys also displayed significantly lower levels of vimentin staining. Further histologic investigation also showed a trend toward decreased chronic inflammation in kidneys preserved with oxygen.</p><p>Conclusions: This new MP system is efficient in preserving DCD kidneys, greatly enhancing the capacity of the graft to withstand preservation stress and improving outcome. Oxygen delivery during preservation is thus valuable for highly damaged organs and offers an important therapeutic tool for transplant teams faced with decreased quality of donor organs. (C) 2013 Elsevier Inc. All rights reserved.</p>

Influence of preservation temperature on endothelial cells and kidney phenotypes

Introduction: Ischemia reperfusion (IR) injury is unavoidable during organ transplantation and leads to complications. With the increased use of marginal donors, more sensitive to IR, solutions must be found to improve outcome. We hypothesized that a higher preservation temperature could offer better protection against IR.[br/]Methods: We tested this in an in vitro model of IR using primary endothelial cells and in ex vivo preserved pig kidneys. In both, 24 h preservation in University of Wisconsin solution was used.[br/]Results: In vitro, compared to 4°C, temperatures between 19 and 32°C provided higher protection against cell death (LDH release test), permitting better mitochondrial function (complexes II and V activity tests) and a lowerexpression of endothelial activation and inflammation markers TLR4, MCP1 and ICAM1. Ex vivo, however, the superiority of 19 or 32°C was lost, as preserved pig kidneys showed similar levels of tissue damage (both tubulardilatation, loss of brush border and endoluminal detachment) during preservation, and at 24 h the 4°C kidneys displayed a trend towards less damage. In addition, the tissular Monocyte/Macrophage infiltration was increased in the 19°C and more in the 32°C temperature conservation as compared to 4°C storage.[br/]Conclusion: Our study shows that although a higher preservation temperature is preferable for cell survival and function, whole organ testing demonstrates that conceptual work needs to be performed to harness the potential of sub-normothermia

Dynamic transcriptomic analysis of ischemic injury in a porcine pre-clinical model mimicking donors deceased after circulatory death

Due to organ shortage, clinicians are prone to consider alternative type of organ donors among them donors deceased after circulatory death (DCD). However, especially using these organs which are more prone to graft dysfunction, there is a need to better understand mechanistic events ocuring during ischemia phase and leading to ischemia/reperfusion injuries (IRI). The aim of this study is to provide a dynamic transcriptomic analysis of preclinical porcine model kidneys subjected to ischemic stress mimicking DCD donor. We compared cortex and corticomedullary junction (CMJ) tissues from porcine kidneys submitted to 60 min warm ischemia (WI) followed by 0, 6 or 24 hours of cold storage in University of Wisconsin solution versus control non-ischemic kidneys (n=5 per group). 29 cortex genes and 113 CMJ genes were significantly up or down-regulated after WI versus healthy kidneys, and up to 400 genes were regulated after WI followed by 6 or 24 hours of cold storage (p < 0.05). Functionnal enrichment analysis (home selected gene kinetic classification, Gene-ontology-biological processes and Gene-ontology-molecular-function) revealed relevant genes implication during WI and cold storage. We uncovered targets which we will further validate as biomarkers and new therapeutic targets to optimize graft kidney quality before transplantation and improve whole transplantation outcome

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Renal auto-transplantation promotes cortical microvascular network remodeling in a preclinical porcine model

International audienceThe vascular network is a major target of ischemia-reperfusion, but has been poorly investigated in renal transplantation. The aim of this study was to characterize the remodeling of the renal vascular network that follows ischemia-reperfusion along with the most highly affected cortex section in a preclinical renal transplantation model. There were two experimental groups. The first was a grafted kidney group consisting of large white pigs for which the left kidney was harvested, cold flushed, preserved for 24 h in the University of Wisconsin’s preservation solution, and then auto-transplanted (n = 5); the right kidney was removed to mimic the situation of human kidney transplantation. The second group (uni-nephrectomized kidney group) consisted of animals that underwent only right nephrectomy, but not left renal transplantation (n = 5). Three months after autotransplantation, the kidneys were studied by X-ray microcomputed tomography. Vessel morphology and density and tortuosity of the network were analyzed using a 3D image analysis method. Cortical blood flow was determined by laser doppler analysis and renal function and tissue injury assessed by plasma creatinine levels and histological analysis. Renal ischemia-reperfusion led to decreased vascular segment volume associated with fewer vessels of less than 30 μm, particularly in the inner cortex:0.79 ± 0.54% in grafted kidneys vs. 7.06 ± 1.44% in uni-nephrectomized kidneys, p < 0.05. Vessels showed higher connectivity throughout the cortex (the arborescence factor of the whole cortex was less in grafted than uni-nephrectomized kidneys 0.90 ± 0.04 vs. 1.07 ± 0.05, p < 0.05, with an increase in the number of bifurcations). Furthermore, cortical blood flow decreased early in kidney grafts and remained low three months after auto-transplantation. The decrease in microvasculature correlated with a deterioration of renal function, proteinuria, and tubular dysfunction, and was associated with the development of fibrous tissue. This work provides new evidence concerning the impact of ischemia-reperfusion injuries on the spectrum of renal vascular diseases and could potentially guide future therapy to preserve microvessels in transplantation ischemia-reperfusion injury

Defining the optimal duration for normothermic regional perfusion in the kidney donor: A porcine preclinical study

International audienceKidneys from donation after circulatory death (DCD) are highly sensitive to ischemia‐reperfusion injury and thus require careful reconditioning, such as normothermic regional perfusion (NRP). However, the optimal NRP protocol remains to be characterized. NRP was modeled in a DCD porcine model (30 minutes of cardiac arrest) for 2, 4, or 6 hours compared to a control group (No‐NRP); kidneys were machine‐preserved and allotransplanted. NRP appeared to permit recovery from warm ischemia, possibly due to an increased expression of HIF1α‐dependent survival pathway. At 2 hours, blood levels of ischemic injury biomarkers increased: creatinine, lactate/pyruvate ratio, LDH, AST, NGAL, KIM‐1, CD40 ligand, and soluble‐tissue‐factor. All these markers then decreased with time; however, AST, NGAL, and KIM‐1 increased again at 6 hours. Hemoglobin and platelets decreased at 6 hours, after which the procedure became difficult to maintain. Regarding inflammation, active tissue‐factor, cleaved PAR‐2 and MCP‐1 increased by 4‐6 hours, but not TNF‐α and iNOS. Compared to No‐NRP, NRP kidneys showed lower resistance during hypothermic machine perfusion (HMP), likely associated with pe‐NRP eNOS activation. Kidneys transplanted after 4 and 6 hours of NRP showed better function and outcome, compared to No‐NRP. In conclusion, our results confirm the mechanistic benefits of NRP and highlight 4 hours as its optimal duration, after which injury markers appear