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Thermal Preconditioning During <em>Ex-vivo</em> Lung Perfusion for the Rehabilitation of Damaged Lung Grafts before Transplantation

Ex-vivo lung perfusion (EVLP) has emerged as a breakthrough in lung transplantation, enabling both functional assessment of donor lungs and therapeutic ...

Lausanne University

The mineralocorticoid hormone aldosterone plays a crucial role in the control of Na and K balance, blood volume, and arterial blood pressure, by acting in the aldosterone-sensitive distal nephron (ASDN) and stimulating a complex transcriptional, translational, and cellular program. Because the complexity of the aldosterone response is still not fully appreciated, we aimed at identifying new elements in this pathway. Here, we demonstrate that the expression of the proto-oncogene PIM3 (Proviral Integration Site of Moloney Murine Leukemia Virus 3), a serine/threonine kinase belonging to the calcium/calmodulin-regulated group of kinases, is stimulated by aldosterone in vitro (mCCD cells), ex vivo (mouse kidney slices), and in vivo in mice. Characterizing a germline Pim3 mouse model, we found that these mice have an upregulated Renin-Angiotensin-Aldosterone System (RAAS), with high circulating aldosterone and plasma renin activity levels on both standard or Na -deficient diet. Surprisingly, we did not observe any obvious salt-losing phenotype in Pim3 KO mice as shown by normal blood pressure, plasma and urinary electrolytes, as well as unchanged expression levels of the major Na transport proteins. These observations suggest that the potential effects of the loss of the Pim3 gene are physiologically compensated. Indeed, the 2 other family members of the PIM kinase family, PIM1 and PIM2 are upregulated in the kidney of Pim3 mice, and may therefore be involved in such compensation. In conclusion, our data demonstrate that the PIM3 kinase is a novel aldosterone-induced protein, but its precise role in aldosterone-dependent renal homeostasis remains to be determined.

The serine-threonine kinase PIM3 is an aldosterone-regulated protein in the distal nephron.

Lung transplantation (LTx) is associated with sterile inflammation, possibly related to the release of damage associated molecular patterns (DAMPs) by injured allograft cells. We have measured cellular damage and the release of DAMPs and cytokines in an experimental model of LTx after cold or warm ischemia and examined the effect of pretreatment with ex-vivo lung perfusion (EVLP).

Effects of cold or warm ischemia and ex-vivo lung perfusion on the release of damage associated molecular patterns and inflammatory cytokines in experimental lung transplantation.

Ex vivo lung perfusion (EVLP) may serve as a platform for the pharmacologic repair of lung grafts before transplantation (LTx). We hypothesized that EVLP could also permit nonpharmacologic repair through the induction of a heat shock response, which confers stress adaptation via the expression of heat shock proteins (HSPs). Therefore, we evaluated whether transient heat application during EVLP (thermal preconditioning [TP]) might recondition damaged lungs before LTx. TP was performed during EVLP (3 hours) of rat lungs damaged by warm ischemia by transiently heating (30 minutes, 41.5 °C) the EVLP perfusate, followed by LTx (2 hours) reperfusion. We also assessed the TP (30 minutes, 42 °C) during EVLP (4 hours) of swine lungs damaged by prolonged cold ischemia. In rat lungs, TP induced HSP expression, reduced nuclear factor κB and inflammasome activity, oxidative stress, epithelial injury, inflammatory cytokines, necroptotic death signaling, and the expression of genes involved in innate immune and cell death pathways. After LTx, heated lungs displayed reduced inflammation, edema, histologic damage, improved compliance, and unchanged oxygenation. In pig lungs, TP induced HSP expression, reduced oxidative stress, inflammation, epithelial damage, vascular resistance, and ameliorated compliance. Collectively, these data indicate that transient heat application during EVLP promotes significant reconditioning of damaged lungs and improves their outcomes after transplantation.

Therapeutic reconditioning of damaged lungs by transient heat stress during ex vivo lung perfusion.

Blood pressure (BP) follows a circadian pattern that rises during the active phase of the day (morning surge) and decreases during the inactive (night dipping) phase of the day. The morning surge coincides with increased circulating glucocorticoids and aldosterone, ligands for glucocorticoid receptors and mineralocorticoid receptors, respectively. Serum- and glucocorticoid-induced kinase 1 (), a clock-controlled and glucocorticoid receptor- and mineralocorticoid receptor-induced gene, plays a role in BP regulation in human and animal models. However, the role of  in BP circadian regulation has not yet been demonstrated. Using telemetry, we analyzed BP in the inducible renal tubule-specific  model under basal K diet (1% K) and high-K diet (HKD; 5% K). Our data revealed that, under basal conditions, renal  plays a minor role in BP regulation; however, after 1 wk of HKD,  mice exhibited significant defects in diastolic BP (DBP), including a blunted surge, a decreased amplitude, and reduced day/night differences. After prolonged HKD (7 wk),  mice had lower BP than control mice and exhibited reduced DBP amplitude, together with decreased DBP day/night differences and midline estimating statistic of rhythm (MESOR). Interestingly, renal SGK1 deletion increased pulse pressure, likely secondary to an increase in circulating aldosterone. Taken together, our data suggest that ) the kidney plays a significant role in setting the BP circadian rhythm; ) renal tubule  mediates the BP surge and, thus, the day/night BP difference; ) long-term renal  deletion results in lower BP in mutant compared with control mice; and ) renal  indirectly regulates pulse pressure due to compensatory alterations in aldosterone levels. Dysregulation of blood pressure (BP) circadian rhythm is associated with metabolic, cardiovascular, and kidney diseases. Our study provides experimental evidence demonstrating, for the first time, that renal tubule serum- and glucocorticoid-induced kinase 1 () plays an essential role in inducing the BP surge. Inhibitors and activators of SGK1 signaling are parts of several therapeutic strategies. Our findings highlight the importance of the drug intake timing to be in phase with  function to avoid dysregulation of BP circadian rhythm.

Renal tubular SGK1 is required to achieve blood pressure surge and circadian rhythm.

The pulmonary endothelium is the primary target of lung ischemia-reperfusion injury leading to primary graft dysfunction after lung transplantation. We hypothesized that treating damaged rat lungs by a transient heat stress during ex-vivo lung perfusion (EVLP) to elicit a pulmonary heat shock response could protect the endothelium from severe reperfusion injury.

Article	Year
The serine-threonine kinase PIM3 is an aldosterone-regulated protein in the distal nephron. Physiological reports\| PubMed ID: 31397090	2019
Effects of cold or warm ischemia and ex-vivo lung perfusion on the release of damage associated molecular patterns and inflammatory cytokines in experimental lung transplantation. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation\| PubMed ID: 34193360	2021
Therapeutic reconditioning of damaged lungs by transient heat stress during ex vivo lung perfusion. American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons\| PubMed ID: 37217006	2023
Renal tubular SGK1 is required to achieve blood pressure surge and circadian rhythm. American journal of physiology. Renal physiology\| PubMed ID: 37676758	2023
Transient heat stress protects from severe endothelial damage and dysfunction during prolonged experimental ex-vivo lung perfusion. Frontiers in immunology\| PubMed ID: 38807604	2024

Anne Debonneville

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