The 6-hydroxychromanol derivative SUL-109 ameliorates renal injury after deep hypothermia and rewarming in rats

Mitochondrial Targeting against Alzheimer's Disease: Lessons from Hibernation

Alzheimer's disease (AD) is the most common cause of dementia worldwide and yet remains without effective therapy. Amongst the many proposed causes of AD, the mitochondrial cascade hypothesis is gaining attention. Accumulating evidence shows that mitochondrial dysfunction is a driving force behind synaptic dysfunction and cognitive decline in AD patients. However, therapies targeting the mitochondria in AD have proven unsuccessful so far, and out-of-the-box options, such as hibernation-derived mitochondrial mechanisms, may provide valuable new insights. Hibernators uniquely and rapidly alternate between suppression and re-activation of the mitochondria while maintaining a sufficient energy supply and without acquiring ROS damage. Here, we briefly give an overview of mitochondrial dysfunction in AD, how it affects synaptic function, and why mitochondrial targeting in AD has remained unsuccessful so far. We then discuss mitochondria in hibernation and daily torpor in mice, covering current advancements in hibernation-derived mitochondrial targeting strategies. We conclude with new ideas on how hibernation-derived dual mitochondrial targeting of both the ATP and ROS pathways may boost mitochondrial health and induce local synaptic protein translation to increase synaptic function and plasticity. Further exploration of these mechanisms may provide more effective treatment options for AD in the future.

Inhibition of Ferroptosis Enables Safe Rewarming of HEK293 Cells following Cooling in University of Wisconsin Cold Storage Solution

The prolonged cooling of cells results in cell death, in which both apoptosis and ferroptosis have been implicated. Preservation solutions such as the University of Wisconsin Cold Storage Solution (UW) encompass approaches addressing both. The use of UW improves survival and thus extends preservation limits, yet it remains unclear how exactly organ preservation solutions exert their cold protection. Thus, we explored cooling effects on lipid peroxidation and adenosine triphosphate (ATP) levels and the actions of blockers of apoptosis and ferroptosis, and of compounds enhancing mitochondrial function. Cooling and rewarming experiments were performed in a cellular transplantation model using Human Embryonic Kidney (HEK) 293 cells. Cell viability was assessed by neutral red assay. Lipid peroxidation levels were measured by Western blot against 4-Hydroxy-Nonenal (4HNE) and the determination of Malondialdehyde (MDA). ATP was measured by luciferase assay. Cooling beyond 5 h in Dulbecco's Modified Eagle Medium (DMEM) induced complete cell death in HEK293, whereas cooling in UW preserved ~60% of the cells, with a gradual decline afterwards. Cooling-induced cell death was not precluded by inhibiting apoptosis. In contrast, the blocking of ferroptosis by Ferrostatin-1 or maintaining of mitochondrial function by the 6-chromanol SUL150 completely inhibited cell death both in DMEM- and UW-cooled cells. Cooling for 24 h in UW followed by rewarming for 15 min induced a ~50% increase in MDA, while concomitantly lowering ATP by >90%. Treatment with SUL150 of cooled and rewarmed HEK293 effectively precluded the increase in MDA and preserved normal ATP in both DMEM- and UW-cooled cells. Likewise, treatment with Ferrostatin-1 blocked the MDA increase and preserved the ATP of rewarmed UW HEK293 cells. Cooling-induced HEK293 cell death from hypothermia and/or rewarming was caused by ferroptosis rather than apoptosis. UW slowed down ferroptosis during hypothermia, but lipid peroxidation and ATP depletion rapidly ensued upon rewarming, ultimately resulting in complete cell death. Treatment throughout UW cooling with small-molecule Ferrostatin-1 or the 6-chromanol SUL150 effectively prevented ferroptosis, maintained ATP, and limited lipid peroxidation in UW-cooled cells. Counteracting ferroptosis during cooling in UW-based preservation solutions may provide a simple method to improve graft survival following cold static cooling.

The Novel Compound SUL-138 Counteracts Endothelial Cell and Kidney Dysfunction in Sepsis by Preserving Mitochondrial Function

Sepsis is defined as a dysregulated host response leading to organ dysfunction, which may ultimately result in the patient’s death. Mitochondrial dysfunction plays a key role in developing organ dysfunction in sepsis. In this study, we explored the efficacy of the novel mitochondrial protective compound, SUL-138, in sepsis models in HUVECs and mice. In LPS-challenged HUVECs, SUL-138 preserved mitochondrial membrane potential and oxygen consumption and limited mitochondrial oxidative stress, resulting in increased survival at 48 h. Further, SUL-138 dampened the LPS-induced expression of IL-1β, but not of NLRP3, and IL-18 in HUVECs. Sepsis in mice induced by cecal ligation and puncture (CLP) led to a lower mitochondrial membrane potential and increased levels of mitochondrial oxidative stress in the kidney, which SUL-138 limited. In addition, SUL-138 mitigated the CLP-induced increase in kidney dysfunction markers NGAL and urea. It dampened the rise in kidney expression of IL-6, IL-1β, and ICAM-1, but not TNF-α and E-selectin. Yet, SUL-138 limited the increase in plasma levels of IL-6 and TNF-α of CLP mice. These results demonstrate that SUL-138 supports mitochondrial function, resulting in a limitation of systemic inflammation and preservation of kidney function.

The hibernation-derived compound SUL-138 shifts the mitochondrial proteome towards fatty acid metabolism and prevents cognitive decline and amyloid plaque formation in an Alzheimer's disease mouse model

BACKGROUND

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide and remains without effective cure. Increasing evidence is supporting the mitochondrial cascade hypothesis, proposing that loss of mitochondrial fitness and subsequent ROS and ATP imbalance are important contributors to AD pathophysiology.

METHODS

Here, we tested the effects of SUL-138, a small hibernation-derived molecule that supports mitochondrial bioenergetics via complex I/IV activation, on molecular, physiological, behavioral, and pathological outcomes in APP/PS1 and wildtype mice.

RESULTS

SUL-138 treatment rescued long-term potentiation and hippocampal memory impairments and decreased beta-amyloid plaque load in APP/PS1 mice. This was paralleled by a partial rescue of dysregulated protein expression in APP/PS1 mice as assessed by mass spectrometry-based proteomics. In-depth analysis of protein expression revealed a prominent effect of SUL-138 in APP/PS1 mice on mitochondrial protein expression. SUL-138 increased the levels of proteins involved in fatty acid metabolism in both wildtype and APP/PS1 mice. Additionally, in APP/PS1 mice only, SUL-138 increased the levels of proteins involved in glycolysis and amino acid metabolism pathways, indicating that SUL-138 rescues mitochondrial impairments that are typically observed in AD.

CONCLUSION

Our study demonstrates a SUL-138-induced shift in metabolic input towards the electron transport chain in synaptic mitochondria, coinciding with increased synaptic plasticity and memory. In conclusion, targeting mitochondrial bioenergetics might provide a promising new way to treat cognitive impairments in AD and reduce disease progression.

Therapeutic effects of apocynin on ovarian ischemia-reperfusion induced lung injury

Ovarian ischemia-reperfusion (I-R) injury may damage remote organs, including the lungs. We investigated whether apocynin, a NADPH oxidase inhibitor, might protect against ovarian I-R induced apoptosis in the lungs of rats. Bilateral ovarian I-R was induced for 3 h, then apocynin was applied at two concentrations. Lung tissue was evaluated using spectrophotometric and immunohistochemical methods. We found that I-R increased total oxidant status (TOS), oxidative stress index (OSI) and myeloperoxidase (MPO) levels, and immunostaining of nuclear factor kappa-B (NF-κB), light chain 3B (LC3B), interleukin 1-beta (IL-1β), caspase-3 and tumor necrosis factor-alpha (TNF-α), but decreased superoxide dismutase (SOD) values. Apocynin application to I-R injured rats enhanced recovery of lung tissue oxidants and improved both histology and frequency of apoptosis.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

Cooling of Cells and Organs Confers Extensive DNA Strand Breaks Through Oxidative Stress and ATP Depletion

Cooling at 4°C is routinely used to lower metabolism and preserve cell and tissue integrity in laboratory and clinical settings, including organ transplantation. However, cooling and rewarming produce cell damage, attributed primarily to a burst of reactive oxygen species (ROS) upon rewarming. While DNA represents a highly vulnerable target of ROS, it is unknown whether cooling and/or rewarming produces DNA damage. Here, we show that cooling alone suffices to produce extensive DNA damage in cultured primary cells and cell lines, including double-strand breaks (DSBs), as shown by comet assay and pulsed-field gel electrophoresis. Cooling-induced DSB formation is time- and temperature-dependent and coincides with an excess production of ROS, rather than a decrease in ATP levels. Immunohistochemistry confirmed that DNA damage activates the DNA damage response marked by the formation of nuclear foci of proteins involved in DSB repair, γ-H2Ax, and 53BP1. Subsequent rewarming for 24 h fails to recover ATP levels and only marginally lowers DSB amounts and nuclear foci. Precluding ROS formation by dopamine and the hydroxychromanol, Sul-121, dose-dependently reduces DSBs. Finally, a standard clinical kidney transplant procedure, using cold static storage in UW preservation solution up to 24 h in porcine kidney, lowered ATP, increased ROS, and produced increasing amounts of DSBs with recruitment of 53BP1. Given that DNA repair is erroneous by nature, cooling-inflicted DNA damage may affect cell survival, proliferation, and genomic stability, significantly impacting cellular and organ function, with relevance in stem cell and transplantation procedures.

Towards prevention of ischemia-reperfusion kidney injury: Pre-clinical evaluation of 6-chromanol derivatives and the lead compound SUL-138✰

Acute kidney injury (AKI) is a global healthcare burden attributable to high mortality and staggering costs of dialysis. The underlying causes of AKI include hypothermia and rewarming (H/R), ischemia/reperfusion (I/R), mitochondrial dysfunction and reactive oxygen species production. Inspired by the mechanisms conferring organ protection in hibernating hamster, 6-chromanol derived compounds were developed to address the need of effective prevention and treatment of AKI. Here we report on the pre-clinical screening of 6-chromanol leads that confer protection during I/R to select compounds with favorable profiles for clinical testing in AKI. A library of 6-chromanols (n = 63) was screened in silico for pharmacochemical properties and druggability. Selected compounds (n = 15) were screened for the potency to protect HEK293 cells from H/R cell death and subjected to a panel of in vitro safety assays. Based on these parameters, SUL-138 was selected as the lead compound and was found to safeguard kidney function and decrease renal injury after I/R in rats. The compound was without cardiovascular or respiratory effects in vivo. SUL-138 pharmacokinetics of control animals (mouse, rat) and those undergoing I/R (rat) was identical, showing a two-phase elimination profile with terminal half-life of about 8 h. Collectively, our phenotype-based screening approach led to the identification of 3 candidates for pre-clinical studies (5%, 3/64). SUL-138 emerged from this small-scale library of 6-chromanols as a novel prophylactic for AKI. The presented efficacy and safety data provide a basis for future development and clinical testing. SECTION ASSIGNMENTS: : Drug discovery and translational medicine, renal, metabolism SIGNIFICANCE STATEMENT: : Based on in silico druggability parameters, a 63 compound 6-chromanol library was narrowed down to 15 compounds. These compounds were subjected to phenotypical screening of cell survival following hypothermia damage and hit compounds were identified. After subsequent assessment of in vivo efficacy, toxicity, pharmacokinetics, and cardiovascular and respiratory safety, SUL-138 emerged as a lead compound that prevented kidney injury after ischemia/reperfusion and demonstrated a favorable pharmacokinetic profile unaffected by renal ischemia.

The Effects of 6-Chromanol SUL-138 during Hypothermic Machine Perfusion on Porcine Deceased Donor Kidneys

Diminishing ischemia-reperfusion injury (IRI) by improving kidney preservation techniques offers great beneficial value for kidney transplant recipients. Mitochondria play an important role in the pathogenesis of IRI and are therefore interesting targets for pharmacological interventions. Hypothermic machine perfusion (HMP), as a preservation strategy, offers the possibility to provide mitochondrial–targeted therapies. This study focuses on the addition of a mitochondrial protective agent SUL—138 during HMP and assesses its effect on kidney function and injury during normothermic reperfusion. In this case, 30 min of warm ischemia was applied to porcine slaughterhouse kidneys before 24 h of non–oxygenated HMP with or without the addition of SUL—138. Functional assessment was performed by 4 h normothermic autologous blood reperfusion. No differences in renal function or perfusion parameters were found between both groups. ATP levels were lower after 30 min of warm ischemia in the SUL–138 group (n.s, p = 0.067) but restored significantly during 24 h of HMP in combination with SUL—138. Aspartate aminotransferase (ASAT) levels were significantly lower for the SUL—138 group. SUL—138 does not influence renal function in this model. Restoration of ATP levels during 24 h of HMP with the addition of SUL in combination with lower ASAT levels could be an indication of improved mitochondrial function.

SUL-151 Decreases Airway Neutrophilia as a Prophylactic and Therapeutic Treatment in Mice after Cigarette Smoke Exposure

Chronic obstructive pulmonary disease (COPD) caused by cigarette smoke (CS) is featured by oxidative stress and chronic inflammation. Due to the poor efficacy of standard glucocorticoid therapy, new treatments are required. Here, we investigated whether the novel compound SUL-151 with mitoprotective properties can be used as a prophylactic and therapeutic treatment in a murine CS-induced inflammation model. SUL-151 (4 mg/kg), budesonide (500 μg/kg), or vehicle were administered via oropharyngeal instillation in this prophylactic and therapeutic treatment setting. The number of immune cells was determined in the bronchoalveolar lavage fluid (BALF). Oxidative stress response, mitochondrial adenosine triphosphate (ATP) production, and mitophagy-related proteins were measured in lung homogenates. SUL-151 significantly decreased more than 70% and 50% of CS-induced neutrophils in BALF after prophylactic and therapeutic administration, while budesonide showed no significant reduction in neutrophils. Moreover, SUL-151 prevented the CS-induced decrease in ATP and mitochondrial mtDNA and an increase in putative protein kinase 1 expression in the lung homogenates. The concentration of SUL-151 was significantly correlated with malondialdehyde level and radical scavenging activity in the lungs. SUL-151 inhibited the increased pulmonary inflammation and mitochondrial dysfunction in this CS-induced inflammation model, which implied that SUL-151 might be a promising candidate for COPD treatment.

Nitric Oxide-cGMP Signaling in Hypertension: Current and Future Options for Pharmacotherapy

For the treatment of systemic hypertension, pharmacological intervention in nitric oxide-cyclic guanosine monophosphate signaling is a well-explored but unexploited option. In this review, we present the identified drug targets, including oxidases, mitochondria, soluble guanylyl cyclase, phosphodiesterase 1 and 5, and protein kinase G, important compounds that modulate them, and the current status of (pre)clinical development. The mode of action of these compounds is discussed, and based upon this, the clinical opportunities. We conclude that drugs that directly target the enzymes of the nitric oxide-cyclic guanosine monophosphate cascade are currently the most promising compounds, but that none of these compounds is under investigation as a treatment option for systemic hypertension.

Hibernator-Derived Cells Show Superior Protection and Survival in Hypothermia Compared to Non-Hibernator Cells

Mitochondrial failure is recognized to play an important role in a variety of diseases. We previously showed hibernating species to have cell-autonomous protective mechanisms to resist cellular stress and sustain mitochondrial function. Here, we set out to detail these mitochondrial features of hibernators. We compared two hibernator-derived cell lines (HaK and DDT1MF2) with two non-hibernating cell lines (HEK293 and NRK) during hypothermia (4 °C) and rewarming (37 °C). Although all cell lines showed a strong decrease in oxygen consumption upon cooling, hibernator cells maintained functional mitochondria during hypothermia, without mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential decline or decreased adenosine triphosphate (ATP) levels, which were all observed in both non-hibernator cell lines. In addition, hibernator cells survived hypothermia in the absence of extracellular energy sources, suggesting their use of an endogenous substrate to maintain ATP levels. Moreover, hibernator-derived cells did not accumulate reactive oxygen species (ROS) damage and showed normal cell viability even after 48 h of cold-exposure. In contrast, non-hibernator cells accumulated ROS and showed extensive cell death through ferroptosis. Understanding the mechanisms that hibernators use to sustain mitochondrial activity and counteract damage in hypothermic circumstances may help to define novel preservation techniques with relevance to a variety of fields, such as organ transplantation and cardiac arrest.

SUL-109 Protects Hematopoietic Stem Cells from Apoptosis Induced by Short-Term Hypothermic Preservation and Maintains Their Engraftment Potential

The newly developed 6-hydroxychromanol derivate SUL-109 was shown to provide protection during hypothermic storage of several cell lines, but has not been evaluated in hematopoietic stem cells (HSCs). Hypothermic preservation of HSCs would be preferred over short-term cryopreservation to prevent cell loss during freezing/thawing and would be particularly useful for short-term storage, such as during conditioning of patients or transport of HSC transplants. Here we cultured human CD34⁺ umbilical cord blood (UCB) cells and lineage-depleted (Lin^-) Balb/c bone marrow (BM) cells for up to 7 days in serum-free HSC expansion medium with hematopoietic growth factors. SUL-109-containing cultures were stored at 4°C for 3 to 14 days. The UCB cells were tested for viability, cell cycle, and reactive oxygen species (ROS). DMSO-cryopreserved Lin^- BM cells or Lin^- BM cells maintained for 14 days at 4°C were transplanted into RAG2^-/- Balb/c mice and engraftment was followed for 6 months. The addition of SUL-109 during the hypothermic storage of expanded CD34⁺ UCB cells provided a significant improvement in cell survival of the immature CD34⁺/CD38^- fraction after 7 days of hypothermic storage through scavenging of hypothermia-induced ROS and was able to preserve the multilineage capacity of human CD34⁺ UCB cells for up to 14 days of cold storage. In addition, SUL-109 protected murine BM Lin^- cells from 14 days of hypothermic preservation and maintained their engraftment potential after transplantation in immune-deficient RAG2^-/- mice. Our data indicate that SUL-109 is a promising novel chemical for use as a protective agent during cold storage of human and murine HSCs to prevent hypothermia-induced apoptosis and promote cell viability.

The (R)-enantiomer of the 6-chromanol derivate SUL-121 improves renal graft perfusion via antagonism of the α1-adrenoceptor

SUL-compounds are protectants from cold-induced ischemia and mitochondrial dysfunction. We discovered that adding SUL-121 to renal grafts during warm machine reperfusion elicits a rapid improvement in perfusion parameters. Therefore, we investigate the molecular mechanisms of action in porcine intrarenal arteries (PIRA). Porcine kidneys were stored on ice overnight and perfusion parameters were recorded during treatment with SUL-compounds. Agonist-induced vasoconstriction was measured in isolated PIRA after pre-incubation with SUL-compounds. Receptor binding and calcium transients were assessed in α₁-adrenoceptor (α₁-AR) transgenic CHO cells. Molecular docking simulation was performed using Schrödinger software. Renal pressure during warm reperfusion was reduced by SUL-121 (−11.9 ± 2.50 mmHg) and its (R)-enantiomer SUL-150 (−13.2 ± 2.77 mmHg), but not by the (S)-enantiomer SUL-151 (−1.33 ± 1.26 mmHg). Additionally, SUL-150 improved renal flow (16.21 ± 1.71 mL/min to 21.94 ± 1.38 mL/min). SUL-121 and SUL-150 competitively inhibited PIRA contraction responses to phenylephrine, while other 6-chromanols were without effect. SUL-150 similarly inhibited phenylephrine-induced calcium influx and effectively displaced [7-Methoxy-³H]-prazosin in CHO cells. Docking simulation to the α₁-AR revealed shared binding characteristics between prazosin and SUL-150. SUL-150 is a novel α₁-AR antagonist with the potential to improve renal graft perfusion after hypothermic storage. In combination with previously reported protective effects, SUL-150 emerges as a novel protectant in organ transplantation.