A quantitative LC-MS/MS method for determination of thiazolidinedione mitoNEET ligand NL-1 in mouse serum suitable for pharmacokinetic studies

The Mitochondrial mitoNEET Ligand NL-1 Is Protective in a Murine Model of Transient Cerebral Ischemic Stroke

PURPOSE

Therapeutic strategies to treat ischemic stroke are limited due to the heterogeneity of cerebral ischemic injury and the mechanisms that contribute to the cell death. Since oxidative stress is one of the primary mechanisms that cause brain injury post-stroke, we hypothesized that therapeutic targets that modulate mitochondrial function could protect against reperfusion-injury after cerebral ischemia, with the focus here on a mitochondrial protein, mitoNEET, that modulates cellular bioenergetics.

METHOD

In this study, we evaluated the pharmacology of the mitoNEET ligand NL-1 in an in vivo therapeutic role for NL-1 in a C57Bl/6 murine model of ischemic stroke.

RESULTS

NL-1 decreased hydrogen peroxide production with an IC50 of 5.95 μM in neuronal cells (N2A). The in vivo activity of NL-1 was evaluated in a murine 1 h transient middle cerebral artery occlusion (t-MCAO) model of ischemic stroke. We found that mice treated with NL-1 (10 mg/kg, i.p.) at time of reperfusion and allowed to recover for 24 h showed a 43% reduction in infarct volume and 68% reduction in edema compared to sham-injured mice. Additionally, we found that when NL-1 was administered 15 min post-t-MCAO, the ischemia volume was reduced by 41%, and stroke-associated edema by 63%.

CONCLUSION

As support of our hypothesis, as expected, NL-1 failed to reduce stroke infarct in a permanent photothrombotic occlusion model of stroke. This report demonstrates the potential therapeutic benefits of using mitoNEET ligands like NL-1 as novel mitoceuticals for treating reperfusion-injury with cerebral stroke.

Nanoparticle formulation and in vitro efficacy testing of the mitoNEET ligand NL-1 for drug delivery in a brain endothelial model of ischemic reperfusion-injury

Ischemic reperfusion injury after a stroke is a leading cause of mortality and disability due to neuronal loss and tissue damage. Mitochondrial dysfunction plays a major role in the reperfusion-injury sequelae, and offers an attractive drug target. Mitochondrial derived reactive oxygen species (ROS) and resultant apoptotic cascade are among the primary mechanisms of neuronal death following ischemia and reperfusion injury. Here we optimized a nanoparticle formulation for the mitoNEET ligand NL-1, to target mitochondrial dysfunction post ischemic reperfusion (IR) injury. NL-1, a hydrophobic drug, was formulated using PLGA polymers with a particle size and entrapment efficiency of 123.9 ± 17.1 nm and 59.7 ± 10.1%, respectively. The formulation was characterized for physical state of NL-1, in vitro release, uptake and nanoparticle localization. A near complete uptake of nanoparticles was found to occur by three hours, with the process being energy-dependent and occurring via caveolar mediated endocytosis. The fluorescent nanoparticles were found to localize in the cytoplasm of the endothelial cells. An in vitro oxygen glucose deprivation (OGD) model to mimic IR was employed for in vitro efficacy testing in murine brain vascular endothelium cells (bEND.3 cells). Efficacy studies showed that both NL-1 and the nanoparticles loaded with NL-1 had a protective activity against peroxide generation, and displayed improved cellular viability, as seen via reduction in cellular apoptosis. Finally, PLGA nanoparticles were found to have a non-toxic profile in vitro, and were found to be safe for intravenous administration. This study lays the preliminary work for potential use of mitoNEET as a target and NL-1 as a therapeutic for the treatment of cerebral ischemia and reperfusion injury.

Bioenergetic restoration and neuroprotection after therapeutic targeting of mitoNEET: New mechanism of pioglitazone following traumatic brain injury

Mitochondrial dysfunction is a pivotal event in many neurodegenerative disease states including traumatic brain injury (TBI) and spinal cord injury (SCI). One possible mechanism driving mitochondrial dysfunction is glutamate excitotoxicity leading to Ca²⁺-overload in neuronal or glial mitochondria. Therapies that reduce calcium overload and enhance bioenergetics have been shown to improve neurological outcomes. Pioglitazone, an FDA approved compound, has shown neuroprotective properties following TBI and SCI, but the underlying mechanism(s) are unknown. We hypothesized that the interaction between pioglitazone and a novel mitochondrial protein called mitoNEET was the basis for neuroprotection following CNS injury. We discovered that mitoNEET is an important mediator of Ca²⁺-mediated mitochondrial dysfunction and show that binding mitoNEET with pioglitazone can prevent Ca²⁺-induced dysfunction. By utilizing wild-type (WT) and mitoNEET null mice, we show that pioglitazone mitigates mitochondrial dysfunction and provides neuroprotection in WT mice, though produces no restorative effects in mitoNEET null mice. We also show that NL-1, a novel mitoNEET ligand, is neuroprotective following TBI in both mice and rats. These results support the crucial role of mitoNEET for mitochondrial bioenergetics, its importance in the neuropathological sequelae of TBI and the necessity of mitoNEET for pioglitazone-mediated neuroprotection. Since mitochondrial dysfunction is a pathobiological complication seen in other diseases such as diabetes, motor neuron disease and cancer, targeting mitoNEET may provide a novel mitoceutical target and therapeutic intervention for diseases that expand beyond TBI.

The MitoNEET Ligand NL-1 Mediates Antileukemic Activity in Drug-Resistant B-Cell Acute Lymphoblastic Leukemia

Disease relapse in B-cell acute lymphoblastic leukemia (ALL), either due to development of acquired resistance after therapy or because of de novo resistance, remains a therapeutic challenge. In the present study, we have developed a cytarabine (Ara-C)-resistant REH cell line (REH/Ara-C) as a chemoresistance model. REH/Ara-C 1) was not crossresistant to vincristine or methotrexate; 2) showed a similar proliferation rate and cell surface marker expression as parental REH; 3) demonstrated decreased chemotaxis toward bone marrow stromal cells; and 4) expressed higher transcript levels of cytidine deaminase (CDA) and mitoNEET (CISD1) than the parental REH cell line. Based on these findings, we tested NL-1, a mitoNEET inhibitor, which induced a concentration-dependent decrease in cell viability with a comparable IC50 value in REH and REH/Ara-C. Furthermore, NL-1 decreased cell viability in six different ALL cell lines and showed inhibitory activity in a hemosphere assay. NL-1 also impaired the migratory ability of leukemic cells, irrespective of the chemoattractant used, in a chemotaxis assay. More importantly, NL-1 showed specific activity in inducing death in a drug-resistant population of leukemic cells within a coculture model that mimicked the acquired resistance and de novo resistance observed in the bone marrow of relapsed patients. Subsequent studies indicated that NL-1 mediates autophagy, and inhibition of autophagy partially decreased NL-1-induced tumor cell death. Finally, NL-1 showed antileukemic activity in an in vivo mouse ALL model. Taken together, our study demonstrates that mitoNEET has potential as a novel antileukemic drug target in treatment refractory or relapsed ALL.

Pioglitazone treatment following spinal cord injury maintains acute mitochondrial integrity and increases chronic tissue sparing and functional recovery

Pioglitazone is an FDA-approved PPAR-γ agonist drug used to treat diabetes, and it has demonstrated neuroprotective effects in multiple models of central nervous system (CNS) injury. Acute treatment after spinal cord injury (SCI) in rats is reported to suppress neuroinflammation, rescue injured tissues, and improve locomotor recovery. In the current study, we additionally assessed the protective efficacy of pioglitazone treatment on acute mitochondrial respiration, as well as functional and anatomical recovery after contusion SCI in adult male C57BL/6 mice. Mice received either vehicle or pioglitazone (10mg/kg) at either 15min or 3h after injury (75kdyn at T9) followed by a booster at 24h post-injury. At 25h, mitochondria were isolated from spinal cord segments centered on the injury epicenters and assessed for their respiratory capacity. Results showed significantly compromised mitochondrial respiration 25h following SCI, but pioglitazone treatment that was initiated either at 15min or 3h post-injury significantly maintained mitochondrial respiration rates near sham levels. A second cohort of injured mice received pioglitazone at 15min post injury, then once a day for 5days post-injury to assess locomotor recovery and tissue sparing over 4weeks. Compared to vehicle, pioglitazone treatment resulted in significantly greater recovery of hind-limb function over time, as determined by serial locomotor BMS assessments and both terminal BMS subscores and gridwalk performance. Such improvements correlated with significantly increased grey and white matter tissue sparing, although pioglitazone treatment did not abrogate long-term injury-induced inflammatory microglia/macrophage responses. In sum, pioglitazone significantly increased functional neuroprotection that was associated with remarkable maintenance of acute mitochondrial bioenergetics after traumatic SCI. This sets the stage for dose-response and delayed administration studies to maximize pioglitazone's efficacy for SCI while elucidating the precise role that mitochondria play in governing its neuroprotection; the ultimate goal to develop novel therapeutics that specifically target mitochondrial dysfunction.

Novel thiazolidinedione mitoNEET ligand-1 acutely improves cardiac stem cell survival under oxidative stress

Ischemic heart disease (IHD) is a leading cause of death worldwide, and regenerative therapies through exogenous stem cell delivery hold promising potential. One limitation of such therapies is the vulnerability of stem cells to the oxidative environment associated with IHD. Accordingly, manipulation of stem cell mitochondrial metabolism may be an effective strategy to improve survival of stem cells under oxidative stress. MitoNEET is a redox-sensitive, mitochondrial target of thiazolidinediones (TZDs), and influences cellular oxidative capacity. Pharmacological targeting of mitoNEET with the novel TZD, mitoNEET Ligand-1 (NL-1), improved cardiac stem cell (CSC) survival compared to vehicle (0.1% DMSO) during in vitro oxidative stress (H2O2). 10 μM NL-1 also reduced CSC maximal oxygen consumption rate (OCR) compared to vehicle. Following treatment with dexamethasone, CSC maximal OCR increased compared to baseline, but NL-1 prevented this effect. Smooth muscle α-actin expression increased significantly in CSC following differentiation compared to baseline, irrespective of NL-1 treatment. When CSCs were treated with glucose oxidase for 7 days, NL-1 significantly improved cell survival compared to vehicle (trypan blue exclusion). NL-1 treatment of cells isolated from mitoNEET knockout mice did not increase CSC survival with H2O2 treatment. Following intramyocardial injection of CSCs into Zucker obese fatty rats, NL-1 significantly improved CSC survival after 24 h, but not after 10 days. These data suggest that pharmacological targeting of mitoNEET with TZDs may acutely protect stem cells following transplantation into an oxidative environment. Continued treatment or manipulation of mitochondrial metabolism may be necessary to produce long-term benefits related to stem cell therapies.