PARP‐1 over‐activation results in cell death via excessive PAR generation in different cell types, including neurons following brain ischemia. Glycolysis, mitochondrial function, and redox balance are key cellular processes altered in brain ischemia. Studies show that PAR generated after PARP‐1 over‐activation can bind hexokinase‐1 (HK‐1) and result in glycolytic defects and subsequent mitochondrial dysfunction. HK‐1 is the neuronal hexokinase and catalyzes the first reaction of glycolysis, converting glucose to glucose‐6‐phosphate (G6P), a common substrate for glycolysis, and the pentose phosphate pathway (PPP). PPP is critical in maintaining NADPH and GSH levels via G6P dehydrogenase activity. Therefore, defects in HK‐1 will not only decrease cellular bioenergetics but will also cause redox imbalance due to the depletion of GSH. In brain ischemia, whether PAR‐mediated inhibition of HK‐1 results in bioenergetics defects and redox imbalance is not known. We used oxygen–glucose deprivation (OGD) in mouse cortical neurons to mimic brain ischemia in neuronal cultures and observed that PARP‐1 activation via PAR formation alters glycolysis, mitochondrial function, and redox homeostasis in neurons. We used pharmacological inhibition of PARP‐1 and adenoviral‐mediated overexpression of wild‐type HK‐1 (wtHK‐1) and PAR‐binding mutant HK‐1 (pbmHK‐1). Our data show that PAR inhibition or overexpression of HK‐1 significantly improves glycolysis, mitochondrial function, redox homeostasis, and cell survival in mouse cortical neurons exposed to OGD. These results suggest that PAR binding and inhibition of HK‐1 during OGD drive bioenergetic defects in neurons due to inhibition of glycolysis and impairment of mitochondrial function.

This study investigated the therapeutic potential of the nuclear retinoid X receptor (RXR) in mitigating the progression of alpha-synucleinopathies (αSNPs), particularly in Parkinson’s disease (PD). PD-like pathology in mice was successfully induced through the co-delivery of AAV expressing human α-synuclein (αS) and αS preformed fibrils (PFFs) into the substantia nigra pars compacta (SNpc). Significant increases in Lewy body (LB)-like inclusions, loss of tyrosine hydroxylase-positive (TH+) neurons, and reductions in dopamine (DA) levels in the striatum were observed. Additionally, diminished levels of PPARα and NURR1—proteins essential for neuronal survival—along with elevated expression of IBA1 and GFAP, markers of microglial activation and astrocytic gliosis, respectively, are associated with the pathogenesis of Parkinson’s disease. AAV-mediated overexpression of human RXRα demonstrated preservation of TH+ neurons, prevention of DA decline, and attenuation of αS accumulation. Furthermore, RXR-treated PD brains showed a reduced number of GFAP+ and Iba1+ cells, decreased GFAP+ and IBA1+ immunoreactivity, and fewer and less widespread LB-like aggregates. RXR overexpression also enhanced the production of PPARα and NURR1. These findings suggest that RXRα upregulation promotes neuroprotection by mitigating αSNPs and chronic neuroinflammation, a major contributor to PD progression. This research underscores the therapeutic potential of targeting nuclear receptors, such as RXR, in neurodegenerative diseases like PD.

Excitotoxicity resulting from over‐stimulation of ionotropic glutamate receptors is a major cause of neuronal death in cerebral ischemic stroke. The over‐stimulated receptors exert their neurotoxic effects in part by over‐activation of calpains which induce neuronal death by catalyzing limited proteolysis of specific cellular proteins. Here, we report that in cultured cortical neurons and in vivo in a rat model of focal ischemic stroke, the tyrosine kinase Src is cleaved by calpains at a site in the N‐terminal unique domain. This generates a truncated Src fragment of ~52 kDa localised predominantly in the cytosol. A synthetic cell membrane‐permeable fusion peptide derived from the Src unique domain prevents calpains from cleaving Src in neurons and protects against excitotoxic neuronal death. To explore the role of the truncated Src fragment in neuronal death, we expressed a recombinant truncated Src fragment in cultured neurons, and demonstrated that expression of this fragment, which lacks the unique domain, was sufficient to induce neuronal death. Furthermore, inactivation of the pro‐survival kinase Akt is a key step in its neurotoxic signaling pathway. As Src maintains neuronal survival, our results implicate calpain cleavage as a key step of neuronal death in excitotoxicity, and suggest blockade of calpain cleavage of Src as a potential therapeutic strategy to minimize brain damage in ischemic stroke. Grant Funding Source : NHMRC Australia