Myelin loss limits neurological recovery and myelin regeneration and is critical for restoration of function. We recently discovered that global knockout of the thrombin receptor, also known as Protease Activated Receptor 1 (PAR1), accelerates myelin development. Here we demonstrate that knocking out PAR1 also promotes myelin regeneration. Outcomes in two unique models of myelin injury and repair, that is lysolecithin or cuprizone-mediated demyelination, showed that PAR1 knockout in male mice improves replenishment of myelinating cells and remyelinated nerve fibers and slows early axon damage. Improvements in myelin regeneration in PAR1 knockout mice occurred in tandem with a skewing of reactive astrocyte signatures toward a prorepair phenotype. In cell culture, the promyelinating effects of PAR1 loss of function are consistent with possible direct effects on the myelinating potential of oligodendrocyte progenitor cells (OPCs), in addition to OPC-indirect effects involving enhanced astrocyte expression of promyelinating factors, such as BDNF. These findings highlight previously unrecognized roles of PAR1 in myelin regeneration, including integrated actions across the oligodendrocyte and astroglial compartments that are at least partially mechanistically linked to the powerful BDNF-TrkB neurotrophic signaling system. Altogether, findings suggest PAR1 may be a therapeutically tractable target for demyelinating disorders of the CNS.

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A diet high in fat and sucrose (HFHS), the so-called Western diet promotes metabolic syndrome, a significant comorbidity for individuals with spinal cord injury (SCI). Here we demonstrate that the spinal cord of mice consuming HFHS expresses reduced insulin-like growth factor 1 (IGF-1) and its receptor and shows impaired tricarboxylic acid cycle function, reductions in PLP and increases in astrogliosis, all prior to SCI. After SCI, Western diet impaired sensorimotor and bladder recovery, increased microgliosis, exacerbated oligodendrocyte loss and reduced axon sprouting. Direct and indirect neural injury mechanisms are suggested since HFHS culture conditions drove parallel injury responses directly and indirectly after culture with conditioned media from HFHS-treated astrocytes. In each case, injury mechanisms included reductions in IGF-1R, SIRT1 and PGC-1α and were prevented by metformin. Results highlight the potential for a Western diet to evoke signs of neural insulin resistance and injury and metformin as a strategy to improve mechanisms of neural neuroprotection and repair.

Excessive activation of the thrombin receptor, protease activated receptor 1 (PAR1) is implicated in diverse neuropathologies from neurodegenerative conditions to neurotrauma. PAR1 knockout mice show improved outcomes after experimental spinal cord injury (SCI), however information regarding the underpinning cellular and molecular mechanisms is lacking. Here we demonstrate that genetic blockade of PAR1 in female mice results in improvements in sensorimotor co‐ordination after thoracic spinal cord lateral compression injury. We document improved neuron preservation with increases in Synapsin‐1 presynaptic proteins and GAP43, a growth cone marker, after a 30 days recovery period. These improvements were coupled to signs of enhanced myelin resiliency and repair, including increases in the number of mature oligodendrocytes, their progenitors and the abundance of myelin basic protein. These significant increases in substrates for neural recovery were accompanied by reduced astrocyte (Serp1) and microglial/monocyte (CD68 and iNOS) pro‐inflammatory markers, with coordinate increases in astrocyte (S100A10 and Emp1) and microglial (Arg1) markers reflective of pro‐repair activities. Complementary astrocyte‐neuron co‐culture bioassays suggest astrocytes with PAR1 loss‐of‐function promote both neuron survival and neurite outgrowth. Additionally, the pro‐neurite outgrowth effects of switching off astrocyte PAR1 were blocked by inhibiting TrkB, the high affinity receptor for brain derived neurotrophic factor. Altogether, these studies demonstrate unique modulatory roles for PAR1 in regulating glial‐neuron interactions, including the capacity for neurotrophic factor signaling, and underscore its position at neurobiological intersections critical for the response of the CNS to injury and the capacity for regenerative repair and restoration of function.

We identified a neuroprotective single fraction among 62 ones of hexane extract from Uncaria sinensis (JGH43IA) and investigated its effects and mechanisms in primary cortical neurons. Pretreatment with JGH43IA showed a significantly increase cell viability in a dose-dependent manner with a decrease in the lactate dehydrogenase release. When we performed morphological assay and flow cytometry to determination of the type of cell death, pretreatment with JGH43IA showed a significant reduction of glutamate-induced apoptotic cell death. Then we explored the downstream signaling pathways of N-methyl-D-aspartate receptor (NMDAR) with calpain activation to elucidate possible pathways of neuroprotection by JGH43IA. Pretreatment with JGH43IA exhibited a significant attenuation of NMDAR GluN2B subunit activation and a decrease in active form of calpain 1 leading to subsequent cleavage of striatal-enriched protein tyrosine phosphatase (STEP). In addition, pretreatment with JGH43IA showed a marked increase of cAMP responsive element binding protein. These results suggest that JGH43IA may have neuroprotective effects through down-regulation of NMDAR GluN2B subunit and calpain 1 activation, and subsequent alleviation of STEP cleavage. This single fraction from U. sinensis might be a useful therapeutic agent for brain disorder associated with glutamate injury.