Abstract

Spinal cord injury (SCI) triggers prolonged immune responses that contribute to neuronal damage, driven in part by chronic neuroinflammation. Persistent microglial activation, a hallmark of several central nervous system (CNS) pathologies, plays a significant role in this process. Recent literature suggests that controlled immune modulation can foster neuro-restoration. Bryostatin-1, a potent protein kinase C (PKC) activator, has demonstrated neuroprotective, synaptogenic, anti-inflammatory, and remyelinating effects in different animal models of traumatic and ischemic brain injury, and multiple sclerosis.
We propose that Bryostatin-1 may offer similar benefits in SCI by modulating microglial activation and promoting regeneration. Therefore, we examined the molecular and functional effect of Bryostatin-1 in immortalized BV-2 cells and primary murine microglia. Western Blot analyses revealed significant increases levels of NF-KB phosphorylation (pNF-KB), a downstream effector of PKC pathway, in Bryostatin-1 treated BV-2 cells. Immunocytochemistry confirmed increased nuclear localization of pNF-KB in both BV-2 cells and primary murine microglia. Moreover, the PKC dependent activity of Bryostatin-1 has been validated using the known PKC inhibitor Bis-III in a PKC activity assay. Microglial morphology and functionality revealed that Broystatin-1 treatment increased microglial cell area and enhanced phagocytic activity. Interestingly, gene expression and flow cytometry analysis indicated a shift toward a neuroregenerative phenotype upon Bryostatin-1 treatment, with reduced CD40 expression after lipopolysaccharide treatment in BV-2 cells and the absence of pro-inflammatory marker upregulation in primary microglia.
Overall, the effects of Bryostatin-1 on microglial signalling reveal a complex interplay of pathways. While NF-KB activation hints at pro-inflammatory responses, CD40 downregulation and lack of cytokine overexpression point to anti-inflammatory mechanisms. As a PKC activator, Bryostatin-1 holds promise for offering a therapeutic avenue for neuroregenerative medicine by modulating microglial responses.