PKC modulator bryostatin-1 therapeutically targets CNS innate immunity to attenuate neuroinflammation and promote remyelination [exvivo]

In multiple sclerosis (MS), microglia and macrophages within the central nervous system (CNS) play an important role in determining the balance between myelin repair and demyelination/neurodegeneration. Phagocytic and regenerative functions of these CNS innate immune cells support remyelination, whereas chronic and maladaptive inflammatory activation promotes lesion expansion and disability, particularly in the progressive forms of MS. No currently approved drugs convincingly target microglia and macrophages within the CNS, contributing to the critical lack of therapies promoting remyelination and slowing progression in MS. Here, we found that the protein kinase C (PKC)-modulating drug bryostatin-1 (bryo-1), a CNS-penetrant compound with an established human safety profile, produces a shift in microglia and CNS macrophage transcriptional programs from pro-inflammatory to regenerative phenotypes, both in vitro and in vivo. Treatment of microglia with bryo-1 stimulated scavenger pathways, phagocytosis, and secretion of factors that prevent the activation of neuroinflammatory reactive astrocytes while promoting neuroaxonal health and oligodendrocyte differentiation. In line with these findings, systemic treatment with bryo-1 augmented remyelination following a focal demyelinating injury in vivo. Our results demonstrate the potential of bryo-1 and possibly a wider class of PKC modulators as myelin regenerative and supportive agents in MS and other neurologic diseases through therapeutic targeting of microglia and CNS-associated macrophages. C57BL/6J Female mice were immunized with myelin peptide and pertussis toxin to induce EAE. Starting at day 19, mice were treated 3 times per week with vehicle or bryostatin 19 days after immunization. On day 35, myeloid cells were sorted from enzymatically dissociated CNS. Data are from two independent experiments. There are 3 replicates for each condition.

在多发性硬化症（multiple sclerosis, MS）中，中枢神经系统（central nervous system, CNS）内的小胶质细胞与巨噬细胞在调控髓鞘修复与脱髓鞘/神经退行性变之间的平衡过程中发挥关键作用。这类中枢神经系统固有免疫细胞的吞噬与再生功能可促进髓鞘再生，而慢性且失调的炎症激活则会推动病灶扩大与残疾进展，尤其在进展型多发性硬化症中更为显著。目前尚无获批药物能够切实靶向中枢神经系统内的小胶质细胞与巨噬细胞，这导致多发性硬化症领域亟需可促进髓鞘再生、延缓疾病进展的治疗手段却长期匮乏。本研究发现，蛋白激酶C（protein kinase C, PKC）调控药物 bryostatin-1（简称bryo-1）是一种可穿透中枢神经系统、且已明确人体安全性的化合物，其在体外与体内实验中均能使小胶质细胞和中枢神经系统巨噬细胞的转录程序从促炎表型转向再生表型。经bryo-1处理的小胶质细胞可激活清道夫通路、增强吞噬作用，并分泌能够抑制神经炎症性反应性星形胶质细胞活化的因子，同时促进神经轴突健康与少突胶质细胞分化。与上述实验结果一致，在体内局灶性脱髓鞘损伤模型中，经系统给予bryo-1可显著增强髓鞘再生能力。本研究结果证实，bryo-1乃至更广范围的蛋白激酶C调控剂，可通过靶向小胶质细胞与中枢神经系统相关巨噬细胞，成为多发性硬化症及其他神经系统疾病中的髓鞘再生与神经支持治疗药物。将C57BL/6J品系雌性小鼠经髓鞘肽与百日咳毒素免疫，以诱导实验性自身免疫性脑脊髓炎（experimental autoimmune encephalomyelitis, EAE）。自免疫后第19天起，每周对小鼠给予溶剂对照或bryostatin-1处理，持续19天。于免疫后第35天，从酶解分离的中枢神经系统组织中分选髓系细胞。本实验数据来自2次独立重复实验，每组实验条件均设置3次生物学重复。