L-3-n-Butylphthalide Protects HSPB8 K141N Mutation-Induced Oxidative Stress by Modulating the Mitochondrial Apoptotic and Nrf2 Pathways

Abstract

Charcot–Marie–Tooth disease (CMT), also known as hereditary motor and sensory neuropathy, is the most common inherited peripheral nerve disorder. Missense mutations, such as K141N, in the small heat shock protein HSPB8 are known to cause distal hereditary motor neuropathy 2A (dHMN2A) or Charcot-Marie-Tooth neuropathy type 2L (CMT2L). However, of critical clinical significance, very few specific therapies for this disease exist. In the present study, we investigated the impact of mutant K141N HSPB8 on mitochondrial distribution and function in a cellular model of CMT2L. Our results indicate that K141N HSPB8 induced mitochondrial aggregation and caused increased oxidative stress injury. As an extraction from Chinese celery Apium graveolens Linn seeds, L-3-n-Butylphthalide (NBP), has been reported to exert many neuroprotective effects, we interrogated whether NBP could elicit a protective effect on the cell injury typically caused by HSPB8 K141N mutations. We found NBP could reverse the pathological processes induced by HSPB8 K141N mutation via an antioxidant effect, modulation of the Bax/Bcl-2 mitochondrial apoptotic and Nrf2 pathways. We propose a novel function of HSPB8, highlighting the consequence of the K141N pathogenic mutation. Furthermore, we suggest NBP may have promising therapeutic potential in the treatment of CMT2L.

HSPB8 and BAG3 cooperate to promote spatial sequestration of ubiquitinated proteins and coordinate the cellular adaptive response to proteasome insufficiency

“…Nonetheless, our findings suggest that deregulation of the HSPB8-BAG3-p62 axis could disable an important stress-response pathway, of relevance for human diseases associated with mutations of BAG3 or HSPB8. In keeping with a role for HSPB8 in Nrf2 regulation, the disease HSPB8 (K141N) mutation causes oxidative stress injury, an effect that correlates with a reduction of Nrf2 proteins level (80).…”

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results

“…When expressed in cultured cells, mutant HSPB8 constructs have been reported to exhibit varying degrees of cytotoxicity [337,396,435,446,447]. Irobi and colleagues reported cytotoxic effects of p.K141N and p.K141E in the N2a neuronal cell line [435] and in primary motoneurons, where transduced cells showed neurite degeneration [446].…”

“…Neurotoxic effects are supported by the decreased number and morphological abnormalities of sensory neurons in patient skin biopsies [448]. The cytotoxicity of mutant HSPB8 has been suggested to depend on its aggregation propensity, which was observed for p.K141E and p.K141N in several in cell models [20,396,435,447,448], including primary patient fibroblasts [448], as well as in vivo in HSPB8 p.K141N-expressing mouse models [396,443]. However, the relationship of aggregation with cytotoxicity is not entirely clear.…”

“…Several lines of evidence suggest that one of the downstream pathways mediating the pathogenic effects of HSPB8 mutations is mitochondrial dysfunction, which can be due to loss of protective or stimulatory functions or toxicity of the mutant proteins, or perhaps both. In addition to the fly models discussed above, alterations in mitochondrial function have been observed in patient fibroblasts [448], SH-SY5Y cells transfected with HSPB8 p.K141N [447], as well as in hearts of p.K141N-overexpressing mice [396]. Sanbe and colleagues also noted an increased mitochondrial localization of HSPB8 p.K141N in cardiomyocytes and transgenic hearts, and-similarly to CRYAB p.R120G-increased interaction with VDAC, although the functional significance of these changes is unclear [396].…”

Oxidative Stress, a Crossroad Between Rare Diseases and Neurodegeneration

“…Missense mutations, such as p.K141N, in the heat shock protein HSPB8 cause CMT2L. According to Yang et al [98], this mutation induced mitochondrial aggregation and caused increased oxidative stress injury in SH-SY5Y cells. L-3-n-butylphthalide (NBP), extracted from seeds of celery (Apium), was able to prevent mitochondrial aggregation and oxidative stress activating the Nrf2 pathway.…”