Mitophagy suppresses motor neuron necroptotic mitochondrial damage and alleviates necroptosis that converges to SARM1 in acrylamide-induced dying-back neuropathy

Acrylamide (ACR), a common industrial ingredient that is also found in many foodstuffs, induces dying-back neuropathy in humans and animals. However, the mechanisms remain poorly understood. Sterile alpha and toll/interleukin 1 receptor motif-containing protein 1 (SARM1) is the central determinant of axonal degeneration and has crosstalk with different cell death programs to determine neuronal survival. Herein, we illustrated the role of SARM1 in ACR-induced dying-back neuropathy. We further demonstrated the upstream programmed cell death mechanism of this SARM1-dependent process. Spinal cord motor neurons that were induced to overexpress SARM1 underwent necroptosis rather than apoptosis in ACR neuropathy. Mechanically, non-canonical necroptotic pathways mediated mitochondrial permeability transition pore (mPTP) opening, reactive oxygen species (ROS) production, and mitochondrial fission. What's more, the final executioner of necroptosis, phosphorylation-activated mixed lineage kinase domain-like protein (MLKL), aggregated in mitochondrial fractions. Rapamycin intervention removed the impaired mitochondria, inhibited necroptosis for axon maintenance and neuronal survival, and alleviated ACR neuropathy. Our work clarified the functional links among mitophagy, necroptosis, and SARM1-dependent axonal destruction during ACR intoxication, providing novel therapeutic targets for dying-back neuropathies.

The Impact of Milk Fat Globule Membrane with Exercise on Age-Related Degeneration of Neuromuscular Junctions

Morphological changes in neuromuscular junctions (NMJs), which are synapses formed between α-motor neurons and skeletal muscle fibers, are considered to be important in age-related motor dysfunction. We have previously shown that the intake of dietary milk fat globule membrane (MFGM) combined with exercise attenuates age-related NMJ alterations in the early phase of aging. However, it is unclear whether the effect of MFGM with exercise on age-related NMJ alterations persists into old age, and whether intervention from old age is still effective when age-related changes in NMJs have already occurred. In this study, 6- or 18-month-old mice were treated with a 1% MFGM diet and daily running wheel exercise until 23 or 24 months of age, respectively. MFGM treatment with exercise was effective in suppressing the progression of age-related NMJ alterations in old age, and even after age-related changes in NMJs had already occurred. Moreover, the effect of MFGM intake with exercise was not restricted to NMJs but extended to the structure and function of peripheral nerves. This study demonstrates that MFGM intake with exercise may be a novel approach for improving motor function in the elderly by suppressing age-related NMJ alterations.