Ultrastructural evidence for altered calcium in motor nerve terminals in amyotrophc lateral sclerosis

TLDR

Amyotrophic lateral sclerosis is associated with increased intracellular calcium, a common factor in motoneuron injury. The study aimed to determine whether motor nerve terminals in ALS patients exhibit elevated intracellular calcium and morphological changes in vivo. Ultrastructural analysis of muscle biopsies from ALS patients and controls, using oxalate‑pyroantimonate fixation, mapped in‑situ calcium distribution. ALS motor nerve terminals displayed markedly higher calcium, larger mitochondria, and more synaptic vesicles than controls, confirming neuronal calcium elevation in ALS in vivo.

Abstract

Abstract Numerous studies of amyotrophic lateral sclerosis have suggested that increased intracellular calcium is a common denominator in motoneuron injury. In experimental models, IgG from patients with amyotrophic lateral sclerosis enhanced calcium entry and induced apoptotic cell death in vitro as well as increased intracellular calcium and induced ultrastructural alterations of the motor nerve terminals in mice in vivo. To determine whether similar increases in intracellular calcium and altered morphology are present in motor nerve terminals of amyotrophic lateral sclerosis patients in vivo, muscle biopsy specimens from 7 patients with amyotrophic lateral sclerosis, 10 nondenervating disease control subjects, and 5 patients with denervating neuropathies were analyzed with ultrastructural techniques, employing oxalate‐pyroantimonate fixation to preserve in situ calcium distribution. Motor nerve terminals from amyotrophic lateral sclerosis specimens contained significantly increased calcium, increased mitochondrial volume, and increased numbers of synaptic vesicles compared to any of the disease control groups, without exhibiting excess Schwann envelopment specific to denervating terminals. These results parallel the effect of amyotrophic lateral sclerosis IgG passively transferred to mice, and provide the first demonstration that neuronal calcium is, in fact, increased in amyotrophic lateral sclerosis in vivo.