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

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.

Mitochondrial dysfunction in familial amyotrophic lateral sclerosis

“…Mitochondrial damage has been well documented in both sporadic and familial ALS. The first evidence of mitochondrial abnormalities came from ultrastructural studies showing aggregates of mitochondria in muscles and spinal cord motor neurons (Sasaki and Iwata 1996) and increased mitochondrial volume in motor nerve terminals of ALS patients (Siklos et al 1996). Consistent with these findings, observations of mitochondrial morphology in cell or animal models of familial ALS showed aggregated, swollen, vacuolated or fragmented mitochondria (Bendotti et al 2001;Coussee et al 2011;Damiano et al 2006;Jaarsma et al 2001;Jung et al 2002;Menzies et al 2002;Raimondi et al 2006;Xu et al 2004).…”

Morphological abnormalities in mitochondria of the skin of patients with sporadic amyotrophic lateral sclerosis

“…The involvement of increased oxidative stress involving mitochondria is a likely explanation, albeit probable incomplete, of SALS neurodegeneration. In this respect, increased mitochondrial volume in motor nerve terminals of SALS patients was first described by Siklós et al in 1996 13 . Other reports also found morphologic abnormalities of mitochondria in SALS patients, either in liver biopsy specimens 11 or in axons, which show accumulation of mitochondria as well 13 .…”

“…In this respect, increased mitochondrial volume in motor nerve terminals of SALS patients was first described by Siklós et al in 1996 13 . Other reports also found morphologic abnormalities of mitochondria in SALS patients, either in liver biopsy specimens 11 or in axons, which show accumulation of mitochondria as well 13 . Interestingly, conglomerates of dark mitochondria at the presynaptic terminals of anterior spinal motor neurons were described by Sasaki and colleagues 28 , suggesting mitochondrial involvement in disabled synaptic contacts between lower motor neurons and their inputs.…”

“…However, to date, no abnormalities had been described in the mitochondria of keratinocytes of these patients. Considering that mitochondria of liver, muscle and other tissues are affected, it became rational to assume that changes would also be seen in the mitochondria of keratinocytes, reinforcing the concept advanced by Siklós et al 13 , that changes of mitochondrial area might be a marker of dysfunction.…”

“…Afifi and colleagues 6 first reported abnormal mitochondrial morphology in the atrophic muscles of SALS patients and, subsequently, mitochondrial abnormalities have been reported in the central nervous system [7][8][9][10] , liver cells 11 and peripheral blood lymphocytes 12 of SALS patients. Muscle biopsies in SALS have shown increased mitochondrial volume associated to increased calcium levels 13 ; also, reduced activity of mitochondrial respiratory chain complex I and complex IV in skeletal muscle and the spinal cord have been reported 14,15 . Along this line, electron microscopy of motor neurons from animal models of ALS, including SOD1 transgenic and Wobbler mice, revealed prominent mitochondrial abnormalities, such as vacuolation, crystolysis, edema and rupture of outer membranes [16][17][18] .…”