Passive Transfer of Sera from ALS Patients with Identified Mutations Evokes an Increased Synaptic Vesicle Number and Elevation of Calcium Levels in Motor Axon Terminals, Similar to Sera from Sporadic Patients

Abstract

Previously, we demonstrated increased calcium levels and synaptic vesicle densities in the motor axon terminals (MATs) of sporadic amyotrophic lateral sclerosis (ALS) patients. Such alterations could be conferred to mice with an intraperitoneal injection of sera from these patients or with purified immunoglobulin G. Later, we confirmed the presence of similar alterations in the superoxide dismutase 1 G93A transgenic mouse strain model of familial ALS. These consistent observations suggested that calcium plays a central role in the pathomechanism of ALS. This may be further reinforced by completing a similar analytical study of the MATs of ALS patients with identified mutations. However, due to the low yield of muscle biopsy samples containing MATs, and the low incidence of ALS patients with the identified mutations, these examinations are not technically feasible. Alternatively, a passive transfer of sera from ALS patients with known mutations was used, and the MATs of the inoculated mice were tested for alterations in their calcium homeostasis and synaptic activity. Patients with 11 different ALS-related mutations participated in the study. Intraperitoneal injection of sera from these patients on two consecutive days resulted in elevated intracellular calcium levels and increased vesicle densities in the MATs of mice, which is comparable to the effect of the passive transfer from sporadic patients. Our results support the idea that the pathomechanism underlying the identical manifestation of the disease with or without identified mutations is based on a common final pathway, in which increasing calcium levels play a central role.

Passive Transfer of Blood Sera from ALS Patients with Identified Mutations Results in Elevated Motoneuronal Calcium Level and Loss of Motor Neurons in the Spinal Cord of Mice

“…In our previous study, we demonstrated a significant calcium increase in the axon terminals of lumbar MNs in a similar experimental paradigm as in the present study [ 21 ]. To analyze whether analogous changes in the intracellular calcium could be evoked by the ALS serum treatment in the peripherally located motor axon terminals and the centrally located motoneuronal cell bodies, calcium data from these anatomical regions were pooled to patients serving as serum donors, plotted ( Figure 6 ), and evaluated using a linear regression analysis.…”

“…Meanwhile, healthy individuals, and patients with negative screening results for all 35 major ALS genes, regarded as sporadic ALS patients, served as the control. Using a short-term repeated injection paradigm, an increased synaptic vesicle density and increased calcium could be detected in the motor axon terminals of the injected mice [ 21 ], similar to those changes detected after the injection of sera from sporadic ALS patients [ 20 ] or seen in muscle biopsy samples of sporadic patients [ 17 ]. Furthermore, on the scatter diagram vesicle number and intracellular calcium, the population of ALS patients could be separated from the controls [ 21 ], again, similarly as in the case of human samples [ 17 ].…”

“…First, a decrease in the number of MNs was observed with increased intracellular calcium in the surviving population. Interestingly, in the scatter plot of these parameters, the population of ALS patients could be separated from the controls, similarly as in the case of the axon terminals [ 21 ]. Secondly, the calcium increase in the motor axon terminals showed a strong correlation with that of the cell bodies, indicating that analogous changes could be induced in these distant anatomical regions of MNs with the injection of the same ALS sera.…”

“…For the present experiments, instead of purified IgG, sera from ALS patients were used for the inoculation, as in our previous studies [ 20 , 21 ], because it demonstrates more complex and more substantial biological effects than the isolated IgG. However, the presence of immunoglobulins was demonstrated in the spinal MNs.…”

“…In both models, the demonstrated calcium increase in the spinal MNs implied the importance of the elevated calcium in the pathomechanism of the disease. Recently, after injecting the whole sera of patients with identified mutations, similar alteration could be observed in the motor axon terminals of the interosseus muscle of the injected animals [ 21 ], suggesting that calcium-mediated processes might be the common denominators of the disease, regardless of the presence of mutations identified in the patients. However, the deleterious effect of the sera from these patients on the perikarya of the MNs has not been documented yet.…”