Amyotrophic lateral sclerosis and autoimmunity

Pathogenic Mechanisms in Sporadic Amyotrophic Lateral Sclerosis

In recognition of the 100th anniversary of Charcot’s death we have reviewed possible pathogenic mechanisms in amyotrophic lateral sclerosis (ALS). Advances in the last 5 years in molecular biology and genetics have identified mutations in the cytosolic dismutase (SODI) gene in some patients with familial ALS raising the possibility that oxidative stress may be involved in the pathogenesis. An excitotoxic pathogenesis has been implicated based on elevated plasma and CSF levels of amino acids and altered contents of amino acids in the nervous system of ALS patients and changes in the number of excitatory amino acid receptors. ALS sera containing antibodies to L-type calcium channels and the development of immune mediated lower and upper and lower motor neuron models have revitalized research efforts focusing on an immune basis for ALS. Other pathogenic mechanisms which have been the subject of recent research include elemental toxicity, apoptosis and programmed cell death and possibly a deficiency or abnormality in growth factors. Pathogenic processes for ALS must account for an increasing incidence of ALS, male preponderance, and the selective vulnerability of the corticomotoneuronal system.

What we truly know about occupation as a risk factor for ALS: a critical and systematic review

Occupational and environmental exposures may contribute to the risk of developing sporadic amyotrophic lateral sclerosis (ALS). To summarize the available evidence, a systematic review of the literature on occupation as a potential determinant of ALS was performed according to the MOOSE guidelines. From MEDLINE, EMBASE, CINAHL, and Cochrane databases, selected studies were methodologically appraised according to Armon's classification system for ALS risk factor studies. Each occupation studied was reclassified according to the International Standard Classification of Occupations (ISCO-88). The vote-counting method was applied to summarize the data. Of 3773 potentially relevant studies, 51 were initially included. Of these, 12 studies provided risk estimates for individual occupations--one case-control, two register-based case-control, and nine register-based cohort studies. All studies fell into Armon's level of evidence class IV, indicating methodological limitations. Due to the heterogeneity of study methodology, data could not be pooled. The vote-counting method revealed several candidate occupations: veterinarians and other health workers, athletes, hairdressers, power-production plant, electrical and military workers. However, well designed studies with standardized assessment of occupation are needed to provide a more definitive answer about exogenous risk factors of ALS.

Biologic effects of and clinical disorders caused by nonprotein amino acids

Despite the fact that nonprotein amino acids are present in many commonly eaten foods, the biologic and clinical significance of this class of molecules has been largely overlooked. This is owing in part to their relatively low concentrations and their negligible nutritive value. Many of these compounds have the ability to interfere with a wide range of fundamental biochemical processes and cause disease. It is likely that the clinical effects of the ingestion of some nonprotein amino acids are yet to be described. Serious disorders in humans have followed the ingestion of these compounds as the result of food faddism, prodded by the commercial promotion of inadequately tested products. In view of the current popularity of herbal remedies and alternative medicine, these facts serve as another reminder to health care providers and the public at large about the need for critical analysis of the alleged benefits and the risks of exotic remedies and nutritional supplements. Beyond the public health issues they raise, non-protein amino acids take on significance because their misincorporation into proteins can trigger vigorous autoimmune attacks. To what extent this mechanism is responsible for highly prevalent diseases of autoimmunity remains to be determined.

Amyotrophic lateral sclerosis is a multifactorial disease

Amyotrophic lateral sclerosis (ALS) is probably biphasic. An initial trigger(s) is followed by a terminal cascade coinciding with the onset of neurological deficits. The terminal cascade involves interactive multifactorial pathogenic mechanisms. Aging must play a crucial role leading to multiple defective or degraded gene products accumulating with progressing years. This in turn leads to failure of receptor integrity and resulting excitotoxicity, free radical accumulation, failure of neurotrophism, and possibly immunological disturbances. These events are predated by months or years by a trigger which is also likely to be multifactorial and cumulative. Evidence suggests that environmental factors may be important triggers. Failure of specific glutamate transporters and calcium binding proteins may account for selective vulnerability of the corticomotoneuronal system. It is postulated that in ALS the primary target cell is the corticomotoneuron or the local circuit interneurons which modulate its activity. Glia cells may play an important role in the demise of the corticomotoneuronal cell. The disordered corticomotoneuron induces excessive excitatory transmitter (glutamate?) release at the corticomotoneuronal-spinal-motoneuronal synapse resulting in the subsequent demise of this neuron.

Neurofilaments, free radicals, excitotoxins, and amyotrophic lateral sclerosis

There is increasing evidence implicating abnormalities of neurofilament function in the pathogenesis of amyotrophic lateral sclerosis (ALS). The observation that the P2 blood protein phenotype is overrepresented in patients with ALS is potentially important, but needs confirmation. It should be shown that this segregation is selective for ALS. If it is, the implications outlined in Meyer's hypothesis will need to be explored, bearing in mind that much of the evidence implicating excitotoxins, free radicals, and neurofilaments in familial and sporadic ALS is still circumstantial. Thus the identification of candidate genes, the pursuit of large segregation studies, and identification of specific point mutations, remain key goals in ALS research.

Treatment of ALS with high dose pulse cyclophosphamide

Autoimmune abnormalities have been described in sporadically acquired amyotrophic lateral sclerosis (ALS), but ALS patients do not benefit from conventional immunosuppressive therapy. Because Multifocal Motor Neuropathy causes a syndrome mimicking the lower motor neuron involvement in ALS and responds to high dose cyclophosphamide, we tested whether ALS patients would respond to the same treatment. Eighteen patients with classical ALS initially received a high loading dose of intravenous cyclophosphamide (3 g/m2) followed by 6-monthly injections of 750-1000 mg/m2. We monitored isometric strength, fine motor coordination and pulmonary function monthly for 3 months prior to the study, during the treatment phase, and for 6 months after treatment. Treatment subjects were matched to control subjects from the WALS natural history data base and compared on the basis of decline rate (megaslopes). Treatment did not alter the course of ALS.

Age and sex associations of 40 autoimmune diseases

Self-injury by the host's immune system is believed to be a factor in the etiology of many diseases. Much attention has been given to the part played by sex hormones in such processes. Current literature frequently maintains that females are more susceptible than males to autoimmune diseases. In order to gain information about this factor, a tabulation has been made of the sex incidence of 40 autoimmune diseases which occur at different periods of life: childhood, early adult life, mature adult life, and old age. To some extent the tabulations substantiate female preponderance, but in some there is no gender difference, and in others, particularly the autoimmune nephropathies, male preponderance is the rule. Findings in experiments with animal analogues of human autoimmune disease, showing that administration of estrogen augments the manifestations, whereas androgen treatment suppresses them, do not correlate closely with clinical experience.