Neurochemistry seminars

Programmed axon death is a widespread and completely preventable mechanism in injury and disease. Mouse and Drosophila studies define a molecular pathway involving activation of SARM1 NA Dase and its prevention by NAD synthesising enzyme NMNAT2 . Loss of axonal NMNAT2 causes its substrate, NMN , to accumulate and activate SARM1 , driving loss of NAD and changes in ATP , ROS and calcium. Animal models caused by genetic mutation, toxins, viruses or metabolic defects can be alleviated by blocking programmed axon death, for example models of CMT1B , chemotherapy-induced peripheral neuropathy (CIPN), rabies and diabetic peripheral neuropathy (DPN). The perinatal lethality of NMNAT2 null mice is completely rescued, restoring a normal, healthy lifespan. Animal models lack the genetic and environmental diversity present in human populations and this is problematic for modelling gene-environment combinations, for example in CIPN and DPN , and identifying rare, pathogenic mutations. Instead, by testing human gene variants in WGS datasets for loss- and gain-of-function, we identified enrichment of rare SARM1 gain-of-function variants in sporadic ALS , despite previous negative findings in SOD1 transgenic mice. We have shown in mice that heterozygous SARM1 loss-of-function is protective from a range of axonal stresses and that naturally-occurring SARM1 loss-of-function alleles are present in human populations. This enables new approaches to identify disorders where blocking SARM1 may be therapeutically useful, and the existence of two dominant negative human variants in healthy adults is some of the best evidence available that drugs blocking SARM1 are likely to be safe. Further loss- and gain-of-function variants in SARM1 and NMNAT2 are being identified and used to extend and strengthen the evidence of association with neurological disorders. We aim to identify diseases, and specific patients, in whom SARM1 -blocking drugs are most likely to be effective.

An imbalance in lipid metabolism in neurodegeneration is still poorly understood. Phospholipids (PLs) have multifactorial participation in vascular dementia as Alzheimer, post-stroke dementia, CADASIL between others. Which include the hyperactivation of phospholipases, mitochondrial stress, peroxisomal dysfunction and irregular fatty acid composition triggering proinflammation in a very early stage of cognitive impairment. The reestablishment of physiological conditions of cholesterol, sphingolipids, phospholipids and others are an interesting therapeutic target to reduce the progression of AD. We propose the positive effect of BACE1 silencing produces a balance of phospholipid profile in desaturase enzymes-depending mode to reduce the inflammation response, and recover the cognitive function in an Alzheimer´s animal and brain stroke models. Pointing out there is a great need for new well-designed research focused in preventing phospholipids imbalance, and their consequent energy metabolism impairment, pro-inflammation and enzymatic over-processing, which would help to prevent unhealthy aging and AD progression.