Characteristics of streptozotocin-induced and okadaic acid-induced models of Alzheimer's disease

alzheimer's disease is the main cause of dementia in people over the age of 65, which affects millions of patients worldwide. Since the prevalence of this pathology increases significantly with the increase in life expectancy, the societal consequences of Alzheimer's disease will be dire if no effective therapy is developed in the near future. Fundamental experimental work is a mandatory and necessary stage of preclinical research for the safe and effective development of new approaches to the treatment of dementia as part of clinical trials in the future. Streptozotocin is a natural chemical obtained from Streptomyces achromogenes, primarily classified as an antibiotic, the introduction of which leads to the activation of oxidative stress and damage to the myelin sheath. This chemical compound promotes the accumulation of characteristic abnormal proteins, called β-amyloid and tau protein, which leads to imitation of neuropathological, behavioral, metabolic and molecular symptoms that resemble human Alzheimer's disease. Okadaic acid is a C38 fatty acid polyester phycotoxin, which is a powerful and selective inhibitor of serine/threonine phosphatases: PP-1c, PP1, PP2A and PP2B, which leads to a decrease in dephosphorylation of phosphorylated tau protein and, accordingly, to hyperphosphorylation of tau protein. Hyperphosphorylation of tau protein is responsible for the deposition of neurofibrillary tangles in vivo and in vitro, which ultimately causes synaptic dysfunction and neuronal death. In addition, okadaic acid activates kinases that regulate tau protein phosphorylation: GSK3β, CDK5, MAPK, ERK1/2, AMPK. The activation of kinases significantly contributes to the phosphorylation of tau protein. Okadain administration is also reported to significantly activate the expression of BACE1, one of the key enzymes in the amyloidogenic cascade. The mechanisms of molecular and morphological changes of the Alzheimer's type in the brain of experimental animals when streptozotocin and okadaic acid are administered are similar in many respects. These include induction and activation of neurodegeneration, apoptosis and necrosis of neurons, development of oxidative stress and inhibition of antioxidant systems, deficiency of neurotransmitters and mitochondrial dysfunction, etc. Both proposed toxins effectively contribute to the simulation of dementia of the Alzheimer's type in the experiment.