Systemic administration of scAAV9-IGF1 extends survival in SOD1G93A ALS mice via inhibiting p38 MAPK and the JNK-mediated apoptosis pathway

Amyotrophic lateral sclerosis (ALS) is closely associated with a reduction of neurotrophic factors in the central nervous system (CNS). Insulin-like growth factor 1 (IGF1)-encoding vectors delivered via intramuscular and intraparenchymal spinal cord injections have conferred therapeutic benefits in ALS model mice, although the development of a noninvasive delivery route is still needed. Intravenous administration of adeno-associated virus (AAV) vectors has been used to induce expression of neurotrophic genes in the lumbar spinal cords of adult mice. Therefore, the aim of this study was to investigate the effect of intravenous delivery of human IGF1 by self-complementary adeno-associated virus (scAAV) vectors in 90-day-old SOD1-G93A ALS mice. We found that IGF1 treatment decreased motor neuron death, mitigated myelin pathology in the ventral root, and prolonged the lifespan in SOD1-G93A mice. We also discovered that IGF1 inhibited phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) and the c-Jun-N-terminal kinase (JNK) pathway in the lumbar spinal cord, as evidenced by downregulated phosphorylated p38 and phosphorylated JNK. Furthermore, we detected the levels of proteins involved in the apoptosis pathway and found that the apoptotic inhibitor Bcl2 increased and the apoptotic promoter Bax, caspase 3, and caspase 9 decreased. In addition, the pro-inflammatory factor TNF-α was reduced after IGF1 treatment. In conclusion, we report a convenient and noninvasive ALS treatment method. Our results revealed a previously unrecognized role of IGF1 in p38 MAPK and the JNK-mediated pathway and its potential role as a therapeutic target for ALS.