Early Aβ-induced changes in the enteric nervous system and gut: structure, function, and motility

Abstract

Alzheimers disease is increasingly recognized as affecting not only the central nervous system but also the autonomic nervous system, comprising the enteric nervous system, and thus the gut. Given the structural and functional similarities between the enteric and central nervous system, including susceptibility to A{beta}, this study investigated the early and acute effects of monomeric A{beta} on primary enteric neurons in vitro and on intestinal motility ex vivo. Acute A{beta} application caused marked neuronal hyperexcitability, with increased spike frequencies and calcium influx, and led to enhanced intestinal contractility without altering frequency or timing. Prolonged 72-hour exposure did not induce cell death or apoptosis but significantly reduced neurite outgrowth and decreased synaptic markers and beta II tubulin. These findings suggest that acute A{beta} primarily drives the excitability of enteric neurons and intestinal motility, while prolonged exposure subsequently leads to structural and synaptic changes. Overall, the study points to early dysfunction of the enteric nervous system in Alzheimers disease and highlights the gut as a potential target for early interventions. Synopsis O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=190 SRC="FIGDIR/small/678722v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@18b5292org.highwire.dtl.DTLVardef@1da0ecforg.highwire.dtl.DTLVardef@1023b09org.highwire.dtl.DTLVardef@171e3fb_HPS_FORMAT_FIGEXP M_FIG C_FIG The pathology of Alzheimers disease is increasingly recognized in the enteric nervous system (ENS), suggesting an early contribution of the gut to the onset of the disease. This study investigated the acute and short-term effects of amyloid-{beta} (A{beta}) on intestinal motility and enteric neurons to elucidate early functional and structural changes beyond the brain. O_LIAcute A{beta} exposure enhanced intestinal contractility ex vivo. C_LIO_LIEnteric neurons showed hyperexcitability and increased Ca{superscript 2} influx. C_LIO_LIAfter 72 h, neuronal viability and apoptosis remained unaffected. C_LIO_LIProlonged exposure reduced neurite outgrowth and {beta}III-tubulin expression. C_LIO_LISynaptic density was significantly decreased. C_LI