Age-Related Decreases in Colonic Neurokinin A Content and Release Monitored Using Electrochemical Immunosensors

Aging increases the risk of bowel dysfunction and reduced quality of life. Although Neurokinin A (NKA)-mediated smooth muscle contraction declines with age, it is unclear whether this reflects altered NKA content and/or release. This study examined age-related changes in colonic NKA content and release and assessed whether changes correlated with fecal NKA.

An electrochemical immunosensor was developed and characterized for NKA detection. Distal colon tissue and fecal pellets were collected from 5- and 22-month-old female C57BL6J mice. Basal and mechanically evoked tissue NKA release was recorded in the presence and absence of ondansetron. NKA content in tissue and fecal pellets were measured.

Sensor fabrication was validated by electrochemical and EDX analyses. The immunosensor detected NKA with a detection limit of 2.76 pM and high selectivity. Basal and mechanically evoked NKA release were significantly reduced with age. Ondansetron inhibited mechanically stimulated NKA release in 5-month-old but not 22-month-old colons. Tissue NKA content declined with age. The proportion of total NKA released decreased from 65% ± 22% in young tissue to 30% ± 23% in aged tissue. Fecal NKA levels were similarly reduced in older mice.

Reduced NKA release with aging is associated with lower tissue content. The electrochemical immunosensor provides a simple, cost-effective method for NKA quantification and could be adapted for other gastrointestinal neuropeptides. The decrease in fecal NKA levels supports further investigation of fecal NKA as a noninvasive marker of age-related changes in bowel function.