Abatement of Forskolin-Induced Intestinal Fluid Secretion with Penicillin

Author(s): Earnest P Chen, Jason L Own, John P Geibel

Background: Antibiotics have been classically used as a method to treat diarrhea-related pathologies by modulating the gut microbiome. We recently reported that penicillin may protect against disease- induced excessive fluid and electrolyte secretion via a genetics-independent, microbiome- independent mechanism in individual colonic crypt cells. Therefore, we examined whether penicillin can be utilized as a microbiome-independent therapeutic for diarrhea, a disease that takes millions of lives every year, especially in developing countries.

Aim: To investigate whether penicillin has microbiome-independent protective effects against fluid secretion in rat small intestine at the whole-tissue level.

Methods: Small intestine segments were harvested from male Sprague Dawley rats, and mounted into an ex-vivo intestinal perfusion machine, which sustains extraluminal (serosa/basolateral) and intraluminal (mucosal/luminal) perfusion. The segments were perfused extraluminally with Ringer-HEPES and with varying doses (0.25mM, 0.50mM, 1.0mM, 2.5mM and 5.0mM) of Penicillin G (Pen-G) sodium salt intraluminally. Experiments were performed with a known secretagogue forskolin (FSK) to induce rapid intraluminal fluid secretion. For all experimental conditions, fluid secretion was observed by changes in fluorescent signal from an intraluminal perfusate fluorescein isothiocyanate (FITC)-inulin, a nonabsorbable fluorescent marker, over a period of 80 minutes with luminal perfusate sampling every 20 minutes. All samples were collected in triplicate and the mean value is recorded. Results: A statistically significant decrease in fluid secretion occurred in the presence of Pen-G at all concentrations tested. As Pen-G dosage increased from 0.25 mM to 5.0 mM, the extent of fluid secretion decrease was proportional to the dose of Pen-G applied in the luminal perfusate.

Conclusion: Penicillin has a significant dose-dependent protective effect against FSK cAMP fluid secretion in induced models of diarrhea in the microbiome deficient rat small intestine. Penicillin can rapidly bring fluid secretion down to levels comparable to healthy controls.