Sulpiride Serves, a Substrate for the Gut Microbiome

Metabolism of Acetaminophen by Enteric Epithelial Cells Mitigates Hepatocellular Toxicity In Vitro

The gut-liver axis is defined by dietary and environmental communication between the gut, microbiome and the liver with its redox and immune systems, the overactivation of which can lead to hepatic injury. We used media preconditioning to mimic some aspects of the enterohepatic circulation by treating the human Caco-2 intestinal epithelial cell line with 5, 10 and 20 mM paracetamol (N-acetyl-para-aminophenol; APAP) for 24 h, after which cell culture supernatants were transferred to differentiated human hepatic HepaRG cells for a further 24 h. Cell viability was assessed by mitochondrial function and ATP production, while membrane integrity was monitored by cellular-based impedance. Metabolism by Caco-2 cells was determined by liquid chromatography with tandem mass spectrometry. Caco-2 cell viability was not affected by APAP, while cell membrane integrity and tight junctions were maintained and became tighter with increasing APAP concentrations, suggesting a reduction in the permeability of the intestinal epithelium. During 24 h incubation, Caco-2 cells metabolised 64-68% of APAP, leaving 32-36% of intact starting compound to be transferred to HepaRG cells. When cultured with Caco-2-preconditioned medium, HepaRG cells also showed no loss of cell viability or membrane integrity, completely in contrast to direct treatment with APAP, which resulted in a rapid loss of cell viability and membrane integrity and, ultimately, cell death. Thus, the pre-metabolism of APAP could mitigate previously observed hepatotoxicity to hepatic tight junctions caused by direct exposure to APAP. These observations could have important implications for the direct exposure of hepatic parenchyma to APAP, administered via the intravenous route.

Human targeted phenobarbital presents a poor substrate of gut microbiome deciphering new drug targets beyond pharmacokinetic curbs

Background

The gut microbiome, a new organ of the body, can potentially alter the pharmacokinetics of orally administered drugs through microbial enzymes. However, absorption of orally administered non-antibiotic drugs by the gut microbiome, during drug-microbiome interaction, is barely addressed. Structural homology studies confirm similar membrane transport proteins in gut epithelial cells and the gut microbiome of the host that may compete for drug substrates with the host itself for its absorbance. Therefore, it is hypothesized that orally administered human targeted phenobarbital may interact and/or be uptake by the gut microbiome during its transit through the small intestine.

Methods

In the current in vivo study, thirty-six male Wistar albino rats were divided into six groups including one control and 5 treatment groups, each having an equal number of rats (n = 6). Phenobarbital was administered orally (single dose of 15 mg/kg bw) to treatment groups. Animals were subsequently sacrificed to harvest microbial mass pallets residing in the small intestine after 2, 3, 4, 5, and 6 h of phenobarbital administration. Phenobarbital absorbance by the microbiome in the microbial lysate was estimated through RP-HPLC–UV at a wavelength of 207 nm.

Results

Maximum phenobarbital absorbance (149.0 ± 5.93 µg) and drug absorbance per milligram of microbial mass (1.19 ± 0.05 µg) were found significantly higher at 4 h of post-administration in comparison to other groups. Percent dose recovery of phenobarbital was 5.73 ± 0.19% at 4 h while the maximum intestinal transit time was 5 h till the drug was absorbed by the microbes. Such results pronounce the idea of the existence of structural homology between membrane transporters of the gut microbiome and intestinal enterocytes of the host that may competitively absorb orally administered phenobarbital during transit in the small intestine. The docking studies revealed that the phenobarbital is a poor substrate for the gut microbiome.

Conclusion

Gut microbiome may competitively absorb the non-antibiotics such as phenobarbital as novel substrates due to the presence of structurally homologous transporting proteins as in enterocytes. This phenomenon suggests the microbiome as a potential candidate that can significantly alter the pharmacokinetics of drugs.

The Competitive Absorption by the Gut Microbiome Suggests the First-Order Absorption Kinetics of Caffeine

In the literature archive, the intestinal microbiome is now considered as a discrete organ system. Despite living symbiotically with the human body, the gut microbiome is represented as potential drug targets because of its ability to modify the pharmacokinetics of orally administered drugs. Structural biology analysis indicates the existence of homology between transport proteins of microbial cells and membranes of enterocytes. It is speculated that structural similarity in the protein transporters may provoke an unwanted phenomenon of drug uptake by the gut microbiome present in the small intestine of the host. Considering this hypothesis, we analyzed the absorbance of orally administered caffeine by the gut microbiota in in vivo albino rat model through the RP-HPLC-UV approach. Microbiome absorbed the caffeine maximally at 2 hours and minimally at 5 hours post-drug administration following first-order absorption kinetics in a nonlinear way. Drug absorbance of microbial pellet and percent dose recovery was found significantly higher (P ≤ .05) at 2 hours post-administration as compared to all other groups. As speculated, our findings advocated the phenomenon that the gut microbiome influences the absorption of caffeine molecules. Members of the gut microbiome exhibited grouped behavior following first-order absorption kinetics in a nonlinear pattern.