Fexofenadine HCl enhances growth, biofilm, and lactic acid production of Limosilactobacillus reuteri and Bifidobacterium longum: implications for allergy treatment

Abstract

Background: It is evident that various drugs influence the gut microbiota, yet the precise mechanism driving these effects remain ambiguous. Considering the growing recognition of gut microbiota's role in health and disease, it is important to explore how commonly used drugs, such as antihistamines, may alter microbial composition and function. Histamine, an essential interkingdom signaling molecule, shapes bacterial virulence, biofilm formation, and immune regulation. However, the effects of antihistamines on bacterial colonization are mostly unknown. This study aimed to investigate the potential effects of antihistamine exposure on critical factors which affect the pathogenicity and colonization of selected gut bacterial species, such as growth, biofilm formation, and adherence to cell lines, at intestinal concentrations. If antihistamines influence bacterial metabolism or composition, they may consequently affect Short Chain Fatty Acid (SCFA) production, which could have downstream effects on gut homeostasis and immune function. Specifically, we examined the impact of three antihistamines - fexofenadine HCl, cyproheptadine HCl, and desloratadine -on bacteria from the four dominant gut phyla: Bifidobacterium longum, Limosilactobacillus reuteri, Bacteroides fragilis, and Escherichia coli.

Results: Our results showed that cyproheptadine HCl and desloratadine inhibited the growth of all tested bacteria, whereas fexofenadine HCl promoted the growth of all species except B. longum. Furthermore, cyproheptadine HCl and desloratadine reduced the biofilm-forming capacity of these bacterial species and altered their effects on adherence to Caco-2/HT-29 cell lines aligning with changes in cell surface hydrophobicity: increased cell surface hydrophobicity correlated with greater bacterial adherence to surfaces. In contrast, fexofenadine HCl enhanced biofilm formation and adherence of B. longum and L. reuterii in Caco-2/HT-29 co-cultures. It also led to increased production of lactic and propionic acids, with a statistically significant increase observed in acetic acid levels (p < 0.05).

Conclusion: In summary, our findings suggest that fexofenadine HCl, unlike cyproheptadine HCl and desloratadine, supports the growth, and colonization of probiotic bacteria such as L. reuteri and B. longum with potential anti allergic benefits, and enhancing their SCFA production. Conversely, cyproheptadine HCl and desloratadine suppressed bacterial growth, hinting at potential antimicrobial properties that may warrant exploration for drug repurposing.

Keywords: Bifidobacterium longum; Limosilactobacillus reuteri; Cyproheptadine HCl; Desloratadine; Fexofenadine HCl; Lactic acid.

Fig. 1

Growth of bacteria under the influence of antihistamine drugs. The effect on Gram-negative bacteria: (A) Bacteroides fragilis and (B) Escherichia coli, and Gram-positive bacteria: (C) Limosilactobacillus reuteri, and (D) Bifidobacterium longum, is represented as viable count (CFU/mL). Tested antihistamines include fexofenadine HCl, cyproheptadine HCl, and desloratadine at intestinal concentrations of 37.165 µM, 4.1168 µM, and 5.3619 µM, respectively. The control group reflects bacterial growth in the presence of DMSO. Statistical significance was assessed using the Mann-Whitney test, with “ns” indicating no significant difference

Fig. 2

Auto-aggregation of bacteria in the presence of antihistamine drugs. Changes in the percentage of auto-aggregation were measured for (A) Bacteroides fragilis, (B) Escherichia coli, (C)Limosilactobacillus reuteri, and (D) Bifidobacterium longum, after incubation with antihistamines at 37 °C for 60 min. Results are expressed as mean percentages from three independent experiments, with error bars representing standard error (SE). Tested antihistamines include fexofenadine HCl, cyproheptadine HCl, and desloratadine at intestinal concentrations of 37.165 µM, 4.1168 µM, and 5.3619 µM, respectively. The control group included bacteria with DMSO. Statistical analysis was performed using multiple unpaired t-tests with Holm-Šídák correction for multiple comparisons. * Significant difference (p < 0.05)

Fig. 3

Hydrophobicity of bacteria in the presence of antihistamine drugs. Changes in percentage hydrophobicity were assessed for (A) Bacteroides fragilis, (B) Escherichia coli, (C) Limosilactobacillus reuteri, and (D) Bifidobacterium longum after incubation with antihistamines at 37 °C for 60 min. Data are presented as mean percentages from three independent experiments, with error bars representing standard error (SE). Tested antihistamines include fexofenadine HCl, cyproheptadine HCl, and desloratadine at intestinal concentrations of 37.165 µM, 4.1168 µM, and 5.3619 µM, respectively. The control group included bacteria with DMSO. Statistical analysis was conducted using multiple unpaired t-tests with Holm-Šídák correction for multiple comparisons. * Significant difference (p < 0.05)

Fig. 4

Biofilm formation ability of selected bacteria in the presence of antihistamine drugs. Changes in the biofilm formation index were measured for (A) Bacteroides fragilis, (B) Escherichia coli, (C) Limosilactobacillus reuteri, and (D) Bifidobacterium longum under the influence of antihistamines. Data are presented as mean percentages from three independent experiments, with error bars representing standard error (SE). Tested antihistamines include fexofenadine HCl, cyproheptadine HCl, and desloratadine at intestinal concentrations of 37.165 µM, 4.1168 µM, and 5.3619 µM, respectively. The control group consisted of bacteria cultured with DMSO. Statistical analysis was performed using multiple unpaired t-tests with Holm-Šídák correction for multiple comparisons. * Significant difference (p < 0.05)

Fig. 5

Bacterial adherence to Caco-2/HT-29 co-culture in the presence of antihistamine drugs. Changes in the percentage of adhered bacterial cells were evaluated for (A) Bifidobacterium longum, (B) Limosilactobacillus reuteri, and (C) Escherichia coli under the influence of antihistamines: fexofenadine HCl, cyproheptadine HCl, and desloratadine at intestinal concentrations of 37.165 µM, 4.1168 µM, and 2.68 µM (0.5x), respectively. Results are expressed as mean percentages from three independent experiments, with error bars indicating standard error (SE). The positive control included bacteria with DMSO at concentrations equivalent to those used for drug dissolution

Fig. 6

Scanning electron micrographs illustrating the effect of cyproheptadine HCl on Escherichia coli adherence to Caco-2/HT-29 co-culture. A Control showing bacterial adherence in the absence of the drug. B Drug-treated cells displaying altered bacterial adherence. Magnification: 5000x. The adherence assay was conducted in RPMI medium under 5% CO₂ at 37°C, and images were captured using a scanning electron microscope (Quanta 250 FEG, West Bengal, India)