Biology subjects

Dvorak, Z.

Publications and source records attributed to Dvorak, Z..

5 recordsLinked to original sources

bioRxiv2025

Inhibition of IL-22-producing cells by Sutterella sp. bacteria

The gut microbiota constitutes a complex ecosystem essential for host defense against infection and maturation of the immune system. Inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohns disease, are characterized by a severe inflammation of the intestine, arising from dysregulated control of host-microbiota crosstalk. However, neither the genetic bases of IBD nor the immune responses involved are fully understood. The pathobionts are currently under investigation for their active role in the development and the severity of IBD. These bacteria are present in the microbiota of healthy individuals without causing disease but have pathogenic potential when the intestinal environment is disturbed. Here, we highlighted Sutterella sp. as a new commensal pathobiont for its capacity to modulate the host immune functions. This anaerobic Gram-negative bacterium inhibits IL-22 production and AhR activity in mice and humans. The effectors responsible for the biological activity are large (>30 kDa) protein-based compounds secreted by Sutterella sp. These data enhance our understanding of the mechanisms that regulate host immune functions and pave the way for new therapeutic strategies to control gut inflammation.

immunology↗

bioRxiv2024

Unlocking the Potential: FKK6 as a Microbial Mimicry Based Therapy for Chronic Inflammation-Associated Colorectal Cancer in a Murine Model

Chronic intestinal inflammation significantly contributes to the development of colorectal cancer (CRC) and remains a pertinent clinical challenge, necessitating novel therapeutic approaches. Indole-based microbial metabolite mimics FKK6, which is a ligand and agonist of the pregnane X receptor (PXR), was recently demonstrated to have PXR-dependent anti-inflammatory and protective effects in a mouse model of dextran sodium sulfate (DSS)-induced acute colitis. Here, we examined the therapeutic potential of FKK6 in a mouse model (C57BL/6 FVB humanized PXR mice) of colitis-associated colon cancer (CAC) induced by azoxymethane (AOM) and dextran sodium sulfate (DSS). FKK6 (2 mg/kg) displayed substantial anti-tumor activity, as revealed by reduced size and number of colon tumors, improved colon histopathology, and decreased expression of tumor markers (c-MYC, {beta}-catenin, Ki-67, cyclin D) in the colon. In addition, we carried out the chronic toxicity (30 days) assessment of FKK6 (1 mg/kg and 2 mg/kg) in C57BL/6 mice. Histological examination of tissues, biochemical blood analyses, and immunohistochemical staining for Ki-67 and {gamma}-H2AX showed no difference between FKK6-treated and control mice. Comparative metabolomic analyses in mice exposed for 5 days to DSS and administered with FKK6 (0.4 mg/kg) revealed no significant effects on several classes of metabolites in the mouse fecal metabolome. Ames and micronucleus tests showed no genotoxic and mutagenic potential of FKK6 in vitro. In conclusion, anticancer effects of FKK6 in AOM/DSS-induced CAC, together with FKK6 safety data from in vitro tests and in vivo chronic toxicity study, and comparative metabolomic study, are supportive of the potential therapeutic use of FKK6 in the treatment of CAC.

pharmacology and toxicology↗

bioRxiv2023

In Vitro Safety Signals for Potential Clinical Development of the Anti-Inflammatory Pregnane X Receptor Agonist FKK6

Background and purposeBased on the mimicry of microbial metabolites, functionalized indoles were demonstrated as the ligands and agonists of the pregnane X receptor (PXR). The lead indole, FKK6, displayed PXR-dependent protective effects in DSS-induced colitis in mice and in vitro cytokine-treated intestinal organoid cultures. Here, we performed the initial in vitro pharmacological profiling of FKK6. Experimental approachA complex series of cell-free and cell-based assays were employed. The organic synthesis, and advanced analytical chemistry methods were used. Key resultsFKK6-PXR interactions were characterized by hydrogen-deuterium exchange mass spectrometry. Screening FKK6 against potential cellular off-targets revealed high PXR selectivity. FKK6 has poor aqueous solubility but was highly soluble in simulated gastric and intestinal fluids. FKK6 was bound to plasma proteins and chemically stable in plasma. The partition coefficient of FKK6 was 2.70, and FKK6 moderately partitioned into red blood cells. In Caco2 cells, FKK6 displayed high permeability (A-B: 22.8 x 10-6 cm.s-1) and no active efflux. These data are indicative of essentially complete in vivo absorption of FKK6. FKK6 was rapidly metabolized by cytochromes P450, notably by CYP3A4 in human liver microsomes. Two oxidized FKK6 derivatives, including N6-oxide and C19-phenol, were detected, and these metabolites had 5-7 x lower potency as PXR agonists than FKK6. This implies that despite high intestinal absorption, FKK6 is rapidly eliminated by the liver, and its PXR effects are predicted to be predominantly in the intestines. Conclusion and implicationsThe PXR ligand and agonist FKK6 has a suitable pharmacological profile supporting its potential preclinical development. BULLET POINT SUMMARYWhat is already known: O_LIMicrobial metabolite mimic FKK6 is a hPXR agonist with anti-inflammatory properties in mice and human. C_LIO_LIThe in vitro PXR binding, absorption, and metabolism have not been completely characterized. C_LI What this study adds: O_LIPXR selectivity with unique binding mode, high intestinal cell permeability, rapid and complex microsomal metabolism. C_LIO_LIInitial testing for predicted metabolites shows reduced potency as PXR agonists. C_LI Clinical significance: O_LIPXR effects of FKK6 are predicted to be predominantly in the intestines. C_LIO_LIFKK6 has a suitable pharmacological profile supporting its potential preclinical development. C_LI

biochemistry↗

bioRxiv2020

DIETARY MONOTERPENOIDS AS A NEW CLASS OF ALLOSTERIC HUMAN ARYL HYDROCARBON RECEPTOR ANTAGONISTS

Carvones, the constituents of essential oils of dill, caraway, and spearmint, were reported to antagonize the human aryl hydrocarbon receptor (AhR); however, the exact molecular mechanism remains elusive. We show that carvones are non-competitive allosteric antagonists of the AhR that inhibit the induction of AhR target genes in a ligand-selective and cell type-specific manner. Carvones do not displace radiolabeled ligand from binding at the AhR, but they bind allosterically within the bHLH/PAS-A region of the AhR. Carvones did not influence a translocation of ligand-activated AhR into the nucleus. Carvones inhibited the heterodimerization of the AhR with its canonical partner ARNT and subsequent binding of the AhR to the promotor of CYP1A1. Interaction of carvones with potential off-targets, including ARNT and protein kinases, was refuted. This is the first report of a small dietary monoterpenoids as a new class of AhR non-competitive allosteric antagonists with the potential preventive and therapeutic application.

pharmacology and toxicology↗

bioRxiv2019

Targeting the Pregnane X Receptor Using Microbial Metabolite Mimicry

The human pregnane X receptor (PXR), a master regulator of drug metabolism, has important roles in intestinal homeostasis and abrogating inflammation. Existing PXR ligands have substantial off-target toxicity. Based on prior work that established microbial (indole) metabolites as PXR ligands, we proposed microbial metabolite mimicry as a novel strategy for drug discovery that allows to exploit previously unexplored parts of chemical space. Here we report functionalized indole-derivatives as first-in-class non-cytotoxic PXR agonists, as a proof-of-concept for microbial metabolite mimicry. The lead compound, FKK6, binds directly to PXR protein in solution, induces PXR specific target gene expression in, cells, human organoids, and mice. FKK6 significantly represses pro-inflammatory cytokine production cells and abrogates inflammation in mice expressing the human PXR gene. The development of FKK6 demonstrates for the first time that microbial metabolite mimicry is a viable strategy for drug discovery and opens the door to mine underexploited regions of chemical space.

biochemistry↗