Targeted inhibition of glucuronidation markedly improves drug efficacy in mice - a model

Evidence of the interactions between immunosuppressive drugs used in autoimmune rheumatic diseases and Chinese herbal medicine: A scoping review

OBJECTIVES

Chinese herbal medicine (CHM) has been shown to be effective in autoimmune rheumatic diseases, but harmful herb-drug interactions might be inherent. We aim to review the evidence regarding herb-drug interactions between immunosuppressive drugs used in autoimmune rheumatic diseases and CHM.

METHODS

We searched PubMed, EMBASE and CINAHL from inception till 30 April 2023 using keywords that encompassed 'herb-drug interactions', 'herbs' and 'immunosuppressants'. Articles were included if they contained reports about interactions between immunosuppressive drugs used in the treatment of rheumatic diseases with CHM. Level of evidence for each pair of interaction was graded using the algorithm developed by Colalto.

RESULTS

A total of 65 articles and 44 unique pairs of interactions were identified. HDIs were reported for cyclophosphamide, cyclosporine, tacrolimus, methotrexate, mycophenolic acid, glucocorticoids, sulfasalazine, tofacitinib and biologic disease-modifying antirheumatic drugs. Among these, cyclosporine (n = 27, 41.5%) and tacrolimus (n = 19, 29.2%) had the highest number of documented interactions. Hypericum perforatum had the highest level of evidence of interaction with cyclosporine and tacrolimus. Consumption reduced the bioavailability and therapeutic effects of the drugs. Schisandra sphenanthera had the highest level of evidence of interaction with tacrolimus and increased the bioavailability of the drug. Majority of the articles were animal studies.

CONCLUSION

Overall level of evidence for the included studies were low, though interactions between cyclosporine, tacrolimus, Hypericum perforatum and Schisandra sphenanthera were the most and well-documented. Healthcare professionals should actively enquire about the concurrent use of CHM in patients, especially when drugs with a narrow therapeutic index are consumed.

UDP-glucose 6-dehydrogenase lessens sorafenib sensitivity via modulating unfolded protein response

As the first-generation targeted therapy, sorafenib remains an effective single-drug treatment for advanced hepatocellular carcinoma (HCC). Unfortunately, the existence of resistance restricts the long-term benefit of patients. UDP-glucose 6-dehydrogenase (UGDH) is the key enzyme of glucuronic acid metabolism which was largely reported in mediating drug systemic elimination. In this study, we explore its critical role in regulating sorafenib sensitivity. Here we find sorafenib exposure could activate glucuronic acid metabolism, accompanied with the elevated expression of UGDH. Interference with the route by silencing UGDH could boost HCC cells sensitivity to sorafenib. Meanwhile, the analysis of HCC patients with sorafenib treatment displayed that low UGDH expression predicted superior prognosis. Further screening assay suggested that unfolded protein response (UPR) involves in UGDH silencing-mediated apoptosis. Xenograft model confirmed that combined UGDH intervention could significantly improve sorafenib efficacy. Our results reveal the impact of sorafenib exposure on glucuronic acid metabolism reprogramming and provide UGDH as a promising target to improve sorafenib efficacy.

Resveratrol and Tumor Microenvironment: Mechanistic Basis and Therapeutic Targets

Resveratrol (3,4′,5 trihydroxystilbene) is a naturally occurring non-flavonoid polyphenol. It has various pharmacological effects including antioxidant, anti-diabetic, anti-inflammatory and anti-cancer. Many studies have given special attention to different aspects of resveratrol anti-cancer properties and proved its high efficiency in targeting multiple cancer hallmarks. Tumor microenvironment has a critical role in cancer development and progression. Tumor cells coordinate with a cast of normal cells to aid the malignant behavior of cancer. Many cancer supporting players were detected in tumor microenvironment. These players include blood and lymphatic vessels, infiltrating immune cells, stromal fibroblasts and the extracellular matrix. Targeting tumor microenvironment components is a promising strategy in cancer therapy. Resveratrol with its diverse biological activities has the capacity to target tumor microenvironment by manipulating the function of many components surrounding cancer cells. This review summarizes the targets of resveratrol in tumor microenvironment and the mechanisms involved in this targeting. Studies discussed in this review will participate in building a solid ground for researchers to have more insight into the mechanism of action of resveratrol in tumor microenvironment.

Multidrug Resistance-Associated Protein 3 Is Responsible for the Efflux Transport of Curcumin Glucuronide from Hepatocytes to the Blood

Curcumin, a major polyphenol present in turmeric, is predominantly converted to curcumin-O-glucuronide (COG) in enterocytes and hepatocytes via glucuronidation. COG is a principal metabolite of curcumin in plasma and feces. It appears that the efflux transport of the glucuronide conjugates of many compounds is mediated largely by multidrug resistance-associated protein (MRP) 3, the gene product of the ATP-binding cassette, subfamily C, member 3. However, it is currently unknown whether this was the case with COG. In this study, Mrp3 knockout (KO) and wild-type (WT) mice were used to evaluate the pharmacokinetics profiles of COG, the liver-to-plasma ratio of COG, and the COG-to-curcumin ratio in plasma, respectively. The ATP-dependent uptake of COG into recombinant human MRP3 inside-out membrane vesicles was measured for further identification, with estradiol-17β-d-glucuronide used in parallel as the positive control. Results showed that plasma COG concentrations were extremely low in KO mice compared with WT mice, that the liver-to-plasma ratios of COG were 8-fold greater in KO mice than in WT mice, and that the ATP-dependent uptake of COG at 1 or 10 μM was 5.0- and 3.1-fold greater in the presence of ATP than in the presence of AMP, respectively. No significant differences in the Abcc2 and Abcg2 mRNA expression levels were seen between Mrp3 KO and WT mice. We conclude that Mrp3 is identified to be the main efflux transporter responsible for the transport of COG from hepatocytes into the blood. SIGNIFICANCE STATEMENT: This study was designed to determine whether multidrug resistance-associated protein (Mrp) 3 could be responsible for the efflux transport of curcumin-O-glucuronide (COG), a major metabolite of curcumin present in plasma and feces, from hepatocytes into the blood using Mrp3 knockout mice. In this study, COG was identified as a typical Mrp3 substrate. Results suggest that herb-drug interactions would occur in patients concomitantly taking curcumin and either an MRP3 substrate/inhibitor or a drug that is predominantly glucuronidated by UDP-glucuronosyltransferases.

Differentiating Isomeric Deprotonated Glucuronide Drug Metabolites via Ion/Molecule Reactions in Tandem Mass Spectrometry

Isomeric O- and N-glucuronides are common drug metabolites produced in phase II of drug metabolism. Distinguishing these isomers by using common analytical techniques has proven challenging. A tandem mass spectrometric method based on gas-phase ion/molecule reactions of deprotonated glucuronide drug metabolites with trichlorosilane (HSiCl₃) in a linear quadrupole ion trap mass spectrometer is reported here to readily enable differentiation of the O- and N-isomers. The major product ion observed upon reactions of HSiCl₃ with deprotonated N-glucuronides is a diagnostic HSiCl₃ adduct that has lost two HCl molecules ([M - H + HSiCl₃ - 2HCl]-). This product ion was not observed for deprotonated O-glucuronides. Reaction mechanisms were explored with quantum chemical calculations at the M06-2X/6-311++G(d,p) level of theory.

Resveratrol and cancer: Challenges for clinical translation

Significant work has been done towards identifying the health-beneficial effects of the grape antioxidant resveratrol in a variety of bioassay- and disease- models, with much research being focused on its possible application to cancer management. Despite the large number of preclinical studies dealing with different aspects of the biological effects of resveratrol, its translation to clinics is far from reality due to a variety of challenges. In this review, we discuss the issues and questions associated with resveratrol becoming an effective in vivo anticancer drug, from basic metabolic issues to the problems faced by incomplete understanding of the mechanism(s) of action in the body. We also explore efforts taken by researchers, both public and private, to contend with some of these issues. By examining the published data and previous clinical trials, we have attempted to identify the problems and issues that hinder the clinical translation of resveratrol for cancer management. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

Protein kinase Cα and Src kinase support human prostate-distributed dihydrotestosterone-metabolizing UDP-glucuronosyltransferase 2B15 activity

Because human prostate-distributed UDP-glucuronosyltransferase (UGT) 2B15 metabolizes 5α-dihydrotestosterone (DHT) and 3α-androstane-5α,17β-diol metabolite, we sought to determine whether 2B15 requires regulated phosphorylation similar to UGTs already analyzed. Reversible down-regulation of 2B15-transfected COS-1 cells following curcumin treatment and irreversible inhibition by calphostin C, bisindolylmaleimide, or röttlerin treatment versus activation by phorbol 12-myristate 13-acetate indicated that 2B15 undergoes PKC phosphorylation. Mutation of three predicted PKC and two tyrosine kinase sites in 2B15 caused 70-100 and 80-90% inactivation, respectively. Anti-UGT-1168 antibody trapped 2B15-His-containing co-immunoprecipitates of PKCα in 130-140- and >150-kDa complexes by gradient SDS-PAGE analysis. Complexes bound to WT 2B15-His remained intact during electrophoresis, whereas 2B15-His mutants at phosphorylation sites differentially dissociated. PKCα siRNA treatment inactivated >50% of COS-1 cell-expressed 2B15. In contrast, treatment of 2B15-transfected COS-1 cells with the Src-specific activator 1,25-dihydroxyvitamin D(3) enhanced activity; treatment with the Src-specific PP2 inhibitor or Src siRNA inhibited >50% of the activity. Solubilized 2B15-His-transfected Src-free fibroblasts subjected to in vitro [γ-(33)P]ATP-dependent phosphorylation by PKCα and/or Src, affinity purification, and SDS gel analysis revealed 2-fold more radiolabeling of 55-58-kDa 2B15-His by PKCα than by Src; labeling was additive for combined kinases. Collectively, the evidence indicates that 2B15 requires regulated phosphorylation by both PKCα and Src, which is consistent with the complexity of synthesis and metabolism of its major substrate, DHT. Whether basal cells import or synthesize testosterone for transport to luminal cells for reduction to DHT by 5α-steroid reductase 2, comparatively low-activity luminal cell 2B15 undergoes a complex pattern of regulated phosphorylation necessary to maintain homeostatic DHT levels to support occupation of the androgen receptor for prostate-specific functions.

First-pass metabolism via UDP-glucuronosyltransferase: a barrier to oral bioavailability of phenolics

Glucuronidation mediated by UDP-glucuronosyltransferases (UGTs) is a significant metabolic pathway that facilitates efficient elimination of numerous endobiotics and xenobiotics, including phenolics. UGT genetic deficiency and polymorphisms or inhibition of glucuronidation by concomitant use of drugs are associated with inherited physiological disorders or drug-induced toxicities. Moreover, extensive glucuronidation can be a barrier to oral bioavailability as the first-pass glucuronidation (or premature clearance by UGTs) of orally administered agents usually results in the poor oral bioavailability and lack of efficacies. This review focused on the first-pass glucuronidation of phenolics including natural polyphenols and pharmaceuticals. The complexity of UGT-mediated metabolism of phenolics is highlighted with species-, gender-, organ- and isoform-dependent specificity, as well as functional compensation between UGT1A and 2B subfamily. In addition, recent advances are discussed with respect to the mechanisms of enzymatic actions, including the important properties such as binding pocket size and phosphorylation requirements.

Redox regulation in cancer: a double-edged sword with therapeutic potential

Oxidative stress, implicated in the etiology of cancer, results from an imbalance in the production of reactive oxygen species (ROS) and cell’s own antioxidant defenses. ROS deregulate the redox homeostasis and promote tumor formation by initiating an aberrant induction of signaling networks that cause tumorigenesis. Ultraviolet (UV) exposures, γ-radiation and other environmental carcinogens generate ROS in the cells, which can exert apoptosis in the tumors, thereby killing the malignant cells or induce the progression of the cancer growth by blocking cellular defense system. Cancer stem cells take the advantage of the aberrant redox system and spontaneously proliferate. Oxidative stress and gene-environment interactions play a significant role in the development of breast, prostate, pancreatic and colon cancer. Prolonged lifetime exposure to estrogen is associated with several kinds of DNA damage. Oxidative stress and estrogen receptor-associated proliferative changes are suggested to play important roles in estrogen-induced breast carcinogenesis. BRCA1, a tumor suppressor against hormone responsive cancers such as breast and prostate cancer, plays a significant role in inhibiting ROS and estrogen mediated DNA damage; thereby regulate the redox homeostasis of the cells. Several transcription factors and tumor suppressors are involved during stress response such as Nrf2, NFκB and BRCA1. A promising strategy for targeting redox status of the cells is to use readily available natural substances from vegetables, fruits, herbs and spices. Many of the phytochemicals have already been identified to have chemopreventive potential, capable of intervening in carcinogenesis.

Herb-drug pharmacokinetic interactions reviewed

IMPORTANCE OF THE FIELD

the global increase in the popularity of alternative medicines has raised renewed concerns regarding herb-drug interactions. These interactions are especially important for drugs with narrow therapeutic indices and may either be pharmacodynamic or pharmacokinetic in nature.

AREAS COVERED IN THIS REVIEW

pharmacokinetic interactions which may exist between herbs and drugs, and the mechanisms of these interactions with appropriate examples based on primary and secondary data in publications are discussed. The mechanisms covered include those that affect oral drug absorption (e.g., modulation of efflux and uptake transporters, complex formation, gastrointestinal motility and pH) and drug biotransformation (e.g., inhibition or induction of enzymes).

WHAT THE READER WILL GAIN

knowledge on the mechanisms of herb-drug pharmacokinetic interactions supported by an extended list of these types of interactions for quick reference. A critical evaluation of certain herb-drug pharmacokinetic interactions reported in the scientific literature.

TAKE HOME MESSAGE

as the incidence and severity of herb-drug pharmacokinetic interactions increase due to a worldwide rise in the use of herbal preparations, more clinical data regarding herb-drug pharmacokinetic interactions are needed to make informed decisions regarding patient safety.

Regulated phosphorylation of a major UDP-glucuronosyltransferase isozyme by tyrosine kinases dictates endogenous substrate selection for detoxification

Whereas UDP-glucuronosyltransferase-2B7 is widely distributed in different tissues, it preferentially detoxifies genotoxic 4-OH-estradiol and 4-OH-estrone (4-OHE(1)) with barely detectable 17β-estradiol (E(2)) conversion following expression in COS-1 cells. Consistent with the UDP-glucuronosyltransferase requirement for regulated phosphorylation, we discovered that 2B7 requires Src-dependent tyrosine phosphorylation. Y236F-2B7 and Y438F-2B7 mutants were null and 90% inactive, respectively, when expressed in COS-1. We demonstrated that 2B7 incorporated immunoprecipitable [(33)P]orthophosphate and that 2B7His, previously expressed in SYF-(Src,Yes,Fyn)(-/-) cells, was Src-supported or phosphorylated under in vitro conditions. Unexpectedly, 2B7 expressed in SYF(-/-) and SYF(+/-) cells metabolized 4-OHE(1) at 10- and 3-fold higher rates, respectively, than that expressed in COS-1, and similar analysis showed that E(2) metabolism was 16- and 9-fold higher than in COS-1. Because anti-Tyr(P)-438-2B7 detected Tyr(P)-438-2B7 in each cell line, results indicated that unidentified tyrosine kinase(s) (TKs) phosphorylated 2B7 in SYF(-/-). 2B7-transfected COS-1 treated with increasing concentrations of the Src-specific inhibitor PP2 down-regulated 4-OHE(1) glucuronidation reaching 60% maximum while simultaneously increasing E(2) metabolism linearly. This finding indicated that increasing PP2 inhibition of Src allows increasing E(2) metabolism caused by 2B7 phosphorylation by unidentified TK(s). Importantly, 2B7 expressed in SYF(-/-) is more competent at metabolizing E(2) in cellulo than 2B7 expressed in COS-1. To confirm Src-controlled 2B7 prevents toxicity, we showed that 2B7-transfected COS-1 efficiently protected against 4-OH-E(1)-mediated depurination. Finally, our results indicate that Src-dependent phosphorylation of 2B7 allows metabolism of 4-OHE(1), but not E(2), in COS-1, whereas non-Src-phosphorylated 2B7 metabolizes both chemicals. Importantly, we determined that 2B7 substrate selection is not fixed but varies depending upon the TK(s) that carry out its required phosphorylation.

Src supports UDP-glucuronosyltransferase-2B7 detoxification of catechol estrogens associated with breast cancer

Mammary gland-distributed and ER-bound UDP-glucuronosyltransferase (UGT)-2B7 metabolizes genotoxic catechol-estrogens (CE) associated with breast cancer initiation. Although UGT2B7 has 3 PKC- and 2 tyrosine kinase (TK)-sites, its inhibition by genistein, herbimycin-A and PP2 with parallel losses in phospho-tyrosine and phospho-Y438-2B7 content indicated it requires tyrosine phosphorylation, unlike required PKC phosphorylation of UGT1A isozymes. 2B7 mutants at PKC-sites had essentially normal activity, while its TK-sites mutants, Y236F- and Y438F-2B7, were essentially inactive. Overexpression of regular or active Src, but not dominant-negative Src, in 2B7-transfected COS-1 cells increased 2B7 activity and phospho-Y438-2B7 by 50%. Co-localization of 2B7 and regular SrcTK in COS-1 cells that was dissociated by pretreatment with Src-specific PP2-inhibitor provided strong evidence Src supports 2B7 activity. Consistent with these findings, evidence indicates an appropriate set of ER proteins with Src-homology binding-domains, including 2B7 and well-known multi-functional Src-engaged AKAP12 scaffold, supports Src-dependent phosphorylation of CE-metabolizing 2B7 enabling it to function as a tumor suppressor.

The major chemical-detoxifying system of UDP-glucuronosyltransferases requires regulated phosphorylation supported by protein kinase C

Finding rapid, reversible down-regulation of human UDP-glucuronosyltransferases (UGTs) in LS180 cells following curcumin treatment led to the discovery that UGTs require phosphorylation. UGTs, distributed primarily in liver, kidney, and gastrointestinal tract, inactivate aromatic-like metabolites and a vast number of dietary and environmental chemicals, which reduces the risk of toxicities, mutagenesis, and carcinogenesis. Our aim here is to determine relevant kinases and mechanism(s) regulating phosphorylation of constitutive UGTs in LS180 cells and 10 different human UGT cDNA-transfected COS-1 systems. Time- and concentration-dependent inhibition of immunodetectable [(33)P]orthophosphate in UGTs and protein kinase Cepsilon (PKCepsilon), following treatment of LS180 cells with curcumin or the PKC inhibitor calphostin-C, suggested UGT phosphorylation is supported by active PKC(s). Immunofluorescent and co-immunoprecipitation studies with UGT-transfected cells showed co-localization of UGT1A7His and PKCepsilon and of UGT1A10His and PKCalpha or PKCdelta. Inhibition of UGT activity by PKCepsilon-specific antagonist peptide or by PKCepsilon-targeted destruction with PKCepsilon-specific small interference RNA and activation of curcumin-down-regulated UGTs with typical PKC agonists verified a central PKC role in glucuronidation. Moreover, in vitro phosphorylation of nascent UGT1A7His by PKCepsilon confirms it is a bona fide PKC substrate. Finally, catalase or herbimycin-A inhibition of constitutive or hydrogen peroxide-activated-UGTs demonstrated that reactive oxygen species-related oxidants act as second messengers in maintaining constitutive PKC-dependent signaling evidently sustaining UGT phosphorylation and activity. Because cells use signal transduction collectively to detect and respond appropriately to environmental changes, this report, combined with our earlier demonstration that specific phospho-groups in UGT1A7 determined substrate selections, suggests regulated phosphorylation allows adaptations regarding differential phosphate utilization by UGTs to function efficiently.

Mapping the UDP-glucuronic acid binding site in UDP-glucuronosyltransferase-1A10 by homology-based modeling: confirmation with biochemical evidence

The UDP-glucuronosyltransferase (UGT) isozyme system is critical for protecting the body against endogenous and exogenous chemicals by linking glucuronic acid donated by UDP-glucuronic acid to a lipophilic acceptor substrate. UGTs convert metabolites, dietary constituents, and environmental toxicants to highly excretable glucuronides. Because of difficulties associated with purifying endoplasmic reticulum-bound UGTs for structural studies, we carried out homology-based computer modeling to aid analysis. The search found structural homology in Escherichia coli UDP-galactose 4-epimerase. Consistent with predicted similarities involving the common UDP moiety in substrate/inhibitor, UDP-glucose and UDP-hexanol amine caused competitive inhibition by Lineweaver-Burk plots. Among predicted binding sites N292, K314, K315, and K404 in UGT1A10, two informative sets of mutants K314R/Q/A/E/G and K404R/E had null activities or 2.7-fold higher/50% less activity, respectively. Scatchard analysis of binding data of the affinity ligand, 5-azidouridine-[beta- (32)P]diphosphoglucuronic acid, to purified UGT1A10-His or UGT1A7-His revealed high- and low-affinity binding sites. 2-Nitro-5-thiocyanobenzoic acid-digested UGT1A10-His bound with the radiolabeled affinity ligand revealed an 11.3 and 14.3 kDa peptide associated with K314 and K404, respectively, in a discontinuous SDS-PAGE system. Similar treatment of 1A10His-K314A bound with the ligand lacked both peptides; 1A10-HisK404R- and 1A10-HisK404E showed 1.3-fold greater and 50% less label in the 14.3 kDa peptide, respectively, compared to 1A10-His without affecting the 11.3 kDa peptide. Scatchard analysis of binding data of the affinity ligand to 1A10His-K404R and -K404E showed a 6-fold reduction and a large increase in K d, respectively. Our results indicate that K314 and K404 are required UDP-glcA binding sites in 1A10, that K404 controls activity and high-affinity sites, and that K314 and K404 are strictly conserved in 70 aligned UGTs, except for S321, equivalent to K314, in UGT2B15 and 2B17 and I321 in the inactive UGT8, which suggests UGT2B15 and 2B17 contain suboptimal activity. Hence our data strongly support UDP-glcA binding to K314 and K404 in UGT1A10.