Single-cell RNA sequencing in juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is one of the most common chronic inflammatory rheumatic diseases in children, with onset before age 16 and lasting for more than 6 weeks. JIA is a highly heterogeneous condition with various consequences for health and quality of life. For some JIA patients, early detection and intervention remain challenging. As a result, further investigation of the complex and unknown mechanisms underlying JIA is required. Advances in technology now allow us to describe the biological heterogeneity and function of individual cell populations in JIA. Through this review, we hope to provide novel ideas and potential targets for the diagnosis and treatment of JIA by summarizing the current findings of single-cell RNA sequencing studies and understanding how the major cell subsets drive JIA pathogenesis.

6-Formylindolo(3,2-b)carbazole Dampens Inflammation and Reduces Endotoxin-Induced Kidney Injury via Nrf2 Activation

Patients with sepsis are at a high risk of morbidity and mortality due to multiple organ injuries caused by pathological inflammation. Although sepsis is accompanied by multiple organ injuries, acute renal injury is a significant contributor to sepsis morbidity and mortality. Thus, dampening inflammation-induced renal injury may limit severe consequences of sepsis. As several studies have suggested that 6-formylindolo(3,2-b)carbazole (FICZ) is beneficial for treating various inflammatory diseases, we aimed to examine the potential protective effect of FICZ on the acute endotoxin-induced sepsis model of kidney injury. To test this, male C57Bl/6N mice were injected with FICZ (0.2 mg/kg) or vehicle 1 h prior to an injection of either lipopolysaccharides (LPS) (10 mg/kg), to induce sepsis, or phosphate-buffered saline for 24 h. Thereafter, gene expression of kidney injury and pro-inflammatory markers, circulating cytokines and chemokines, and kidney morphology were assessed. Our results show that FICZ reduced LPS-induced acute injury in kidneys from LPS-injected mice. Furthermore, we found that FICZ dampens both renal and systemic inflammation in our sepsis model. Mechanistically, our data indicated that FICZ significantly upregulates NAD(P)H quinone oxidoreductase 1 and heme oxygenase 1 via aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) in the kidneys to lessen inflammation and improve septic acute kidney injury. Overall, the data of our study show that FICZ possesses a beneficial reno-protective effect against sepsis-induced renal injury via dual activation of AhR/Nrf2.

Design of Cytochrome P450 1B1 Inhibitors via a Scaffold-Hopping Approach

Cytochrome P450 1B1 (CYP1B1) is a potential drug target in cancer research that is overexpressed in several solid tumors but is present only at low levels in healthy tissues. Its expression is associated with resistance to common chemotherapeutics, while inhibitors restore efficacy to these drugs in model systems. The majority of CYP1B1 inhibitors are derived from a limited number of scaffolds, and few have achieved outstanding selectivity against other human CYPs, which could impede clinical development. This study explores a new chemical space for CYP1B1 inhibitors using a scaffold-hopping approach and establishes 2,4-diarylthiazoles as a promising framework for further development. From a small library, compound 15 emerged as the lead, with picomolar CYP1B1 inhibition, and over 19,000-fold selectivity against its relative, CYP1A1. To investigate the activity of 15, molecular dynamics, optical spectroscopy, point mutations, and traditional structure-activity relationships were employed and revealed key interactions important for the development of CYP1B1 inhibitors.

Heteromeric complex formation between human cytochrome P450 CYP1A1 and heme oxygenase-1

P450 and heme oxygenase-1 (HO-1) receive their necessary electrons by interaction with the NADPH-cytochrome P450 reductase (POR). As the POR concentration is limiting when compared with P450 and HO-1, they must effectively compete for POR to function. In addition to these functionally required protein-protein interactions, HO-1 forms homomeric complexes, and several P450s have been shown to form complexes with themselves and with other P450s, raising the question, 'How are the HO-1 and P450 systems organized in the endoplasmic reticulum?' Recently, CYP1A2 was shown to associate with HO-1 affecting the function of both proteins. The goal of this study was to determine if CYP1A1 formed complexes with HO-1 in a similar manner. Complex formation among POR, HO-1, and CYP1A1 was measured using bioluminescence resonance energy transfer, with results showing HO-1 and CYP1A1 form a stable complex that was further stabilized in the presence of POR. The POR•CYP1A1 complex was readily disrupted by the addition of HO-1. CYP1A1 also was able to affect the POR•HO-1 complex, although the effect was smaller. This interaction between CYP1A1 and HO-1 also affected function, where the presence of CYP1A1 inhibited HO-1-mediated bilirubin formation by increasing the KmPOR•HO-1 without affecting the Vmaxapp. In like manner, HO-1 inhibited CYP1A1-mediated 7-ethoxyresorufin dealkylation by increasing the KmPOR•CYP1A1. Based on the mathematical simulation, the results could not be explained by a model where CYP1A1 and HO-1 simply compete for POR, and are consistent with the formation of a stable CYP1A1•HO-1 complex that affected the functional characteristics of both moieties.

The tryptophan derivative 6-formylindolo[3,2-b]carbazole, FICZ, a dynamic mediator of endogenous aryl hydrocarbon receptor signaling, balances cell growth and differentiation

The aryl hydrocarbon receptor (AHR) is not essential to survival, but does act as a key regulator of many normal physiological events. The role of this receptor in toxicological processes has been studied extensively, primarily employing the high-affinity ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, regulation of physiological responses by endogenous AHR ligands remains to be elucidated. Here, we review developments in this field, with a focus on 6-formylindolo[3,2-b]carbazole (FICZ), the endogenous ligand with the highest affinity to the receptor reported to date. The binding of FICZ to different isoforms of the AHR seems to be evolutionarily well conserved and there is a feedback loop that controls AHR activity through metabolic degradation of FICZ via the highly inducible cytochrome P450 1A1. Several investigations provide strong evidence that FICZ plays a critical role in normal physiological processes and can ameliorate immune diseases with remarkable efficiency. Low levels of FICZ are pro-inflammatory, providing resistance to pathogenic bacteria, stimulating the anti-tumor functions, and promoting the differentiation of cancer cells by repressing genes in cancer stem cells. In contrast, at high concentrations FICZ behaves in a manner similar to TCDD, exhibiting toxicity toward fish and bird embryos, immune suppression, and activation of cancer progression. The findings are indicative of a dual role for endogenously activated AHR in barrier tissues, aiding clearance of infections and suppressing immunity to terminate a vicious cycle that might otherwise lead to disease. There is not much support for the AHR ligand-specific immune responses proposed, the differences between FICZ and TCDD in this context appear to be explained by the rapid metabolism of FICZ.

Cytochrome P4501-inhibiting chemicals amplify aryl hydrocarbon receptor activation and IL-22 production in T helper 17 cells

The aryl hydrocarbon receptor (AHR) controls interleukin 22 production by T helper 17 cells (Th17). IL-22 contributes to intestinal homeostasis but has also been implicated in chronic inflammatory disorders and colorectal cancer, highlighting the need for appropriate regulation of IL-22 production. Upon activation, the AHR induces expression of cytochrome P4501 (CYP1) enzymes which in turn play an important feedback role that curtails the duration of AHR signaling by metabolizing AHR ligands. Recently we described how agents that inhibit CYP1 function potentiate AHR signaling by disrupting metabolic clearance of the endogenous ligand 6-formylindolo[3,2-b]carbazole (FICZ). In the present study, we investigated the immune-modulating effects of environmental pollutants such as polycyclic aromatic hydrocarbons on Th17 differentiation and IL-22 production. Using Th17 cells deficient in CYP1 enzymes (Cyp1a1/1a2/1b1-/-) we show that these chemicals potentiate AHR activation through inhibition of CYP1 enzymes which leads to increases in intracellular AHR agonists. Our findings demonstrate that IL-22 production by Th17 cells is profoundly enhanced by impaired CYP1-function and strongly suggest that chemicals able to modify CYP1 function or expression may disrupt AHR-mediated immune regulation by altering the levels of endogenous AHR agonist(s).

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

Transcription factor KLF13 inhibits AKT activation and suppresses the growth of prostate carcinoma cells

BACKGROUND

Krüppel-like factor 13 (KLF13), a member of the KLF family, is involved in the development of immunological diseases and tumor progression. However, the expression patterns and potential functions of KLF13 in prostate carcinoma are still unknown. Here, we aimed to study the roles and mechanisms of KLF13 in prostate cancer.

METHODS

The expression levels of KLF13 was detected by Immunohistochemistry in prostate tumor tissues and the paired non-tumor tissues. The effects of KLF13 up-regulation was tested by performing CCK8, cell colon formation, flow cytometric analysis and measurement of tumor proliferation in nude mice. Signaling pathway was analyzed by Western blot.

RESULTS

The current study, for the first time, found that KLF13 was downregulated in prostate tumor tissues as compared to the paired non-tumor tissues. The overexpression of KLF13 dramatically inhibited cell proliferation and induced apoptosis by suppressing the AKT pathway in human prostate cancer cells. Moreover, the ectopic expression of KLF13 efficiently delayed the onset of PC3 xenografts and inhibited the tumor growth in vivo.

CONCLUSIONS

KLF13 functions as a tumor suppressor protein in PCa, and the pharmacological activation of KLF13 might represent a potential approach for the treatment of prostate cancer.