The natural killer cell: a further innate mediator of gouty inflammation?

Traditional herbal medicine: Therapeutic potential in acute gouty arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Acute gouty arthritis (AGA) is characterized by a rapid inflammatory reaction caused by the build-up of monosodium urate (MSU) crystals in the tissues surrounding the joints. This condition often associated with hyperuricemia (HUA), is distinguished by its symptoms of intense pain, active inflammation, and swelling of the joints. Traditional approaches in AGA management often fall short of desired outcomes in clinical settings. However, recent ethnopharmacological investigations have been focusing on the potential of Traditional Herbal Medicine (THM) in various forms, exploring their therapeutic impact and targets in AGA treatment.

AIM OF THE REVIEW

This review briefly summarizes the current potential pharmacological mechanisms of THMs - including active ingredients, extracts, and prescriptions -in the treatment of AGA, and discusses the relevant potential mechanisms and molecular targets in depth. The objective of this study is to offer extensive information and a reference point for the exploration of targeted AGA treatment using THMs.

MATERIALS AND METHODS

This review obtained scientific publications focused on in vitro and in vivo studies of anti-AGA THMs conducted between 2013 and 2023. The literature was collected from various journals and electronic databases, including PubMed, Elsevier, ScienceDirect, Web of Science, and Google Scholar. The retrieval and analysis of relevant articles were guided by keywords such as "acute gouty arthritis and Chinese herbal medicine," "acute gouty arthritis herbal prescription," "acute gouty arthritis and immune cells," "acute gouty arthritis and inflammation," "acute gouty arthritis and NOD-like receptor thermoprotein domain associated protein 3 (NLRP3)," "acute gouty arthritis and miRNA," and "acute gouty arthritis and oxidative stress."

RESULTS

We found that AGA has a large number of therapeutic targets, highlighting the effectiveness the potential of THMs in AGA treatment through in vitro and in vivo studies. THMs and their active ingredients can mitigate AGA symptoms through a variety of therapeutic targets, such as influencing macrophage polarization, neutrophils, T cells, natural killer (NK) cells, and addressing factors like inflammation, NLRP3 inflammasome, signaling pathways, oxidative stress, and miRNA multi-target interactions. The anti-AGA properties of THMs, including their active components and prescriptions, were systematically summarized and categorized based on their respective therapeutic targets.

CONCLUSION

phenolic, flavonoid, terpenoid and alkaloid compounds in THMs are considered the key ingredients to improve AGA. THMs and their active ingredients achieve enhanced efficacy through interactions with multiple targets, of which NLRP3 is a main therapeutic target. Nonetheless, given the intricate composition of traditional Chinese medicine (TCM), additional research is required to unravel the underlying mechanisms and molecular targets through which THMs alleviate AGA.

Immune and inflammatory mechanisms and therapeutic targets of gout: An update

Gout is an autoimmune disease characterized by acute or chronic inflammation and damage to bone joints induced due to the precipitation of monosodium urate (MSU) crystals. In recent years, with the continuous development of animal models and ongoing clinical investigations, more immune cells and inflammatory factors have been found to play roles in gouty inflammation. The inflammatory network involved in gout has been discovered, providing a new perspective from which to develop targeted therapy for gouty inflammation. Studies have shown that neutrophil macrophages and T lymphocytes play important roles in the pathogenesis and resolution of gout, and some inflammatory cytokines, such as those in the interleukin-1 (IL-1) family, have been shown to play anti-inflammatory or proinflammatory roles in gouty inflammation, but the mechanisms underlying their roles are unclear. In this review, we explore the roles of inflammatory cytokines, inflammasomes and immune cells in the course of gout development and the research status of therapeutic drugs used for inflammation to provide insights into future targeted therapy for gouty inflammation and the direction of gout pathogenesis research.

A review on gout: Looking back and looking ahead

Gout is a metabolic disease caused by the deposition of monosodium urate (MSU) crystals inside joints, which leads to inflammation and tissue damage. Increased concentration of serum urate is an essential step in the development of gout. Serum urate is regulated by urate transporters in the kidney and intestine, especially GLUT9 (SLC2A9), URAT1 (SLC22A12) and ABCG. Activation of NLRP3 inflammasome bodies and subsequent release of IL-1β by monosodium urate crystals induce the crescendo of acute gouty arthritis, while neutrophil extracellular traps (NETs) are considered to drive the self-resolving of gout within a few days. If untreated, acute gout may eventually develop into chronic tophaceous gout characterized by tophi, chronic gouty synovitis, and structural joint damage, leading the crushing burden of treatment. Although the research on the pathological mechanism of gout has been gradually deepened in recent years, many clinical manifestations of gout are still unable to be fully elucidated. Here, we reviewed the molecular pathological mechanism behind various clinical manifestations of gout, with a view to making contributions to further understanding and treatment.

Expansion of Polymorphonuclear Myeloid-Derived Suppressor Cells in Patients With Gout

Gout is an inflammatory joint disease caused by monosodium urate (MSU) crystals; however, the mechanism underlying MSU-induced inflammation is unclear. Previous research has suggested that inflammation or cancer can drive the expansion of myeloid-derived suppressor cells (MDSCs). In this study, the role of MDSCs in MSU-induced gout inflammation was evaluated. A total of 28 patients with gout, and 20 healthy controls were recruited for the study. MDSCs, and their functions, were analyzed by flow cytometry and a T cell co-culture assay, respectively. We observed a higher frequency of PMN-MDSCs, and a stronger immunosuppressive function, in patients with gout compared to the controls. Moreover, circulating PMN-MDSCs were positively correlated with pathological indicators, including uric acid and C-reactive protein levels. We also demonstrated that MSU can induce significant PMN-MDSC expansion, using in vivo and in vitro experiments. Finally, MSU-induced PMN-MDSCs produced higher levels of IL-1β, which mediated gout inflammatory progression. Our results demonstrate that MSU modulates the expansion and suppressive function of PMN-MDSCs, providing insights into a novel mechanism underlying the pathogenesis of MSU-induced gout. Thus, MDSCs may be useful for the development of novel therapeutic strategies for the prevention and treatment of gout.

Gout in males: a possible role for COMT hypomethylation

OBJECTIVE

Gout is a common inflammatory disease, and the prevalence of gout in men is significantly higher than in women. Catechol-O-methyltransferase (COMT) regulates dopamine activity and metabolism, thereby participating in the uric acid metabolism, which in turn affects the occurrence of gout. Our study aimed to investigate the association between COMT methylation and gout in men.

METHODS

This study involved 57 male gout patients and 103 age-matched healthy men. We used quantitative methylation-specific polymerase chain reaction (qMSP) to determine DNA methylation levels in the blood. The COMT methylation level was represented by the percentage of methylation reference (PMR).

RESULTS

Our results showed that COMT methylation levels were significantly lower in gout patients than in the control group (median PMR 9.50 vs 31.34, p = 3E-5). The area under the curve (AUC) was 0.701 (95% CI 0.611-0.790, p = 2.7E-5) with a sensitivity of 68% and a specificity of 68.4%.

CONCLUSION

Our study found that there was a significant correlation between COMT hypomethylation and the risk of gout in males, and this provides an epigenetic mechanism of COMT in gout. COMT hypomethylation might be used as a potential diagnostic biomarker for gout in the future.

Effect of internal contamination with tritiated water on the neoplastic colonies in the lungs, innate anti-tumour reactions, cytokine profile, and haematopoietic system in radioresistant and radiosensitive mice

Tritium is a potentially significant source of internal radiation exposure which, at high levels, can be carcinogenic. We evaluated whether single intraperitoneal injection of BALB/c and C57BL/6 mice with tritiated water (HTO) leading to exposure to low (0.01 or 0.1 Gy) and intermediate (1.0 Gy) cumulative whole-body doses of β radiation is immunosuppressive, as judged by enhancement of artificial tumour metastases, functioning of NK lymphocytes and macrophages, circulating cytokine's levels, and numbers of bone marrow, spleen, and peripheral blood cells. We demonstrate that internal contamination of radiosensitive BALB/c and radioresistant C57BL/6 mice with HTO at all the absorbed doses tested did not affect the development of neoplastic colonies in the lungs caused by intravenous injection of syngeneic cancer cells. However, internal exposure of BALB/c and C57BL/6 mice to 0.1 and 0.01 Gy of β radiation, respectively, up-regulated cytotoxic activity of and IFN-γ synthesis in NK lymphocytes and boosted macrophage secretion of nitric oxide. Internal contamination with HTO did not affect the serum levels of pro- (IL-1β, IL-2, IL-6, TNF-α,) and anti-inflammatory (IL-1Ra, IL-4, IL-10) cytokines. In addition, exposure of mice of both strains to low and intermediate doses from the tritium-emitted β-particles did not result in any significant changes in the numbers of bone marrow, spleen, and peripheral blood cells. Overall, our data indicate that internal tritium contamination of both radiosensitive and radioresistant mice leading to low and intermediate absorbed β-radiation doses is not immunosuppressive but may enhance some but not all components of anticancer immunity.

Immunohistochemical Analysis of Scarring Trachoma Indicates Infiltration by Natural Killer and Undefined CD45 Negative Cells

INTRODUCTION

The phenotype and function of immune cells infiltrating the conjunctiva in scarring trachoma have yet to be fully characterized. We assessed tissue morphology and immunophenotype of cellular infiltrates found in trachomatous scarring compared to control participants.

METHODOLOGY

Clinical assessments and conjunctival biopsy samples were obtained from 34 individuals with trachomatous scarring undergoing trichiasis surgery and 33 control subjects undergoing cataract or retinal detachment surgery. Biopsy samples were fixed in buffered formalin and embedded in paraffin wax. Hematoxylin and eosin (H&E) staining was performed for assessment of the inflammatory cell infiltrate. Immunohistochemical staining of single markers on individual sections was performed to identify cells expressing CD3 (T-cells), CD4 (helper T-cells), CD8 (suppressor/cytotoxic T-cells and Natural Killer, NK, cells), NCR1 (NK cells), CD20 (B-cells), CD45 (nucleated hematopoietic cells), CD56 (NK and T-cells), CD68 (macrophages/monocytes) and CD83 (mature dendritic cells). The degree of scarring was assessed histologically using cross-polarized light to visualize collagen fibres.

PRINCIPLE FINDINGS

Scarring, regardless of clinical inflammation, was associated with increased inflammatory cell infiltrates on H&E and CD45 staining. Scarring was also associated with increased CD8+ and CD56+ cells, but not CD3+ cells, suggestive of a NK cell infiltrate. This was supported by the presence of NCR1+ cells. There was some increase in CD20+ cells, but no evidence for increased CD4+, CD68+ or CD83+ cells. Numerous CD45 negative cells were also seen in the population of infiltrating inflammatory cells in scarred conjunctiva. Disorganization of the normal collagen architecture was strongly associated with clinical scarring.

CONCLUSIONS/SIGNIFICANCE

These data point to the infiltration of immune cells with a phenotype suggestive of NK cells in conjunctival trachomatous scarring. A large proportion of CD45 negative inflammatory cells were also present. Future work should seek to understand the stimuli leading to the recruitment of these cells and their role in progressive scarring.

Blocking transforming growth factor-β signaling pathway augments antitumor effect of adoptive NK-92 cell therapy

Natural killer (NK) cells hold great potential for improving the immunotherapy of cancer. However, existing data indicate that tumor cells can effectively escape NK cell-mediated apoptosis through immunosuppressive effect in the tumor microenvironment. Transforming growth factor-β (TGF-β) is a potent immunosuppressant. The present study was intended to develop a treatment strategy through adoptive transfer of TGF-β insensitive NK-92 cells. To block TGF-β signaling pathway, NK-92 cells were genetically modified with dominant negative TGF-β type II receptor (DNTβRII) by optimizing electroporation using the Amaxa Nucleofector system. These genetically modified NK-92 cells were insensitive to TGF-β and able to resist the suppressive effect of TGF-β on Calu-6 lung cancer cells in vitro. To determine the antitumor activity in vivo, recipient mice were challenged with a single subcutaneous injection of Calu-6 cells. Adoptive transfer of TGF-β insensitive NK-92 cells decreased tumor proliferation, reduced lung metastasis, produced more IFN-γ, and increased the survival rate of nude mice bearing established Calu-6 cells. Hence, we have demonstrated that blocking transforming growth factor-β signaling pathway in NK cells provides a novel therapeutic strategy and warrants further investigation.

Critical role of natural killer cells in lung immunopathology during influenza infection in mice

Influenza viral infection results in excessive pulmonary inflammation that has been linked to the damage caused by immune responses and viral replication. The multifunctional cytokine interleukin (IL-15), influences the proliferation and maintenance of immune cells such as CD8(+) T cells and natural killer (NK) cells. Here we show that IL-15(-/-) mice are protected from lethal influenza infection. Irrespective of the mouse strains, the protection observed was linked to the lack of NK cells. Increased survival in the IL-15(-/-) or NK1.1(+) cell-depleted wild-type mice was associated with significantly lower lung lesions as well as decreased mononuclear cells and neutrophils in the airway lumen. Levels of interleukin 10 were significantly higher and levels of proinflammatory cytokines, including interleukin 6 and interleukin 12, were significantly lower in the bronchoalveolar lavage fluid from IL-15(-/-) and NK1.1(+) cell-depleted wild-type mice than in that from control mice. Our data suggest that NK cells significantly augment pulmonary inflammation, contributing to the pathogenesis of influenza infection.

Activation of cord blood myeloid dendritic cells by Trypanosoma cruzi and parasite-specific antibodies, proliferation of CD8+ T cells, and production of IFN-γ

We previously reported that Trypanosoma cruzi, the agent of Chagas disease, induces in congenitally infected fetuses a strong, adult-like parasite-specific CD8(+) T cell response producing IFN-γ (Hermann et al. in Blood 100:2153-2158, 2002). This suggests that the parasite is able to overcome the immaturity of neonatal antigen presenting cells, an issue which has not been previously addressed. We therefore investigated in vitro the ability of T. cruzi to activate cord blood DCs and compared its effect to that on adult cells. We show that T. cruzi induces phenotypic maturation of cord blood CD11c(+) myeloid DCs (mDCs), by enhancing surface expression of CD40, CD80, and CD83, and that parasite-specific IgG purified from cord blood of neonates born to T. cruzi-infected mothers amplify such expression. CD83, considered as the best marker of mature DCs, reaches higher level on cord blood than on adult mDCs. Allo-stimulation experiments showed that T. cruzi-activated cord blood mononuclear cells enriched in DCs (eDCs) stimulate proliferation of cord blood and adult CD3(+) T cells to a similar extent. Of note, T. cruzi-activated eDCs from cord blood trigger more potent proliferation of CD8(+) than CD8(-) (mainly CD4(+)) adult T cells, a feature not observed with adult eDCs. T cell proliferation is associated with IFN-γ release and down-regulation of IL-13 production. These data show that T. cruzi potently activates human cord blood mDCs and endows eDCs to trigger CD8(+) T cell proliferation and favor type 1 immune response. Interestingly, maternal antibodies can strengthen the development of mature DCs that might contribute to overcome the immunological immaturity associated with early life.

Phenotypic variation in IgG receptors by nonclassical FCGR2C alleles

The balance between activating and inhibitory signals from the different FcγRs for IgG ensures homeostasis of many inflammatory responses. FCGR2C is the product of an unequal crossover of the FCGR2A and FCGR2B genes encoding the activating FcγRIIa (CD32a) and inhibitory FcγRIIb (CD32b), respectively. A single nucleotide polymorphism (SNP) in exon 3 of FCGR2C results in either expression of the activating FcγRIIc (CD32c) (FCGR2C-open reading frame [ORF]) or its absence because of a stop codon (FCGR2C-Stop). Two additional variations in FcγRIIb/c expression on leukocytes have now been identified. In case of "nonclassical" FCGR2C-ORF alleles, FcγRIIc expression was unexpectedly absent, because of novel splice site mutations near exon 7 leading to another stop codon. In some individuals with FCGR2C-Stop alleles FcγRIIb was detected on NK cells, which normally are devoid of this protein. Individuals with these nonclassical FCGR2C-Stop alleles carried a deletion of FCGR2C-FCGR3B that extends into the promoter region of the adjacent FCGR2B gene and probably deletes a negative regulatory element in the FCGR2B promoter in NK cells. FcγRIIb expression on NK cells effectively inhibited killing mediated by FcγRIIIa (CD16a) in Ab-dependent cytotoxicity tests. Our findings demonstrate a more extensive and previously unnoticed variation in FcγR expression with relevance to immunity and inflammation.