Urate crystals, inflammation, and colchicine

GEF-H1 Is Required for Colchicine Inhibition of Neutrophil Rolling and Recruitment in Mouse Models of Gout

Gout is a painful arthritic inflammatory disease caused by buildup of monosodium urate (MSU) crystals in the joints. Colchicine, a microtubule-depolymerizing agent that is used in prophylaxis and treatment of acute gout flare, alleviates the painful inflammatory response to MSU crystals. Using i.p. and intra-articular mouse models of gout-like inflammation, we found that GEF-H1/GEF-H1/AHRGEF2, a microtubule-associated Rho-GEF, was necessary for the inhibitory effect of colchicine on neutrophil recruitment. GEF-H1 was required for neutrophil polarization in response to colchicine, characterized by uropod formation, accumulation of F-actin and myosin L chain at the leading edge, and accumulation of phosphorylated myosin L chain, flotillin-2, and P-selectin glycoprotein ligand-1 (PSGL-1) in the uropod. Wild-type neutrophils that were pre-exposed to colchicine failed to roll or accumulate on activated endothelial monolayers, whereas GEF-H1 knockout (GEF-H1^-/-) neutrophils were unaffected by treatment with colchicine. In vivo, colchicine blocked MSU-induced recruitment of neutrophils to the peritoneum and the synovium in wild-type mice, but not in GEF-H1^-/- mice. Inhibition of macrophage IL-1β production by colchicine was independent of GEF-H1, supporting a neutrophil-intrinsic mode of action. Our results suggest that the anti-inflammatory effects of colchicine in acute gout-like inflammation can be accounted for by inhibition of neutrophil-rolling interactions with the inflamed vasculature and occurs through GEF-H1-dependent neutrophil stimulation by colchicine. These results contribute to our understanding of the therapeutic action of colchicine, and could inform the application of this drug in other conditions.

Mitotic Poisons in Research and Medicine

Cancer is one of the greatest challenges of the modern medicine. Although much effort has been made in the development of novel cancer therapeutics, it still remains one of the most common causes of human death in the world, mainly in low and middle-income countries. According to the World Health Organization (WHO), cancer treatment services are not available in more then 70% of low-income countries (90% of high-income countries have them available), and also approximately 70% of cancer deaths are reported in low-income countries. Various approaches on how to combat cancer diseases have since been described, targeting cell division being among them. The so-called mitotic poisons are one of the cornerstones in cancer therapies. The idea that cancer cells usually divide almost uncontrolled and far more rapidly than normal cells have led us to think about such compounds that would take advantage of this difference and target the division of such cells. Many groups of such compounds with different modes of action have been reported so far. In this review article, the main approaches on how to target cancer cell mitosis are described, involving microtubule inhibition, targeting aurora and polo-like kinases and kinesins inhibition. The main representatives of all groups of compounds are discussed and attention has also been paid to the presence and future of the clinical use of these compounds as well as their novel derivatives, reviewing the finished and ongoing clinical trials.

The therapeutic potential of colchicine in the complications of COVID19. Could the immunometabolic properties of an old and cheap drug help?

The present study analyzes the importance of the inflammasome that involves the NLRP3 complex in the state of hypercytokinemia observed in patients with COVID-19, significantly increasing IL-1β, IL18, IL-6, and TNF. Unfortunately, improving the immune response can sometimes worsen the outcome of the disease. Studies show that colchicine, among other actions, inhibits the assembly of NLRP3 complex that is responsible for generating the active form of Caspase-1 that will convert Pro-IL-1β and Pro-IL-18 into their active forms. We suggest using colchicine, a class of drugs with low-cost, extensively tested, well-tolerated medicine as a complementary treatment for patients with COVID-19, in early stages of the disease based on knowledge of its immunomodulatory properties.

Urate-induced immune programming: Consequences for gouty arthritis and hyperuricemia

Trained immunity is a process in which innate immune cells undergo functional reprogramming in response to pathogens or damage-associated molecules leading to an enhanced non-specific immune response to subsequent stimulation. While this capacity to respond more strongly to stimuli is beneficial for host defense, in some circumstances it can lead to maladaptive programming and chronic inflammation. Gout is characterized by persistent low-grade inflammation and is associated with an increased number of comorbidities. Hyperuricemia is the main risk factor for gout and is linked to the development of comorbidities. Several experimental studies have shown that urate can mechanistically alter the inflammatory capacity of myeloid cells, while observational studies have indicated an association of hyperuricemia to a wide spectrum of common adult inflammatory diseases. In this review, we argue that hyperuricemia is a main culprit in the development of the long-term systemic inflammation seen in gout. We revisit existing evidence for urate-induced transcriptional and epigenetic reprogramming that could lead to an altered functional state of circulating monocytes consisting in enhanced responsiveness and maladaptive immune responses. By discussing specific functional adaptations of monocytes and macrophages induced by soluble urate or monosodium urate crystals and their contribution to inflammation in vitro and in vivo, we further enforce that urate is a metabolite that can induce innate immune memory and we discuss future research and possible new therapeutic approaches for gout and its comorbidities.

Colchicine--Update on mechanisms of action and therapeutic uses

OBJECTIVES

To review the literature and provide an update on the mechanisms of action and therapeutic uses of oral colchicine in arthritis and inflammatory conditions.

METHODS

We performed PubMed database searches through June 2014 for relevant studies in the English literature published since the last update of colchicine in 2008. Searches encompassed colchicine mechanisms of action and clinical applications in medical conditions. A total of 381 articles were reviewed.

RESULTS

The primary mechanism of action of colchicine is tubulin disruption. This leads to subsequent down regulation of multiple inflammatory pathways and modulation of innate immunity. Newly described mechanisms include various inhibitory effects on macrophages including the inhibition of the NACHT-LRRPYD-containing protein 3 (NALP3) inflammasome, inhibition of pore formation activated by purinergic receptors P2X7 and P2X2, and stimulation of dendritic cell maturation and antigen presentation. Colchicine also has anti-fibrotic activities and various effects on endothelial function. The therapeutic use of colchicine has extended beyond gouty arthritis and familial Mediterranean fever, to osteoarthritis, pericarditis, and atherosclerosis.

CONCLUSION

Further understanding of the mechanisms of action underlying the therapeutic efficacy of colchicine will lead to its potential use in a variety of conditions.

Uric acid as a danger signal in gout and its comorbidities

Uric acid is a waste product of purine catabolism. This molecule comes to clinical attention when it nucleates to form crystals of monosodium urate (MSU) in joints or other tissues, and thereby causes the inflammatory disease of gout. Patients with gout frequently suffer from a number of comorbid conditions including hypertension, diabetes mellitus and cardiovascular disease. Why MSU crystals trigger inflammation and are associated with comorbidities of gout has been unclear, but recent studies provide new insights into these issues. Rather than simply being a waste product, uric acid could serve a pathophysiological role as a local alarm signal that alerts the immune system to cell injury and helps to trigger both innate and adaptive immune responses. The inflammatory component of these immune responses is caused when urate crystals trigger both inflammasome-dependent and independent pathways to generate the proinflammatory cytokine IL-1. The resulting bioactive IL-1 stimulates the inflammation of gout and might contribute to the development of other comorbidities. Surprisingly, the same mechanisms underlie the inflammatory response to a number of irritant particles, many of which also cause disease. These new insights help to explain the pathogenesis of gout and point to potential new therapeutic targets for this and other sterile inflammatory diseases.

Colchicine: its mechanism of action and efficacy in crystal-induced inflammation

New light has been shed on the mechanisms of action of colchicine in crystal-associated arthropathies. Colchicine, long used to treat gout, arrests microtubule assembly and inhibits many cellular functions. At micromolar concentrations, it suppresses monosodium urate crystal-induced NACHT-LRR-PYD-containing protein-3 (NALP3) inflammasome-driven caspase-1 activation, IL-1beta processing and release, and L-selectin expression on neutrophils. At nanomolar concentrations, colchicine blocks the release of a crystal-derived chemotactic factor from neutrophil lysosomes, blocks neutrophil adhesion to endothelium by modulating the distribution of adhesion molecules on the endothelial cells, and inhibits monosodium urate crystal-induced production of superoxide anions from neutrophils. Cyto-chrome P450 3A4, the multidrug transporter P-glycoprotein, and the drugs that bind these proteins influence its pharmacokinetics and pharmacodynamics. Trial evidence supports its efficacy in acute gout and in preventing gout flares, but it has narrow therapeutic index, and overdosage is associated with gastrointestinal, hepatic, renal, neuromuscular, and cerebral toxicity; bone marrow damage; and high mortality.