[Ru(bpy)2(NO)SO3](PF6), a Nitric Oxide Donating Ruthenium Complex, Reduces Gout Arthritis in Mice

CXCL5 activates CXCR2 in nociceptive sensory neurons to drive joint pain and inflammation in experimental gouty arthritis

Gouty arthritis evokes joint pain and inflammation. Mechanisms driving gout pain and inflammation remain incompletely understood. Here we show that CXCL5 activates CXCR2 expressed on nociceptive sensory neurons to drive gout pain and inflammation. CXCL5 expression was increased in ankle joints of gout arthritis model mice, whereas CXCR2 showed expression in joint-innervating sensory neurons. CXCL5 activates CXCR2 expressed on nociceptive sensory neurons to trigger TRPA1 activation, resulting in hyperexcitability and pain. Neuronal CXCR2 coordinates with neutrophilic CXCR2 to contribute to CXCL5-induced neutrophil chemotaxis via triggering CGRP- and substance P-mediated vasodilation and plasma extravasation. Neuronal Cxcr2 deletion ameliorates joint pain, neutrophil infiltration and gait impairment in model mice. We confirmed CXCR2 expression in human dorsal root ganglion neurons and CXCL5 level upregulation in serum from male patients with gouty arthritis. Our study demonstrates CXCL5-neuronal CXCR2-TRPA1 axis contributes to gouty arthritis pain, neutrophil influx and inflammation that expands our knowledge of immunomodulation capability of nociceptive sensory neurons.

Total Saponin Fraction of Dioscorea Nipponica Makino Improves Gouty Arthritis Symptoms in Rats via M1/M2 Polarization of Monocytes and Macrophages Mediated by Arachidonic Acid Signaling

OBJECTIVE

To explore the mechanism of effects of total saponin fraction from Dioscorea Nipponica Makino (TSDN) on M1/M2 polarization of monocytes/macrophages and arachidonic acid (AA) pathway in rats with gouty arthritis (GA).

METHODS

Seventy-two Sprague Dawley rats were randomly divided into 4 groups (n=18 in each): normal, model, TSDN at 160 mg/kg, and celecoxib at 43.3 mg/kg. Monosodium urate crystal (MSU) was injected into the rats' ankle joints to induce an experimental GA model. Blood and tissue samples were collected on the 3rd, 5th, and 8th days of drug administration. Histopathological changes in the synovium of joints were observed via hematoxylin and eosin (HE) staining. The expression levels of arachidonic acid (AA) signaling pathway were assessed via real-time polymerase chain reaction (qPCR) and Western blot. Flow cytometry was used to determine the proportion of M1 and M2 macrophages in the peripheral blood. An enzyme-linked immunosorbent assay (ELISA) was used to detect interleukine (IL)-1 β, tumor necrosis factor-alpha (TNF-α), IL-4, IL-10, prostaglandin E2 (PGE2), and leukotriene B4 (LTB4).

RESULTS

HE staining showed that TSDN improved the synovial tissue. qPCR and Western blot showed that on the 3rd, 5th and 8th days of drug administration, TSDN reduced the mRNA and protein expressions of cyclooxygenase (COX)2, microsomal prostaglandin E synthase-1 derived eicosanoids (mPGES-1), 5-lipoxygenase (5-LOX), recombinant human mothers against decapentaplegic homolog 3 (Smad3), nucleotide-binding oligomerization domain-like receptor protein 3 (NALP3), and inducible nitric oxide synthase (iNOS) in rats' ankle synovial tissues (P<0.01). TSDN decreased COX1 mRNA and protein expression on 3rd and 5th day of drug administration and raised it on the 8th day (both P<0.01). It lowered CD68 protein expression on days 3 (P<0.01), as well as mRNA and protein expression on days 5 and 8 (P<0.01). On the 3rd, 5th, and 8th days of drug administration, TSDN elevated the mRNA and protein expression of Arg1 and CD163 (P<0.01). Flow cytometry results showed that TSDN decreased the percentage of M1 macrophages while increasing the percentage of M2 in peripheral blood (P<0.05 or P<0.01). ELISA results showed that on the 3rd, 5th, and 8th days of drug administration, TSDN decreased serum levels of IL-1 β, TNF-α, and LTB4 (P<0.01), as well as PGE2 levels on days 3rd and 8th days (P<0.05 or P<0.01); on day 8 of administration, TSDN increased IL-4 serum levels and enhanced IL-10 contents on days 5 and 8 (P<0.05 or P<0.01).

CONCLUSION

The anti-inflammatory effect of TSDN on rats with GA may be achieved by influencing M1/M2 polarization through AA signaling pathway.

Local delivery of gaseous signaling molecules for orthopedic disease therapy

Over the past decade, a proliferation of research has used nanoparticles to deliver gaseous signaling molecules for medical purposes. The discovery and revelation of the role of gaseous signaling molecules have been accompanied by nanoparticle therapies for their local delivery. While most of them have been applied in oncology, recent advances have demonstrated their considerable potential in diagnosing and treating orthopedic diseases. Three of the currently recognized gaseous signaling molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), are highlighted in this review along with their distinctive biological functions and roles in orthopedic diseases. Moreover, this review summarizes the progress in therapeutic development over the past ten years with a deeper discussion of unresolved issues and potential clinical applications.

Nitroprusside─Expanding the Potential Use of an Old Drug Using Nanoparticles

For more than 70 years, sodium nitroprusside (SNP) has been used to treat severe hypertension in hospital emergency settings. During this time, a few other clinical uses have also emerged such as in the treatment of acute heart failure as well as improving mitral incompetence and in the intra- and perioperative management during heart surgery. This drug functions by releasing nitric oxide (NO), which modulates several biological processes with many potential therapeutic applications. However, this small molecule has a short lifetime, and it has been administered through the use of NO donor molecules such as SNP. On the other hand, SNP also has some setbacks such as the release of cyanide ions, high water solubility, and very fast NO release kinetics. Currently, there are many drug delivery strategies that can be applied to overcome many of these limitations, providing novel opportunities for the use of old drugs, including SNP. This Perspective describes some nitroprusside properties and highlights new potential therapeutic uses arising from the use of drug delivery systems, mainly silica-based nanoparticles. There is a series of great opportunities to further explore SNP in many medical issues as reviewed, which deserves a closer look by the scientific community.

Reactivity of a nitrosyl ruthenium complex and its potential impact on the fate of DNA - An in vitro investigation

The role of metal complexes on facing DNA has been a topic of major interest. However, metallonitrosyl compounds have been poorly investigated regarding their reactivities and interaction with DNA. A nitrosyl compound, cis-[Ru(bpy)₂(SO₃)(NO)](PF₆)(A), showed a variety of promising biological activities catching our attention. Here, we carried out a series of studies involving the interaction and damage of DNA mediated by the metal complex A and its final product after NO release, cis-[Ru(bpy)₂(SO₃)(H₂O](B). The fate of DNA with these metal complexes was investigated upon light or chemical stimuli using electrophoresis, electronic absorption spectroscopy, circular dichroism, size-exclusion resin, mass spectrometry, electron spin resonance (ESR) and viscometry. Since many biological disorders involve the production of oxidizing species, it is important to evaluate the reactivity of these compounds under such conditions as well. Indeed, the metal complex B exhibited important reactivity with H₂O₂ enabling DNA degradation, with detection of an unusual oxygenated intermediate. ESR spectroscopy detected mainly the DMPO-OOH adduct, which only emerges if H₂O₂ and O₂ are present together. This result indicated HOO^• as a key radical likely involved in DNA damage as supported by agarose gel electrophoresis. Notably, the nitrosyl ruthenium complex did not show evidence of direct DNA damage. However, its aqua product should be carefully considered as potentially harmful to DNA deserving further in vivo studies to better address any genotoxicity.

RvD1 disrupts nociceptor neuron and macrophage activation, and neuroimmune communication reducing pain and inflammation in gouty arthritis in mice

BACKGROUND AND PURPOSE

Gouty arthritis is characterised by an intense inflammatory response to monosodium urate crystals (MSU), which induces severe pain. Current therapies are often ineffective in reducing gout-related pain. Resolvin D1 (RvD1) is a specialised pro-resolving lipid mediator with anti-inflammatory and analgesic proprieties. In this study, we evaluated the effects and mechanisms of action of RvD1 in an experimental mouse model of gouty arthritis, an aim that was not pursued previously in the literature.

EXPERIMENTAL APPROACH

Male mice were treated with RvD1 (intrathecally or intraperitoneally) before or after intraarticular stimulation with MSU. Mechanical hyperalgesia was assessed using an electronic von Frey aesthesiometer. Leukocyte recruitment was determined by knee joint wash cell counting and immunofluorescence. IL-1β production was measured by ELISA. Phosphorylated NF-kB and apoptosis-associated speck-like protein containing CARD (ASC) were detected by immunofluorescence, and mRNA expression was determined by RT-qPCR. CGRP release was determined by EIA and immunofluorescence. MSU crystal phagocytosis was evaluated by confocal microscopy.

KEY RESULTS

RvD1 inhibited MSU-induced mechanical hyperalgesia in a dose- and time-dependent manner by reducing leukocyte recruitment and IL-1β production in the knee joint. Intrathecal RvD1 reduced the activation of peptidergic neurons and macrophages as well as silenced nociceptor to macrophage communication and macrophage function. CGRP stimulated MSU phagocytosis and IL-1β production by macrophages. RvD1 downmodulated this phenomenon directly by acting on macrophages, and indirectly by inhibiting CGRP release and CGRP-dependent activation of macrophages.

CONCLUSIONS AND IMPLICATIONS

This study reveals a hitherto unknown neuro-immune axis in gouty arthritis that is targeted by RvD1.

Inflammatory Response to Regulated Cell Death in Gout and Its Functional Implications

Gout, a chronic inflammatory arthritis disease, is characterized by hyperuricemia and caused by interactions between genetic, epigenetic, and metabolic factors. Acute gout symptoms are triggered by the inflammatory response to monosodium urate crystals, which is mediated by the innate immune system and immune cells (e.g., macrophages and neutrophils), the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation, and pro-inflammatory cytokine (e.g., IL-1β) release. Recent studies have indicated that the multiple programmed cell death pathways involved in the inflammatory response include pyroptosis, NETosis, necroptosis, and apoptosis, which initiate inflammatory reactions. In this review, we explore the correlation and interactions among these factors and their roles in the pathogenesis of gout to provide future research directions and possibilities for identifying potential novel therapeutic targets and enhancing our understanding of gout pathogenesis.

The nitric oxide pathway is involved in the anti-inflammatory effect of the rutheniumcomplex [Ru(bpy)2(2-MIM)(NO)](PF6)3

Metal coordination complexes are chemotherapeutic and anti-inflammatory agents. The ruthenium complex FOR811A ([Ru(bpy)₂(2-MIM)Cl](PF₆)₃) FOR811A was evaluated in mice models of acute inflammation and behavioral tests. Animals received FOR811A (3, 10 or 30 mg/Kg; i.p.), indomethacin (20 mg/Kg; i.p.), L-NAME (20 mg/Kg; i.v.) aminoguanidine (50 mg/Kg; i.p.) or dexamethasone (0.5 mg/Kg; s.c.) 30 min before inflammatory stimulation. Paw edema was induced by carrageenan (400 μg/paw), TNF-α or L-arginine (15 nmol/paw) (5 ng/paw) and evaluated by hydroplestimometry 4 h later. Peritonitis was induced by carrageenan (500 μg; i.p.) and evaluated 4 h later for hypernociception and quantification of total/differential leukocytes, total protein reduced glutathione (GSH) and myeloperoxidase (MPO). FOR811A inhibited the paw edema induced by carrageenan at 3 (64%; p < 0.0001), 10 (73%; p < 0.0001) and 30 mg/kg (66%; p < 0.0001), and at 10 mg/kg that induced with L-arginine by 75% or TNF-α by 55% (p = 0.0012). Paw tissues histological analysis showed reduction in mast cells (46%; p = 0.0027), leukocyte infiltrate (66%; p < 0.0001), edema and hemorrhagic areas. Immunohistochemical evaluation revealed inhibition of iNOS (62%; p < 0.0001) and TNF-α (35%; p < 0.0001). In the peritonitis model FOR811A increased (2.8X; p < 0.0001) hypernociceptive threshold, reduced total leukocytes (29%; p < 0.0001), neutrophils (47%; p = 0.0003) and total proteins (36%; p = 0.0082). FOR811A also inhibited MPO (47%; p = 0.0296) and increased GSH (1.8X; p < 0.0001). In the behavioral tests, FOR811A reduced (30.6%) the number of crossings in the open field, and increased (16%) the number of falls in the Rota rod. Concluding, FOR811A presents anti-inflammatory and antioxidant effects, via nitric oxide pathway.

Influence of Pinealectomy and Long-term Melatonin Administration on Inflammation and Oxidative Stress in Experimental Gouty Arthritis

Gout is an inflammatory arthritis characterized by the deposition of monosodium urate (MSU) crystals in the joints or soft tissue. MSU crystals are potent inflammation inducers. Melatonin (MLT) is a powerful endogenous anti-inflammatory agent and effective in reducing cellular damage. In the present study, possible underlying mechanisms associated with anti-inflammatory and antioxidative effects were investigated in rats with gouty arthritis and melatonin deprivation treated with MLT. Fifty-six rats were divided into seven groups: control, sham control, pinealectomy (PNX), MSU (on the 30th day, single-dose 20 mg/ml, intraperitoneal), MSU + MLT (10 mg/kg/day for 30 days, intraperitoneal), MSU + PINX and MSU + PINX + MLT. PNX procedure was performed on the first day of the study. As compared to the controls, the results showed that MSU administration caused significant increases in oxidative stress parameters (malondialdehyde and total oxidant status). Besides, significant decreases in antioxidant defense systems (glutathione, superoxide dismutase and total antioxidant status) were observed. A statistically significant increase was found in the mean histopathological damage score in the groups that received MSU injection. It was found that histopathological changes were significantly reduced in the MSU + MLT group given MLT. In our study, it was determined that many histopathological changes, as well as swelling and temperature increase in the joint, which are markers of inflammation, were significantly reduced with MLT supplementation. These results suggest that melatonin ameliorates MSU-induced gout in the rat through inhibition of oxidative stress and proinflammatory cytokine production.

Ruthenium-nitrosyl complexes as NO-releasing molecules and potential anticancer drugs

The synthesis of new types of mono- and polynuclear ruthenium nitrosyl complexes is driving progress in the field of NO generation for a variety of applications. Light-induced Ru-NO bond dissociation...

NFIL3 Facilitates Neutrophil Autophagy, Neutrophil Extracellular Trap Formation and Inflammation During Gout via REDD1-Dependent mTOR Inactivation

Autophagy pathways play an important role in immunity and inflammation via pathogen clearance mechanisms mediated by immune cells, such as macrophages and neutrophils. In particular, autophagic activity is essential for the release of neutrophil extracellular traps (NETs), a distinct form of active neutrophil death. The current study set out to elucidate the mechanism of the NFIL3/REDD1/mTOR axis in neutrophil autophagy and NET formation during gout inflammation. Firstly, NFIL3 expression patterns were determined in the peripheral blood neutrophils of gout patients and monosodium urate (MSU)-treated neutrophils. Interactions between NFIL3 and REDD1 were identified. In addition, gain- or loss-of-function approaches were used to manipulate NFIL3 and REDD1 in both MSU-induced neutrophils and mice. The mechanism of NFIL3 in inflammation during gout was evaluated both in vivo and in vitro via measurement of cell autophagy, NET formation, MPO activity as well as levels of inflammatory factors. NFIL3 was highly-expressed in both peripheral blood neutrophils from gout patients and MSU-treated neutrophils. NFIL3 promoted the transcription of REDD1 by binding to its promoter. REDD1 augmented neutrophil autophagy and NET formation by inhibiting the mTOR pathway. In vivo experimental results further confirmed that silencing of NFIL3 reduced the inflammatory injury of acute gouty arthritis mice by inhibiting the neutrophil autophagy and NET formation, which was associated with down-regulation of REDD1 and activation of the mTOR pathway. Taken together, NFIL3 can aggravate the inflammatory reaction of gout by stimulating neutrophil autophagy and NET formation via REDD1/mTOR, highlighting NFIL3 as a potential therapeutic target for gout.

A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl₂ (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t_1/2) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl₂ complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.

Nitro-imidazole-based ruthenium complexes with antioxidant and anti-inflammatory activities

Inflammation is a physiological process triggered in response to tissue damage, and involves events related to cell recruitment, cytokines release and reactive oxygen species (ROS) production. Failing to control the process duration lead to chronification and may be associated with the development of various pathologies, including autoimmune diseases and cancer. Considering the pharmacological potential of metal-based compounds, two new ruthenium complexes were synthesized: cis-[Ru(NO₂)(bpy)₂(5NIM)]PF₆ (1) and cis-[RuCl(bpy)₂(MTZ)]PF₆ (2), where bpy = 2,2'-bipyridine, 5NIM = 5-nitroimidazole and MTZ = metronidazole. Both products were characterized by spectroscopic techniques, followed by Density Functional Theory (DFT) calculations in order to support experimental findings. Afterwards, their in vitro cytotoxic, antioxidant and anti-inflammatory activities were investigated. Compounds 1 and 2 presented expressive in vitro antioxidant activity, reducing lipid peroxidation and decreasing intracellular ROS levels with comparable effectiveness to the standard steroidal drug dexamethasone or α-tocopherol. These complexes showed no noticeable cytotoxicity on the tested cancer cell lines. Bactericidal assay against metronidazole-resistant Helicobacter pylori, a microorganism able to disrupt oxidative balance, unraveled compound 1 moderate activity over that strain. Besides this, it was able to inhibit interleukin-6 (IL-6) and tumor necrosis factor-α (TNF- α) production as well as interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) expression in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. This latter activity is remarkable, which has not been reported for other ruthenium-based complexes. Altogether, these results suggest cis-[Ru(NO₂)(bpy)₂(5NIM)]PF₆ complex has potential pharmacological application as an anti-inflammatory agent that deserve further biological investigation.

Eucalyptol alleviates inflammation and pain responses in a mouse model of gout arthritis

BACKGROUND AND PURPOSE

Gout arthritis, which is provoked by monosodium urate (MSU) crystal accumulation in the joint and periarticular tissues, induces severe pain and affects quality of life of the patients. Eucalyptol (1,8-cineol), the principal component in the essential oils of eucalyptus leaves, is known to possess anti-inflammatory and analgesic properties. We aimed to examine the therapeutic effects of eucalyptol on gout arthritis and related mechanisms.

EXPERIMENTAL APPROACH

A mouse model of gout arthritis was established via MSU injection into the ankle joint. Ankle oedema, mechanical allodynia, neutrophil infiltration, oxidative stress, NLRP3 inflammasome, and TRPV1 expression were examined.

KEY RESULTS

Eucalyptol attenuated MSU-induced mechanical allodynia and ankle oedema in dose-dependently, with effectiveness similar to indomethacin. Eucalyptol reduced inflammatory cell infiltrations in ankle tissues. Eucalyptol inhibited NLRP3 inflammasome activation and pro-inflammatory cytokine production induced by MSU in ankle tissues in vivo. Eucalyptol reduced oxidative stress induced by MSU in RAW264.7 cells in vitro as well as in ankle tissues in vivo, indicated by an increase in activities of antioxidant enzymes and reduction of ROS. Eucalyptol attenuated MSU-induced up-regulation of TRPV1 expression in ankle tissues and dorsal root ganglion neurons innervating the ankle. The in vivo effects of eucalyptol on ankle oedema, mechanical allodynia, NLRP3 inflammasome, IL-1β, and TRPV1 expression were mimicked by treating MSU-injected mice with antioxidants.

CONCLUSION AND IMPLICATIONS

Eucalyptol alleviates MSU-induced pain and inflammation via mechanisms possibly involving anti-oxidative effect. Eucalyptol and other antioxidants may represent promising therapeutic options for gout arthritis.

Probucol Ameliorates Complete Freund's Adjuvant-Induced Hyperalgesia by Targeting Peripheral and Spinal Cord Inflammation

The effect of the lipid-lowering agent probucol in inflammatory hyperalgesia and leukocyte recruitment was evaluated in a model of subacute inflammation by Complete Freund's adjuvant (CFA). As CFA induces long-lasting nociception characterized by peripheral and spinal cord inflammation, the anti-inflammatory activity of probucol was assessed at both foci. Probucol at 0.3-3 mg/kg was administrated per oral daily starting 24 h after CFA intraplantar injection. Mechanical and thermal hyperalgesia induced by CFA were determined using an electronic anesthesiometer and hot plate apparatus, respectively. Post-treatment with probucol at 3 mg/kg inhibited CFA-induced hyperalgesia over the course of 7 days as well as paw edema. Overt pain-like behaviors, which were determined by the number of flinches and time spent licking paw immediately following CFA injection, were also reduced by probucol at 3 mg/kg administered as a pre-treatment. To investigate the mechanisms underlying the analgesic effect of probucol, neutrophil recruitment to paw was assessed by myeloperoxidase activity, cytokine production, Cox-2 expression, and NF-κB activation in both paw and spinal cord by ELISA. Iba-1, GFAP, and substance P protein expression and nuclear localization of phosphorylated NF-κB were evaluated in the spinal cord by immunofluorescence. Probucol at 3 mg/kg attenuated neutrophil recruitment, cytokine levels, and NF-κB activation as well microglia and astrocyte activation, and substance P staining in the spinal cord. Taken together, the results suggest that probucol exerts its analgesic and anti-inflammatory activity in an experimental model of persistent inflammation by targeting the NF-κB pathway in peripheral and spinal cord foci.