Methylene Blue Attenuates iNOS Induction Through Suppression of Transcriptional Factor Binding Amid iNOS mRNA Transcription

Investigating the role of itaconate in macrophage activation and oxidative stress injury in sepsis-associated acute kidney injury

BACKGROUND

Sepsis may be linked to oxidative stress and can be controlled by itaconate, an activator of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. Nevertheless, the itaconate impact on sepsis-associated acute kidney injury (SA-AKI) has yet to be definitively established.

METHODS

We employed SA-AKI mouse model through a cecal ligation and puncture (CLP) procedure for the in vivo investigation of the potential nephroprotective effect of itaconate in this study. A plasmid was transfected into RAW264.7 cells to examine the Nrf2 pathway function after itaconate administration. Finally, the immune-responsive gene 1-knockout (IRG1-/-) mice were used to study the itaconate impacts on oxidative stress-induced SA-AKI.

RESULTS

We have shown that 4-octyl itaconate (OI) significantly reduced CD11b-positive macrophage aggregation and activated the Nrf2 pathway in the bone marrow-derived macrophages (BMDM). The impacts of Nrf2 inhibitor ML385 on the anti-inflammatory and antioxidant properties of itaconate were found to be partial. OI inhibited lipopolysaccharide-induced oxidative stress injury in RAW264.7 macrophages and activated Nrf2 in the nucleus to hinder the expression of nuclear factor kappa B p65, thereby suppressing oxidative stress injury in the macrophages. Additionally, the introduction of the transfected plasmid resulted in a partial inhibition of the anti-inflammatory impact of itaconate. The kidney injury caused by sepsis exhibited greater severity in the IRG1-/- mice than in the wild type mice. Exogenous OI partially attenuated the kidney injury induced by sepsis in the IRG1-/- mice and suppressed the oxidative stress injury in macrophages.

CONCLUSIONS

This investigation offers new proof to support the itaconate function in the development and progression of SA-AKI and shows a new possible therapeutic agent for the SA-AKI treatment.

The NLRP3 Inflammasome Pathway: A Review of Mechanisms and Inhibitors for the Treatment of Inflammatory Diseases

The NLRP3 inflammasome is a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Upon activation by PAMPs and DAMPs, NLRP3 oligomerizes and activates caspase-1 which initiates the processing and release of pro-inflammatory cytokines IL-1β and IL-18. NLRP3 is the most extensively studied inflammasome to date due to its array of activators and aberrant activation in several inflammatory diseases. Studies using small molecules and biologics targeting the NLRP3 inflammasome pathway have shown positive outcomes in treating various disease pathologies by blocking chronic inflammation. In this review, we discuss the recent advances in understanding the NLRP3 mechanism, its role in disease pathology, and provide a broad review of therapeutics discovered to target the NLRP3 pathway and their challenges.

Granisetron attenuates liver injury and inflammation in a rat model of cecal ligation and puncture-induced sepsis

BACKGROUND AND AIMS

Sepsis induced liver injury is recognized as a serious complication in intensive care units, it is deeply associated with oxidative stress, inflammation and subsequent pyroptosis. Hepatic pyroptosis known to aggravate sepsis-induced liver injury. Previous studies proved that granisetron has anti-inflammatory and antioxidant properties. Accordingly, this study aimed to evaluate the efficacy of granisetron on sepsis-induced liver damage using a cecal ligation and puncture (CLP) model in rats.

MAIN METHODS

Male albino rats were randomly divided into four groups: a sham control group, a granisetron control group, a CLP-induced sepsis group and a granisetron-treated CLP group. Markers of oxidative stress, inflammation, pyroptosis-related proteins and liver function were measured in addition to the histopathological study.

KEY FINDINGS

Granisetron pretreatment significantly decreased mortality and improved liver function, as indicated by decreased ALT, AST, and total bilirubin and increased albumin content. Moreover, granisetron increased GPx activity and downregulated hepatic MDA. Furthermore, granisetron administration significantly reduced TNF-α, IL-6, HMGB1 and NF-κB. It also decreased the expression of receptor for advanced glycation end and TLR4 in the liver tissue. Interestingly, granisetron inhibited pyroptosis as it reduced NLRP3, IL-1β and caspase-1. Granisetron was shown to increase Nrf2 and HO-1. In addition, granisetron treatment repaired, to some extent, the abnormal architecture of hepatic tissue.

SIGNIFICANCE

Our results suggested that granisetron is a potential therapeutic agent for sepsis-associated liver injury, possibly acting by inhibiting oxidative stress, inflammation and subsequent pyroptosis.

Methylene Blue Application to Lessen Pain: Its Analgesic Effect and Mechanism

Methylene blue (MB) is a cationic thiazine dye, widely used as a biological stain and chemical indicator. Growing evidence have revealed that MB functions to restore abnormal vasodilation and notably it is implicated even in pain relief. Physicians began to inject MB into degenerated disks to relieve pain in patients with chronic discogenic low back pain (CDLBP), and some of them achieved remarkable outcomes. For osteoarthritis and colitis, MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain. However, despite this clinical efficacy, MB has not attracted much public attention in terms of pain relief. Accordingly, this review focuses on how MB lessens pain, noting three major actions of this dye: anti-inflammation, sodium current reduction, and denervation. Moreover, we showed controversies over the efficacy of MB on CDLBP and raised also toxicity issues to look into the limitation of MB application. This analysis is the first attempt to illustrate its analgesic effects, which may offer a novel insight into MB as a pain-relief dye.

Hydroxyapatite nanocomposite as a potential agent in osteosarcoma PDT

Using Nanoplatforms as a hauler for photosensitizers is a bespoke paradigm to improve its bioavailability and to boost the PDT efficacy. Herein, the photodynamic cytotoxicity of methylene blue (MB) loaded on hydroxyapatite nanoparticles (HA-NPs) was tested against human osteosarcoma-derived cells (Saos-2 cell line). HA-NPs and HA-NPs loaded with MB (HA-NPs-MB) were prepared by a chemical precipitation method and characterized by TEM, Zeta potential, FTIR, and XRD. TEM images revealed that HA-NPs have a rod shape with a diameter of 14-17 nm and length around 46-64 nm. FTIR and Zeta potential confirmed the adsorption of cationic MB on HA-NPs. XRD pattern was identical to the standard XRD pattern of HA-NPs. Incubation of Saos-2 cells (24 h) with HA-NPs-MB then irradiation of cells (5 min) with a diode laser (808 nm), causes a higher decrement of cell viability (determined by MTT assay) than that caused by free MB. The LC₅₀ was 57.53 µg/mL and 86.99 µg/mL for HA-NPs-MB and free MB, respectively. Thus, the nanoformulation of MB greatly reduced the dose of MB required for effective PDT. This study also investigated the mode of cell death after incubation of cells with free MB or HA-NPs-MB composite then exposure to laser radiation. The results revealed that the majority of cells died by apoptosis while a minor fraction of cells died by necrosis, especially in the case of HA-NPs-MB. Levels of caspase-3 and death receptor-4 (DR-4) were more elevated in the case of HA-NPs-MB than free MB. The effect of the prepared nanocomposite and free MB on Raw murine macrophage (RAW 264.7) viability was also examined using the MTT assay. The results indicated that HA-NPs-MB in the presence of laser has a great cytotoxic effect on macrophage cells compared to other treatments. This may present an advantage through decreasing macrophage that promotes tumor growth. In conclusion, HA-NPs-MB nanocomposite surmounts free MB and HA-NPs in destroying macrophage cells and Saos-2 cells through apoptosis in the presence of laser irradiation. This study introduces a thorough and new insight on osteosarcoma (cancer cell line Saos-2) PDT using HA-NPs-MB exploiting the biosafety of HA-NPs.

Legumain-deficient macrophages promote senescence of tumor cells by sustaining JAK1/STAT1 activation

Macrophages serve as the first line of communication between tumors and the rest of the immune system, and understanding the interplay between macrophage and tumor cells is essential for developing novel macrophage-based strategy against tumor. Here, we show that deletion of legumain in macrophages activates senescence of tumor cells. Macrophage derived IL-1β mediates the pro-senescent effect of Lgmn^-/- macrophages since blockage of IL-1β reverses the senescence phenotype in both a coculture model of macrophage and tumor cells and an orthotopic mouse model of breast cancer. Sustained activation of JAK1/STAT1 signaling and increased iNOS were found in the tumor cell-cocultured Lgmn^-/- macrophages, which were necessary for IL-1β expression and secretion. Applying a specific STAT1 agonist mimics the inductive effect of legumain deletion on IL-1β expression in macrophages, and the effect can be blocked via inhibition of iNOS. Legumain and integrin αvβ3 interact to prevent STAT1 signaling in macrophages, and blockage of integrin αvβ3 stimulates STAT1 activation. Therapeutically, transplantation of bone marrow from Lgmn^-/- mice suppresses the malignant growth of tumor by upregulating tumor cell senescence. Therefore, our finding highlights legumain in macrophages as a potential therapeutic target for tumors.

Farnesyl thiosalicylic acid prevents iNOS induction triggered by lipopolysaccharide via suppression of iNOS mRNA transcription in murine macrophages

Inducible nitric oxide synthase (iNOS) is a molecule critical for the development of inflammation-associated disorders. Its induction should be tightly controlled in order to maintain cellular homeostasis. Upon lipopolysaccharide (LPS) stimulation, iNOS, in most settings, is induced by the activation of inhibitor of κB-α (IκB-α)-nuclear factor κB (NF-κB) signaling. Farnesyl thiosalicylic acid (FTS), a synthetic small molecule that is considered to detach Ras from the inner cell membrane, has been shown to exhibit numerous anti-inflammatory functions. However, it remains unclear whether and how it affects iNOS induction in macrophages. The present study addressed this issue in cultured macrophages and endotoxemic mice. Results showed that FTS pretreatment significantly prevented LPS-induced increases in iNOS protein and mRNA expression levels in murine cultured macrophages, which were confirmed in organs in vivo from endotoxemic mice, such as the liver and lung. Mechanistic studies revealed that FTS pretreatment did not affect IκB-α degradation and NF-κB activation in LPS-treated macrophages. The nuclear transport of the active NF-κB was also not affected by FTS. But FTS pretreatment reduced the binding of NF-κB to its DNA elements, and reduced NF-κB bindings to iNOS promoter inside LPS-treated macrophages. Finally, our results showed that FST pretreatment increased mouse survival rate compared to LPS alone treatment. Taken together, these results indicate that FTS attenuates iNOS induction in macrophages likely through inhibition of iNOS mRNA transcription, providing further insight into the molecular mechanism of action of FTS in inflammatory disorder therapy.

Ulinastatin attenuates liver injury and inflammation in a cecal ligation and puncture induced sepsis mouse model

Sepsis is a syndrome of life-threatening multiorgan dysfunction caused by host response dysregulation to infection. Ulinastatin (UTI), a serine protease inhibitor, possesses anti-inflammatory properties and has been suggested to modulate lipopolysaccharide-induced sepsis. However, little is known about the mechanism underlying its effects on sepsis. In the current study, we investigated the protective effect of UTI on liver injury in a cecal ligation and puncture (CLP)-induced sepsis of C57BL/6 mouse model and explored the possible mechanisms. Mice underwent CLP as sepsis models and were randomized into five groups including the sham group, UTI group, CLP group, UTI-L group, and UTI-H group. UTI was intraperitoneally administered at doses of UTI 1500 U/100 g (UTI-L group) or 3000 U/100 g (UTI-H group), before CLP. The mice were killed, and immunohistochemical changes, cytokine levels, and antioxidant enzyme activities were detected. Our results showed that UTI ameliorated CLP-mediated increases in serum aspartate aminotransferase and alanine aminotransferase activities, histological activity index, degenerative region ratio, and infiltrated inflammatory cell numbers. Moreover, UTI also decreased nitrotyrosine and 4-hydroxynonenal, activated caspase-3, and activated poly (ADP-ribose) polymerase (PARP) levels and inhibited the mitogen-activated protein kinase pathway activation in liver tissues. Our results indicated that UTI could inhibit CLP-induced liver injury by suppressing inflammation and oxidation. Our results indicated that UTI may serve as a potential therapeutic agent for sepsis.

Regulation of HSF1 protein stabilization: An updated review

Heat shock factor 1 (HSF1) is a transcriptional factor that determines the efficiency of heat shock responses (HSRs) in the cell. Given its function has been extensively studied in recent years, HSF1 is considered a potential target for the treatment of disorders associated with protein aggregation. The activity of HSF1 is traditionally regulated at the transcriptional level in which the transactivation domain of HSF1 is modified by extensive array of pos-translational modifications, such as phosphorylation, sumoylation, and acetylation. Recently, HSF1 is also reported to be regulated at the monomeric level. For example, in neurodegenerative disorders such as Huntington's disease and Alzheimer's disease the expression levels of the monomeric HSF1 are found to be reduced markedly. Methylene blue (MB) and riluzole, two clinical available drugs, increase the amount of the monomeric HSF1 in both cells and animals. Since the monomeric HSF1 not only determines the efficiency of HSRs, but exerts protective effects in a trimerization-independent manner, increasing the amount of the monomeric HSF1 via stabilization of HSF1 may be an alternative strategy for the amplification of HSR. However, to date we have no outlined knowledges about HSF1 protein stabilization, though studies regarding the regulation of the monomeric HSF1 have been documented in recent years. Here, we summarize the regulation of the monomeric HSF1 by some previously reported factors, such as synuclein, Huntingtin (Htt), TDP-43, unfolded protein response (UPR), MB and doxorubicin (DOX), as well as their possible mechanisms, aiming to push the understanding about HSF1 protein stabilization.

Methylene blue inhibits NLRP3, NLRC4, AIM2, and non-canonical inflammasome activation

Methylene blue (MB), which has antioxidant, anti-inflammatory, neuroprotective, and mitochondria protective effects, has been widely used as a dye and medication. However, the effect of MB on inflammasome activation has not yet been studied. Inflammasomes are multi-protein complexes that induce maturation of interleukins (ILs)-1β and -18 as well as caspase-1-mediated cell death, known as pyroptosis. Dysregulation of inflammasomes causes several diseases such as type 2 diabetes, Alzheimer’s disease, and gout. In this study, we assess the effect of MB on inflammasome activation in macrophages. As the result, MB attenuated activation of canonical inflammasomes such as NLRP3, NLRC4, and AIM2 as well as non-canonical inflammasome activation. In addition, MB inhibited upstream signals such as inflammasome assembly, phagocytosis, and gene expression of inflammasome components via inhibition of NF-κB signaling. Furthermore, MB reduced the activity of caspase-1. The anti-inflammasome properties of MB were further confirmed in mice models. Thus, we suggest that MB is a broad-spectrum anti-inflammasome candidate molecule.

Methylene blue and normobaric hyperoxia combination therapy in experimental ischemic stroke

INTRODUCTION

Ischemic stroke is a global burden that contributes to the disability and mortality of millions of patients. This study aimed to evaluate the efficacy of combined MB (methylene blue) and NBO (normobaric hyperoxia) therapy in experimental ischemic stroke.

METHODS

Rats with transient (60 min) MCAO (middle cerebral artery occlusion) were treated with: (1) air + vehicle (N = 8), (2) air + MB (N = 8), (3) NBO + vehicle (N = 7), and (4) NBO + MB (N = 9). MB (1 mg/kg) was administered at 30 min, again on days 2, 7, and 14 after stroke. NBO was given during MRI (30-150 min) on day 0, and again 1 h each during MRI on subsequent days. Serial diffusion, perfusion and T2 MRI were performed to evaluate lesion volumes. Foot-fault and cylinder tests were performed to evaluate sensorimotor function.

RESULTS

The major findings were: (1) NBO + MB therapy showed a greater decrease in infarct volume compared to NBO alone, but similar infarct volume compared to MB alone, (2) NBO + MB therapy accelerated sensorimotor functional recovery compared to NBO or MB alone, (3) Infarct volumes on day 2 did not change significantly from those on day 28 for all four groups, but behavioral function continued to show improved recovery in the NBO + MB group.

CONCLUSIONS

These findings support the hypothesis that combined NBO + MB further improves functional outcome and reduces infarct volume compared to either treatment alone and these improvements extended up to 28 days.

Methylene Blue inhibits the inflammatory process of the acetic acid-induced colitis in the rat colonic mucosa

Inflammatory bowel disease is a serious health problem. Although it has been widely investigated, treatment of inflammatory bowel diseases currently remains as a challenging clinical problem. Over production of nitric oxide has been demonstrated to cause tissue damage and inflammation. In this study, the effect of methylene blue (MB), a well-known inhibitor of nitric oxide synthesis, was investigated in acetic acid (AA)-induced colitis model in Sprague-Dawley rats. Eighty male rats randomized into 4 groups (control, control MB, colitis, colitis + MB). AA was applied to groups 3 and 4. MB was added into group 2 and 4. Three days later, animals were sacrificed and 8 cm distal colonic segment resected and the specimens are examined using macroscopical, histological, and biochemical methods. The results of the macroscopic and microscopic examination showed that in group 4 the mucosal damage and inflammation score significantly lower than group 3. Increased intestinal permeability in acetic acid-administered group was significantly reversed by MB application. Myeloperoxidase activity and malondialdehyde levels increased significantly, while superoxide dismutase and catalase activities were suppressed after AA-administration. These biochemical parameters were reversed in MB-treated group. Administration of acetic acid resulted in increased levels of tumor necrosis factor-α, interleukin-1β, interleukin-6, total nitrite/nitrate levels and nitric oxide synthase activity. These biochemical alterations were significantly reversed by MB application also. In conclusion, our results indicate that MB decreases the level of nitric oxide and decreases inflammation in acetic acid-induced colitis.