The NALP3 inflammasome is required for collagen synthesis via the NF‑κB pathway

A combination of β-hydroxybutyrate and citrate ameliorates disease progression in a rat model of polycystic kidney disease

Our research has shown that interventions producing a state of ketosis are highly effective in rat, mouse, and cat models of polycystic kidney disease (PKD), preventing and partially reversing cyst growth and disease progression. The ketone β-hydroxybutyrate (BHB) appears to underlie this effect. In addition, we have demonstrated that naturally formed microcrystals within kidney tubules trigger a renoprotective response that facilitates tubular obstruction clearance in healthy animals but, alternatively, leads to cyst formation in PKD. The administration of citrate prevents microcrystal formation and slows PKD progression. Juvenile Cy/+ rats, a nonorthologous PKD model, were supplemented from 3 to 8 wk of age with water containing titrated BHB, citrate, or in combination to find minimal effective and optimal dosages, respectively. Adult rats were given a reduced BHB/citrate combination or equimolar control K/NaCl salts from 8 to 12 wk of age. In addition, adult rats were placed in metabolic cages following BHB, citrate, and BHB/citrate administration to determine the impact on mineral, creatinine, and citrate excretion. BHB or citrate alone effectively ameliorates disease progression in juvenile rats, decreasing markers of cystic disease and, in combination, producing a synergistic effect. BHB/citrate leads to partial disease regression in adult rats with established cystic disease, inhibiting cyst formation and kidney injury. BHB/citrate confers benefits via multiple mechanisms, increases creatinine and citrate excretion, and normalizes mineral excretion. BHB and citrate are widely available and generally recognized as safe compounds and, in combination, exhibit high promise for supporting kidney health in polycystic kidney disease.NEW & NOTEWORTHY Combining β-hydroxybutyrate (BHB) and citrate effectively slows and prevents cyst formation and expansion in young Cy/+ rats using less BHB and citrate than when used alone, demonstrating synergy. In adult rats, the combination causes a partial reversal of existing disease, reducing cyst number and cystic area, preserving glomerular health, and decreasing markers of kidney injury. Our results suggest a safe and feasible strategy for supporting kidney health in polycystic kidney disease (PKD) using a combination of BHB and citrate.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Pyrroloquinoline Quinone Disodium (PQQ2Na) Has an NLRP Inflammasome-Induced Caspase-1 Release Influence in UVB-Irradiated but Not ATP-Treated Human Keratinocytes but Has No Influence in Increasing Skin Cell Mitochondrial Biogenesis in Either Human Keratinocytes or Fibroblasts

Introduction

Pyrroloquinoline quinone is a bacterial-derived redox factor that has been shown to have numerous benefits in humans. Recently, a model for examining the ability of normal human epidermal keratinocytes (NHEKs) to demonstrate anti-inflammatory benefits via nod-like receptor protein (NLRP)-activated caspase-1 release was reported. The question of whether PQQ2Na might have anti-inflammatory benefits that function through NLRP-activated release of active caspase-1 has not been explored. In addition, it has been reported that PQQ2Na will induce mitochondrial biogenesis in humans when taken orally. Whether or not this effect occurs in skin cells is presently unknown.

Methods

The inflammation studies followed previously published methods that demonstrated both UVB and ATP were able to upregulate the NLRP-activated release of caspase-1 in NHEKs. In addition, NHEK and normal dermal human fibroblasts (NHDF) were treated with PQQ2Na to see if the molecule might stimulate mitochondrial biogenesis measured by increased expression of cyclooxygenase-1 (COX-1) and succinate dehydrogenase complex, subunit A (SDHA).

Results

At non-cytotoxic concentrations between 5 µg/mL and 100 µg/mL in NHEKs and between 0.1 µg/mL and 5 µg/mL in fibroblasts, the PQQ2Na had no influence on cellular mitochondrial biogenesis. In ATP-activated NHEKs at concentrations of PQQ2Na between 0.05 µg/mL and 50 µg/mL, there was no influence of PQQ2Na on release of active caspase-1. In NHEKs irradiated with 60mJ/cm² of UVB radiation as previously described and treated with 0.05 µg/mL to 50 µg/mL of PQQ2Na, the molecule showed a dose-dependent benefit at reducing the expression of active caspase-1 in the irradiated cells.

Discussion

Benefits of PQQ2Na on various skin cell types which had not been investigated previously were addressed. Surprisingly, the PPQ2Na had no apparent influence on skin cell mitochondrial biogenesis. However, the molecule has a strong suppressing influence on UVB-induced active caspase-1 release in UVB-irradiated NHEKs.

The Ameliorative Effects of Arctiin and Arctigenin on the Oxidative Injury of Lung Induced by Silica via TLR-4/NLRP3/TGF-β Signaling Pathway

Silicosis remains one of the most serious diseases worldwide, with no effective drug for its treatment. Our research results have indicated that arctiin and arctigenin could increase the mitochondrial membrane potential, which in turn reduces the production of reactive oxygen species (ROS), blocks the polarization of macrophages, and inhibits the differentiation of myofibroblasts to reduce oxidative stress, inflammation, and fibrosis. Further, our study revealed that arctiin and arctigenin suppressed the activation of NLRP3 inflammasome through the TLR-4/Myd88/NF-κB pathway and the silica-induced secretion of TNF-α, IL-1β, TGF-β, and α-SMA. Besides, the silica-induced increase in the levels of serum ceruloplasmin and HYP was also inhibited. Results of metabolomics indicated that arctiin and arctigenin could regulate the abnormal metabolic pathways associated with the development of silicosis, which involve pantothenate and CoA biosynthesis, cysteine and methionine metabolism, linoleic acid metabolism, and arginine and proline metabolism successively. Furthermore, the analysis of metabolomics, together with network topological analysis in different phases of silicosis, revealed that urine myristic acid, serum 4-hydroxyproline, and L-arginine could be regarded as diagnosis biomarkers in the early phase and formation of pulmonary fibrosis in the latter phases of silicosis. Arctiin and arctigenin could downregulate the increased levels of myristic acid in the early phase and serum 4-hydroxyproline in the latter phase of silicosis. Interestingly, the integration of TLR-4/NLRP3/TGF-β signaling and metabolomics verified the importance of macrophage polarization in the silicosis fibrosis process. To the best of our knowledge, this is the first study reporting that arctiin and arctigenin both can ameliorate silicosis effectively, and the former is a little stronger than its aglycone arctigenin because of its high oral bioavailability, low toxicity, and multimolecular active metabolites as determined by AdmetSAR and molecular docking analysis.

The Improvement Effect of Sodium Ferulate on the Formation of Pulmonary Fibrosis in Silicosis Mice Through the Neutrophil Alkaline Phosphatase 3 (NALP3)/Transforming Growth Factor-β1 (TGF-β1)/α-Smooth Muscle Actin (α-SMA) Pathway

Background

Pneumoconiosis is a chronic progressive fibrotic interstitial pneumonia for which the pathogenesis and treatment remain unclear. Previous studies showed that sodium ferulate (SF) may have a therapeutic effect, and this study explored the mechanism underlying SF-related improvement.

Material/Methods

In this study, a silicosis mouse model and primary cultured mouse lung fibroblasts were established. Hematoxylin-eosin staining, western blot analysis, quantitative real-time polymerase chain reaction, and Masson staining were used to observe the lung injury, expression of vimentin, and the degree of pulmonary fibrosis. The extracted lung fibroblasts were identified by immunofluorescence. The expression of fibrosis-related genes encoding transforming growth factor-β1 (TGF-β1), neutrophil alkaline phosphatase 3 (NALP3), collagen-1, α-smooth muscle actin (α-SMA), and phosphorylated p38 (p-p38) and p38 proteins were detected by western blot. The effects of SF and the TGF-β pathway agonist SRI-011381 on cell proliferation and the expression of fibrosis-related protein in mouse lung fibroblasts were measured by Cell Counting Kit-8, immunofluorescence, and western blot as needed.

Results

SF reduced the lung lesions in silicosis mice and inhibited the expression of vimentin and fibrosis-related genes, while having no effect on body weight. Vimentin expression was positive in the extracted cells. In vitro experiments showed that SF inhibited the proliferation of lung fibroblasts and the expression of fibrosis-related proteins. In addition, SF partly reversed the opposite regulatory effect of SRI-011381 on lung fibroblasts.

Conclusions

SF inhibited lung injury and fibrosis in silicosis mice through the NALP3/TGF-β1/α-SMA pathway.

Diesel Exhaust Particulates Enhances Susceptibility of LPS-Induced Acute Lung Injury through Upregulation of the IL-17 Cytokine-Derived TGF-β1/Collagen I Expression and Activation of NLRP3 Inflammasome Signaling in Mice

Diesel exhaust particulates (DEP) adversely affect the respiratory system and exacerbate lung diseases, resulting in high mortality rates. However, its pathogenesis is complicated, and the mechanisms involved are incompletely understood. We investigated the effects of DEP pre-exposure on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and identified the roles of interleukin (IL)-17 in mice. Mice were divided into vehicle control, DEP, LPS, and DEP pre-exposed and LPS-instilled groups. Pre-exposure to DEP enhanced the number of total cells, neutrophils, and lymphocytes in the BAL fluid of LPS-instilled mice. Pre-exposure to DEP synergistically exacerbated pulmonary acute lung inflammation and granulomatous inflammation/pulmonary fibrosis, concomitant with the enhanced expression of inflammatory cytokines in the BAL fluid and of collagen I and TGF-β1 in the lungs of LPS-instilled mice. The number of TGF-β1-positive cells in the DEP pre-exposed and LPS-instilled group was higher than that in the LPS group. The expression of NLR family pyrin domain containing 3 (NLRP3) inflammasome components was markedly increased in the DEP pre-exposed and LPS-instilled group. IL-17 levels in the BAL fluid and IL-17-positive cells in the lungs were significantly increased by pre-exposure to DEP in the LPS-induced group compared to that in the DEP or LPS group. These results suggest that DEP predominantly contributes to fibrotic lung disease in LPS-related acute lung injury by upregulating IL-17 cytokine-mediated collagen I and TGF-β1 and, at least in part, by activating LPS-induced NLRP3 inflammasome signaling. The study should be useful in devising better strategies for prevention and management of ALI.

A pathologic two-way street: how innate immunity impacts lung fibrosis and fibrosis impacts lung immunity

Lung fibrosis is characterised by the accumulation of extracellular matrix within the lung and is secondary to both known and unknown aetiologies. This accumulation of scar tissue limits gas exchange causing respiratory insufficiency. The pathogenesis of lung fibrosis is poorly understood, but immunologic‐based treatments have been largely ineffective. Despite this, accumulating evidence suggests that innate immune cells and receptors play important modulatory roles in the initiation and propagation of the disease. Paradoxically, while innate immune signalling may be important for the pathogenesis of fibrosis, there is also evidence to suggest that innate immune function against pathogens may be impaired, leading to dysregulated and/or impaired host defence. This review summarises the evidence for this pathologic two‐way street, highlights new concepts of pathogenesis and recommends future directions for research emphasis.

NLRP3 inflammasome activation from Kupffer cells is involved in liver fibrosis of Schistosoma japonicum-infected mice via NF-κB

BACKGROUND

NOD-like receptor protein 3 (NLRP3) inflammasome was reported as expressed in schistosomiasis-induced liver fibrosis (SSLF). We used an NLRP3 inflammasome inhibitor, MCC950, to investigate whether it inhibited liver fibrosis, and explored the preliminary molecular mechanism.

METHODS

BALB/c mice were infected with 15 cercariae through the abdominal skin. They received intraperitoneal injections of MCC950 on the day of infection and at day 22 post-infection. We examined their SSLF phenotype and the effect on liver fibrosis, primary Kupffer cells (KCs), and HSCs. Human hepatic stellate cell lines (human LX-2 cells) were treated with soluble egg antigen (SEA) released from the eggs. We then determined the expression of NLRP3 inflammasome and liver fibrosis-associated markers, liver granuloma and ALT/AST.

RESULTS

NLRP3 inflammasome expression in the liver was significantly increased, and eosinophilic granuloma and collagen deposition were found around the eggs in mice infected for 56 days. Additionally, IL-1β, ALT/AST in plasma, and NF-κB in liver tissue and in KCs were all greatly significantly increased. The above-mentioned indicators were largely reduced in mice treated with MCC950 on the day of infection. In vitro, lipopolysaccharide (LPS)/SEA could induce LX-2 cells to express NLRP3 and fibrosis markers, and the SEA-treated group was reversed by MCC950. Furthermore, NLRP3 inflammasome and liver fibrosis-associated markers were both increased in the primary KCs and HSCs isolated from infected mice. However, this effect was not observed in the same cells from the mice treated with MCC950 on the day of infection. Contrary to the aforementioned results, MCC950 treatment at day 22 post-infection aggravated this process. Surprisingly, NLRP3 inflammasome was involved in liver fibrosis mostly from KCs.

CONCLUSIONS

MCC950 acts dually on SSLF pathology and fibrosis in infected mice. Although MCC950 treatment improved SSLF on the day of infection, it exacerbated the pathological effects at day 22 post-infection. These dual effects were mediated via NF-κB. Moreover, NLRP3 inflammasome mainly came from KCs. Our results suggest that blocking NLRP3 on the day of infection may prove to be a promising direction in preventing SSLF.