Sphingosine-1-phosphate receptor modulator FTY720 attenuates experimental myeloperoxidase-ANCA vasculitis in a T cell-dependent manner

Protective effect of astaxanthin on ANCA-associated vasculitis

OBJECTIVE

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease characterized by inflammation and fibrinoid necrosis of medium and small vessels, and its pathogenesis is closely related to inflammation and oxidative stress. Astaxanthin (ATX) is a carotenoid with anti-inflammatory, antioxidant, and immunomodulatory effects. We hypothesized that ATX could play a role in AAV treatment. This study aimed to investigate whether ATX has a protective effect against AAV and to elucidate its regulatory mechanism.

METHODS

In vitro experiments, neutrophils isolated from healthy people were treated with ATX or not and cultured with serum from myeloperoxidase (MPO) -ANCA-positive patients and healthy persons. The levels of IL-6 and TNF-α in neutrophil culture supernatant before and after stimulation were measured. Neutrophil extracellular traps (NETs) and intracellular reactive oxygen species (ROS) in neutrophils were detected after stimulation. In vivo study, experimental autoimmune vasculitis (EAV) rat models were established and then treated with ATX via intragastric administration for 6 consecutive weeks. Urinary erythrocytes, urinary proteins, and serum creatinine were detected and HE staining was performed to assess renal injury in rats. Lung hemorrhage was observed by gross dissection and microscopic Prussian blue staining. The level of serum MPO-ANCA was detected. Serum IL-6, TNF-α, superoxide dismutase (SOD), and glutathione peroxidase (GSH-px) in rats were measured to explore the effects of ATX on oxidative stress and inflammation in EAV rats. The deposition of MPO in kidney and lung of rats was detected by immunohistochemistry.

RESULTS

ATX significantly inhibited neutrophil secretion of inflammatory factors IL-6 and TNF-α. ATX reduced the elevated levels of ROS in neutrophils stimulated by serum from AAV patients and alleviated the release of NETs. ATX administration was observed to reduce the degree of hematuria, proteinuria, and glomerular crescent formation in EAV rats. The degree of pulmonary hemorrhage was significantly reduced. Besides, the serum levels of IL-6 and TNF-α were attenuated, and antioxidant SOD and GSH-px increased in serum. Pathological results showed that MPO deposition was decreased in lung and kidney tissues after ATX treatment.

CONCLUSION

ATX could ameliorate the organ damages in EAV rats. It could serve as a hopeful therapy for AAV by its anti-inflammatory and anti-oxidative feature as a unique nature carotenoid.

Endoplasmic Reticulum Stress and Mitochondrial Stress in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a widespread and harmful disease closely linked to mitochondrial and endoplasmic reticulum stress (ERS). Globally, severe drug-induced hepatitis, cirrhosis, and liver cancer are the primary causes of liver-related morbidity and mortality. A hallmark of DILI is ERS and changes in mitochondrial morphology and function, which increase the production of reactive oxygen species (ROS) in a vicious cycle of mutually reinforcing stress responses. Several pathways are maladapted to maintain homeostasis during DILI. Here, we discuss the processes of liver injury caused by several types of drugs that induce hepatocyte stress, focusing primarily on DILI by ERS and mitochondrial stress. Importantly, both ERS and mitochondrial stress are mediated by the overproduction of ROS, destruction of Ca2+ homeostasis, and unfolded protein response (UPR). Additionally, we review new pathways and potential pharmacological targets for DILI to highlight new possibilities for DILI treatment and mitigation.

Ceramides in Autoimmune Rheumatic Diseases: Existing Evidence and Therapeutic Considerations for Diet as an Anticeramide Treatment

Autoimmune rheumatic diseases (AIRDs) constitute a set of connective tissue disorders and dysfunctions with akin clinical manifestations and autoantibody responses. AIRD treatment is based on a comprehensive approach, with the primary aim being achieving and attaining disease remission, through the control of inflammation. AIRD therapies have a low target specificity, and this usually propels metabolic disturbances, dyslipidemias and increased cardiovascular risk. Ceramides are implicated in inflammation through several different pathways, many of which sometimes intersect. They serve as signaling molecules for apoptosis, altering immune response and driving endothelial dysfunction and as regulators in the production of other molecules, including sphingosine 1-phosphate (S1P) and ceramide 1-phosphate (C1P). With lipid metabolism being severely altered in AIRD pathology, several studies show that the concentration and variety of ceramides in human tissues is altered in patients with rheumatic diseases compared to controls. As a result, many in vitro and some in vivo (animal) studies research the potential use of ceramides as therapeutic targets in rheumatoid arthritis (RA), ankylosing spondylitis, systemic lupus erythematosus, fibromyalgia syndrome, primary Sjögren's syndrome, systemic sclerosis, myositis, systemic vasculitis and psoriatic arthritis. Furthermore, the majority of ceramide synthesis is diet-centric and, as a result, dietary interventions may alter ceramide concentrations in the blood and affect health. Subsequently, more recently several clinical trials evaluated the possibility of distinct dietary patterns and nutrients to act as anti-ceramide regimes in humans. With nutrition being an important component of AIRD-related complications, the present review details the evidence regarding ceramide levels in patients with AIRDs, the results of anti-ceramide treatments and discusses the possibility of using medical nutritional therapy as a complementary anti-ceramide treatment in rheumatic disease.

S1PR2/RhoA/ROCK1 pathway promotes inflammatory bowel disease by inducing intestinal vascular endothelial barrier damage and M1 macrophage polarization

Vascular and immune dysfunctions are thought to be related to the pathogenesis of inflammatory bowel disease (IBD), but behind this, the exact mechanism of mucosal vascular endothelial barrier dysfunction and macrophage phenotypic transition is not fully understood. Here, we explored the mechanistic role of sphingosine 1-phosphate receptor 2 (S1PR2) and its downstream G protein RhoA/Rho kinase 1 (ROCK1) signaling pathway in the intestinal endothelial barrier damage and M1 macrophage polarization in IBD. We found that the expression of S1PR2 in intestinal mucosal vascular endothelial cells and macrophages of IBD patients and DSS-induced colitis mice as well as vascular endothelial cells and macrophages treated with LPS in vitro was significantly increased. Knocking down or pharmacologically inhibiting S1PR2 significantly downregulated the expression of RhoA and ROCK1 in vascular endothelial cells and macrophages. Furthermore, inhibition of S1PR2 and ROCK1 reversed the impaired vascular barrier function and M1 macrophage polarization in vivo and in vitro, while reducing ER stress in vascular endothelial cells and glycolysis in macrophages. In addition, inhibition of ER stress or glycolysis reversed LPS-induced impairment of vascular endothelial cell barrier function and M1 macrophage polarization. Collectively, our results indicate that the S1PR2/RhoA/ROCK1 signaling pathway may participate in the pathogenesis of IBD by regulating vascular endothelial barrier function and M1 macrophage polarization.

Sphingosine-1-Phosphate Metabolism and Signaling in Kidney Diseases

In the past few decades, sphingolipids and sphingolipid metabolites have gained attention because of their essential role in the pathogenesis and progression of kidney diseases. Studies in models of experimental and clinical nephropathies have described accumulation of sphingolipids and sphingolipid metabolites, and it has become clear that the intracellular sphingolipid composition of renal cells is an important determinant of renal function. Proper function of the glomerular filtration barrier depends heavily on the integrity of lipid rafts, which include sphingolipids as key components. In addition to contributing to the structural integrity of membranes, sphingolipid metabolites, such as sphingosine-1-phosphate (S1P), play important roles as second messengers regulating biologic processes, such as cell growth, differentiation, migration, and apoptosis. This review will focus on the role of S1P in renal cells and how aberrant extracellular and intracellular S1P signaling contributes to the pathogenesis and progression of kidney diseases.