Decreased Expression of Sphingosine-1-Phosphate Receptor 1 in the Blood Leukocyte of Rheumatoid Arthritis Patients

Role of efferocytosis in chronic pain -- From molecular perspective

The complex nature of pain pathophysiology complicates the establishment of objective diagnostic criteria and targeted treatments. The heterogeneous manifestations of pain stemming from various primary diseases contribute to the complexity and diversity of underlying mechanisms, leading to challenges in treatment efficacy and undesirable side effects. Recent evidence suggests the presence of apoptotic cells at injury sites, the distal dorsal root ganglia (DRG), spinal cord, and certain brain regions, indicating a potential link between the ineffective clearance of dead cells and debris and pain persistence. This review highlights recent research findings indicating that efferocytosis plays a significant yet often overlooked role in lesion expansion while also representing a potentially reversible impairment that could be targeted therapeutically to mitigate chronic pain progression. We examine recent advances into how efferocytosis, a process by which phagocytes clear apoptotic cells without triggering inflammation, influences pain initiation and intensity in both human diseases and animal models. This review summarizes that efferocytosis contributes to pain progression from the perspective of defective and inefficient efferocytosis and its subsequent secondary necrocytosis, cascade inflammatory response, and the shift of phenotypic plasticity and metabolism. Additionally, we investigate the roles of newly discovered genetic alterations or modifications in biological signaling pathways in pain development and chronicity, providing insights into innovative treatment strategies that modulate efferocytosis, which are promising candidates and potential avenues for further research in pain management and prevention.

Geniposide alleviates VEGF-induced angiogenesis by inhibiting VEGFR2/PKC/ERK1/2-mediated SphK1 translocation

BACKGROUND

Rheumatoid arthritis (RA) is an angiogenesis-dependent disease caused by the imbalance of pro- and anti-angiogenic factors. More effective strategies to block synovial angiogenesis in RA should be studied. Geniposide (GE), a natural product isolated from the fruit of Gardenia jasminoides Ellis (GJ), is reported to have anti-inflammatory, anti-angiogenic and other pharmacological effects. However, the underlying mechanism through which GE affects synovial angiogenesis in RA remains unclear.

PURPOSE

In this research, we aimed to elucidate the effect and potential mechanisms of GE on angiogenesis in RA.

MATERIALS AND METHODS

Synovial angiogenesis in patients with RA and a rat model of adjuvant arthritis (AA) was detected by hematoxylin and eosin (HE) staining, immunohistochemistry (IHC), and western blottiing. The biological functions of vascular endothelial cells (VECs) and sphingosine kinase 1 (SphK1) translocation were checked by CCK-8, EdU, Transwell, tube formation, co-immunoprecipitation assays, and laser scanning confocal microscopy. The effect of the SphK1 gene on angiogenesis was assessed by transfection of SphK1-siRNA in cells and mices. The effect of GE on VEGF-induced angiogenesis was measured by Matrigel plug assay in a mouse model of AA.

RESULTS

GE effectively inhibited synovial angiogenesis and alleviated the disease process. SphK1, as a new regulatory molecule, has a potentially important relationship in regulating VEGF/VEGFR2 and S1P/S1PR1 signals. SphK1 translocation was activated via the VEGFR2/PKC/ERK1/2 pathway and was closely linked to the biological function of VECs. GE significantly reduced SphK1 translocation, thereby ameliorating the abnormal biological function of VECs. Furthermore, after transfection of SphK1 siRNA in VECs and C57BL/6 mice, silencing SphK1 caused effectively attenuation of VEGF-induced VEC biological functions and angiogenesis. In vivo, the Matrigel plug experiment indicated that GE significantly inhibited pericyte coverage, basement membrane formation, vascular permeability, and fibrinogen deposition.

CONCLUSIONS

Our findings suggest that GE inhibited VEGF-induced VEC biological functions and angiogenesis by reducing SphK1 translocation. Generally, studies have revealed that GE down-regulated VEGFR2/PKC/ERK1/2-mediated SphK1 translocation and inhibited S1P/S1PR1 signaling activation, thereby alleviating VEGF-stimulated angiogenesis. The above evidences indicated that angiogenesis inhibition may provide a new direction for RA treatment.

Inhibition of sphingosine 1-phosphate (S1P) receptor 1/2/3 ameliorates biological dysfunction in rheumatoid arthritis fibroblast-like synoviocyte MH7A cells through Gαi/Gαs rebalancing

Sphingosine 1-phosphate (S1P) exerts its various physiological and pathological effects by interacting with G protein-coupled receptors. In addition, S1P can induce biological dysfunction in fibroblast-like synoviocytes (FLSs) in the development of rheumatoid arthritis (RA). However, the mechanism underlying this S1P-induced dysfunction remains unclear. An imbalance between Gαi and Gαs can affect the level of cAMP, an important regulator of numerous cell functions. Therefore, we studied the effects of S1P receptor (S1PR) 1-, 2-, and 3-associated Gαi/Gαs imbalance on the biological function of rheumatoid arthritis fibroblast-like synoviocyte (MH7A cells). The results showed that blocking S1PR1/3 and Gαi, and activating Gαs, inhibited the proliferation, migration, invasion, and proinflammatory cytokine release of MH7A cells in a S1P-induced inflammation model, whereas suppressing S1PR2 only affected the invasion and the release of proinflammatory cytokines of these cells. Analysis of the expression of S1PR1/2/3 and Gαi/Gαs further showed that S1PR1/2/3 could regulate the Gαi/Gαs balance. Furthermore, our data suggested that the level of cAMP was also affected. Combined, our results showed that impaired S1PR1/2/3 signalling can affect MH7A cells biological function via Gαi/Gαs-cAMP signalling, which can provide a new idea for the treatment of RA.

The interplay between fibroblast-like synovial and vascular endothelial cells leads to angiogenesis via the sphingosine-1-phosphate-induced RhoA-F-Actin and Ras-Erk1/2 pathways and the intervention of geniposide

The changes of fibroblast-like synoviocytes (FLSs) and vascular endothelial cells (VECs) biological functions are closely related to angiogenesis in rheumatoid arthritis (RA). Nevertheless, how the crosstalk between FLSs and VECs interferes with RA is far from being clarified. Herein, we studied the effect of the reciprocal interactions between FLSs and VECs on angiogenesis and mechanism of geniposide (GE). After administration of GE, improvement of synovial hyperplasia in adjuvant arthritis rats was accompanied by downregulation of SphK1 and p-Erk1/2. The dynamic interaction between FLSs and VECs triggers the release of S1P by activating p-Erk1/2 and SphK1, then activating RhoA-F-actin and Ras-Erk1/2 pathways. When exposed to the inflammatory microenvironment mediated by FLSs-VECs crosstalk, proliferation, migration, and permeability of VECs were enhanced, the angiogenic factors were imbalanced. Meanwhile, the proliferation and secretory ability of FLSs increased. Interestingly, depletion of S1P or blocking of the activation of SphK1 by GE and PF-543 prevented the changes. In conclusion, S1P released during FLSs-VECs crosstalk changed their biological functions by activating RhoA-F-actin and Ras-Erk1/2 pathways. GE acted on p-Erk1/2 and SphK1, inhibited the secretion of S1P, and blocked the interplay between FLSs and VECs. These results provide new insights into the mechanism of angiogenesis in RA.

Increased Sphingosine-1-Phosphate Serum Concentrations in Subjects with Periodontitis: A Matter of Inflammation

PURPOSE

Periodontitis is an inflammatory disease of the oral cavity with an alarmingly high prevalence within the adult population. The signaling lipid sphingosine-1-phosphate (S1P) plays a crucial role in inflammatory and immunomodulatory responses. In addition to cardiovascular disease, sepsis and tumor entities, S1P has been recently identified as both mediator and biomarker in osteoporosis. We hypothesized that S1P may play a role in periodontitis as an inflammation-prone bone destructive disorder. The goal of our study was to evaluate associations between periodontitis and S1P serum concentrations in the Study of Health in Pomerania (SHIP)-Trend cohort. In addition, we investigated the expression of S1P metabolizing enzymes in inflamed gingival tissue.

PATIENTS AND METHODS

We analyzed data from 3371 participants (51.6% women) of the SHIP-Trend cohort. Periodontal parameters and baseline characteristics were assessed. Serum S1P was measured by liquid chromatography tandem mass spectrometry. The expression of S1P metabolizing enzymes was determined by immunofluorescence staining of human gingival tissue.

RESULTS

S1P serum concentrations were significantly increased in subjects with both moderate and severe periodontitis, assessed as probing depth and clinical attachment loss. In contrast, no significant association of S1P was seen with caries variables (number and percentage of decayed or filled surfaces). S1P concentrations significantly increased with increasing high-sensitivity C-reactive protein (hs-CRP) levels. Interestingly, inflamed compared to normal human gingival tissue exhibited elevated expression levels of the S1P-generating enzyme sphingosine kinase 1 (SphK1).

CONCLUSION

We report an intriguingly significant association of various periodontal parameters with serum levels of the inflammatory lipid mediator S1P. Our data point towards a key role of S1P during periodontitis pathology. Modulation of local S1P levels or its signaling properties may represent a potential future therapeutic strategy to prevent or to retard periodontitis progression and possibly reduce periodontitis-related tooth loss.

U-shaped association between plasma sphingosine-1-phosphate levels and mortality in patients with chronic systolic heart failure: a prospective cohort study

Background

The endogenous lipid molecule sphingosine-1-phosphate (S1P) has received attention in the cardiovascular field due to its significant cardioprotective effects, as revealed in animal studies. The purpose of our study was to identify the distribution characteristics of S1P in systolic heart failure patients and the prognostic value of S1P for long-term prognosis.

Methods

We recruited 210 chronic systolic heart failure patients from June 2014 to December 2015. Meanwhile 54 healthy people in the same area were selected as controls. Plasma S1P was measured by liquid chromatography-tandem mass spectrometry. Patients were grouped according to the baseline S1P level quartiles, and restricted cubic spline plots described the association between S1P and all-cause death. Cox proportional hazard analysis was used to determine the relationship between category of S1P and all-cause death.

Results

Compared with the control group, the plasma S1P in chronic heart failure patients demonstrated a higher mean level (1.269 μmol/L vs 1.122 μmol/L, P = 0.006) and a larger standard deviation (0.441 vs 0.316, P = 0.022). Based on multivariable Cox regression with restricted cubic spline analysis, a non-linear and U-shaped association between S1P levels and the risk of all-cause death was observed. After a follow-up period of 31.7 ± 10.3 months, the second quartile (0.967–1.192 μml/L) with largely normal S1P levels had the lowest all-cause mortality and either an increase (adjusted HR = 2.368, 95%CI 1.006–5.572, P = 0.048) or a decrease (adjusted HR = 0.041, 95%CI 0.002–0.808, P = 0.036) predicted a worse prognosis. The survival curves showed that patients in the lowest quartile and highest quartile were at a higher risk of death.

Conclusions

Plasma S1P levels in systolic heart failure patients are related to the long-term all-cause mortality with a U-shaped correlation.

Trial registration

CHiCTR, ChiCTR-ONC-14004463. Registered 20 March 2014.

The Roles of CCR7 for the Homing of Memory CD8+ T Cells into Their Survival Niches

Memory CD8+ T cells in the immune system are responsible for the removal of external Ags for a long period of time to protect against re-infection. Naïve to memory CD8+ T cell differentiation and memory CD8+ T cell maintenance require many different factors including local environmental factors. Thus, it has been suggested that the migration of memory CD8+ T cells into specific microenvironments alters their longevity and functions. In this review, we have summarized the subsets of memory CD8+ T cells based on their migratory capacities and described the niche hypothesis for their survival. In addition, the basic roles of CCR7 in conjunction with the migration of memory CD8+ T cells and recent understandings of their survival niches have been introduced. Finally, the applications of altering CCR7 signaling have been discussed.

Functional Lipids in Autoimmune Inflammatory Diseases

Lipids are apolar small molecules known not only as components of cell membranes but also, in recent literature, as modulators of different biological functions. Herein, we focused on the bioactive lipids that can influence the immune responses and inflammatory processes regulating vascular hyperreactivity, pain, leukocyte trafficking, and clearance. In the case of excessive pro-inflammatory lipid activity, these lipids also contribute to the transition from acute to chronic inflammation. Based on their biochemical function, these lipids can be divided into different families, including eicosanoids, specialized pro-resolving mediators, lysoglycerophospholipids, sphingolipids, and endocannabinoids. These bioactive lipids are involved in all phases of the inflammatory process and the pathophysiology of different chronic autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, type-1 diabetes, and systemic lupus erythematosus.

Inhibition of miR‑155‑5p attenuates the valvular damage induced by rheumatic heart disease

Autoimmunity is involved in the valvular damage caused by rheumatic heart disease (RHD). Increased evidence has linked microRNAs (miRNAs/miRs) to autoimmune disease. Signal transducer and activator of transcription 3 (STAT3) and sphingosine-1-phosphate receptor 1 (S1PR1) and suppressor of cytokine signaling 1 (SOCS1) have been widely studied for their roles in autoimmunity and inflammation. Thus, the current study aims to investigate the role played by miR-155-5p in RHD-induced valvular damage via the S1PR1, SOCS1/STAT3 and interleukin (IL)-6/STAT3 signaling pathways. An RHD rat model was induced by inactivated Group A streptococci and complete Freund's adjuvant. A recombinant adeno-associated virus (AAV-miR155-inhibitor) was used to inhibit the expression of miR-155-5p in the heart. Inflammation and fibrosis were assessed by hematoxylin and eosin staining and Sirius red staining. The expression of miR-155-5p in valvular tissues and serum exosomes was detected by reverse transcription-quantitative PCR. S1PR1, SOCS1, STAT3, phosphorylated STAT3, IL-6 and IL-17 protein expression was detected by western blotting and immunohistochemistry. The relationships between miR-155-5p and S1PR1 and SOCS1 were detected by dual luciferase assays. Cytokine concentrations were measured by ELISA. The expression of miR-155-5p in valve tissues and serum exosomes was increased along with decreased S1PR1 and activated SOCS1/STAT3 signaling in the RHD model. The expression of IL-6 and IL-17 was increased in the valves and the serum. Dual luciferase assays showed that miR-155-5p directly targeted S1PR1 and SOCS1. Inhibition of valvular miR-155-5p through AAV pretreatment increased S1PR1 expression and inhibited activation of the SOCS1/STAT3 signal pathway as a result of attenuated valvular inflammation and fibrosis as well as a decrease in IL-6 and IL-17 in the valves and serum. These results suggest that inhibition of miR-155-5p can reduce RHD-induced valvular damage via the S1PR1, SOCS1/STAT3 and IL-6/STAT3 signaling pathways.

Crosstalk Between Lipids and Mitochondria in Diabetic Kidney Disease

PURPOSE OF REVIEW

The goal of this review is to review the role that renal parenchymal lipid accumulation plays in contributing to diabetic kidney disease (DKD), specifically contributing to the mitochondrial dysfunction observed in glomerular renal cells in the context of DKD development and progression.

RECENT FINDINGS

Mitochondrial dysfunction has been observed in experimental and clinical DKD. Recently, Ayanga et al. demonstrate that podocyte-specific deletion of a protein involved in mitochondrial dynamics protects from DKD progression. Furthermore, our group has recently shown that ATP-binding cassette A1 (a protein involved in cholesterol and phospholipid efflux) is significantly reduced in clinical and experimental DKD and that genetic or pharmacological induction of ABCA1 is sufficient to protect from DKD. ABCA1 deficiency in podocytes leads to mitochondrial dysfunction observed with alterations of mitochondrial lipids, in particular, cardiolipin (a mitochondrial-specific phospholipid). However, through pharmacological reduction of cardiolipin peroxidation DKD progression is reverted. Lipid metabolism is significantly altered in the diabetic kidney and renders cellular components, such as the podocyte, susceptible to injury leading to worsened DKD progression. Dysfunction of the lipid metabolism pathway can also lead to mitochondrial dysfunction and mitochondrial lipid alteration. Future research aimed at targeting mitochondrial lipids content and function could prove to be beneficial for the treatment of DKD.

Lipid mediators of insulin signaling in diabetic kidney disease

Diabetic kidney disease (DKD) affects ∼40% of patients with diabetes and is associated with high mortality rates. Among different cellular targets in DKD, podocytes, highly specialized epithelial cells of the glomerular filtration barrier, are injured in the early stages of DKD. Both clinical and experimental data support the role of preserved insulin signaling as a major contributor to podocyte function and survival. However, little is known about the key modulators of podocyte insulin signaling. This review summarizes the novel knowledge that intracellular lipids such as cholesterol and sphingolipids are major determinants of podocyte insulin signaling. In particular, the implications of these lipids on DKD development, progression, and treatment will be addressed.