Netrin-1 regulates the inflammatory response of neutrophils and macrophages, and suppresses ischemic acute kidney injury by inhibiting COX-2-mediated PGE2 production

The Protecting Role of Black Seed Oil and Its Nano-Formulation in LPS-Induced Acute Kidney Injury in Mice: Evaluation of Oxidative Stress, Biochemical & Molecular Parameters

Background

Acute kidney injury (AKI) is a medical concern that is accompanied by the rapid deterioration of kidney function. It can be triggered by lipopolysaccharide (LPS) of gram-negative bacteria as it activates a complicated immune response, resulting in widespread inflammation and potential organ dysfunction. Black seed oil (BSO) is rich in beneficial constituents and has been widely used owing to its nutritional advantages.

Purpose

This research is aimed to investigate the potential protective effects of BSO and its nano-formulation on AKI induced by LPS. It also aimed to compare their anti-inflammatory activity with indomethacin, a known synthetic anti-inflammatory drug.

Materials and Methods

Forty-eight mice were placed randomly into 8 groups. A single intraperitoneal (i.p.) injection of 2.5 mg/kg B.W. of LPS was used to trigger inflammation, and pretreatment with BSO and its nano-formulation was at 0.2 mL/kg/day for 14 consecutive days. Indomethacin was used as a reference drug and its efficacy was tested alone or in combination with BSO at lower doses. Renal function was assessed using urea, creatinine, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). Also, oxidative and inflammatory markers were assessed by measuring levels of reduced glutathione (GSH), nitric oxide (NO), cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), and toll-like receptor-4 (TLR-4). Histopathological examination of the kidney tissues was also performed.

Results

The study showed that BSO and its nano-formulation had anti-inflammatory effects comparable to or better than those of indomethacin. They greatly decreased the oxidative stress and inflammatory markers induced by LPS. Their protective effect against pathological alterations in kidney tissues was significantly noticed.

Conclusion

BSO and its nano-formulation could be used as nephroprotective and anti-inflammatory supplements.

Netrin-1 Promotes M2 Type Activation and Inhibits Pyroptosis of Microglial Cells by Depressing RAC1/Nf-?B Pathway to Alleviate Inflammatory Pain

Netrin-1 (NTN-1) plays a vital role in the progress of nervous system development and inflammatory diseases. However, the role and underlying mechanism of NTN-1 in inflammatory pain (IP) are unclear. BV2 microglia were treated with LPS to mimic the cell status under IP. Adeno-associated virus carrying the NTN-1 gene (AAV-NTN-1) was used to overexpress NTN-1. Complete Freund's Adjuvant (CFA)-induced mouse was recruited as an in vivo model. MTT and commercial kits were utilized to evaluate cell viability and cell death of BV2 cells. The mRNA expressions and secretions of cytokines were measured using the ELISA method. Also, the pyroptosis and activation of BV2 cells were investigated based on western blotting. To verify the role of Rac1/NF-kappaB signaling, isochamaejasmin (ISO) and AAV-Rac1 were presented. The results showed that NTN-1 expression was decreased in LPS-treated BV2 microglia and spinal cord tissues of CFA-injected mice. Overexpressing NTN-1 dramatically reversed cell viability and decreased cell death rate of BV2 microglia under lipopolysaccharide (LPS) stimulation, while the level of pyroptosis was inhibited. Besides, AAV-NTN-1 rescued the activation of microglia and inflammatory injury induced by LPS, decreasing IBA-1 expression, as well as iNOS, IL-1beta and IL-6 secretions. Meanwhile AAV-NTN-1 promoted the anti-inflammation response, including increases in Arg-1, IL-4 and IL-10 levels. In addition, the LPS-induced activation of Rac1/NF-kappaB signaling was depressed by NTN-1 overexpression. The same results were verified in a CFA-induced mouse model. In conclusion, NTN-1 alleviated IP by suppressing pyroptosis and promoting M2 type activation of microglia via inhibiting Rac1/NF-?B signaling, suggesting the protective role of NTN-1 in IP. Keywords: Netrin-1, Inflammatory pain, Pyroptosis, Microglia M2 activation, Rac1/NF-kappaB.

Phytochemical characterization and multifaceted bioactivity assessment of essential oil from Ptychotis verticillata Duby: Anti-diabetic, anti-tyrosinase, and anti-inflammatory activity

The aim of this study is to explore the pharmacological properties of the essential oil derived from Ptychotis verticillata Duby (PVEO), a medicinal plant native to Morocco, focusing on its antidiabetic, anti-tyrosinase, and anti-inflammatory effects. Additionally, the study aims to characterize the phytochemical composition of PVEO and evaluate its potential as a natural therapeutic alternative for various health conditions. To achieve this, phytochemical analysis was conducted using gas chromatography-mass spectrometry (GC-MS). Furthermore, in vitro assessments were conducted to investigate PVEO's antidiabetic activity by inhibiting α-amylase, xanthine oxidase, and α-glucosidase. Tests were also undertaken to evaluate the anti-inflammatory effect of PVEO on RAW 264.7 cells stimulated by lipopolysaccharide (LPS), as well as its efficacy as an anti-tyrosinase agent and its lipoxygenase inhibition activity. The results of the phytochemical analysis revealed that PVEO is rich in terpene compounds, with percentages of 40.35 % γ-terpinene, 22.40 % carvacrol, and 19.77 % β-cymene. Moreover, in vitro evaluations demonstrated that PVEO exhibits significant inhibitory activity against α-amylase, xanthine oxidase, and α-glucosidase, indicating promising antidiabetic, and anti-gout potential. Furthermore, PVEO showed significant anti-tyrosinase activity, with an IC50 of 27.39 ± 0.44 μg/mL, and remarkable lipoxygenase inhibition (87.33 ± 2.6 %), suggesting its candidacy for dermatoprotection. Additionally, PVEO displayed a dose-dependent capacity to attenuate the production of NO and PGE2, two inflammatory mediators implicated in various pathologies, without compromising cellular viability. The findings of this study provide a solid foundation for future research on natural therapies and the development of new drugs, highlighting the therapeutic potential of PVEO in the treatment of gout, diabetes, pigmentation disorders, and inflammation.

Protective Effects of Sesamol on Renal Ischemia-Reperfusion Injury Via Regulation of Nuclear Factor Erythroid 2-Related Factor 2 Pathway

BACKGROUND

Sesamol is a natural antioxidant known for its potent antioxidant and free radical scavenging properties. This study aimed to explore the therapeutic effects and underlying mechanisms of sesamol in the development of renal ischemia-reperfusion injury (IRI) in mice.

METHODS

C57BL/6J wild-type mice were divided into 3 groups: IR group, treated with normal saline after undergoing the IRI procedure; Sesamol + IR group, treated with 30 mg/kg/d of sesamol after the IRI procedure; and Sham group, treated with normal saline but not subjected to the IRI process. Renal IRI was induced by performing a right kidney nephrectomy and subjecting the left kidney to 30-minute ischemia, followed by 24-hour reperfusion. Kidney tissues and serum were collected 24 hours post-IRI to assess the impact of sesamol on renal function after IRI. Serum creatinine and blood urea nitrogen levels were assessed, and renal cell apoptosis was detected through terminal deoxynucleotidyl transferase dUTP nick-end labeling staining. The levels of interleukin 1β and interleukin 18 in kidney tissues, as well as indicators of oxidative stress, were also measured. Furthermore, Nrf2-deficient mice were used to examine the protective function of the nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) signaling pathways induced by sesamol, as determined by western blot assay.

RESULTS

Sesamol demonstrated significant improvement in renal function, along with reductions in renal tubular injury, cell necrosis, and apoptosis in mice. It also effectively lowered key inflammatory mediator levels. Sesamol exhibited antioxidant properties by reducing malondialdehyde levels and enhancing superoxide dismutase activities 24 hours after IRI. Western blot assay revealed increased Nrf2, HO-1, and NQO-1 protein levels with sesamol treatment. Notably, Nrf2-deficient mice did not exhibit the beneficial effects of sesamol.

CONCLUSIONS

This study demonstrates that sesamol effectively alleviates renal IRI by enhancing antioxidant defenses and reducing inflammation potentially through the Nrf2/HO-1 and NQO1 signaling pathways.

The nuclear factor kappa B signaling pathway is a master regulator of renal fibrosis

Renal fibrosis is increasingly recognized as a global public health problem. Acute kidney injury (AKI) and chronic kidney disease (CKD) both result in renal fibrosis. Oxidative stress and inflammation play central roles in progressive renal fibrosis. Oxidative stress and inflammation are closely linked and form a vicious cycle in which oxidative stress induces inflammation through various molecular mechanisms. Ample evidence has indicated that a hyperactive nuclear factor kappa B (NF-ƙB) signaling pathway plays a pivotal role in renal fibrosis. Hyperactive NF-ƙB causes the activation and recruitment of immune cells. Inflammation, in turn, triggers oxidative stress through the production of reactive oxygen species and nitrogen species by activating leukocytes and resident cells. These events mediate organ injury through apoptosis, necrosis, and fibrosis. Therefore, developing a strategy to target the NF-ƙB signaling pathway is important for the effective treatment of renal fibrosis. This Review summarizes the effect of the NF-ƙB signaling pathway on renal fibrosis in the context of AKI and CKD (immunoglobulin A nephropathy, membranous nephropathy, diabetic nephropathy, hypertensive nephropathy, and kidney transplantation). Therapies targeting the NF-ƙB signaling pathway, including natural products, are also discussed. In addition, NF-ƙB-dependent non-coding RNAs are involved in renal inflammation and fibrosis and are crucial targets in the development of effective treatments for kidney disease. This Review provides a clear pathophysiological rationale and specific concept-driven therapeutic strategy for the treatment of renal fibrosis by targeting the NF-ƙB signaling pathway.

Sustained activation of 12/15 lipoxygenase (12/15 LOX) contributes to impaired renal recovery post ischemic injury in male SHR compared to females

BACKGROUND

Acute kidney injury (AKI) due to ischemia-reperfusion (IR) is a serious and frequent complication in clinical settings, and mortality rates remain high. There are well established sex differences in renal IR, with males exhibiting greater injury following an ischemic insult compared to females. We recently reported that males have impaired renal recovery from ischemic injury vs. females. However, the mechanisms mediating sex differences in renal recovery from IR injury remain poorly understood. Elevated 12/15 lipoxygenase (LOX) activity has been reported to contribute to the progression of numerous kidney diseases. The goal of the current study was to test the hypothesis that enhanced activation of 12/15 LOX contributes to impaired recovery post-IR in males vs. females.

METHODS

13-week-old male and female spontaneously hypertensive rats (SHR) were randomized to sham or 30-minute warm bilateral IR surgery. Additional male and female SHR were randomized to treatment with vehicle or the specific 12/15 LOX inhibitor ML355 1 h prior to sham/IR surgery, and every other day following up to 7-days post-IR. Blood was collected from all rats 1-and 7-days post-IR. Kidneys were harvested 7-days post-IR and processed for biochemical, histological, and Western blot analysis. 12/15 LOX metabolites 12 and 15 HETE were measured in kidney samples by liquid chromatography-mass spectrometry (LC/MS).

RESULTS

Male SHR exhibited delayed recovery of renal function post-IR vs. male sham and female IR rats. Delayed recovery in males was associated with activation of renal 12/15 LOX, increased renal 12-HETE, enhanced endoplasmic reticulum (ER) stress, lipid peroxidation, renal cell death and inflammation compared to females 7-days post-IR. Treatment of male SHR with ML355 lowered levels of 12-HETE and resulted in reduced renal lipid peroxidation, ER stress, tubular cell death and inflammation 7-days post-IR with enhanced recovery of renal function compared to vehicle-treated IR male rats. ML355 treatment did not alter IR-induced increases in plasma creatinine in females, however, tubular injury and cell death were attenuated in ML355 treated females compared to vehicle-treated rats 7 days post-IR.

CONCLUSION

Our data demonstrate that sustained activation 12/15 LOX contributes to impaired renal recovery post ischemic injury in male and female SHR, although males are more susceptible on this mechanism than females.

The role of IL-17 in acute kidney injury

Acute kidney injury (AKI) is a common clinical kidney disease with a high mortality rate. AKI is caused by a variety of factors, including sepsis, ischemia, and nephrotoxic drugs, and can progress to chronic kidney disease and end-stage renal disease. Numerous studies have suggested that cytokines can be used as therapeutic targets for AKI. IL-17 is a pro-inflammatory cytokine that not only participates in the host defense and the development of autoimmune diseases but also is linked to AKI due to a variety of factors. This review will give an overview of the structure, signaling pathways, and biological functions of IL-17, as well as its role in AKI, to show that IL-17 is a potential target for the prevention and treatment of AKI.

Macrophage efferocytosis in health and disease

Creating cellular homeostasis within a defined tissue typically relates to the processes of apoptosis and efferocytosis. A great example here is cell debris that must be removed to prevent unwanted inflammatory responses and then reduce autoimmunity. In view of that, defective efferocytosis is often assumed to be responsible for the improper clearance of apoptotic cells (ACs). This predicament triggers off inflammation and even results in disease development. Any disruption of phagocytic receptors, molecules as bridging groups, or signaling routes can also inhibit macrophage efferocytosis and lead to the impaired clearance of the apoptotic body. In this line, macrophages as professional phagocytic cells take the lead in the efferocytosis process. As well, insufficiency in macrophage efferocytosis facilitates the spread of a wide variety of diseases, including neurodegenerative diseases, kidney problems, types of cancer, asthma, and the like. Establishing the functions of macrophages in this respect can be thus useful in the treatment of many diseases. Against this background, this review aimed to recapitulate the knowledge about the mechanisms related to macrophage polarization under physiological or pathological conditions, and shed light on its interaction with efferocytosis.

Niacin mitigates blood-brain barrier tight junctional proteins dysregulation and cerebral inflammation in ketamine rat model of psychosis: Role of GPR109A receptor

Dysregulated inflammatory responses and blood-brain barrier (BBB) dysfunction are recognized as central factors in the development of psychiatric disorders. The present study was designed to evaluate the effect of niacin on BBB integrity in ketamine-induced model of psychosis. Meanwhile, mepenzolate bromide (MPN), a GPR109A receptor blocker, was used to investigate the role of this receptor on the observed niacin's effect. Male Wistar rats received ketamine (30 mg/kg/day, i.p) for 5 consecutive days and then niacin (40 mg/kg/day, p.o), with or without MPN (5 mg/kg/day, i.p), was given for the subsequent 15 days. Three days before the end of experiment, rats were behaviorally tested using open field, novel object recognition, social interaction, and forced swimming tests. Niacin significantly ameliorated ketamine-induced behavioral deficits, amended gamma aminobutyric acid and glutamate concentration, decreased tumor necrosis factor-α and matrix metallopeptidase 9 levels, and increased netrin-1 contents in the hippocampus of rats. Niacin also augmented the hippocampal expression of ZO-1, occludin, and claudin-5 proteins, indicating the ability of niacin to restore the BBB integrity. Moreover, the histopathologic changes in hippocampal neurons were alleviated. Since all the beneficial effects of niacin in the present investigation were partially abolished by the co-administration of MPN; GPR109A receptor was proven to partially mediate the observed antipsychotic effects of niacin. These data revealed that GPR109A-mediated signaling pathways might represent potential targets for therapeutic interventions to prevent or slow the progression of psychosis.

Serum netrin-1 and netrin receptor levels in fibromyalgia and osteoarthritis

Objectives: This study aims to define serum levels of netrin-1 and netrin receptors in patients with fibromyalgia (FM) and osteoarthritis (OA).

Patients and methods: This cross-sectional study was conducted with a total of 150 female participants (mean age: 47.2±16.1 years; range, 18 to 89 years) at Fırat University between June 2016 and December 2016. The participants were evaluated in three groups: the FM group with 50 patients, the OA group with 50 patients, and the control group, which included 50 healthy volunteers. Netrin-1, netrin receptors (DCC, UNC5B, and UNC5D), interleukin (IL)-6, IL-10, and IL-17 levels were analyzed by the enzyme-linked immunosorbent assay from the serum samples of the participants.

Results: The level of serum netrin-1 was significantly lower in the FM group than in the control and OA groups (p<0.01 and p<0.001, respectively). However, the difference between patients with OA and healthy controls in terms of netrin-1 was not statistically significant (p>0.05). In addition, serum levels of netrin receptors and cytokines in the FM group were similar to the control group (p>0.05). However, serum DCC, UNC5D, IL-6, and IL-10 levels were higher in the OA group compared to the control group (p<0.001, p<0.05, p<0.01, and p<0.001, respectively).

Conclusion: Serum netrin-1 level is suppressed in FM, which suggests that netrin-1 is influential in FM pathogenesis.

Persistent vascular congestion in male spontaneously hypertensive rats contributes to delayed recovery of renal function following ischemia-reperfusion compared to females

Acute kidney injury (AKI) is a serious and frequent clinical complication with mortality rates up to 80%. Vascular congestion in the renal outer medulla occurs early after ischemia reperfusion (IR) injury, and congestion has been linked to worsened outcomes following IR. There is evidence implicating both male sex and preexisting hypertension as risk factors for poor outcomes following IR. The present study tested the hypothesis that male spontaneously hypertensive rats (SHR) have greater vascular congestion and impaired renal recovery following renal IR vs. female SHR and normotensive male Sprague-Dawley rats (SD). 13 wk old male and female SHR and SD were subjected to sham surgery or 30 minutes of warm bilateral ischemia followed by reperfusion. Rats were euthanized 24 hours or 7 days post-IR. IR increased renal injury in all groups vs. sham controls at 24 hours. At 7 days post-IR, injury remained elevated only in male SHR. Histological examination of SD and SHR kidneys 24 hours post-IR showed vascular congestion in males and females. Vascular congestion was sustained only in male SHR 7 days post-IR. To assess the role of vascular congestion on impaired recovery following IR, additional male and female SHR were pretreated with heparin (200 U/kg) prior to IR. Heparin pre-treatment reduced IR-induced congestion and improved renal function in male SHR 7 days post-IR. Interestingly, preventing increases in BP in male SHR did not alter sustained vascular congestion. Our data demonstrate that IR-induced vascular congestion is a major driving factor for impaired renal recovery in male SHR.

Celecoxib has Preventive and Therapeutic Benefits against Nephrotoxicity Caused by Gentamicin in Mice

It's crucial to comprehend the impact of oxidative stress and pro-inflammatory cytokines in the gentamicin-induced kidney injury mechanism. Celecoxib was administered orally either before or after intraperitoneal therapy with gentamicin in mice. The serum levels of creatinine (SCr), blood urea nitrogen (BUN), IL-6, and TNF-α were measured by ELISA test, as well as the levels of the kidney tissue malondialdehyde (MDA), and glutathione (GSH) were also estimated spectrophotometrically. The renal expression of nuclear factor-κB (NF-κB), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and cyclooxygenase 2 (COX-2) mRNAs were evaluated by qPCR. Histopathological evaluation and Immunohistochemical examination of kidney NF-κB, IL-6, and COX-2 were also, performed. Celecoxib successfully prevented gentamicin-induced kidney damage as indicated by reducing blood BUN, SCr, and tissue MDA levels and increasing renal tissue GSH levels as well as lowering the blood IL-6 and TNF-α in comparison to mice received gentamicin. Furthermore, celecoxib has inhibited COX-2, NF-κB, IL-6, and TNF-α expression in the renal tissue. It is noteworthy that celecoxib therapy after gentamicin administration brought about substantially the same results as celecoxib treatment before gentamicin injection in mice. Our results showed the role of celecoxib as a therapeutic tool for gentamicin-induced nephrotoxicity as well as raised its beneficial prophylactic role in this medical challenge by attenuating oxidative stress and inflammation.

Therapeutic role of uterine-derived stem cells in acute kidney injury

BACKGROUND

Acute kidney injury (AKI) causes abrupt deterioration in kidney function that disrupts metabolic, electrolyte and fluid homeostasis. Although the prevalence of AKI is steadily increasing, no definitive treatment options are available, leading to severe morbidity and mortality. We evaluated the role of uterine-derived multipotent stem cells in kidney regeneration after ischemic AKI.

METHODS

Female C57BL/6J mice were hysterectomized and subsequently subject to AKI by either unilateral or bilateral renal ischemia-reperfusion injury. Uterine-derived cells (UDCs), containing a population of uterine stem cells, were isolated from the uteri of female transgenic DsRed mice and injected intravenously to AKI mice. Engraftment of DsRed cells was analyzed by flow cytometry while serum creatinine levels were determined colorimetrically. Expression of UDC markers and cytokine markers were analyzed by immunohistochemical and qRT-PCR methods, respectively. The Kaplan-Meier method was used to analyze survival time while unpaired t test with Welch's correction used for data analysis between two groups.

RESULTS

Mice with an intact uterus, and hence an endogenous source of UDCs, had a higher survival rate after bilateral ischemic AKI compared to hysterectomized mice. Mice treated with infusion of exogenous UDCs after hysterectomy/AKI had lower serum creatinine levels and higher survival rates compared to controls that did not receive UDCs. Engraftment of labeled UDCs was significantly higher in kidneys of bilateral ischemic AKI mice compared to those that underwent a sham surgery. When unilateral ischemic AKI was induced, higher numbers of UDCs were found in the injured than non-injured kidney. Immunofluorescence staining demonstrated double-positive DsRed/Lotus tetragonolobus agglutinin (LTA) positive cells and DsRed/CD31 positive cells indicating contribution of UDCs in renal tubular and vascular regeneration. Expression of Cxcl12, Bmp2, Bmp4, and Ctnf in renal tissue was significantly higher in the UDCs injection group than the control group.

CONCLUSIONS

UDCs engrafted injured kidneys, contributed to proximal tubule and vascular regeneration, improved kidney function and increased survival in AKI mice. UDC administration is a promising new therapy for AKI. Endogenous uterine stem cells likely also preserve kidney function, suggesting a novel interaction between the uterus and kidney. We suggest that hysterectomy may have a detrimental effect on response to renal injury.

Is netrin-1 a reliable inflammatory marker for periodontitis?

Background

The current study tested netrin-1 as a reliable inflammatory marker of periodontal disease.

Methods

Gingival crevicular fluid (GCF) samples were taken at baseline from 30 systemically healthy individuals. Fifteen subjects had stage II grade A or B periodontitis, and 15 were periodontally and clinically healthy. Whole-mouth periodontal parameters [probing depth (PD), clinical attachment loss (CAL), plaque index (PI), and gingival index (GI)] were recorded. The GCF samples were re-collected, and clinical parameters were re-recorded after six weeks following full-mouth scaling and root planing (SRP) in the periodontitis group.

Results

Netrin-1 GCF levels were significantly lower in periodontitis patients than periodontally healthy individuals at baseline with a significant increase in netrin-1 GCF levels after SRP (P<0.05).

Conclusion

Netrin-1 may have a significant role in the inflammatory process of chronic periodontitis; thus, it could be a promising anti-inflammatory marker in periodontal disease.

Dietary intake of n-3 polyunsaturated fatty acids alters the lipid mediator profile of the kidney but does not attenuate renal insufficiency

The efficacy of n-3 polyunsaturated fatty acids (PUFAs) in improving outcomes in a renal ischemia-reperfusion injury (IRI) model has previously been reported. However, the underlying mechanisms remain poorly understood and few reports demonstrate how dietary n-3 PUFAs influence the composition of membrane phospholipids in the kidney. Additionally, it has not been elucidated whether perilla oil (PO), which is mainly composed of the n-3 alpha-linolenic acid, mitigates renal IRI. In this study, we investigated the effect of dietary n-3 PUFAs (PO), compared with an n-6 PUFA-rich soybean oil (SO) diet, on IRI-induced renal insufficiency in a rat model. Levels of membrane phospholipids containing n-3 PUFAs were higher in the kidney of PO-rich diet-fed rats than the SO-rich diet-fed rats. Levels of blood urea nitrogen and serum creatinine were significantly higher in the ischemia-reperfusion group than the sham group under both dietary conditions. However, no significant differences were observed in blood urea nitrogen, serum creatinine, or histological damage between PO-rich diet-fed rats and SO-rich diet-fed rats. In the kidney of PO-rich diet-fed rats, levels of arachidonic acid and arachidonic acid-derived pro-inflammatory lipid mediators were lower than SO-rich diet-fed rats. Eicosapentaenoic acid and eicosapentaenoic acid-derived lipid mediators were significantly higher in the kidney of PO-rich than SO-rich diet-fed rats. These results suggest that dietary n-3 PUFAs alter the fatty acid composition of membrane phospholipids and lipid mediators in the kidney; however, this does not attenuate renal insufficiency or histological damage in a renal IRI model.

Recent advances in studies of 15-PGDH as a key enzyme for the degradation of prostaglandins

15-hydroxyprostaglandin dehydrogenase (15-PGDH; encoded by HPGD) is ubiquitously expressed in mammalian tissues and catalyzes the degradation of prostaglandins (PGs; mainly PGE2, PGD2, and PGF2α) in a process mediated by solute carrier organic anion transport protein family member 2A1 (SLCO2A1; also known as PGT, OATP2A1, PHOAR2, or SLC21A2). As a key enzyme, 15-PGDH catalyzes the rapid oxidation of 15-hydroxy-PGs into 15-keto-PGs with lower biological activity. Increasing evidence suggests that 15-PGDH plays a key role in many physiological and pathological processes in mammals and is considered a potential pharmacological target for preventing organ damage, promoting bone marrow graft recovery, and enhancing tissue regeneration. Additionally, results of whole-exome analyses suggest that recessive inheritance of an HPGD mutation is associated with idiopathic hypertrophic osteoarthropathy. Interestingly, as a tumor suppressor, 15-PGDH inhibits proliferation and induces the differentiation of cancer cells (including those associated with colorectal, lung, and breast cancers). Furthermore, a recent study identified 15-PGDH as a marker of aging tissue and a potential novel therapeutic target for resisting the complex pathology of aging-associated diseases. Here, we review and summarise recent information on the molecular functions of 15-PGDH and discuss its pathophysiological implications.

Scutellarein relieves the death and inflammation of tubular epithelial cells in ischemic kidney injury by degradation of COX-2 protein

OBJECTIVES

Acute kidney injury (AKI) is a clinical syndrome that usually caused by ischemia/reperfusion (I/R). Previous studies have revealed the protection of scutellarein against ischemia in nervous system. This study aimed to demonstrate the potential of scutellarein in ischemic AKI.

METHODS

Animal model of ischemic AKI was established by clamping bilateral kidney pedicles in Sprague-Dawley rats. HK-2 cells were exposed to oxygen glucose deprivation/reoxygenation (OGD/R) to induce a cell model of AKI. The effects of scutellarein pre-treatment were detected by H&E staining, TUNEL, ELISA, CCK-8, LDH activity assay, ROS generation, flow cytometry, qRT-PCR and western blotting. Bioinformatic analysis was performed to probe the targets of scutellarein.

RESULTS

The blood urea nitrogen (BUN) and serum creatinine (SCr) levels in rats treated with scutellarein were lower than that in model groups. Scutellarein suppressed the pathological injury of kidney, and dose-dependently inhibited the apoptosis and pro-inflammatory cytokines release (IL-1β, IL-6 and IL-18). Scutellarein prevented OGD/R-induced HK-2 cell loss and cytotoxicity. ROS generation, apoptosis, and inflammation induced by OGD/R were all inhibited by scutellarein. By searching on the TCMSP and Symmap databases, COX-2 was screened out as a target of scutellarein. Scutellarein has no significant impacts on COX-2 mRNA expression, but could inhibit its protein level. Scutellarein promoted COX-2 protein degradation via enhancing autophagy. Furthermore, overexpression of COX-2 partly eliminated the renal protection of scutellarein in HK-2 cells.

CONCLUSIONS

Scutellarein was suggested as a renal protective agent against ischemia-induced damage in AKI. The protective properties of scutellarein may be through inhibition of COX-2.

Role of prostaglandin E2 in tissue repair and regeneration

Tissue regeneration following injury from disease or medical treatment still represents a challenge in regeneration medicine. Prostaglandin E2 (PGE2), which involves diverse physiological processes via E-type prostanoid (EP) receptor family, favors the regeneration of various organ systems following injury for its capabilities such as activation of endogenous stem cells, immune regulation, and angiogenesis. Understanding how PGE2 modulates tissue regeneration and then exploring how to elevate the regenerative efficiency of PGE2 will provide key insights into the tissue repair and regeneration processes by PGE2. In this review, we summarized the application of PGE2 to guide the regeneration of different tissues, including skin, heart, liver, kidney, intestine, bone, skeletal muscle, and hematopoietic stem cell regeneration. Moreover, we introduced PGE2-based therapeutic strategies to accelerate the recovery of impaired tissue or organs, including 15-hydroxyprostaglandin dehydrogenase (15-PGDH) inhibitors boosting endogenous PGE2 levels and biomaterial scaffolds to control PGE2 release.

Hypoxia-inducible factor-dependent induction of myeloid-derived netrin-1 attenuates natural killer cell infiltration during endotoxin-induced lung injury

Sepsis and sepsis‐associated lung inflammation significantly contribute to the morbidity and mortality of critical illness. Here, we examined the hypothesis that neuronal guidance proteins could orchestrate inflammatory events during endotoxin‐induced lung injury. Through a targeted array, we identified netrin‐1 as the top upregulated neuronal guidance protein in macrophages treated with lipopolysaccharide (LPS). Furthermore, we found that netrin‐1 is highly enriched in infiltrating myeloid cells, particularly in macrophages during LPS‐induced lung injury. Transcriptional studies implicate hypoxia‐inducible factor HIF‐1α in the transcriptional induction of netrin‐1 during LPS treatment. Subsequently, the deletion of netrin‐1 in the myeloid compartment (Ntn1^loxp/loxp LysM Cre) resulted in exaggerated mortality and lung inflammation. Surprisingly, further studies revealed enhanced natural killer cells (NK cells) infiltration in Ntn1^loxp/loxp LysM Cre mice, and neutralization of NK cell chemoattractant chemokine (C‐C motif) ligand 2 (CCL2) reversed the exaggerated lung inflammation. Together, these studies provide functional insight into myeloid cell‐derived netrin‐1 in controlling lung inflammation through the modulation of CCL2‐dependent infiltration of NK cells.

Thalidomide reduces glycerol-induced acute kidney injury by inhibition of NF-κB, NLRP3 inflammasome, COX-2 and inflammatory cytokines

Acute kidney injury (AKI) is an important clinical complication of rhabdomyolysis. The inflammatory processes are involved in the pathogenesis of AKI induced by rhabdomyolysis. Thalidomide is an anti-inflammatory agent that has been used in the treatment of inflammatory disorders. The aim of this study was to investigate the therapeutic effect of thalidomide and its underlying mechanisms on a mouse model of rhabdomyolysis-induced AKI. Mice were injected with a single dose of glycerol (50%, 10 ml/kg, im) to induce AKI, and treated with thalidomide (40 and 80 mg/kg/day, orally) for 2 days. Renal tissue and blood samples were collected for histological and biochemical analysis. In thalidomide treated mice, blood urea nitrogen (BUN) (59.3 ± 19.6 vs. 223 ± 33 mg/dl), plasma creatinine (0.58 ± 0.3 vs. 1.28 ± 0.3 mg/dl), relative kidney weight (0.93 ± 0.13% vs. 1.22 ± 0.1%) and histopathological damage (1.5 ± 0.8 vs. 3.3 ± 1.1 score) were significantly lower as compared to the glycerol group. The results also showed that the levels of malondialdehyde (MDA) (0.13 ± 0.02 vs. 0.2 ± 0.01 µM/mg), myeloperoxidase (MPO) (0.1 ± 0.05 vs. 0.25 ± 0.02 U/mg) and the expression of nuclear factor kappa B (NF-κB) (1.7-fold), NLRP3 inflammasome (1.4-fold) and cyclooxygenase (COX)-2 (3-fold) in renal tissue were significantly lower in thalidomide treated group than those in the glycerol group. Thalidomide treatment resulted in lower renal pro-inflammatory cytokines tumor necrosis factor (TNF)-α (6.7 ± 0.8 vs. 12.3 ± 1.2 ng/ml), interleukin (IL)-1β (3.2 ± 0.5 vs. 5.1 ± 0.3 pg/mg), IL-6 (24.7 ± 2.4 vs. 33 ± 3 pg/mg) and transforming growth factor (TGF)-β1 (0.6 ± 0.17 vs. 1.56 ± 0.24 ng/ml) than those in the glycerol treated mice. In addition the levels of monocyte chemoattractant protein (MCP)-1 (9.5 ± 1 vs. 12.8 ± 1.1 pg/mg) and intercellular adhesion molecule (ICAM)-1 (22.8 ± 7.8 vs. 53.3 ± 5.5 pg/mg) were significantly lower in renal tissue of mice treated with thalidomide as compared to the glycerol treated mice. In conclusion these data revealed that thalidomide may be a potential therapeutic approach against rhabdomyolysis-induced AKI through inhibition of inflammatory responses.

Dp44mT regulates the levels of inflammatory mediators through blocking NF-κB nuclear translocation in LPS-stimulated RAW 264.7 macrophages

Inflammation is increased by infection with pathogens such as viruses, bacteria, and parasites. High levels of inflammatory mediators and infiltration of macrophages into inflammatory lesions were reported in severe inflammatory diseases. Here, the aim of this study was to evaluate an anti-inflammatory activity of di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Dp44mT (1–100 ng/mL) had no effect on viability of RAW 264.7 macrophages. Dp44mT (100 ng/mL) significantly reduced LPS-induced release of nitric oxide and expression of inducible nitric oxide synthase and cyclooxygenase-2. A significant upregulation of tumor necrosis factor (TNF)-α and interleukin (IL)-6 by LPS stimulation was downregulated by treatment with Dp44mT. Dp44mT blocked activation of nuclear factor-κB by the interruption of IκBα phosphorylation. Dp44mT suppressed the phagocytosis. Furthermore, administration of Dp44mT significantly reduced the serum levels of TNF-α and IL-6 in LPS-treated mice without side effects. In conclusion, these results indicate that Dp44mT has an anti-inflammatory activity and may be of therapeutic significant for the prevention and treatment of inflammatory diseases.

Greater high-mobility group box 1 in male compared with female spontaneously hypertensive rats worsens renal ischemia-reperfusion injury

Renal ischemia is the most common cause of acute kidney injury. Damage-associated molecular patterns (DAMPs) initiate an inflammatory response and contribute to ischemia-reperfusion (IR) injury in males, yet the contribution of DAMPs to IR injury in females is unknown. The goal of the current study was to test the hypothesis that males have greater increases in the DAMP high-mobility group box 1 (HMGB1), worsening injury compared with females. Thirteen-week-old male and female spontaneously hypertensive rats (SHR) were subjected to sham or 45-min warm bilateral ischemia followed by 24 h of reperfusion before measurement of HMGB1 and renal function. Additional SHR were pre-treated with control (IgG) or HMGB1 neutralizing antibody (300 µg/rat) 1 h prior to renal ischemia. Blood, urine and kidneys were harvested 24 h post-IR for histological and Western blot analyses. Initial studies confirmed that IR resulted in greater increases in renal HMGB1 in male SHR compared with females. Greater renal HMGB1 in male SHR post-IR resulted in greater increases in serum TNF-α and renal IL-1β, neutrophil infiltration and tubular cell death. Neutralization of HMGB1 attenuated IR-induced increases in plasma creatinine, blood urea nitrogen (BUN), inflammation, tubular damage and tubular cell death only in male SHR. In conclusion, our data demonstrate that there is a sex difference in the contribution of HMGB1 to IR-induced injury, where males exhibit greater increases in HMGB1-mediated renal injury in response to IR compared with females.

Netrin-1: Focus on its role in cardiovascular physiology and atherosclerosis

The netrins form a family of laminin-related proteins which were first described as modulators of cell migration and axonal guidance during fetal development. Netrin-1 is the most extensively studied member of this family and, since its discovery, non-neural roles have been associated with it. Together with its receptors, DCC/neogenin and UNC5, netrin-1 has been shown to be involved in the regulation of angiogenesis, organogenesis, cancer and inflammation. An NF-κB-dependent truncated isoform of netrin-1 has also been shown to be produced in endothelial and some types of cancer cells, which both accumulates in and affects the function of the nucleus. In atherosclerosis, conflicting roles for netrin-1 have been reported on plaque progression via its receptor UNC5b. Whereas endothelial-derived netrin-1 inhibits chemotaxis of leukocytes and reduces the migration of monocytes to the atherosclerotic plaque, netrin-1 expressed by macrophages within the plaque plays a pro-atherogenic role, promoting cell survival, recruiting smooth muscle cells and inhibiting foam cell egress to the lymphatic system. In contrast, there is evidence that netrin-1 promotes macrophage differentiation to an alternative activated phenotype and induces expression of IL-4 and IL-13, while downregulate expression of IL-6 and COX-2. Further work is needed to elucidate the precise roles of the two isoforms of netrin-1 in different cell types in the context of atherosclerosis, and its potential as a putative novel therapeutic target in this disease.

Design, synthesis and biological evaluation of novel arylpropionic esters for the treatment of acute kidney injury

Acute kidney injury (AKI) is associated with a strong inflammatory response, and inhibiting the response effectively prevents or ameliorates AKI. A series of novel arylpropionic esters were designed, synthesized and evaluated their biological activity in LPS-stimulated RAW264.7 cells. Novel arylpropionic esters bearing multi-functional groups showed significant anti-inflammatory activity, in which, compound 13b exhibited the most potent activity through dose-dependent inhibiting the production of nitric oxide (NO, IC₅₀ = 3.52 μM), TNF-α and IL-6 (84.1% and 33.6%, respectively), as well as suppressing the expression of iNOS, COX-2 and TLR4 proteins. In C57BL/6 mice with cisplatin-induced AKI, compound 13b improved kidney function, inhibited inflammatory development, and reduced pathological damage of kidney tissues. In brief, this arylpropionic ester scaffold may be developed as anti-inflammatory agents.

BPTF cooperates with p50 NF-κB to promote COX-2 expression and tumor cell growth in lung cancer

Cyclooxygenase-2 (COX-2) is overexpressed in most human cancers, but its precise regulatory mechanism in cancer cells remains unclear. The aims of this study are to discover and identify the new regulatory factors which bind to the COX-2 promoter and regulate COX-2 expression and cancer cell growth, and to elucidate the mechanisms of action of these factors in lung cancer. In this study, the COX-2 promoter-binding protein BPTF (bromodomain PHD finger transcription factor) was detected, identified and verified by biotin-streptavidin-agarose pulldown, mass spectrum analysis and chromatin immunoprecipitation (ChIP) in lung cancer cells, respectively. The expressions of COX-2 and BPTF in lung cancer cell lines, mouse tumor tissues and human clinical samples were detected by RT-PCR, Western blot and immunohistochemistry assays. The interaction of BPTF with NF-kB was analyzed by immunoprecipitation and confocal immunofluorescence assays. We discovered and identified BPTF as a new COX-2 promoter-binding protein in human lung cancer cells. Knockdown of BPTF inhibited COX-2 promoter activity and COX-2 expression in lung cancer cells in vitro and in vivo. We also found that BPTF functioned as a transcriptional regulator through its interaction with the p50 subunit of NF-kB. Knockdown of BPTF abrogated the binding of p50 to the COX-2 promoter, while the inhibition of p50 activity abolished the decreased trend of COX-2 expression and lung cancer cell proliferation caused by BPTF silencing. Moreover, we showed that the expressions of BPTF and COX-2 in tumor tissues of lung cancer patients were positively correlated, and high co-expression of BPTF and COX-2 predicted poor prognosis in lung cancer patients. Collectively, our results indicated that BPTF cooperated with p50 NF-κB to regulate COX-2 expression and lung cancer growth, suggesting that the BPTF/p50/COX-2 axis could be a potential therapeutic target for lung cancer.

Netrin-1 and its receptor Unc5b as markers of periodontal disease

OBJECTIVES

The aim of this present study was to evaluate the levels of Netrin-1 and Unc5b in periodontal health and disease.

BACKGROUND

Netrin-1, acting via its receptor UNC5b, regulates the inflammatory response and takes apart in bone destructive diseases.

METHODS

Samples of gingival crevicular fluid (GCF), whole saliva, and serum were taken from systemically healthy, nonsmoking 20 periodontitis , 20 gingivitis patients, and 20 periodontally healthy subjects at baseline and 4 weeks after nonsurgical periodontal treatment (NSPT). Whole-mouth and site-specific clinical periodontal parameters were recorded. Netrin-1 and Unc5b levels were measured by enzyme-linked immunosorbent assay. Data were analyzed by nonparametric tests.

RESULTS

Total amount of Netrin-1 in GCF was significantly higher in periodontitis than the others, and the levels were significantly reduced after NSPT. Salivary and serum concentrations of Netrin-1 were significantly different among the study groups (P = .000), and NSPT significantly increased the concentration levels of both salivary and serum Netrin-1 (P < .05). Healthy subjects had significantly lower GCF (P = .001) and conversely, higher salivary and serum levels of Unc5b than the other groups (P = .002). The GCF levels of Unc5b were significantly reduced (P < .01), and conversely, serum concentrations were significantly increased after NSPT (P < .05). GCF Netrin-1 and Unc5b total amounts were positively correlated with clinical parameters (P < .01 and P < .05) whereas salivary Netrin-1 and Unc5b concentrations were negatively correlated with clinical parameters (P < .01 and P < .05).

CONCLUSIONS

The results of this study indicate that Netrin-1 and its receptor Unc5b may have essential roles in periodontal inflammation and those can be assumed as useful therapeutic agent to control inflammation and periodontal breakdown.

Vaccaria n-Butanol Extract Lower the Production of Proinflammatory Cytokines and the Infection Risk of T. spiralis In Vivo

INTRODUCTION

Trichinellosis is a severe zoonosis involving the activation of inflammatory cells, accompanied by the prominent expressions of proinflammatory cytokines in the host. Semen vaccariae, the seeds of Vaccaria segetalis (Neck.) Garcke. ex Asch. (Caryophyllaceae), is a famous traditional herb that is rich in vaccaria n-butanol extract (VNE). Vaccarin is one major active component of VNE, and it is reported in the treatment of stranguria disease. Hypaphorine is another main active component of VNE and has good anti-inflammatory effect, whereas the potential bioactivity of VNE in trichinellosis treatment is still unknown.

MATERIALS AND METHODS

This study was designed to evaluate the potential anthelmintic and anti-inflammatory activity of VNE toward T. spiralis infection. ICR mice were used to assess the effect of VNE on repression larvae and adult worms in vivo. Immunohistochemistry analysis was performed to evaluate the expression levels of IL-1β, IL-6, TNF-α, and COX-2.

RESULTS

Our results showed that VNE could effectively depress the expressions of proinflammatory cytokines, including IL-1β, IL-6, TNF-α, and COX-2. The adult worms were decreased by 79.53%, while the muscle larvae were diminished by 77.70% as compared to the control.

CONCLUSION

These results demonstrated that VNE may be a promising therapeutic agent against the inflammation and diseases caused by T. spiralis infection.

Lack of netrin-4 alters vascular remodeling in the retina

PURPOSE

Netrin-4 (NTN4) is a protein that plays an important role in the regulation of angiogenesis in the pathological retina. Some evidences show that it can also have a role in inflammation and vascular stability. We will explore these questions in vivo in the mature mouse retina.

METHODS

We created a NTN4 knockout that expresses EGFP in mononuclear phagocytes (CSFR1-positive cells) to track inflammation in vivo in the retina by scanning laser ophthalmoscopy (SLO). Fundus angiography permitted to study blood vessels. Retinal function was assessed with electroretinography (ERG).

RESULTS

Lack of NTN4 leads to an increased amount of amoeboid mononuclear phagocytes in the adult retina, and blood vessels displayed increased tortuosity when compared with the wildtype. Inner retina function also seemed affected in NTN4 null. Lack of NTN4 resulted in a higher persistence of hyaloid artery and spontaneous leakage in the adult retina. No differences were found regarding vessel bifurcation, vessel width, or vein/artery ratio.

CONCLUSIONS

These in vivo data show for the first time that lack of NTN4 induces changes in the retinal vascular phenotype in a non-pathological scenario. This evidence widens the role of NTN4 as a guidance cue in vascular remodeling.

Netrin-1 Alters Adipose Tissue Macrophage Fate and Function in Obesity

Macrophages accumulate prominently in the visceral adipose tissue (VAT) of obese humans and high fat diet (HFD) fed mice, and this is linked to insulin resistance and type II diabetes. While the mechanisms regulating macrophage recruitment in obesity have been delineated, the signals directing macrophage persistence in VAT are poorly understood. We previously showed that the neuroimmune guidance cue netrin-1 is expressed in the VAT of obese mice and humans, where it promotes macrophage accumulation. To better understand the source of netrin-1 and its effects on adipose tissue macrophage (ATM) fate and function in obesity, we generated mice with myeloid-specific deletion of netrin-1 (Ntn1^fl/flLysMCre^+/–; Ntn1^Δmac). Interestingly, Ntn1^Δmac mice showed a modest decrease in HFD-induced adiposity and adipocyte size, in the absence of changes in food intake or leptin, that was accompanied by an increase in markers of adipocyte beiging (Prdm16, UCP-1). Using single cell RNA-seq, combined with conventional histological and flow cytometry techniques, we show that myeloid-specific deletion of netrin-1 caused a 50% attrition of ATMs in HFD-fed mice, particularly of the resident macrophage subset, and altered the phenotype of residual ATMs to enhance lipid handling. Pseudotime analysis of single cell transcriptomes showed that in the absence of netrin-1, macrophages in the obese VAT underwent a phenotypic switch with the majority of ATMs activating a program of genes specialized in lipid handling, including fatty acid uptake and intracellular transport, lipid droplet formation and lipolysis, and regulation of lipid localization. Furthermore, Ntn1^Δmac macrophages had reduced expression of genes involved in arachidonic acid metabolism, and targeted LCMS/MS metabololipidomics analysis revealed decreases in proinflammatory eicosanoids (5-HETE, 6-trans LTB₄, TXB₂, PGD₂) in the obese VAT. Collectively, our data show that targeted deletion of netrin-1 in macrophages reprograms the ATM phenotype in obesity, leading to reduced adipose inflammation, and improved lipid handling and metabolic function.

Netrin-1 Dampens Hypobaric Hypoxia-Induced Lung Injury in Mice

Background: This study aimed to explore the effects of netrin-1 on hypobaric hypoxia-induced lung injury in mice. Methods: We exposed 6-8-week-old C57BL/6 mice to hypobaric stress at 340 mmHg for 30 minutes followed by 260 mmHg for different periods (6, 12, 18, and 24 hours) to observe the severity of lung injury (O₂ concentration, 21%; 54.6 mmHg). The wet/dry weight ratio and protein leakage from the mouse lung were used to determine the suitable exposure time. Netrin-1 was injected into the tail vein of mice before 18-hour decompression. Inflammatory cytokines, lung injury scores, and activity of nuclear factor κB were evaluated. The expression of apoptosis-related proteins was also examined. Results: Protein concentration in the bronchoalveolar lavage fluid was significantly higher in the 18-hour group (p < 0.05). Pulmonary pathology revealed neutrophil infiltration, alveolar septum thickening, and tissue edema. Injury score and macrophage inflammatory protein 2 levels were also increased. Intrinsic apoptosis pathway was activated. Hypoxia decreased the expression of Bcl2 protein, the number of active caspase-3-stained cells, and UNC5HB receptors. Pretreatment with netrin-1 reduced protein leakage, inhibited neutrophil migration, lowered the injury score, attenuated apoptosis, and increased UNC5HB receptor expression. Conclusion: Netrin-1 dampens hypobaric hypoxia-induced lung injury by inhibiting neutrophil migration and attenuating apoptosis.

Axon Guidance Molecules Guiding Neuroinflammation

Axon guidance molecules (AGMs), such as Netrins, Semaphorins, and Ephrins, have long been known to regulate axonal growth in the developing nervous system. Interestingly, the chemotactic properties of AGMs are also important in the postnatal period, such as in the regulation of immune and inflammatory responses. In particular, AGMs play pivotal roles in inflammation of the nervous system, by either stimulating or inhibiting inflammatory responses, depending on specific ligand-receptor combinations. Understanding such regulatory functions of AGMs in neuroinflammation may allow finding new molecular targets to treat neurodegenerative diseases, in which neuroinflammation underlies aetiology and progression.

The role of netrin-1 in the mouse cornea during Aspergillus fumigatus infection

PURPOSE

To explore the effects of netrin-1 on inflammation in Aspergillus fumigatus-infected mouse corneas and on proliferation and migration in human corneal epithelial cells (HCECs).

METHODS

Netrin-1 and the receptor A2BAR were detected in normal and infected corneas from C57BL/6 mice and RAW 264.7 cells. The mice were injected subconjunctivally with recombinant netrin-1. The severity of the disease was determined by clinical scores, photography with a slit lamp, RT-PCR, western blotting, myeloperoxidase (MPO) assays and immunofluorescence staining of polymorphonuclear neutrophilic leukocytes (PMNs). The effects of netrin-1 on RAW 264.7 cells in vitro were determined by RT-PCR. The role of A2BAR was demonstrated in vivo by detecting the expression of IL-1β, TNF-α, and IL-10 in corneas pretreated subconjunctivally with an A2BAR antagonist (PSB1115). RAW 264.7 cells were stimulated with Aspergillus fumigatus (A. fumigates) and netrin-1 with or without PSB1115 pretreatment. A cell counting kit-8 (CCK-8) assay was used to evaluate cell proliferation ability, and cell migration ability was determined by cell scratch experiments with HCECs.

RESULTS

Netrin-1 expression decreased slightly after A. fumigatus infection and then increased to its peak. A2BAR expression increased at 1 day post infection (p.i.), with a subsequent decline. Compared to the PBS control, exogenous netrin-1 attenuated the inflammatory response, PMN infiltration, and expression of the proinflammatory factors IL-1β and TNF-α, while IL-10 expression was up-regulated. In RAW 264.7 cells, recombinant netrin-1 obviously inhibited the mRNA expression of IL-1β and TNF-α and promoted the mRNA expression of the anti-inflammatory cytokine IL-10. Pretreatment with PSB1115 resulted in disease aggravation and higher levels of the proinflammatory factors IL-1β and TNF-α both in vivo and in vitro. And the effect of netrin-1 on inflammatory factors was abolished by PSB1115. Moreover, compared to the control treatment, exogenous netrin-1 significantly facilitated the proliferation and migration of HCECs.

CONCLUSIONS

Netrin-1 attenuates inflammation in C57BL/6 mice infected with A. fumigatus, and it may play this role via the receptor A2BAR. Additionally, netrin-1 can promote the proliferation and migration of HCECs.

M2 macrophages in kidney disease: biology, therapies, and perspectives

Tissue macrophages are crucial players in homeostasis, inflammation, and immunity. They are characterized by heterogeneity and plasticity, due to which they display a continuum of phenotypes with M1/M2 presenting 2 extremes of this continuum. M2 macrophages are usually termed in the literature as anti-inflammatory and wound healing. Substantial progress has been made in elucidating the biology of M2 macrophages and their potential for clinical translation. In this review we discuss the current state of knowledge in M2 macrophage research with an emphasis on kidney disease. We explore their therapeutic potential and the challenges in using them as cellular therapies. Some new regulators that shape macrophage polarization and potential areas for future research are also examined.

CXCR4 signaling regulates metastatic onset by controlling neutrophil motility and response to malignant cells

Developing tumors interact with the surrounding microenvironment. Myeloid cells exert both anti- and pro-tumor functions and chemokines are known to drive immune cell migration towards cancer cells. It is documented that CXCR4 signaling supports tumor metastasis formation in tissues where CXCL12, its cognate ligand, is abundant. On the other hand, the role of the neutrophilic CXCR4 signaling in driving cancer invasion and metastasis formation is poorly understood. Here, we use the zebrafish xenotransplantation model to study the role of CXCR4 signaling in driving the interaction between invasive human tumor cells and host neutrophils, supporting early metastasis formation. We found that zebrafish cxcr4 (cxcr4b) is highly expressed in neutrophils and experimental micrometastases fail to form in mutant larvae lacking a functional Cxcr4b. We demonstrated that Cxcr4b controls neutrophil number and motility and showed that Cxcr4b transcriptomic signature relates to motility and adhesion regulation in neutrophils in tumor-naïve larvae. Finally, Cxcr4b deficient neutrophils failed to interact with cancer cells initiating early metastatic events. In conclusion, we propose that CXCR4 signaling supports the interaction between tumor cells and host neutrophils in developing tumor metastases. Therefore, targeting CXCR4 on tumor cells and neutrophils could serve as a double bladed razor to limit cancer progression.

Netrin-1 alleviates subarachnoid haemorrhage-induced brain injury via the PPARγ/NF-KB signalling pathway

Netrin‐1 (NTN‐1) is a novel drug to alleviate early brain injury following subarachnoid haemorrhage (SAH). However the molecular mechanism of NTN‐1‐mediated protection against early brain injury following SAH remains largely elusive. This study aims to evaluate the effects and mechanisms of NTN‐1 in protecting SAH‐induced early brain injury. The endovascular perforation SAH model was constructed using male C57BL/6J mice, and recombinant NTN‐1 was administrated intravenously. Mortality rates, SAH grade, brain water content, neurological score and neuronal apoptosis were evaluated. The expression of PPARγ, Bcl‐2, Bax and nuclear factor‐kappa B (NF‐κB) were detected by Western blot. Small interfering RNA specific to NTN‐1 receptor, UNC5B, and a selective PPARγ antagonist, bisphenol A diglycidyl ether (BADGE), were applied in combination with NTN‐1. The results suggested that NTN‐1 improved the neurological deficits, reduced the brain water content and alleviated neuronal apoptosis. In addition, NTN‐1 enhanced PPARγ and Bcl‐2 expression and decreased the levels of Bax and NF‐κB. However, the neuroprotection of NTN‐1 was abolished by UNC5B and BADGE. In conclusion, our results demonstrated that NTN‐1 attenuates early brain injury following SAH via the UNC5B PPARγ/NF‐κB signalling pathway.

ADAMTS13 protects mice against renal ischemia-reperfusion injury by reducing inflammation and improving endothelial function

Acute kidney injury (AKI) is a serious condition without efficient therapeutic options. Recent studies have indicated that recombinant human a disintegrin and metalloprotease with thrombospondin motifs 13 (rhADAMTS13) provides protection against inflammation. Therefore, we hypothesized that ADAMTS13 might protect against AKI by reducing inflammation. Bilateral renal ischemia-reperfusion injury (I/R) was used as AKI models in this study. Prophylactic infusion of rhADAMTS13 was employed to investigate potential mechanisms of renal protection. Renal function, inflammation, and microvascular endothelial function were assessed after 24 h of reperfusion. Our results showed that I/R mice increased plasma von Willebrand factor levels but decreased ADAMTS13 expression. Administration of rhADAMTS13 to I/R mice recovered renal function, histological injury, and apoptosis. Renal inflammation was reduced by rhADAMTS13, accompanied with the downregulation of p38/extracellular signal-regulated protein kinase phosphorylation and cyclooxygenase-2 expression. rhADAMTS13 restored vasodilation in afferent arterioles in I/R mice. Furthermore, rhADAMTS13 treatment enhanced phosphorylation of Akt at Ser473 and eNOS at Ser1177. Administration of the Akt pathway inhibitor wortmannin reduced the protective effect of rhADAMTS13. Our conclusions are that treatment with rhADAMTS13 ameliorates renal I/R injury by reducing inflammation, tubular cell apoptosis, and improving microvascular endothelial dysfunction. rhADAMTS13 could be a promising strategy to treat AKI in clinical settings.

Macrophage-derived netrin-1 promotes abdominal aortic aneurysm formation by activating MMP3 in vascular smooth muscle cells

Abdominal aortic aneurysms (AAA) are characterized by extensive extracellular matrix (ECM) fragmentation and inflammation. However, the mechanisms by which these events are coupled thereby fueling focal vascular damage are undefined. Here we report through single-cell RNA-sequencing of diseased aorta that the neuronal guidance cue netrin-1 can act at the interface of macrophage-driven injury and ECM degradation. Netrin-1 expression peaks in human and murine aneurysmal macrophages. Targeted deletion of netrin-1 in macrophages protects mice from developing AAA. Through its receptor neogenin-1, netrin-1 induces a robust intracellular calcium flux necessary for the transcriptional regulation and persistent catalytic activation of matrix metalloproteinase-3 (MMP3) by vascular smooth muscle cells. Deficiency in MMP3 reduces ECM damage and the susceptibility of mice to develop AAA. Here, we establish netrin-1 as a major signal that mediates the dynamic crosstalk between inflammation and chronic erosion of the ECM in AAA.

Abdominal aortic aneurysms (AAA) are characterized by extensive extracellular matrix degradation. Here Hadi et al. identify a netrin-1/neogenin-based crosstalk between macrophages and vascular smooth muscle cells (VSMCs), leading to the secretion of the matrix metalloproteinase MMP-3 by VSMCs and subsequent matrix degradation in AAA lesions.

Netrin-1 attenuates brain injury after middle cerebral artery occlusion via downregulation of astrocyte activation in mice

Background

Netrin-1 functions largely via combined receptors and downstream effectors. Evidence has shown that astrocytes express netrin-1 receptors, including DCC and UNC5H2. However, whether netrin-1 influences the function of astrocytes was previously unknown.

Methods

Lipopolysaccharide was used to stimulate the primary cultured astrocytes; interleukin release was used to track astrocyte activation. In vivo, shRNA and netrin-1 protein were injected in the mouse brain. Infarct volume, astrocyte activation, and interleukin release were used to observe the function of netrin-1 in neuroinflammation and brain injury after middle cerebral artery occlusion.

Results

Our results demonstrated that netrin-1 reduced lipopolysaccharide-induced interleukin-1β and interleukin-12β release in cultured astrocytes, and blockade of the UNC5H2 receptor with an antibody reversed this effect. Additionally, netrin-1 increased p-AKT and PPAR-γ expression in primary cultured astrocytes. In vivo studies showed that knockdown of netrin-1 increased astrocyte activation in the mouse brain after middle cerebral artery occlusion (p < 0.05). Moreover, injection of netrin-1 attenuated GFAP expression (netrin-1 0.27 ± 0.06 vs. BSA 0.62 ± 0.04, p < 0.001) and the release of interleukins and reduced infarct volume after brain ischemia (netrin-1 0.27 ± 0.06 vs. BSA 0.62 ± 0.04 mm³, p < 0.05).

Conclusion

Our results indicate that netrin-1 is an important molecule in regulating astrocyte activation and neuroinflammation in cerebral ischemia and provides a potential target for ischemic stroke therapy.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1291-5) contains supplementary material, which is available to authorized users.

Tisp40 deficiency limits renal inflammation and promotes tubular cell proliferation in renal ischemia reperfusion injury

Renal ischemia reperfusion (IR) is a common cause of acute kidney injury (AKI), and no effective treatment is available to date. In our previous studies, we demonstrated that Tisp40 exacerbates tubular cell apoptosis and tubulointerstitial fibrosis after renal IR injury. However, the role of Tisp40 in renal inflammatory responses and tubular cell proliferation during renal IR injury remains unknown. In this study, Tisp40 knockout (KO) and wild-type (WT) mice were induced with or without renal IR injury. For renal IR, bilateral renal pedicels were exposed and clamped to induce 30 min of ischemia. After 48 h of reperfusion, the kidneys were collected for analyses. Results showed that Tisp40 deficiency attenuates neutrophil and macrophage infiltration after renal IR. Consistently, the protein levels of TNF-α and MCP-1 were markedly decreased, and the phosphorylation levels of IκBα and P65 were inhibited in Tisp40-deficient mice than in WT mice in renal IR injury. In addition, compared with WT mice, Tisp40 deficiency significantly increased the expression levels of proliferative cellular nuclear antigen and phosphorylated Erk1/2 after renal IR injury. In conclusion, Tisp40 deficiency limits renal inflammatory responses and promotes tubular cell proliferation in ischemic AKI.

Phenotype and influx kinetics of leukocytes and inflammatory cytokine production in kidney ischemia/reperfusion injury

BACKGROUND AND AIM

Kidney ischemia/reperfusion (IR) injury is characterized by tubular epithelial cell (TEC) death and an inflammatory response involving cytokine production and immune cell infiltration. In various kidney diseases, increased macrophage numbers correlate with injury severity and poor prognosis. However, macrophage plasticity enables a diverse range of functions, including wound healing, making them a key target for novel therapies. This study aimed to comprehensively characterize the changes in myeloid and epithelial cells and the production of cytokines throughout the experimental IR model of acute kidney injury to aid in the identification of targets to promote and enhance kidney regeneration and repair.

METHODS

Flow cytometric analysis of murine unilateral IR injury was used to assess TEC and myeloid cell subpopulations in conjunction with histological analysis and cytokine production at 6 h, 1, 3, 5 and 7 days post IR injury, spanning the initial inflammatory phase and the following reparative phase.

RESULTS

IR injury resulted in a rapid infiltration of Ly6C^high monocytes and neutrophils with a steady rise in F4/80^high MHCII^high macrophages over the injury time. The production of the inflammatory cytokines IL-6, MCP-1 and TNF coincided with an increase in IL-10 production.

CONCLUSION

This characterization will provide a reference point for future studies designed to manipulate immune cell phenotype and function in order to promote endogenous repair of damaged kidneys.

G-CSF mediates lung injury in mice with adenine-induced acute kidney injury

Acute lung injury (ALI) is a serious complication among patients with acute kidney injury (AKI) that is a systemic inflammatory disease with high morbidity and mortality. The pathophysiology of AKI-associated ALI is poorly understood. G-CSF regulates the production and function of neutrophils that mediate lung injury via elastase and other mediators. Here, we used a mouse model of adenine-induced AKI to determine the roles of G-CSF and neutrophil elastase in AKI-associated ALI. We confirmed that ALI was associated with high serum G-CSF levels, and elevated neutrophil elastase activity in the lungs and serum of mice with adenine-induced AKI. Systemic administration of G-CSF-specific neutralizing antibody normalized granulopoiesis, pulmonary neutrophil infiltration, and neutrophil elastase activity, conferring improved lung architecture in mice with adenine-induced AKI. Further studies revealed that macrophages secreted G-CSF upon urea stimulation. Consequently, G-CSF could be a target for new anti-lung injury strategy in patients with AKI.

Prostaglandins in the pathogenesis of kidney diseases

Prostaglandins (PGs) are important lipid mediators produced from arachidonic acid via the sequential catalyzation of cyclooxygenases (COXs) and specific prostaglandin synthases. There are five subtypes of PGs, namely PGE2, PGI2, PGD2, PGF2α, and thromboxane A2 (TXA2). PGs exert distinct roles by combining to a diverse family of membrane-spanning G protein-coupled prostanoid receptors. The distribution of these PGs, their specific synthases and receptors vary a lot in the kidney. This review summarized the recent findings of PGs together with the COXs and their specific synthases and receptors in regulating renal function and highlighted the insights into their roles in the pathogenesis of various kidney diseases.

Resolution of inflammation pathways in preeclampsia-a narrative review

Preeclampsia (PE) is one of the leading causes of maternal morbidity and mortality worldwide. This disease is believed to occur in two stages with placental dysfunction in early pregnancy leading to maternal clinical findings after 20 weeks of gestation, as consequence of systemic inflammation, oxidative stress, and endothelial dysfunction. Much evidence suggests that PE women display an overshooting inflammatory response throughout pregnancy due to an unbalanced regulation of innate and adaptive immune responses. Recently, it has been suggested that dysregulation of endogenous protective pathways might be associated with PE etiopathogenesis. Resolution of inflammation is an active process coordinated by mediators from diverse nature that regulate key cellular events to restore tissue homeostasis. Inadequate or insufficient resolution of inflammation is believed to play an important role in the development of chronic inflammatory diseases, like PE. In this narrative review, we discuss possible pro-resolution pathways that might be compromised in PE women, which could be targets to novel therapeutic strategies in this disease.

Recombinant Netrin-1 binding UNC5B receptor attenuates neuroinflammation and brain injury via PPARγ/NFκB signaling pathway after subarachnoid hemorrhage in rats

Neuroinflammation is an essential mechanism involved in the pathogenesis of subarachnoid hemorrhage (SAH)-induced brain injury. Recently, Netrin-1 (NTN-1) is well established to exert anti-inflammatory property in non-nervous system diseases through inhibiting infiltration of neutrophil. The present study was designed to investigate the effects of NTN-1 on neuroinflammation, and the potential mechanism in a rat model of SAH. Two hundred and ninety-four male Sprague Dawley rats (weight 280-330 g) were subjected to the endovascular perforation model of SAH. Recombinant human NTN-1 (rh-NTN-1) was administered intravenously. Small interfering RNA (siRNA) of NTN-1 and UNC5B, and a selective PPARγ antagonist bisphenol A diglycidyl ether (BADGE) were applied. Post-SAH evaluations included neurobehavioral function, brain water content, Western blot analysis, and immunohistochemistry. Our results showed that endogenous NTN-1 and its receptor UNC5B level were increased after SAH. Administration of rh-NTN-1 reduced brain edema, ameliorated neurological impairments, and suppressed microglia activation after SAH, which were concomitant with PPARγ activation, inhibition of NFκB, and decrease in TNF-α, IL-6, and ICAM-1, as well as myeloperoxidase (MPO). Knockdown of endogenous NTN-1 increased expression of pro-inflammatory mediators and MPO, and aggravated neuroinflammation and brain edema. Moreover, knockdown of UNC5B using specific siRNA and inhibition of PPARγ with BADGE blocked the protective effects of rh-NTN-1. In conclusion, our findings indicated that exogenous rh-NTN-1 treatment attenuated neuroinflammation and neurological impairments through inhibiting microglia activation after SAH in rats, which is possibly mediated by UNC5B/PPARγ/NFκB signaling pathway. Exogenous NTN-1 may be a novel therapeutic agent to ameliorating early brain injury via its anti-inflammation effect.

Bioinformatics Analysis of Genes and Pathways of CD11b+/Ly6Cintermediate Macrophages after Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), which could induce the poor prognosis. The purpose of this study was to characterize the molecular mechanism of the functional changes of CDllb+/Ly6Cintermediate macrophages after renal IRI. The gene expression profiles of CDllb+/Ly6Cintermcdiate macrophages of the sham surgery mice, and the mice 4 h, 24 h and 9 days after renal IRI were downloaded from the Gene Expression Omnibus database. Analysis of mRNA expression profiles was conducted to identify differentially expressed genes (DEGs), biological processes and pathways by the series test of cluster. Protein-protein interaction network was constructed and analysed to discover the key genes. A total of 6738 DEGs were identified and assigned to 20 model profiles. DEGs in profile 13 were one of the predominant expression profiles, which are involved in immune cell chemotaxis and proliferation. Signet analysis showed that Atp5al, Atp5o, Cox4i, Cdc42, Rac2 and Nhp2 were the key genes involved in oxidation-reduction, apoptosis, migration, M1-M2 differentiation, and proliferation of macrophages. RPS18 may be an appreciate reference gene as it was stable in macrophages. The identified DEGs and their enriched pathways investigate factors that may participate in the functional changes of CD 1lb+Ly6Cintermediate macrophages after renal IRI. Moreover, the vital gene Nhp2 may involve the polarization of macrophages, which may be a new target to affect the process of AKI.

Mitochondrial oxidative stress activates COX-2/mPGES-1/PGE2 cascade induced by albumin in renal proximal tubular cells

COX-2/mPGES-1/PGE2 cascade is of importance in the pathogenesis of kidney injury. Meanwhile, recent studies documented a detrimental role of mitochondrial oxidative stress in kidney diseases. The present study was undertaken to investigate the role of mitochondrial oxidative stress in albumin-induced activation of COX-2/mPGES-1/PGE2 cascade in renal proximal tubular cells. Following albumin overload in mice, we observed a significant increase of oxidative stress and mitochondrial abnormality determined by transmission electron microscope, which was attenuated by the administration of MnTBAP, a mitochondrial SOD2 mimic. More interestingly, albumin overload-induced upregulation of COX-2 and mPGES-1 at mRNA and protein levels was largely abolished by MnTBAP treatment in mice. Meanwhile, urinary PGE2 excretion was also blocked by MnTBAP treatment. Furthermore, mouse proximal tubule epithelial cells (mPTCs) were treated with albumin. Similarly, COX-2/mPGES-1/PGE2 cascade was significantly activated by albumin in dose- and time-dependent manners, which was abolished by MnTBAP treatment in parallel with a blockade of oxidative stress. Collectively, the findings from current study demonstrated that mitochondrial oxidative stress could activate COX-2/mPGES-1/PGE2 cascade in proximal tubular cells under the proteinuria condition. Mitochondrial oxidative stress/COX-2/mPGES-1/PGE2 could serve as the important targets for the treatment of proteinuria-associated kidney injury.