Exogenous CGRP upregulates profibrogenic growth factors through PKC/JNK signaling pathway in kidney proximal tubular cells

Signalling of the neuropeptide calcitonin gene-related peptide (CGRP) through RAMP1 promotes liver fibrosis via TGFβ1/Smad2 and YAP pathways

The liver is innervated by primary sensory nerve fibres releasing the neuropeptide calcitonin gene-related peptide (CGRP). Elevated plasma levels of CGRP have been found in patients with liver fibrosis or cirrhosis. We hypothesised that signalling of CGRP and its receptors might regulate liver fibrosis and propose a novel potential target for the treatment. In this study, hepatic expression of CGRP and its receptor component, the receptor activity-modifying protein 1 (RAMP1), was dramatically increased in diseased livers of patients. In a murine liver fibrosis model, deficiency of RAMP1 resulted in attenuated fibrogenesis characterized by less collagen deposition and decreased activity of hepatic stellate cells (HSC). Mechanistically, activity of the TGFβ1 signalling core component Smad2 was severely impaired in the absence of RAMP1, and Yes-associated protein (YAP) activity was found to be diminished in RAMP1-deficient liver parenchyma. In vitro, stimulation of the HSC line LX-2 cells with CGRP induces TGFβ1 production and downstream signalling as well as HSC activation documented by increased α-SMA expression and collagen synthesis. We further demonstrate in LX-2 cells that CGRP promotes YAP activation and its nuclear translocation subsequent to TGFβ1/Smad2 signals. These data support a promotive effect of CGRP signalling in liver fibrosis via stimulation of TGFβ1/Smad2 and YAP activity.

Neuroimmune interplay in kidney health and disease: Role of renal nerves

Renal nerves and their role in physiology and disease have been a topic of increasing interest in the past few decades. Renal inflammation contributes to many cardiorenal disease conditions, including hypertension, chronic kidney disease, and polycystic kidney disease. Much is known about the role of renal sympathetic nerves in physiology - they contribute to the regulation of sodium reabsorption, renin release, and renal vascular resistance. In contrast, far less is known about afferent, or "sensory," renal nerves, which convey signals from the kidney to the brain. While much remains unknown about these nerves in the context of normal physiology, even less is known about their contribution to disease states. Furthermore, it has become apparent that the crosstalk between renal nerves and the immune system may augment or modulate disease. Research from other fields, especially pain research, has provided critical insight into neuroimmune crosstalk. Sympathetic renal nerve activity may increase immune cell recruitment, but far less work has been done investigating the interplay between afferent renal nerves and the immune system. Evidence from other fields suggests that inflammation may augment afferent renal nerve activity. Furthermore, these nerves may exacerbate renal inflammation through the release of afferent-specific neurotransmitters.

Relationship between knee osteophytes and calcitonin gene-related peptide concentrations of serum and synovial fluid in knee of osteoarthritis

To explore the relationship between knee osteophytes of osteoarthritic knee and calcitonin gene-related peptide (CGRP) concentrations of serum and synovial fluid (SF). 65 patients with knee medial compartment osteoarthritis (OA) were recruited and examined with weight-bearing radiographs of the entire lower limb. The concentrations of CGRP in serum/SF were also detected in surgery. The relationship between the concentrations of CGRP in serum/SF and osteophyte scores were detected with Spearman rank correlation coefficient. CGRP concentrations in serum and SF were significantly correlated with osteophyte score of overall knee respectively (R = 0.462, P < .001; R = 0.435, P < .001). In addition, a correlation tended to be observed about the relationship between CGRP concentrations in serum and SF and osteophyte scores of medial compartment (R = 0.426, P < .001; R = 0.363, P = .003), and osteophyte scores of lateral compartment (R = 0.429, P < .001; R = 0.444, P < .001). In this study, the relationship between CGRP in serum/SF and knee osteophyte scores in different subregions were explored, which showed significant positive correlations, that possibly reflecting the contribution of CGRP influencing osteophyte formation. Positive correlations between osteophyte scores and CGRP suggest that CGRP promote the growth of osteophyte formation. It has the potential to be selected as a biomarker for the assessment of severity in knee OA patients and predict the progression of knee OA. It also provides a potential therapeutic target to delay the progression and relieve the symptom of OA.

Current Perspectives of Neuroendocrine Regulation in Liver Fibrosis

Liver fibrosis is a complicated process that involves different cell types and pathological factors. The excessive accumulation of extracellular matrix (ECM) and the formation of fibrotic scar disrupt the tissue homeostasis of the liver, eventually leading to cirrhosis and even liver failure. Myofibroblasts derived from hepatic stellate cells (HSCs) contribute to the development of liver fibrosis by producing ECM in the area of injuries. It has been reported that the secretion of the neuroendocrine hormone in chronic liver injury is different from a healthy liver. Activated HSCs and cholangiocytes express specific receptors in response to these neuropeptides released from the neuroendocrine system and other neuroendocrine cells. Neuroendocrine hormones and their receptors form a complicated network that regulates hepatic inflammation, which controls the progression of liver fibrosis. This review summarizes neuroendocrine regulation in liver fibrosis from three aspects. The first part describes the mechanisms of liver fibrosis. The second part presents the neuroendocrine sources and neuroendocrine compartments in the liver. The third section discusses the effects of various neuroendocrine factors, such as substance P (SP), melatonin, as well as α-calcitonin gene-related peptide (α-CGRP), on liver fibrosis and the potential therapeutic interventions for liver fibrosis.

Repeated Administration of Cisplatin Transforms Kidney Fibroblasts through G2/M Arrest and Cellular Senescence

Cisplatin is a potent chemotherapeutic used for the treatment of many types of cancer, but it has nephrotoxic side effects leading to acute kidney injury and subsequently chronic kidney disease (CKD). Previous work has focused on acute kidney tubular injury induced by cisplatin, whereas the chronic sequelae post-injury has not been well-explored. In the present study, we established a kidney fibroblast model of CKD induced by repeated administration of cisplatin (RAC) as a clinically relevant model. In NRK-49F rat kidney fibroblasts, RAC upregulated α-smooth muscle actin (α-SMA) and fibronectin proteins, suggesting that RAC induces kidney fibroblast-to-myofibroblast transformation. RAC also enhanced cell size, including the cell attachment surface area, nuclear area, and cell volume. Furthermore, RAC induced p21 expression and senescence-associated β-galactosidase activity, suggesting that kidney fibroblasts exposed to RAC develop a senescent phenotype. Inhibition of p21 reduced cellular senescence, hypertrophy, and myofibroblast transformation induced by RAC. Intriguingly, after RAC, kidney fibroblasts were arrested at the G2/M phase. Repeated treatment with paclitaxel as an inducer of G2/M arrest upregulated p21, α-SMA, and fibronectin in the kidney fibroblasts. Taken together, these data suggest that RAC transforms kidney fibroblasts into myofibroblasts through G2/M arrest and cellular senescence.

The role of nerve fibers and their neurotransmitters in regulating intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) has been the major contributor to chronic lower back pain (LBP). Abnormal apoptosis, senescence, and pyroptosis of IVD cells, extracellular matrix (ECM) degradation, and infiltration of immune cells are the major molecular alternations during IVDD. Changes at tissue level frequently occur at advanced IVD tissue. Ectopic ingrowth of nerves within inner annulus fibrosus (AF) and nucleus pulposus (NP) tissue has been considered as the primary cause for LBP. Innervation at IVD tissue mainly included sensory and sympathetic nerves, and many markers for these two types of nerves have been detected since 1940. In fact, in osteoarthritis (OA), beyond pain transmission, the direct regulation of neuropeptides on functions of chondrocytes have attracted researchers' great attention recently. Many physical and pathological similarities between joint and IVD have shed us the light on the neurogenic mechanism involved in IVDD. Here, an overview of the advances in the nervous system within IVD tissue will be performed, with a discussion on in the role of nerve fibers and their neurotransmitters in regulating IVDD. We hope this review can attract more research interest to address neuromodulation and IVDD itself, which will enhance our understanding of the contribution of neuromodulation to the structural changes within IVD tissue and inflammatory responses and will help identify novel therapeutic targets and enable the effective treatment of IVDD disease.

LncRNA HOTAIRM1 Involved in Nano NiO-Induced Pulmonary Fibrosis via Regulating PRKCB DNA Methylation-Mediated JNK/c-Jun Pathway

Nickel oxide nanoparticles (Nano NiO) lead to pulmonary fibrosis, and the mechanisms are associated with epigenetics. This study aimed to clarify the regulatory relationship among long noncoding RNA HOXA transcript antisense RNA myeloid-specific 1 (HOTAIRM1), DNA methylation and expression of protein kinase C beta (PRKCB), and JNK/c-Jun pathway in Nano NiO-induced pulmonary fibrosis. Therefore, we constructed the rat pulmonary fibrosis model by intratracheal instillation of Nano NiO twice a week for 9 weeks and established the collagen deposition model by treating BEAS-2B cells with Nano NiO for 24 h. Here, the DNA methylation pattern was analyzed by whole-genome bisulfite sequencing in rat fibrotic lung tissues. Then, we integrated mRNA transcriptome data and found 93 DNA methylation genes with transcriptional significance. Meanwhile, the data showed that Nano NiO caused the down-regulation of lncRNA HOTAIRM1, the hypomethylation, and up-regulation of PRKCB2, JNK/c-Jun pathway activation, and collagen deposition (the up-regulated Col-I and α-SMA) both in vivo and in vitro. DNMTs inhibitor 5-AZDC attenuated Nano NiO-induced PRKCB2 expression, JNK/c-Jun pathway activation, and collagen deposition, but overexpression of PRKCB2 aggravated the changes mentioned indicators in Nano NiO-induced BEAS-2B cells. Furthermore, JNK/c-Jun pathway inhibitor (SP600125) alleviated Nano NiO-induced excessive collagen formation. Additionally, overexpression of HOTAIRM1 restrained the PRKCB hypomethylation, the activation of JNK/c-Jun pathway, and collagen formation induced by Nano NiO in BEAS-2B cells. In conclusion, these findings demonstrated that HOTAIRM1 could arrest Nano NiO-induced pulmonary fibrosis by suppressing the PRKCB DNA methylation-mediated JNK/c-Jun pathway.

2-Mercaptoethanol protects against DNA double-strand breaks after kidney ischemia and reperfusion injury through GPX4 upregulation

BACKGROUND

Kidney ischemia reperfusion injury (IRI) is characterized by tubular cell death. DNA double-strand breaks is one of the major sources of tubular cell death induced by IRI. 2-Mercaptoethanol (2-ME) is protective against DNA double-strand breaks derived from calf thymus and bovine embryo. Here, we sought to determine whether treatment with 2-ME attenuated DNA double-strand breaks, resulting in reduced kidney dysfunction and structural damage in IRI.

METHODS

Kidney IRI or sham-operation in mice was carried out. The mice were treated with 2-ME, Ras-selective lethal 3, or vehicle. Kidney function, tubular injury, DNA damage, antioxidant enzyme expression, and DNA damage response (DDR) kinases activation were assessed.

RESULTS

Treatment with 2-ME significantly attenuated kidney dysfunction, tubular injury, and DNA double-strand breaks after IRI. Among DDR kinases, IRI induced phosphorylation of ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3 related (ATR), but IRI reduced phosphorylation of other DDR kinases including ataxia telangiectasia and Rad3 related, checkpoint kinase 1 (Chk1), Chk2, and Chinese hamster cells 1 (XRCC1). Treatment with 2-ME enhanced phosphorylation of ATM and ATM-mediated effector kinases in IRI-subjected kidneys, suggesting that 2-ME activates ATM-mediated DDR signaling pathway. Furthermore, 2-ME dramatically upregulated glutathione peroxidase 4 (GPX4) in IRI-subjected kidneys. Inhibition of GPX4 augmented adverse IRI consequences including kidney dysfunction, tubular injury, DNA double-strand breaks, and inactivation of ATM-mediated DDR signaling pathway after IRI in 2-ME-treated kidneys.

CONCLUSIONS

We have demonstrated that exogenous 2-ME protects against DNA double-strand breaks after kidney IRI through GPX4 upregulation and ATM activation.

Management of arthrofibrosis in neuromuscular disorders: a review

Arthrofibrosis, or rigid contracture of major articular joints, is a significant morbidity of many neurodegenerative disorders. The pathogenesis depends on the mechanism and severity of the precipitating neuromuscular disorder. Most neuromuscular disorders, whether spastic or hypotonic, culminate in decreased joint range of motion. Limited range of motion precipitates a cascade of pathophysiological changes in the muscle-tendon unit, the joint capsule, and the articular cartilage. Resulting joint contractures limit functional mobility, posing both physical and psychosocial burdens to patients, economic burdens on the healthcare system, and lost productivity to society. This article reviews the pathophysiology of arthrofibrosis in the setting of neuromuscular disorders. We describe current non-surgical and surgical interventions for treating arthrofibrosis of commonly affected joints. In addition, we preview several promising modalities under development to ameliorate arthrofibrosis non-surgically and discuss limitations in the field of arthrofibrosis secondary to neuromuscular disorders.

The Effects of Taurocholic Acid on Biliary Damage and Liver Fibrosis Are Mediated by Calcitonin-Gene-Related Peptide Signaling

BACKGROUND & AIMS

Cholangiocytes are the target cells of liver diseases that are characterized by biliary senescence (evidenced by enhanced levels of senescence-associated secretory phenotype, SASP, e.g., TGF-β1), and liver inflammation and fibrosis accompanied by altered bile acid (BA) homeostasis. Taurocholic acid (TC) stimulates biliary hyperplasia by activation of 3',5'-cyclic cyclic adenosine monophosphate (cAMP) signaling, thereby preventing biliary damage (caused by cholinergic/adrenergic denervation) through enhanced liver angiogenesis. Also: (i) α-calcitonin gene-related peptide (α-CGRP, which activates the calcitonin receptor-like receptor, CRLR), stimulates biliary proliferation/senescence and liver fibrosis by enhanced biliary secretion of SASPs; and (ii) knock-out of α-CGRP reduces these phenotypes by decreased cAMP levels in cholestatic models. We aimed to demonstrate that TC effects on liver phenotypes are dependent on changes in the α-CGRP/CALCRL/cAMP/PKA/ERK1/2/TGF-β1/VEGF axis.

METHODS

Wild-type and α-CGRP-/- mice were fed with a control (BAC) or TC diet for 1 or 2 wk. We measured: (i) CGRP levels by both ELISA kits in serum and by qPCR in isolated cholangiocytes (CALCA gene for α-CGRP); (ii) CALCRL immunoreactivity by immunohistochemistry (IHC) in liver sections; (iii) liver histology, intrahepatic biliary mass, biliary senescence (by β-GAL staining and double immunofluorescence (IF) for p16/CK19), and liver fibrosis (by Red Sirius staining and double IF for collagen/CK19 in liver sections), as well as by qPCR for senescence markers in isolated cholangiocytes; and (iv) phosphorylation of PKA/ERK1/2, immunoreactivity of TGF-β1/TGF- βRI and angiogenic factors by IHC/immunofluorescence in liver sections and qPCR in isolated cholangiocytes. We measured changes in BA composition in total liver by liquid chromatography/mass spectrometry.

RESULTS

TC feeding increased CALCA expression, biliary damage, and liver inflammation and fibrosis, as well as phenotypes that were associated with enhanced immunoreactivity of the PKA/ERK1/2/TGF-β1/TGF-βRI/VEGF axis compared to BAC-fed mice and phenotypes that were reversed in α-CGRP-/- mice fed TC coupled with changes in hepatic BA composition.

CONCLUSION

Modulation of the TC/ α-CGRP/CALCRL/PKA/ERK1/2/TGF-β1/VEGF axis may be important in the management of cholangiopathies characterized by BA accumulation.

Intranasal calcitonin gene-related peptide administration impairs fear memory retention in mice through the PKD/p-HDAC5/Npas4 pathway

The calcitonin gene-related peptide (CGRP) suppresses fear memory retention in mice. Although intracerebroventricular administration of CGRP alters the fear memory processes, making it a promising therapeutic strategy for post-traumatic stress disorder (PTSD), direct brain injection into patients is not practical. Therefore, we propose that intranasal application may be an effective way to deliver CGRP to the brain. This study tested whether CGRP nasal administration exerts the same effect as intracerebroventricular administration using C57BL6J mice. The amount of CGRP in the cerebrospinal fluid and hippocampus 30 min after nasal administration of CGRP was significantly higher when compared with saline. Intranasal CGRP also elicited photophobic behaviors similar to intracerebroventricular injection. Moreover, intranasal CGRP decreased fear memory retention but did not affect reactivation and extinction of fear memory. We found intranasal CGRP significantly increased the expression of protein kinase D (PKD), phosphorylated histone deacetylase 5 (p-HDAC5) and neuronal PAS domain protein 4 (Npas4) in the hippocampus. CGRP-mediated impairment of fear memory and Npas4 expression increases were attenuated significantly by the CGRP receptor antagonist BIBN4096. Together, our data demonstrate that intranasal CGRP delivery activates the PKD/p-HDAC5/Npas4 pathway, decreases fear memory retention.

CGRP, adrenomedullin and adrenomedullin 2 display endogenous GPCR agonist bias in primary human cardiovascular cells

Agonist bias occurs when different ligands produce distinct signalling outputs when acting at the same receptor. However, its physiological relevance is not always clear. Using primary human cells and gene editing techniques, we demonstrate endogenous agonist bias with physiological consequences for the calcitonin receptor-like receptor, CLR. By switching the receptor-activity modifying protein (RAMP) associated with CLR we can “re-route” the physiological pathways activated by endogenous agonists calcitonin gene-related peptide (CGRP), adrenomedullin (AM) and adrenomedullin 2 (AM2). AM2 promotes calcium-mediated nitric oxide signalling whereas CGRP and AM show pro-proliferative effects in cardiovascular cells, thus providing a rationale for the expression of the three peptides. CLR-based agonist bias occurs naturally in human cells and has a fundamental purpose for its existence. We anticipate this will be a starting point for more studies into RAMP function in native environments and their importance in endogenous GPCR signalling.

Clark et al. explore the ability of ligands to activate the calcitonin-like receptor (CLR) in primary endothelial cells, and the influence of co-expressed receptor-activity modifying proteins (RAMPs). Their study reveals that GPCR agonist bias occurs naturally in human cells and plays a fundamental role in providing unique functions to endogenous agonists.

Maladjustment of β-CGRP/α-CGRP Regulation of AQP5 Promotes Transition of Alveolar Epithelial Cell Apoptosis to Pulmonary Fibrosis

This study explored the triggering mechanism of interstitial lung disease (ILD). We established the effects of immunogenic and neurogenic calcitonin gene-related peptide (CGRP) imbalance on the regulation of aquaporin 5 (AQP5) expression and the repair responses that promote the transition from alveolar epithelial cell (AEC) apoptosis to pulmonary fibrosis. Newly diagnosed ILD patients (n = 60) were enrolled, whose serological levels of β-CGRP, α-CGRP, AQP5, receptor activity modifying protein 1, and receptor component protein were detected by ELISA. Th1 and Th2 cytokines and CD4⁺ and CD8⁺ cells were measured by flow cytometry method. In vivo, bleomycin (BLM) was set for modeling pulmonary fibrosis. A CALCA-HET model was set as a chronic pulmonary fibrosis model. Hematoxylin-eosin, immunohistochemistry, and Masson's trichrome staining were performed to assess the role of apoptosis in the injured lung. The concentrations of cytokines were determined by cytokine antibody arrays. Abnormal activation of serological CD4⁺ T lymphocytes and predominant Th2 response was established in the patients with ILD. Moreover, the ratio of β-CGRP/α-CGRP positively correlated with the increased level of AQP5 in patients with ILD. In vivo, a significant increase of AQP5 and β-CGRP at the chronic stage of pulmonary fibrosis was induced by BLM in the mice model, whereas the expression of AQP5 protein was generally lower in the acute alveolitis phase. Moreover, the levels of AQP5 and α-CGRP in the CALCA-HET rats were lower than those of the normal saline group. The high ratio β-CGRP/α-CGRP enhanced the expression of AQP5, inhibited transforming growth factor-β1 (TGFβ1)/P-Smad1/Smad4 pathway, and upregulated the NRF2 signal, whereas the apoptosis of AECs was significantly reduced in late-stage pulmonary fibrosis. The imbalance of β-CGRP/α-CGRP may be associated with the predominance of Th2 response and participate in the process of AEC apoptosis in lung fibrosis. The high ratio of β-CGRP/α-CGRP may elevate the level of AQP5 through inactivation of the TGF-β1/smad1 signaling pathway and upregulation of the Nrf2 signaling in the chronic stage of pulmonary fibrosis.

Cisplatin nephrotoxicity is induced via poly(ADP-ribose) polymerase activation in adult zebrafish and mice

Cisplatin is a well-known chemotherapy medication used to treat numerous cancers. However, treatment with cisplatin in cancer therapy has major side effects, such as nephrotoxic acute kidney injury. Adult vertebrate kidneys are commonly used as models of cisplatin-induced nephrotoxic acute kidney injury. Embryonic zebrafish kidney is more simplified and is composed simply of two nephrons and thus is an excellent model for the investigation of cisplatin nephrotoxicity. Here, we developed a novel model to induce cisplatin nephrotoxicity in adult zebrafish and demonstrated that intraperitoneal injection of cisplatin caused a decline in kidney proximal tubular function based on fluorescein-labeled dextran uptake and alkaline phosphatase staining. We also showed that cisplatin induced histological injury of the kidney tubules, quantified by tubular injury scores on the periodic acid-Schiff-stained kidney sections. As shown in a mouse model of cisplatin-induced nephrotoxicity, the activation of poly(ADP-ribose) polymerase (PARP), an enzyme implicated in cisplatin-induced cell death, was markedly increased after cisplatin injection in adult zebrafish. Furthermore, pharmacological inhibition of PARP using a specific PARP inhibitor PJ 34 hydrochloride (PJ34) or 3-aminobenzamide ameliorated kidney proximal tubular functional and histological damages in cisplatin-injected adult zebrafish kidneys. Administration of a combination of PARP inhibitors PJ34 and 3-aminobenzamide additively protected renal function and histology in zebrafish and mouse models of cisplatin nephrotoxicity. In conclusion, these data suggest that adult zebrafish are not only suitable for drug screening and genetic manipulation but also useful as a simplified but powerful model to study the pathophysiology of cisplatin nephrotoxicity and establish new therapies for treating human kidney diseases.

miR-122 Exerts Inhibitory Effects on Osteoblast Proliferation/Differentiation in Osteoporosis by Activating the PCP4-Mediated JNK Pathway

Osteoporosis is characterized by the reduction of bone mineral density and deterioration of bone quality which leads to high risk of fractures. Some microRNAs (miRNAs) have been confirmed as potential modulators of osteoblast differentiation to maintain bone mass maintenance. We aimed to clarify whether miR-122 could regulate osteoblast differentiation in ovariectomized rats with osteoporosis. miR-122 was upregulated and Purkinje cell protein 4 (PCP4) was downregulated in ovariectomized rats. PCP4 was identified as a target of miR-122 by dual-luciferase reporter gene assay. We transfected isolated osteoblasts from ovariectomized rats with miR-122 mimic or inhibitor or PCP4 overexpression vectors. Proliferation and differentiation of osteoblasts were repressed by the overexpression of miR-122 but enhanced by overexpression of PCP4. miR-122 could induce the activation of the c-Jun NH2-terminal kinase (JNK) signaling pathway, while PCP4 blocked this pathway. Rescue experiments further demonstrated that the inhibiting effects of miR-122 on osteoblast differentiation could be compensated by activation of the PCP4 or inhibition of JNK signaling pathway. Collectively, our data imply that miR-122 inhibits osteoblast proliferation and differentiation in rats with osteoporosis, highlighting a novel therapeutic target for osteoporotic patients.

Calcitonin Gene-Related Peptide (CGRP) and Cluster Headache

Cluster headache (CH) is a severe primary headache with a prevalence of 1/1000 individuals, and a predominance in men. Calcitonin gene-related peptide (CGRP) is a potent vasodilator, originating in trigeminal neurons and has a central role in CH pathophysiology. CGRP and the CGRP receptor complex have recently taken center stage as therapeutic targets for primary headaches, such as migraine. Multiple CGRP and CGRP receptor monoclonal antibodies, as well as small molecule antagonists (gepants) are on their way constituting a new frontier of migraine and possibly CH medication. During a CH attack, there is an activation of the trigeminal-autonomic reflex with the release of CGRP, and inversely if CGRP is administered to a CH patient in an active disease phase, it triggers an attack. Increased levels of CGRP have been found in ipsilateral jugular vein blood during the active phase of CH. This process is hypothesized to have a key role in the intense pain perception and in the associated distinctive vasodilation. So far, clinical tests of CGRP antibodies have been inconclusive in CH patients. This review summarizes the current state of knowledge on the role of CGRP in CH pathology, and as a target for future treatments.

Cyclosporin A aggravates hydrogen peroxide-induced cell death in kidney proximal tubule epithelial cells

Cyclosporin A (CsA) does not only exert a toxic effect on kidney parenchymal cells, but also protects them against necrotic cell death by inhibiting opening of mitochondrial permeability transition pore. However, whether CsA plays a role in hydrogen peroxide-induced kidney proximal tubular cell death is currently unclear. In the present study, treatment with CsA further increased apoptosis and necrosis in HK-2 human kidney proximal tubule epithelial cells during exposure to hydrogen peroxide. In addition, hydrogen peroxide-induced p53 activation and BH3 interacting-domain death agonist (BID) expression were higher in CsA-treated cells than those in non-treated cells, whereas hydrogen peroxide-induced activation of mitogen-activated protein kinases including p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase and activation of protein kinase B were not significantly altered by treatment with CsA. In oxidant-antioxidant system, reactive oxygen species (ROS) production induced by hydrogen peroxide was further enhanced by treatment with CsA. However, expression levels of antioxidant enzymes including manganese superoxide dismutase, copper/zinc superoxide dismutase, and catalase were not altered by treatment with hydrogen peroxide or CsA. Treatment with CsA further enhanced mitochondrial membrane potential induced by exposure to hydrogen peroxide, although it did not alter endoplasmic reticulum stress based on expression of glucose-regulated protein 78 and 94. Taken together, these data suggest that CsA can aggravate hydrogen peroxide-induced cell death through p53 activation, BID expression, and ROS production.

Yeast extract inhibits the proliferation of renal cell carcinoma cells via regulation of iron metabolism

The microbiome has recently attracted research interest in a variety of subjects, including cancer. In the present study, it was determined that reinforced clostridium media (RCM) for microbiome culture, exerts antitumor effects on renal cell carcinoma cells when compared to the microbiome 'X'. The antitumor effects of RCM were investigated for all ingredients of RCM, and the results revealed that yeast extract could be a candidate for the ingredient driving this phenomenon. Further experiments including MTT assay, cell counting, cell death analysis, cell cycle analysis and western blotting were conducted with yeast extract on renal cell carcinoma cells (Caki‑1 and Caki‑2) and normal human proximal tubular cells (HK‑2). As a result, yeast extract exhibited dose‑dependent antitumor effects on Caki‑1 and Caki‑2, but only slight effects on HK‑2. In addition, yeast extract only exhibited slight effects on necrosis, autophagy, or apoptosis of Caki‑1 and Caki‑2. Yeast extract produced cell cycle arrest with an increased G0/G1 fraction and a decreased S fraction, and this was considered to be related to the decreased cyclin D1. Although yeast extract treatment increased anti‑oxidant activities, the antitumor effects of yeast extract were also related to iron metabolism, based on the decreased transferrin receptor and increased ferritin. In addition, decreased GPX4 may be related to iron‑dependent cell death, particularly in Caki‑2. These results revealed that yeast extract may inhibit proliferation of renal cell carcinoma cells by regulating iron metabolism. Since an increased iron requirement is a classic phenomenon of cancer cells, yeast extract may be a candidate for adjuvant treatment of renal cell carcinoma.

Knockout of α-calcitonin gene-related peptide attenuates cholestatic liver injury by differentially regulating cellular senescence of hepatic stellate cells and cholangiocytes

α-Calcitonin gene-related peptide (α-CGRP) is a 37-amino acid neuropeptide involved in several pathophysiological processes. α-CGRP is involved in the regulation of cholangiocyte proliferation during cholestasis. In this study, we aimed to evaluate if α-CGRP regulates bile duct ligation (BDL)-induced liver fibrosis by using a α-CGRP knockout (α-CGRP^-/-) mouse model. α-CGRP^-/- and wild-type (WT) mice were subjected to sham surgery or BDL for 7 days. Then, liver fibrosis and cellular senescence as well as the expression of kinase such as p38 and C-Jun N-terminal protein kinase (JNK) in mitogen-activated protein kinases (MAPK) signaling pathway were evaluated in total liver, together with measurement of cellular senescence in cholangiocytes or hepatic stellate cells (HSCs). There was enhanced hepatic expression of Calca (coding α-CGRP) and the CGRP receptor components (CRLR, RAMP-1 and RCP) in BDL and in both WT α-CGRP^-/- and BDL α-CGRP^-/- mice, respectively. Moreover, there was increased CGRP serum levels and hepatic mRNA expression of CALCA and CGRP receptor components in late-stage PSC samples compared to healthy control samples. Depletion of α-CGRP reduced liver injury and fibrosis in BDL mice that was associated with enhanced cellular senescence of hepatic stellate cells and reduced senescence of cholangiocytes as well as decreased activation of p38 and JNK MAPK signaling pathway. Cholangiocyte supernatant from BDL α-CGRP^-/- mice inhibited the activation and increased cellular senescence of cultured human HSCs (HHSCs) compared to HHSCs stimulated with BDL cholangiocyte supernatant. Taken together, endogenous α-CGRP promoted BDL-induced cholestatic liver fibrosis through differential changes in senescence of HSCs and cholangiocytes and activation of p38 and JNK signaling. Modulation of α-CGRP/CGRP receptor signaling may be key for the management of biliary senescence and liver fibrosis in cholangiopathies.

Expression and role of calcitonin gene-related peptide in mouse Aspergillus fumigatus keratitis

AIM

To investigate the expression and role of calcitonin gene-related peptide (CGRP) in the mouse models induced by Aspergillus fumigatus (A. fumigatus).

METHODS

C57BL/6 mice were randomized into a control group and A. fumigatus keratitis group. The cornea photography was assessed under the slit lamp and the clinical score was recorded after infection. Western blot, real-time polymerase chain reaction (PCR) and immunohistofluorescence analysis were applied to detect CGRP expression in cornea of both groups. In vitro, tests were conducted with C57BL/6 mice macrophages to investigate CGRP expression after interaction with A. fumigatus. Cytokines expression induced by exogenous CGRP and the antagonist CGRP8-37 in A. fumigatus-exposed macrophages was evaluated by real-time PCR and ELISA.

RESULTS

The cornea expression of CGRP was significantly elevated in C57BL/6 mice corneas and macrophages after A. fumigatus infection. After treatment with exogenous CGRP, the levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and IL-6 were reduced, and IL-10 level was increased in the A. fumigatus stimulated-macrophages. However, IL-1β, TNF-α and IL-6 levels were upregulated after pretreatment of CGRP8-37. But the mRNA levels of MIP-2, TGF-β and IL-10 were not changed.

CONCLUSION

This study provides evidence that A. fumigatus increased CGRP expression. CGRP may play a protective role against inflammation in A. fumigatus keratitis.

Exogenous spermidine ameliorates tubular necrosis during cisplatin nephrotoxicity

The hallmark of cisplatin-induced acute kidney injury is the necrotic cell death in the kidney proximal tubules. However, an effective approach to limit cisplatin nephrotoxicity remains unknown. Spermidine is a polyamine that protects against oxidative stress and necrosis in aged yeasts, and the present study found that exogenous spermidine markedly attenuated tubular necrosis and kidney dysfunction, but not apoptosis, during cisplatin nephrotoxicity. In addition, exogenous spermidine potently inhibited oxidative/nitrative DNA damage, poly(ADP-ribose) polymerase 1 (PARP1) activation and ATP depletion after cisplatin injection. Conversely, inhibition of ornithine decarboxylase (ODC) via siRNA transfection in vivo significantly increased DNA damage, PARP1 activation and ATP depletion, resulting in acceleration of tubular necrosis and kidney dysfunction. Finally, exogenous spermidine removed severe cisplatin injury induced by ODC inhibition. In conclusion, these data suggest that spermidine protects kidneys against cisplatin injury through DNA damage and tubular necrosis, and this finding provides a novel target to prevent acute kidney injury including nephrotoxicity.

Spermidine is protective against kidney ischemia and reperfusion injury through inhibiting DNA nitration and PARP1 activation

Kidney ischemia and reperfusion injury (IRI) is associated with a high mortality rate, which is attributed to tubular oxidative and nitrative stresses; however, an effective approach to limit IRI remains elusive. Spermidine, a naturally occurring polyamine, protects yeast cells against aging through the inhibition of oxidative stress and necrosis. In the present study, spermidine supplementation markedly attenuated histological damage and kidney dysfunction during IRI. In addition, exogenous spermidine potently inhibited poly(ADP-ribose) polymerase 1 (PARP1) activation and DNA nitrative/oxidative stress following IRI. Conversely, inhibition of ornithine decarboxylase (ODC) via siRNA transfection in vivo significantly enhanced DNA nitration, PARP1 activation, and functional damage during IRI. Finally, in ODC knockdown kidneys, PARP1 inhibition attenuated histological and functional damage induced by IRI, but not DNA nitrative stress. In conclusion, these data suggest that spermidine protects kidneys against IRI through blocking DNA nitration and PARP1 activation and this finding provides a novel target for prevention of acute kidney injury including IRI.