Apoptosis Induced in Vascular Smooth Muscle Cells by Oxidative Stress Is Partly Prevented by Pretreatment with CGRP

Intrinsic diving reflex induces potent antioxidative response by activation of NRF2 signaling

Aims

This study aims to elucidate the underlying mechanisms of diving reflex, a powerful endogenous mechanism supporting underwater mammalian survival. Antioxidative responses, observed in marine mammals, may be contributing factors. Using a multi-organ approach, this study assesses whether acute and chronic diving reflex activate nuclear factor-erythroid-2-related factor 2 (NRF2) signaling pathways, which regulate cellular antioxidant responses.

Methods

Male Sprague-Dawley rats ( n =38) underwent either a single diving session to elicit acute diving reflex, or daily diving sessions for 4-weeks to produce chronic diving reflex. NRF2 (total, nuclear, phosphorylated), NRF2-downstream genes, and malondialdehyde were assessed via Western blot, immunofluorescence, RT-PCR, and ELISA in brain, lung, kidney, and serum.

Results

Diving reflex increased nuclear NRF2, phosphorylated NRF2, and antioxidative gene expression, in an organ-specific and exposure time-specific manner. Comparing organs, the brain had the highest increase of phosphorylated NRF2 expression, while kidney had the highest degree of nuclear NRF2 expression. Comparing acute and chronic sessions, phosphorylated NRF2 increased the most with chronic diving reflex, but acute diving reflex had the highest antioxidative gene expression. Notably, calcitonin gene-related peptide appears to mediate diving reflex' effects on NRF2 activation.

Conclusions

Acute and chronic diving reflex activate potent NRF2 signaling in the brain and peripheral organs. Interestingly, acute diving reflex induces higher expression of downstream antioxidative genes compared to chronic diving reflex. This result contradicts previous assumptions requiring chronic exposure to diving for induction of antioxidative effects and implies that the diving reflex has a strong translational potential during preconditioning and postconditioning therapies.

Key Points

Diving reflex activates potent NRF2 signaling via multiple mechanisms, including phosphorylation, nuclear translocation, and KEAP1 downregulation with both acute and chronic exposure.Diving reflex activates NRF2 via differential pathways in the brain and other organs; phosphorylated NRF2 increases more in the brain, while nuclear NRF2 increases more in the peripheral organs.Acute diving reflex exposure induces a more pronounced antioxidative effect than chronic diving reflex exposure, indicating that the antioxidative response activated by diving reflex is not dependent upon chronic adaptive responses and supports diving reflex as both a preconditioning and postconditioning treatment.

Impact of Transferrin Saturation and Anemia on Radial Artery Calcification in Patients with End-Stage Kidney Disease

Background: Arterial calcification is an important factor in determining the prognosis of patients with chronic kidney disease (CKD). Few studies on aortic calcification have involved radial artery calcification (RAC). This study aimed to analyze risk factors for RAC in patients with end-stage kidney disease (ESKD) and investigate the relationship between subsequent cardiovascular events (CVE) and vascular access trouble (VAT). Methods: This cohort study included 64 consecutive patients with ESKD who initiated hemodialysis and underwent a procedure for the creation of a primary radiocephalic arteriovenous fistula (RCAVF). Small arterial specimens were obtained from patients during RCAVF surgery. Tissue samples were stained with von Kossa, and arterial microcalcification was evaluated. We analyzed the association between preexisting arterial microcalcifications, clinical characteristics, CVE, and VAT. Results: In the univariate analysis, RAC patients demonstrated high systolic blood pressure (sBP), low hemoglobin (Hb), and low transferrin saturation (TSAT) (<0.05, <0.05, and <0.05, respectively). In the multivariate analysis, Hb (HR−0.516 (0.278−0.959), p < 0.05), TSAT (HR−0.0012 (0.00000248−0.597), p < 0.05), and sBP (HR−1.037 (1.001−1.073), p < 0.05) were independent risk factors for RAC. The cumulative incidence rate of CVE/VAT was not associated with RAC for one year. Conclusion: RAC was associated with sBP, TSAT, and anemia; however, no association with CVE/VAT was observed.

Non-Transferrin-Bound Iron in the Spotlight: Novel Mechanistic Insights into the Vasculotoxic and Atherosclerotic Effect of Iron

Significance: While atherosclerosis is an almost inevitable consequence of aging, food preferences, lack of exercise, and other aspects of the lifestyle in many countries, the identification of new risk factors is of increasing importance to tackle a disease, which has become a major health burden for billions of people. Iron has long been suspected to promote the development of atherosclerosis, but data have been conflicting, and the contribution of iron is still debated controversially. Recent Advances: Several experimental and clinical studies have been recently published about this longstanding controversial problem, highlighting the critical need to unravel the complexity behind this topic. Critical Issues: The aim of the current review is to provide an overview of the current knowledge about the proatherosclerotic impact of iron, and discuss the emerging role of non-transferrin-bound iron (NTBI) as driver of vasculotoxicity and atherosclerosis. Finally, I will provide detailed mechanistic insights on the cellular processes and molecular pathways underlying iron-exacerbated atherosclerosis. Overall, this review highlights a complex framework where NTBI acts at multiple levels in atherosclerosis by altering the serum and vascular microenvironment in a proatherogenic and proinflammatory manner, affecting the functionality and survival of vascular cells, promoting foam cell formation and inducing angiogenesis, calcification, and plaque destabilization. Future Directions: The use of additional iron markers (e.g., NTBI) may help adequately predict predisposition to cardiovascular disease. Clinical studies are needed in the aging population to address the atherogenic role of iron fluctuations within physiological limits and the therapeutic value of iron restriction approaches. Antioxid. Redox Signal. 35, 387-414.

Overexpression of calcitonin gene-related peptide protects mouse cerebral microvascular endothelial cells from high-glucose-induced damage via ERK/HIF-1/VEGF signaling

In the diabetic brain, hyperglycemia damages the cerebrovasculature and impairs neurovascular crosstalk. Calcitonin gene-related peptide (CGRP) is an important neuropeptide that is active in the vascular system. In this study, we aimed to investigate whether CGRP is involved in the high-glucose-induced damage in mouse cerebral microvascular endothelial (b.END3) cells and the possible mechanism in vitro. The overexpression of CGRP by lentiviral transduction inhibited cell apoptosis but not proliferation. In contrast to the promoting of angiogenesis and migration under normal glucose, CGRP inhibited hyperglycemia-induced tube formation but had no effect on migration. Calcitonin gene-related peptide partly reduced the increased level of intracellular reactive oxygen species (ROS) and altered nitric oxide synthase mRNA expression. Furthermore, CGRP suppressed the increased HIF-1α/VEGF-A expression and the phosphorylation of ERK1/2 in hyperglycemia. The ERK inhibitor U0126 showed similar inhibition of cell apoptosis, tube formation and HIF-1α/VEGF expression as that exhibited by lenti-CGRP. These findings demonstrate the protective role of CGRP overexpression against high-glucose-induced cerebrovascular changes in b.END3 cells, possibly through the inhibition of ERK/HIF-1/VEGF signaling.

The protective role of calcitonin gene-related peptide (CGRP) in high-glucose-induced oxidative injury in rat aorta endothelial cells

Endothelial dysfunction is considered to be an initial indicator in diabetes-induced macrovascular complications. Evidence has shown that CGRP is an important neuropeptide active in vascular system, especially in vasorelaxation. This study aimed to investigate the role of CGRP in high-glucose-induced endothelial dysfunction in rat aorta endothelial cells (RAECs). Quantitative-real time PCR and western blots were used to determine the efficiency of overexpression and interference of CGRP. After incubation with normal glucose (5.5 mM) or high glucose (33 mM), the cell viability and cell apoptosis were tested. Afterwards, the Nitric Oxide (NO) production, the mRNA expression of inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS) and angiotensin II (Ang II) and the level of reactive oxygen species (ROS) were determined. The involvement of ERK1/2-NOX4 was determined through western blots and the translocation of p47phox was also observed via cell immunofluorescence. CGRP alleviated the high-glucose-induced cell apoptosis while CGRP did not have an obvious impact on cell viability. Meanwhile, CGRP increased the NO production as well as the eNOS mRNA expression and reversely decreased the stimulated expression of iNOS and Ang II by high glucose. In addition, CGRP attenuated the high-glucose-stimulated intracellular ROS production by ERK1/2-NOX4 and the translocation of p47phox. These results indicated the protective role of CGRP in high-glucose-induced oxidative injury in RAECs possibly through inhibiting ERK1/2-NOX4. Our findings might help to further understand the potential role and possible mechanism of CGRP in endothelial dysfunction caused by high glucose.

CGRP Receptor Signalling Pathways

Calcitonin gene-related peptide (CGRP) is a promiscuous peptide, similar to many other members of the calcitonin family of peptides. The potential of CGRP to act on many different receptors with differing affinities and efficacies makes deciphering the signalling from the CGRP receptor a challenging task for researchers.Although it is not a typical G protein-coupled receptor (GPCR), in that it is composed not just of a GPCR, the CGRP receptor activates many of the same signalling pathways common for other GPCRs. This includes the family of G proteins and a variety of protein kinases and transcription factors. It is now also clear that in addition to the initiation of cell-surface signalling, GPCRs, including the CGRP receptor, also activate distinct signalling pathways as the receptor is trafficking along the endocytic conduit.Given CGRP's characteristic of activating multiple GPCRs, we will first consider the complex of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1) as the CGRP receptor. We will discuss the discovery of the CGRP receptor components, the molecular mechanisms controlling its internalization and post-endocytic trafficking (recycling and degradation) and the diverse signalling cascades that are elicited by this receptor in model cell lines. We will then discuss CGRP-mediated signalling pathways in primary cells pertinent to migraine including neurons, glial cells and vascular smooth muscle cells.Investigation of all the CGRP- and CGRP receptor-mediated signalling cascades is vital if we are to fully understand CGRP's role in migraine and will no doubt unearth new targets for the treatment of migraine and other CGRP-driven diseases.

Clinical detection, risk factors, and cardiovascular consequences of medial arterial calcification: a pattern of vascular injury associated with aberrant mineral metabolism

Patients with end-stage renal disease are characterized by extensive vascular calcification and high cardiovascular disease (CVD) risk. Calcification in end-stage renal disease patients represents at least two distinct pathologic processes. Calcification within the tunica intima frequently is associated with lipid-laden, flow-limiting atherosclerotic plaques. These appear as spotty areas of calcification interspersed with noncalcified arterial segments on plain radiography and generally are found near arterial branch points in medium-sized conduit arteries. In contrast, medial arterial calcification (MAC) involves deeper layers of the arterial wall; tends to affect the artery diffusely, appearing as a linear contiguous tram-track pattern of calcification on plain radiography; and often involves smaller muscular arteries such as the radial artery, intermammary arteries, and arteries in the ankle and foot. Both are related to CVD events, but potentially through different mechanisms. Atherosclerotic calcification may be marking the total burden of atherosclerosis, whereas MAC may lead to arterial stiffness and left ventricular hypertrophy. Existing data suggest that altered mineral metabolism may promote MAC, whereas heightened inflammation and oxidative stress contribute to atherosclerosis. Dysregulation of normal anticalcification factors and elastin degradation are common to both processes. Risk of vascular calcification also may be increased by the use of certain medications in the setting of chronic kidney disease. This review compares and contrasts known risk factors for MAC and atherosclerosis, describes existing and emerging technologies to distinguish between them, and reviews the existing literature linking each with CVD events in dialysis patients and in other settings.

Iron and vascular calcification. Is there a link?

Iron deficiency is frequently seen in patients with end-stage renal disease, particularly in those treated by dialysis, this is because of an impairment in gastrointestinal absorption and ongoing blood losses or alternatively, due to an impaired capacity to mobilize iron from its stores, called functional iron deficiency. Therefore, these patients may require intravenous iron to sustain adequate treatment with erythropoietin-stimulating agents. Aside from this, they are also prone to vascular calcification, which has been reported a major contributing factor in the development of cardiovascular disease and the increased mortality associated herewith. Several factors and mechanisms underlying the development of vascular calcification in chronic kidney diseased patients have been put forward during recent years. In view of the ability of iron to exert direct toxic effects and to induce oxidative stress on the one hand versus its essential role in various cellular processes on the other hand, the possible role of iron in the development of vascular calcification should be considered.

Pretreatment with calcitonin gene-related peptide attenuates hepatic ischemia/reperfusion injury in rats

OBJECTIVE

Oxygen free radicals and apoptosis play important roles in liver ischemia/reperfusion (I/R) injury. We sought to investigate the protective effect of calcitonin gene-related peptide (CGRP) to attenuate liver I/R injury due to oxygen free radicals and apoptosis.

MATERIALS AND METHODS

Harvested rat livers were perfused via the portal vein with 60 mL of 4 degrees C histidine-tryptophan-ketoglutarate (HTK) solution alone in the control group, or with the same solution containing CGRP (3 microg/10 g body weight) in the experimental group. After 24 hours of cold storage, hepatic enzyme leakage, portal venous pressure, oxygen consumption, total adenine nucleotides (TAN), bile production, lipoperoxide (LPO) release, apoptosis, and histochemical changes were evaluated upon 45 minutes of isolated reperfusion.

RESULTS

Compared with control livers, CGRP-treated organs showed significantly decreased alanine aminotransferase (ALT) and glutamate-lactate dehydrogenase (GLDH) leakage and portal venous pressure (2.0 +/- 0.3 vs 4.0 +/- 0.4 mmHg; P < .01), with significantly increased bile production (8.56 +/- 0.76 vs 3.34 +/- 0.68 microL/g/45 min; P < .01), oxygen consumption (5.14 +/- 0.4 vs 2.57 +/- 0.2 microL/g/min; P < .01), and total adenine nucleotides (TAN) (11.1 +/- 0.71 vs 7.02 +/- 0.53 micromol/g; P < .01) upon reperfusion as signs of recovered viability. We observed infrequent positive terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) staining, especially in sinusoidal lining cells (SLC). The percentage of TUNEL-positive cells in the CGRP group was significantly decreased compared with the control group: (4.1 +/- 0.67 vs 8.0 +/- 1.27; P < .05). Perfusate levels of low molecular weight (LMW) histone-associated DNA fragments (0.36 +/- 0.04 vs 0.53 +/- 0.06 AU; P < .05) were also decreased, coupled with strong 5'-nucleotidase (5'-NT) and LDH activity staining concentrated on the endothelial cells. LPO release in the perfusate was largely decreased: (0.12 +/- 0.02 vs 0.36 +/- 0.04 nmoL/g, P < .01).

CONCLUSION

CGRP ameliorated liver I/R injury due to reactive oxygen species and apoptosis.

Calcitonin gene-related peptide is a survival factor, inhibiting apoptosis in neonatal rat gubernaculum in vitro

BACKGROUND

Testicular descent is proposed to occur in 2 stages. During the second stage, calcitonin gene-related peptide (CGRP) released from the genitofemoral nerve (GFN) causes maximal mitosis in the gubernacular bulb. As normal development requires a balance between cell proliferation and apoptosis, this study explored the effect of CGRP on apoptosis in the rat gubernacular bulb.

METHODS

Gubernacula were collected from male Sprague-Dawley rats at birth (D0) or 2 days post birth (D2), and placed in organ culture for 24 hours with or without CGRP (0.001 mol/L). The D2 rats were pretreated with capsaicin (sensory nerve toxin) or flutamide (antiandrogen) or untreated. D0 rats were untreated (n = 64). Sections of the bulb were stained using the TUNEL method to identify apoptotic cells. Apoptosis was calculated as the percentage of positive cells per hundred cells.

RESULTS

Normal Sprague-Dawley rat gubernacula showed reduced apoptosis when cultured with CGRP, in D0 (7.0% vs 4.8%, P < .05) and D2 (4.9% vs 2.3%, P < .001). Greater apoptosis occurred at D0 compared to D2, without CGRP added (7.0% vs 4.9%, P < .05) and with CGRP (4.8% vs 2.3%, P < .001). For D2 gubernacula, capsaicin treatment increased apoptosis compared to controls, without CGRP added (4.9% vs 7.3%, P < .05) and with CGRP (2.3% vs 6.7%, P < .001). There was no difference in apoptosis when cultured with or without CGRP (7.3% vs 6.7%, nonsignificant) after capsaicin treatment. Flutamide treatment increased apoptosis compared to controls, but only with CGRP (2.3% vs 7.3%, P < .001). There was no difference in apoptosis when cultured with or without CGRP (7.1% vs 7.3%, nonsignificant) after flutamide.

CONCLUSIONS

Calcitonin gene-related peptide (CGRP) acts as a survival factor in the rat gubernaculum, possibly to steer cells away from a defined apoptotic pathway. Greater apoptosis occurs earlier in development. However, in vivo CGRP released from the genitofemoral nerve may be required to prevent apoptosis, as shown by pretreatment with the sensory nerve toxin capsaicin. Androgen is also involved in the pathway controlling apoptosis, as androgen blockade with flutamide inhibited the action of CGRP.

Zinc, antioxidant systems and metallothionein in metal mediated-apoptosis: biochemical and cytochemical aspects

Copper, zinc and iron are essential metals for different physiological functions, even though their excess can lead to biological damage. This review provides a background of toxicity related to copper, iron and zinc excess, biological mechanisms of their homeostasis and their respective roles in the apoptotic process. The antioxidant action of metallothionein has been highlighted by summarizing the most important findings that confirm the role of zinc in cellular protection in relation to metallothionein expression and apoptotic processes. In particular, we show that a complex and efficient antioxidant system, the induction of metallothionein and the direct action of zinc have protective roles against oxidative damage and the resulting apoptosis induced by metals with redox proprieties. In addition, to emphasize the protective effects of Zn and Zn-MT in Cu and Fe-mediated oxidative stress-dependent apoptosis, some aspects of apoptotic cell death are shown. The most widely used cytochemical techniques also have been examined in order to critically evaluate the available data from a methodological point of view. The observations on the role of Zn and MT could potentially develop new applications for this metal and MT in biomedical research.

TRPV1 gene knockout impairs preconditioning protection against myocardial injury in isolated perfused hearts in mice

Although the transient receptor potential vanilloid type 1 (TRPV1)-containing afferent nerve fibers are widely distributed in the heart, the relationship between TRPV1 function and cardiac ischemic preconditioning (PC) has not been well defined. Using TRPV1 knockout mice (TRPV1−/−), we studied the role of TRPV1 in PC-induced myocardial protection. Hearts of gene-targeted TRPV1-null mutant (TRPV1−/−) or wild-type (WT) mice were Langendorffly perfused in the presence or absence of CGRP8-37, a selective calcitonin gene-related peptide (CGRP) receptor antagonist; or RP-67580, a selective neurokinin-1 receptor antagonist when hearts were subjected to three 5-min periods of ischemia PC followed by 30 min of global ischemia and 40 min of reperfusion (I/R). PC before I/R decreased left ventricular (LV) end-diastolic pressure and increased LV developed pressure, coronary flow (CF), peak-positive maximum rate of rise of LV pressure in WT mice (PC-WT) compared with PC-TRPV1−/−, TRPV1−/−, or WT hearts ( P < 0.05), and PC also decreased LV end-diastolic pressure in PC-TRPV1−/− compared with TRPV1−/−. CGRP8-37 or RP-67580 abolished PC-induced protection in WT but not TRPV1−/− hearts ( P < 0.05). Moreover, PC decreased lactate dehydrogenase release and infarct size in PC-WT compared with PC-TRPV1−/−, TRPV1−/−, or WT hearts, and it also lowered these parameters in PC-TRPV1−/− compared with TRPV1−/− hearts ( P < 0.05). Radioimmunoassay showed that the release of substance P and CGRP after PC was higher in WT hearts than in TRPV1−/− hearts ( P < 0.05), which was attenuated by capsazepine in WT but not TRPV1−/− hearts. Thus PC-induced protection of the heart was impaired in TRPV1−/− hearts, indicating that TRPV1 contributes to the beneficial effects of preconditioning against I/R injury through release substance P and CGRP.

Potential role of the neuropeptide CGRP in the induction of differentiation of rat hepatic portal vein wall

The media of the rat hepatic portal vein is composed of an internal circular muscular layer (CL) and an external longitudinal muscular layer (LL). These two perpendicular layers differentiate progressively from mesenchymal cells within the first month after birth. In this paper, we studied the development of calcitonin gene-related peptide (CGRP) innervation during post-natal differentiation of the vessel. We show that CGRP innervation is already present around the vessel at birth in the future adventitia but far from the lumen of the vessel. Progressively, CGRP immunoreactive fibers reached first LL then CL. CL by itself become only innervated at day 14 after birth. This corresponds to the time at which thick filaments (myosin) are visible in electron microscopy and desmin visualisable by immunocytochemistry. Furthermore, we provide evidence by autoradiography, that binding sites for CGRP are transiently expressed on the portal vein media at day 1 and 14 after birth. Vascular smooth muscle cells were transfected with constructs containing promoters for desmin or smooth muscle myosin heavy chain (smMHC). CGRP treatment of the cells significantly increased the expression of smMHC. Overall these results suggest that CGRP can potentially influence the differentiation of smooth muscle cells from the vessel wall.