Transactivation of ErbB Family of Receptor Tyrosine Kinases Is Inhibited by Angiotensin-(1-7) via Its Mas Receptor

Targeting the epidermal growth factor receptor (EGFR/ErbB) for the potential treatment of renal pathologies

Epidermal growth factor receptor (EGFR), which is referred to as ErbB1/HER1, is the prototype of the EGFR family of receptor tyrosine kinases which also comprises ErbB2 (Neu, HER2), ErbB3 (HER3), and ErbB4 (HER4). EGFR, along with other ErbBs, is expressed in the kidney tubules and is physiologically involved in nephrogenesis and tissue repair, mainly following acute kidney injury. However, its sustained activation is linked to several kidney pathologies, including diabetic nephropathy, hypertensive nephropathy, glomerulonephritis, chronic kidney disease, and renal fibrosis. This review aims to provide a summary of the recent findings regarding the consequences of EGFR activation in several key renal pathologies. We also discuss the potential interplay between EGFR and the reno-protective angiotensin-(1-7) (Ang-(1-7), a heptapeptide member of the renin-angiotensin-aldosterone system that counter-regulates the actions of angiotensin II. Ang-(1-7)-mediated inhibition of EGFR transactivation might represent a potential mechanism of action for its renoprotection. Our review suggests that there is a significant body of evidence supporting the potential inhibition of EGFR/ErbB, and/or administration of Ang-(1-7), as potential novel therapeutic strategies in the treatment of renal pathologies. Thus, EGFR inhibitors such as Gefitinib and Erlinotib that have an acceptable safety profile and have been clinically used in cancer chemotherapy since their FDA approval in the early 2000s, might be considered for repurposing in the treatment of renal pathologies.

Bibliometric and visual analysis of ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications from 2000 to 2023

Background

The pathogenesis of diabetes and its microvascular complications are intimately associated with renin angiotensin system dysregulation. Evidence suggests the angiotensin converting enzyme 2 (ACE2)/angiotensin 1-7 (Ang 1-7)/Mas receptor (MasR) axis regulates metabolic imbalances, inflammatory responses, reduces oxidative stress, and sustains microvascular integrity, thereby strengthening defences against diabetic conditions. This study aims to conduct a comprehensive analysis of the ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications over the past two decades, focusing on key contributors, research hotspots, and thematic trends.

Methods

This cross-sectional bibliometric analysis of 349 English-language publications was performed using HistCite, VOSviewer, CiteSpace, and Bibliometrix R for visualization and metric analysis. Primary analytical metrics included publication count and keyword trend dynamics.

Results

The United States, contributing 105 articles, emerged as the most productive country, with the University of Florida leading institutions with 18 publications. Benter IF was the most prolific author with 14 publications, and Clinical Science was the leading journal with 13 articles. A total of 151 of the 527 author's keywords with two or more occurrences clustered into four major clusters: diabetic microvascular pathogenesis, metabolic systems, type 2 diabetes, and coronavirus infections. Keywords such as "SARS", "ACE2", "coronavirus", "receptor" and "infection" displayed the strongest citation bursts. The thematic evolution in this field expanded from focusing on the renin angiotensin system (2002-2009) to incorporating ACE2 and diabetes metabolism (2010-2016). The latter period (2017-2023) witnessed a significant surge in diabetes research, reflecting the impact of COVID-19 and associated conditions such as diabetic retinopathy and cardiomyopathy.

Conclusions

This scientometric study offers a detailed analysis of the ACE2/Ang 1-7/MasR axis in diabetes and its microvascular complications, providing valuable insights for future research directions.

Anticancer pan-ErbB inhibitors reduce inflammation and tissue injury and exert broad-spectrum antiviral effects

Targeting host factors exploited by multiple viruses could offer broad-spectrum solutions for pandemic preparedness. Seventeen candidates targeting diverse functions emerged in a screen of 4,413 compounds for SARS-CoV-2 inhibitors. We demonstrated that lapatinib and other approved inhibitors of the ErbB family of receptor tyrosine kinases suppress replication of SARS-CoV-2, Venezuelan equine encephalitis virus (VEEV), and other emerging viruses with a high barrier to resistance. Lapatinib suppressed SARS-CoV-2 entry and later stages of the viral life cycle and showed synergistic effect with the direct-acting antiviral nirmatrelvir. We discovered that ErbB1, ErbB2, and ErbB4 bind SARS-CoV-2 S1 protein and regulate viral and ACE2 internalization, and they are required for VEEV infection. In human lung organoids, lapatinib protected from SARS-CoV-2-induced activation of ErbB-regulated pathways implicated in non-infectious lung injury, proinflammatory cytokine production, and epithelial barrier injury. Lapatinib suppressed VEEV replication, cytokine production, and disruption of blood-brain barrier integrity in microfluidics-based human neurovascular units, and reduced mortality in a lethal infection murine model. We validated lapatinib-mediated inhibition of ErbB activity as an important mechanism of antiviral action. These findings reveal regulation of viral replication, inflammation, and tissue injury via ErbBs and establish a proof of principle for a repurposed, ErbB-targeted approach to combat emerging viruses.

Anticancer pan-ErbB inhibitors reduce inflammation and tissue injury and exert broad-spectrum antiviral effects

Targeting host factors exploited by multiple viruses could offer broad-spectrum solutions for pandemic preparedness. Seventeen candidates targeting diverse functions emerged in a screen of 4,413 compounds for SARS-CoV-2 inhibitors. We demonstrated that lapatinib and other approved inhibitors of the ErbB family receptor tyrosine kinases suppress replication of SARS-CoV-2, Venezuelan equine encephalitis virus (VEEV), and other emerging viruses with a high barrier to resistance. Lapatinib suppressed SARS-CoV-2 entry and later stages of the viral life cycle and showed synergistic effect with the direct-acting antiviral nirmatrelvir. We discovered that ErbB1, 2 and 4 bind SARS-CoV-2 S1 protein and regulate viral and ACE2 internalization, and they are required for VEEV infection. In human lung organoids, lapatinib protected from SARS-CoV-2-induced activation of ErbB-regulated pathways implicated in non-infectious lung injury, pro-inflammatory cytokine production, and epithelial barrier injury. Lapatinib suppressed VEEV replication, cytokine production and disruption of the blood-brain barrier integrity in microfluidic-based human neurovascular units, and reduced mortality in a lethal infection murine model. We validated lapatinib-mediated inhibition of ErbB activity as an important mechanism of antiviral action. These findings reveal regulation of viral replication, inflammation, and tissue injury via ErbBs and establish a proof-of-principle for a repurposed, ErbB-targeted approach to combat emerging viruses.

Mitigating Cardiotoxicity of Dendrimers: Angiotensin-(1-7) via Its Mas Receptor Ameliorates PAMAM-Induced Cardiac Dysfunction in the Isolated Mammalian Heart

AIM

The influence of the physiochemical properties of dendrimer nanoparticles on cardiac contractility and hemodynamics are not known. Herein, we investigated (a) the effect of polyamidoamine (PAMAM) dendrimer generation (G7, G6, G5, G4 and G3) and surface chemistry (-NH₂, -COOH and -OH) on cardiac function in mammalian hearts following ischemia-reperfusion (I/R) injury, and (b) determined if any PAMAM-induced cardiotoxicity could be mitigated by Angiotensin-(1-7) (Ang-(1-7), a cardioprotective agent.

METHODS

Hearts isolated from male Wistar rats underwent regional I/R and/or treatment with different PAMAM dendrimers, Ang-(1-7) or its MAS receptors antagonists. Thirty minutes of regional ischemia through ligation of the left anterior descending coronary artery was followed by 30 min of reperfusion. All treatments were initiated 5 min prior to reperfusion and maintained during the first 10 min of reperfusion. Cardiac function parameters for left ventricular contractility, hemodynamics and vascular dynamics data were acquired digitally, whereas cardiac enzymes and infarct size were used as measures of cardiac injury.

RESULTS

Treatment of isolated hearts with increasing doses of G7 PAMAM dendrimer progressively exacerbated recovery of cardiac contractility and hemodynamic parameters post-I/R injury. Impairment of cardiac function was progressively less on decreasing dendrimer generation with G3 exhibiting little or no cardiotoxicity. Cationic PAMAMs (-NH₂) were more toxic than anionic (-COOH), with neutral PAMAMs (-OH) exhibiting the least cardiotoxicity. Cationic G7 PAMAM-induced cardiac dysfunction was significantly reversed by Ang-(1-7) administration. These cardioprotective effects of Ang-(1-7) were significantly revoked by administration of the MAS receptor antagonists, A779 and D-Pro⁷-Ang-(1-7).

CONCLUSIONS

PAMAM dendrimers can impair the recovery of hearts from I/R injury in a dose-, dendrimer-generation-(size) and surface-charge dependent manner. Importantly, PAMAM-induced cardiotoxicity could be mitigated by Ang-(1-7) acting through its MAS receptor. Thus, this study highlights the activation of Ang-(1-7)/Mas receptor axis as a novel strategy to overcome dendrimer-induced cardiotoxicity.

Hydrogen sulfide donor GYY4137 attenuates vascular complications in mesenteric bed of streptozotocin-induced diabetic rats

Hydrogen sulfide (H₂S) has been reported to have beneficial effects in different pathological conditions.

OBJECTIVES

the effects of chronic treatment of diabetic rats with GYY4137 (slow releasing H₂S donor) or NaHS (fast releasing H₂S donor) on the reactivity of the mesenteric bed to vasoactive agonists and the changes in its downstream effectors, ERK1/2 and p38 MAP Kinase have been investigated. In addition, the levels of nitric oxide (NO) and H₂S in all groups were measured.

METHODS

diabetes was induced by a single intraperitoneal (ip) injection of streptozotocin (STZ; 55 mg/kg). Sprague Dawley (SD; n = 10-12/group) rats were randomly divided into six groups: control, STZ-induced diabetic rats, GYY4137-treated control, NaHS-treated control, GYY4137-treated diabetic, and NaHS-treated diabetic. After 28 days of treatment, rats were sacrificed and mesenteric beds were isolated for functional or biochemical studies. The vascular reactivity of the perfused mesenteric bed to norepinephrine, carbachol and sodium nitroprusside were determined by measurement of changes in perfusion pressure. Western blotting was performed to measure the protein expression of ERK1/2, p38, eNOS, and H₂S biosynthesizing enzymes cystathionine-β-synthase and cystathionine-γ-lyase. NO and H₂S levels were measured in all groups in isolated mesenteric tissues or plasma.

RESULTS

diabetes resulted in a significant increase in vasoconstrictor responses to norepinephrine (e.g., 129.6 ± 6.77 mmHg in diabetic vs 89.3 ± 8.48 mmHg in control at 10^-7 dose), and carbachol-induced vasodilation was significantly reduced in diabetic mesenteric bed (e.g., 68.9 ± 4.8 mmHg in diabetic vs 90.6 ± 2.2 mmHg in control at 10^-7 dose). Chronic treatment of the diabetic rats with GYY4137 resulted in a significant improvement in the response to norepinephrine (e.g., 86.66 ± 8.04 mmHg in GYY4137-treated diabetic vs 129.6 ± 6.77 mmHg in untreated diabetic at 10^-7 dose) or carbachol (e.g., 84.90 ± 2.48 mmHg in GYY4137-treated diabetic vs 68.9 ± 4.8 mmHg in untreated diabetic at 10^-7 dose). The biochemical studies showed a marked reduction of the protein expression of ERK and p38 and a significant upregulation of the expression of eNOS and H₂S synthesizing enzymes after chronic treatment with GYY4137. Plasma levels of NO and H₂S were significantly elevated after treatment with GYY4137. However, H₂S production in the mesenteric bed showed a marginal elevation in diabetic tissues compared to controls.

CONCLUSION

the results indicate that GYY4137 may be a novel therapeutic tool to prevent diabetes-associated vascular dysfunction.

The rs705708 A allele of the ERBB3 gene is associated with lower prevalence of diabetic retinopathy and arterial hypertension and with improved renal function in type 1 diabetic patients

INTRODUCTION

The Erb-b2 receptor tyrosine kinase 3 (ERBB3) is involved in autoimmune processes related to type 1 diabetes mellitus (T1DM) pathogenesis. Accordingly, some studies have suggested that single nucleotide polymorphisms (SNPs) in the ERBB3 gene confer risk for T1DM. Proliferation-associated protein 2G4 (PA2G4) is another candidate gene for this disease because it regulates cell proliferation and adaptive immunity. Moreover, PA2G4 regulates ERBB3. To date, no study has evaluated the association of PA2G4 SNPs and T1DM.

AIM

To evaluate the association of ERBB3 rs705708 (G/A) and PA2G4 rs773120 (C/T) SNPs with T1DM and its clinical and laboratory characteristics.

METHODS

This case-control study included 976 white subjects from Southern Brazil, categorized into 501 cases with T1DM and 475 non-diabetic controls. The ERBB3 and PA2G4 SNPs were genotyped by allelic discrimination-real-time PCR.

RESULTS

ERBB3 rs705708 and PA2G4 rs773120 SNPs were not associated with T1DM considering different inheritance models and also when controlling for covariables. However, T1DM patients carrying the ERBB3 rs705708 A allele developed T1DM at an earlier age vs. G/G patients. Interestingly, in the T1DM group, the rs705708 A allele was associated with lower prevalence of diabetic retinopathy and arterial hypertension as well as with improved renal function (higher estimated glomerular filtration rate and lower urinary albumin excretion levels) compared to G/G patients.

CONCLUSIONS

Although no association was observed between the ERBB3 rs705708 and PA2G4 rs773120 SNPs and T1DM, the rs705708 A allele was associated, for the first time in literature, with lower prevalence of diabetic retinopathy and arterial hypertension. Additionally, this SNP was associated with improved renal function.

Emerging innate biological properties of nano-drug delivery systems: A focus on PAMAM dendrimers and their clinical potential

Drug delivery systems or vectors are usually needed to improve the bioavailability and effectiveness of a drug through improving its pharmacokinetics/pharmacodynamics at an organ, tissue or cellular level. However, emerging technologies with sensitive readouts as well as a greater understanding of physiological/biological systems have revealed that polymeric drug delivery systems are not biologically inert but can have innate or intrinsic biological actions. In this article, we review the emerging multiple innate biological/toxicological properties of naked polyamidoamine (PAMAM) dendrimer delivery systems in the absence of any drug cargo and discuss their correlation with the defined physicochemical properties of PAMAMs in terms of molecular size (generation), architecture, surface charge and chemistry. Further, we assess whether any of the reported intrinsic biological actions of PAMAMs such as their antimicrobial activity or their ability to sequester glucose and modulate key protein interactions or cell signaling pathways, can be exploited clinically such as in the treatment of diabetes and its complications.

The Role of Epidermal Growth Factor Receptor Family of Receptor Tyrosine Kinases in Mediating Diabetes-Induced Cardiovascular Complications

Diabetes mellitus is a major debilitating disease whose global incidence is progressively increasing with currently over 463 million adult sufferers and this figure will likely reach over 700 million by the year 2045. It is the complications of diabetes such as cardiovascular, renal, neuronal and ocular dysfunction that lead to increased patient morbidity and mortality. Of these, cardiovascular complications that can result in stroke and cardiomyopathies are 2- to 5-fold more likely in diabetes but the underlying mechanisms involved in their development are not fully understood. Emerging research suggests that members of the Epidermal Growth Factor Receptor (EGFR/ErbB/HER) family of tyrosine kinases can have a dual role in that they are beneficially required for normal development and physiological functioning of the cardiovascular system (CVS) as well as in salvage pathways following acute cardiac ischemia/reperfusion injury but their chronic dysregulation may also be intricately involved in mediating diabetes-induced cardiovascular pathologies. Here we review the evidence for EGFR/ErbB/HER receptors in mediating these dual roles in the CVS and also discuss their potential interplay with the Renin-Angiotensin-Aldosterone System heptapeptide, Angiotensin-(1-7), as well the arachidonic acid metabolite, 20-HETE (20-hydroxy-5, 8, 11, 14-eicosatetraenoic acid). A greater understanding of the multi-faceted roles of EGFR/ErbB/HER family of tyrosine kinases and their interplay with other key modulators of cardiovascular function could facilitate the development of novel therapeutic strategies for treating diabetes-induced cardiovascular complications.

GPCR-ErbB transactivation pathways and clinical implications

Cell surface receptors including the epidermal growth factor receptor (EGFR) family and G-protein coupled receptors (GPCRs) play quintessential roles in physiology, and in diseases, including cardiovascular diseases. While downstream signaling from these individual receptor families has been well studied, the cross-talk between EGF and GPCR receptor families is still incompletely understood. Including members of both receptor families, the number of receptor and ligand combinations for unique interactions is vast, offering a frontier of pharmacologic targets to explore for preventing and treating disease. This molecular cross-talk, called receptor transactivation, is reviewed here with a focus on the cardiovascular system featuring the well-studied GPCR receptors, but also discussing less-studied receptors from both families for a broad understanding of context of expansile interactions, repertoire of cellular signaling, and disease consequences. Attention is given to cell type, level of chronicity, and disease context given that transactivation and comorbidities, including diabetes, hypertension, coronavirus infection, impact cardiovascular disease and health outcomes.

Anti‑HER3 monoclonal antibody exerts antitumor activity in a mouse model of colorectal adenocarcinoma

HER3 belongs to the epidermal growth factor receptor (EGFR) family and is known to form an active heterodimer with other three family members EGFR, HER2, and HER4. HER3 is overexpressed in lung, breast, colon, prostate, and gastric cancers. In the present study, we developed and validated an anti-HER3 monoclonal antibody (mAb), H₃Mab-17 (IgG_2a, kappa), by immunizing mice with HER3-overexpressed CHO-K1 cells (CHO/HER3). H₃Mab-17 was found to react specifically with endogenous HER3 in colorectal carcinoma cell lines, using flow cytometry. The K_D for H₃Mab-17 in CHO/HER3 and Caco-2 (a colon cancer cell line) were determined to be 3.0×10⁻⁹ M and 1.5×10⁻⁹ M via flow cytometry, respectively, suggesting high binding affinity of H₃Mab-17 to HER3. Then, we assessed the H₃Mab-17 antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against Caco-2, and evaluated its antitumor capacity in a Caco-2 ×enograft model. In vitro experiments revealed H₃Mab-17 had strongly induced both ADCC and CDC against Caco-2 cells. In vivo experiments on Caco-2 ×enografts revealed that H₃Mab-17 treatment significantly reduced tumor growth compared with the control mouse IgG. These data indicated that H₃Mab-17 could be a promising treatment option for HER3-expressing colon cancers.

Circulating ERBB3 levels are inversely associated with the risk of overweight-related hypertension: a cross-sectional study

BACKGROUND

Hypertension and overweight are independent risk factors for cardiovascular disease, and overweight increase the risk of developing high blood pressure. ERBB3( also known as HER3) plays a considerable role in the development of cardiovascular diseases. However, the effect of ERBB3 levels in hypertensive overweight patients is unknown. The aim of this study was to assess the association between ERBB3 levels and hypertension in overweight Chinese patients.

METHODS

We evaluated the height,weight, blood pressure, biochemical indicators, and ERBB3 levels in 128 Chinese adults aged 33-79 years. Plasma ERBB3 levels were assessed by the enzyme-linked immunosorbent assay, and body mass index(BMI) was calculated as body weight divided by height squared. Participants were allocated into three groups according to blood pressure and BMI: healthy control (CNT, n = 31; normotensive and non-overweight), hypertension (HT, n = 33; hypertension and non-overweight), and hypertension with overweight (HTO, n = 64; hypertension and overweight). Statistical significance was defined as a two-tailed P < 0.05.

RESULTS

There was no significant difference in mean ERBB3 levels among the three groups, although a linear decrease from CNT (1.13 ± 0.36), HT (1.03 ± 0.36), to HTO (0.84 ± 0.26 ng/mL) was observed in men (P = 0.007). Among the drinking population, the ERBB3 level was significantly reduced in the HTO group as compared with those of the CNT and HT groups (0.76 ± 0.23 versus 1.18 ± 0.37 and 1.20 ± 0.30, respectively). ERBB3 levels were negatively correlated with diastolic blood pressure in men (r= - 0.293, P = 0.012), smoking (r= - 0.47, P = 0.004), and drinking (r = - 0.387, P = 0.008). BMI in men and among drinkers, and uric acid among drinkers were negatively correlated with ERBB3 levels. Multivariate conditional logistic regression showed that plasma ERBB3 levels were associated with a reduced risk of HTO in men [odds ratio (OR) 0.054; 95 % confidence interval (CI): 0.007-0.412) and drinkers (OR 0.002; 95 % CI: 0.000-0.101).

CONCLUSIONS

ERBB3 may contribute to the pathogenesis of hypertension in overweight patients, with BMI, gender, and drinking all potentially modulating the process.

Pharmacotherapy in COVID-19 patients: a review of ACE2-raising drugs and their clinical safety

The COVID-19 pandemic is caused by the severe acute-respiratory-syndrome-coronavirus-2 that uses ACE2 as its receptor. Drugs that raise serum/tissue ACE2 levels include ACE inhibitors (ACEIs) and angiotensin-II receptor blockers (ARBs) that are commonly used in patients with hypertension, cardiovascular disease and/or diabetes. These comorbidities have adverse outcomes in COVID-19 patients that might result from pharmacotherapy. Increasing ACE2 could potentially increase the risk of infection, severity or mortality in COVID-19 or it might be protective as it forms angiotensin-(1-7) which exhibits anti-inflammatory/anti-oxidative effects and prevents diabetes- and/or hypertension-induced end-organ damage. Thus, there existed clinical uncertainty. Here, we review studies implicating 15 classes of drugs in increasing ACE2 levels in vivo and the available literature on the clinical safety of these drugs in COVID-19 patients. Further, in a re-analysis of clinical data from a meta-analysis of 9 studies, we show that ACEIs/ARBs usage was not associated with an increased risk of all-cause mortality. Literature suggests that ACEIs/ARBs usage generally appears to be clinically safe though their use in severe COVID-19 patients might increase the risk of acute renal injury. For definitive clarity, further clinical and mechanistic studies are needed in assessing the safety of all classes of ACE2 raising medications.

Nanotoxicology of Dendrimers in the Mammalian Heart: ex vivo and in vivo Administration of G6 PAMAM Nanoparticles Impairs Recovery of Cardiac Function Following Ischemia-Reperfusion Injury

Aim

The effects of polyamidoamine (PAMAM) dendrimers on the mammalian heart are not completely understood. In this study, we have investigated the effects of a sixth-generation cationic dendrimer (G6 PAMAM) on cardiac function in control and diabetic rat hearts following ischemia-reperfusion (I/R) injury.

Methods

Isolated hearts from healthy non-diabetic (Ctr) male Wistar rats were subjected to ischemia and reperfusion (I/R). LV contractility and hemodynamics data were computed digitally whereas cardiac damage following I/R injury was assessed by measuring cardiac enzymes. For ex vivo acute exposure experiments, G6 PAMAM was administered during the first 10 mins of reperfusion in Ctr animals. In chronic in vivo studies, nondiabetic rats (Ctr) received either vehicle or daily i.p. injections of G6 PAMAM (40 mg/kg) for 4 weeks. Diabetic (D) animals received either vehicle or daily i.p. injections of G6 PAMAM (10, 20 or 40 mg/kg) for 4 weeks. The impact of G6 PAMAM on pacing-postconditioning (PPC) was also studied in Ctr and D rats.

Results

In ex vivo studies, acute administration of G6 PAMAM to isolated Ctr hearts during reperfusion dose-dependently impaired recovery of cardiac hemodynamics and vascular dynamics parameters following I/R injury. Chronic daily i.p. injections of G6 PAMAM significantly (P<0.01) impaired recovery of cardiac function following I/R injury in nondiabetic animals but this was not generally observed in diabetic animals except for CF which was impaired by about 50%. G6 PAMAM treatment completely blocked the protective effects of PPC in the Ctr animals.

Conclusion

Acute ex vivo or chronic in vivo treatment with naked G6 PAMAM dendrimer can significantly compromise recovery of non-diabetic hearts from I/R injury and can further negate the beneficial effects of PPC. Our findings are therefore extremely important in the nanotoxicological evaluation of G6 PAMAM dendrimers for potential clinical applications in physiological and pathological settings.

Vitamin D and Its Potential Interplay With Pain Signaling Pathways

About 50 million of the U.S. adult population suffer from chronic pain. It is a complex disease in its own right for which currently available analgesics have been deemed woefully inadequate since ~20% of the sufferers derive no benefit. Vitamin D, known for its role in calcium homeostasis and bone metabolism, is thought to be of clinical benefit in treating chronic pain without the side-effects of currently available analgesics. A strong correlation between hypovitaminosis D and incidence of bone pain is known. However, the potential underlying mechanisms by which vitamin D might exert its analgesic effects are poorly understood. In this review, we discuss pathways involved in pain sensing and processing primarily at the level of dorsal root ganglion (DRG) neurons and the potential interplay between vitamin D, its receptor (VDR) and known specific pain signaling pathways including nerve growth factor (NGF), glial-derived neurotrophic factor (GDNF), epidermal growth factor receptor (EGFR), and opioid receptors. We also discuss how vitamin D/VDR might influence immune cells and pain sensitization as well as review the increasingly important topic of vitamin D toxicity. Further in vitro and in vivo experimental studies will be required to study these potential interactions specifically in pain models. Such studies could highlight the potential usefulness of vitamin D either alone or in combination with existing analgesics to better treat chronic pain.

Neuropeptide bombesin receptor activation stimulates growth of lung cancer cells through HER3 with a MAPK-dependent mechanism

Despite recent advances in treatment of non-small cell lung cancer (NSCLC), prognosis still remains poor and new therapeutic approaches are needed. Studies demonstrate the importance of the EGFR/HER-receptor family in NSCLC growth, as well as that of other tumors. Recently, HER3 is receiving increased attention because of its role in drug resistance and aggressive growth. Activation of overexpressed G-protein-coupled receptors (GPCR) can also initiate growth by transactivating EGFR/HER-family members. GPCR transactivation of EGFR has been extensively studied, but little is known of its ability to transactivate other EGFR/HER-members, especially HER3. To address this, we studied the ability of bombesin receptor (BnR) activation to transactivate all EGFR/HER-family members and their principal downstream signaling cascades, the PI3K/Akt- and MAPK/ERK-pathways, in human NSCLC cell-lines. In all three cell-lines studied, which possessed EGFR, HER2 and HER3, Bn rapidly transactivated EGFR, HER2 and HER3, as well as Akt and ERK. Immunoprecipitation studies revealed Bn-induced formation of both HER3/EGFR- and HER3/HER2-heterodimers. Specific EGFR/HER3 antibodies or siRNA-knockdown of EGFR and HER3, demonstrated Bn-stimulated activation of EGFR/HER members is initially through HER3, not EGFR. In addition, specific inhibition of HER3, HER2 or MAPK, abolished Bn-stimulated cell-growth, while neither EGFR nor Akt inhibition had an effect. These results show HER3 transactivation mediates all growth effects of BnR activation through MAPK. These results raise the possibility that targeting HER3 alone or with GPCR activation and its signal cascades, may be a novel therapeutic approach in NSCLC. This is especially relevant with the recent development of HER3-blocking antibodies.

Ang-(1-7)/ MAS1 receptor axis inhibits allergic airway inflammation via blockade of Src-mediated EGFR transactivation in a murine model of asthma

The angiotensin-(1–7) [Ang-(1–7)]/MAS1 receptor signaling axis is a key endogenous anti-inflammatory signaling pathway. However, the mechanisms by which its mediates the anti-inflammatory effects are not completely understood. Using an allergic murine model of asthma, we investigated whether Ang-1(1–7)/MAS1 receptor axis a): inhibits allergic inflammation via modulation of Src-dependent transactivation of the epidermal growth factor receptor (EGFR) and downstream signaling effectors such as ERK1/2, and b): directly inhibits neutrophil and/or eosinophil chemotaxis ex vivo. Ovalbumin (OVA)-induced allergic inflammation resulted in increased phosphorylation of Src kinase, EGFR, and ERK1/2. In addition, OVA challenge increased airway cellular influx, perivascular and peribronchial inflammation, fibrosis, goblet cell hyper/metaplasia and airway hyperresponsiveness (AHR). Treatment with Ang-(1–7) inhibited phosphorylation of Src kinase, EGFR, ERK1/2, the cellular and histopathological changes and AHR. Ang-(1–7) treatment also inhibited neutrophil and eosinophil chemotaxis ex vivo. These changes were reversed following pre-treatment with A779. These data show that the anti-inflammatory actions of Ang-(1–7)/ MAS1 receptor axis are mediated, at least in part, via inhibition of Src-dependent transactivation of EGFR and downstream signaling molecules such as ERK1/2. This study therefore shows that inhibition of the Src/EGRF/ERK1/2 dependent signaling pathway is one of the mechanisms by which the Ang-(1–7)/ MAS1 receptor axis mediates it anti-inflammatory effects in diseases such as asthma.

Chronic administration of nano-sized PAMAM dendrimers in vivo inhibits EGFR-ERK1/2-ROCK signaling pathway and attenuates diabetes-induced vascular remodeling and dysfunction

We investigated whether chronic administration of nano-sized polyamidoamine (PAMAM) dendrimers can have beneficial effects on diabetes-induced vascular dysfunction by inhibiting the epidermal growth factor receptor (EGFR)-ERK1/2-Rho kinase (ROCK)-a pathway known to be critical in the development of diabetic vascular complications. Daily administration of naked PAMAMs for up to 4 weeks to streptozotocin-induced diabetic male Wistar rats inhibited EGFR-ERK1/2-ROCK signaling and improved diabetes-induced vascular remodeling and dysfunction in a dose, generation (G6 > G5) and surface chemistry-dependent manner (cationic > anionic > neutral). PAMAMs, AG1478 (a selective EGFR inhibitor), or anti-EGFR siRNA also inhibited vascular EGFR-ERK1/2-ROCK signaling in vitro. These data showed that naked PAMAM dendrimers have the propensity to modulate key (e.g. EGFR) cell signaling cascades with associated pharmacological consequences in vivo that are dependent on their physicochemical properties. Thus, PAMAMs, alone or in combination with vasculoprotective agents, may have a beneficial role in the potential treatment of diabetes-induced vascular complications.

Src-dependent EGFR transactivation regulates lung inflammation via downstream signaling involving ERK1/2, PI3Kδ/Akt and NFκB induction in a murine asthma model

The molecular mechanisms underlying asthma pathogenesis are poorly characterized. In this study, we investigated (1) whether Src mediates epidermal growth factor receptor (EGFR) transactivation; (2) if ERK1/2, PI3Kδ/Akt and NF-κB are signaling effectors downstream of Src/EGFR activation; and (3) if upstream inhibition of Src/EGFR is more effective in downregulating the allergic inflammation than selective inhibition of downstream signaling pathways. Allergic inflammation resulted in increased phosphorylation of EGFR, Akt, ERK1/2 and IκB in the lung tissues from ovalbumin (OVA)-challenged BALB/c mice. Treatment with inhibitors of Src (SU6656) or EGFR (AG1478) reduced EGFR phosphorylation and downstream signaling which resulted in the inhibition of the OVA-induced inflammatory cell influx in bronchoalveolar lavage fluid (BALF), perivascular and peribronchial inflammation, fibrosis, goblet cell hyper/metaplasia and airway hyper-responsiveness. Treatment with pathway-selective inhibitors for ERK1/2 (PD89059) and PI3Kδ/Akt (IC-87114) respectively, or an inhibitor of NF-κB (BAY11-7085) also reduced the OVA-induced asthmatic phenotype but to a lesser extent compared to Src/EGFR inhibition. Thus, Src via EGFR transactivation and subsequent downstream activation of multiple pathways regulates the allergic airway inflammatory response. Furthermore, a broader upstream inhibition of Src/EGFR offers an attractive therapeutic alternative in the treatment of asthma relative to selectively targeting the individual downstream signaling effectors.

Angiotensin-(1-7) protects cardiomyocytes against high glucose-induced injuries through inhibiting reactive oxygen species-activated leptin-p38 mitogen-activated protein kinase/extracellular signal-regulated protein kinase 1/2 pathways, but not the leptin-c-Jun N-terminal kinase pathway in vitro

Aims/Introduction

Angiotensin‐(1–7) (Ang‐[1–7]), recognized as a new bioactive peptide in the renin–angiotensin system, shows biological and pharmacological properties in diabetic cardiovascular diseases. The leptin‐induced p38 mitogen‐activated protein kinase (MAPK) pathway has been reported to contribute to high glucose (HG)‐induced injury. In the present study, we showed the mechanism of how Ang‐(1–7) can protect against HG‐stimulated injuries in H9c2 cells.

Materials and Methods

H9c2 cells were treated with 35 mmol/L glucose (HG) for 24 h to establish a model of HG‐induced damage. Apoptotic cells were observed by Hoechst 33258 staining. Cell viability was analyzed by cell counter kit‐8. The expression of protein was detected by western blot. Reactive oxygen species was tested by 2′,7′‐dichlorodihydrofluorescein diacetate staining. Mitochondrial membrane potential was measured by 5,5′,6,6′‐Tetrachloro‐1,1′,3,3′‐tetraethyl‐imidacarbocyanine iodide staining.

Results

The present results showed that treating H9c2 cells with HG obviously enhanced the expressions of both the leptin and phosphorylated (p)‐MAPK pathway. However, the overexpression levels of leptin and p‐p38 MAPK/p‐extracellular signal‐regulated protein kinase 1/2 (ERK1/2), but not p‐c‐Jun N‐terminal kinase, were significantly suppressed by treatment of the cells with Ang‐(1–7). Additionally, leptin antagonist also markedly suppressed the overexpressions of p38 and ERK1/2 induced by HG, whereas leptin antagonist had no influence on the overexpression of c‐Jun N‐terminal kinase. More remarkable, Ang‐(1–7), leptin antagonist, SB203580 or SP600125, respectively, significantly inhibited the injuries induced by HG, such as the increased cell viability, decreased apoptotic rate, reduction of ROS production and increased mitochondrial membrane potential. Furthermore, the overexpressions of p38 MAPK, ERK1/2 and leptin were suppressed by N‐actyl‐L‐cystine.

Conclusions

The present findings show that Ang‐(1–7) protects from HG‐stimulated damage as an inhibitor of the reactive oxygen species–leptin–p38 MAPK/ERK1/2 pathways, but not the leptin–c‐Jun N‐terminal kinase pathway in vitro.

Angiotensin 1-7 Is a Negative Modulator of Aldosterone Secretion In Vitro and In Vivo

Angiotensin (1-7) [Ang 1-7] is a 7 amino acid peptide generated predominantly from Ang II by the action of Ang-converting enzyme 2. We previously showed that Ang 1-7 reduced plasma aldosterone and plasma renin activity in high fructose-fed rats, and that the reduction in circulating aldosterone seemed to accord a parallel reduction in plasma renin activity. Here, we tested the possibility that Ang 1-7 affects aldosterone secretion acting directly in glomerulosa cells. First, as detected by immunofluorescence, the receptor for Ang 1-7, Mas1 is localized predominantly at the rat adrenal subcapsular region. Second, in isolated rat glomerulosa cells incubates, Ang 1-7 attenuated the aldosterone response to Ang II, with the strongest effect seen on Ang II (10(-9) M) (control 22±2.5 pg/10(5) cells; Ang II [10(-9) M] 189±11 pg/10(5) cells; Ang II [10(-9) M]+Ang 1-7 [10(-6) M] 33±3.6 pg/10(5) cells; P<0.001) and the largest effect on adrenocorticotropic hormone (10(-8) M) (control 30±3.4 pg/10(5) cells; ACTH [10(-8) M] 409±32.5 pg/10(5) cells; ACTH [10(-8) M]+Ang 1-7 [10(-6) M] 280±12.5 pg/10(5) cells; P<0.001). In contrast, Ang 1-7 did not affect the aldosterone response to potassium (K(+)). In rats subjected to a low-salt diet for 7 days, continuous infusion of Ang 1-7 (576 μg/kg per day) resulted in a lesser rise in aldosterone (salt deplete+Ang 1-7, 16.4±4.8 ng/dL) compared with rats receiving vehicle (salt deplete+vehicle, 27.6±5.3 ng/dL; P<0.01) but did not modify plasma renin activity. Taken together, these results indicate that Ang 1-7 can act as a negative modulator of aldosterone secretion in vitro and in vivo.

Impact of PAMAM delivery systems on signal transduction pathways in vivo: Modulation of ERK1/2 and p38 MAP kinase signaling in the normal and diabetic kidney

The in vivo impact of two generation 6 cationic polyamidoamine (PAMAM) dendrimers on cellular signaling via extracellular-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK), as well as their relationship to epidermal growth factor receptor (EGFR), were studied in the normal and/or diabetic rat kidney. A single 10mg/kg/i.p administration of Polyfect (PF; with an intact branching architecture) or Superfect (SF; with a fragmented branching architecture) modulated renal ERK1/2 and p38 MAPK phosphorylation in a dendrimer-specific and animal model-dependent manner. AG1478 treatment (a selective EGFR inhibitor) confirmed that renal ERK1/2 and p38 MAPK signaling was downstream of EGFR. Surprisingly, both PAMAMs induced hyperphosphorylation of ERK1/2 and p38 MAPK (at 1 or 5mg/kg) despite inhibiting EGFR phosphorylation in the diabetic kidney. PAMAMs did not alter renal morphology but their effects on p38 MAPK and EGFR phosphorylation were reversed by ex vivo treatment of kidneys with the anti-oxidant, Tempol. Thus, PAMAMs can intrinsically modulate signaling of mitogen-activated protein kinases (MAPKs) depending on the type of dendrimer (fragmented vs intact branching architecture) and animal model (normal vs diabetic) used and likely occurs via an EGFR-independent and oxidative-stress dependent mechanism. These findings might have important toxicological implications for PAMAM-based delivery systems.

Transactivation of Epidermal Growth Factor Receptor by G Protein-Coupled Receptors: Recent Progress, Challenges and Future Research

Both G protein-coupled receptors (GPCRs) and receptor-tyrosine kinases (RTKs) regulate large signaling networks, control multiple cell functions and are implicated in many diseases including various cancers. Both of them are also the top therapeutic targets for disease treatment. The discovery of the cross-talk between GPCRs and RTKs connects these two vast signaling networks and complicates the already complicated signaling networks that regulate cell signaling and function. In this review, we focus on the transactivation of epidermal growth factor receptor (EGFR), a subfamily of RTKs, by GPCRs. Since the first report of EGFR transactivation by GPCR, significant progress has been made including the elucidation of the mechanisms underlying the transactivation. Here, we first provide a basic picture for GPCR, EGFR and EGFR transactivation by GPCR. We then discuss the progress made in the last five years and finally provided our view of the future challenge and future researches needed to overcome these challenges.