Erythropoietin-responsive sites in normal and malignant human lung tissues

Cytoprotective effects of erythropoietin: What about the lung?

Erythropoietin (Epo) is a pleiotropic cytokine, essential for erythropoiesis. Epo and its receptor (Epo-R) are produced by several tissues and it is now admitted that Epo displays other physiological functions than red blood cell synthesis. Indeed, Epo provides cytoprotective effects, which consist in prevention or fight against pathological processes. This perspective article reviews the various protective effects of Epo in several organs and tries to give a proof of concept about its effects in the lung. The tissue-protective effects of Epo could be a promising approach to limit the symptoms of acute and chronic lung diseases.

TAM-ing the CIA-Tumor-Associated Macrophages and Their Potential Role in Unintended Side Effects of Therapeutics for Cancer-Induced Anemia

Cancer-induced anemia (CIA) is a common consequence of neoplasia and has a multifactorial pathophysiology. The immune response and tumor treatment, both intended to primarily target malignant cells, also affect erythropoiesis in the bone marrow. In parallel, immune activation inevitably induces the iron-regulatory hormone hepcidin to direct iron fluxes away from erythroid progenitors and into compartments of the mononuclear phagocyte system. Moreover, many inflammatory mediators inhibit the synthesis of erythropoietin, which is essential for stimulation and differentiation of erythroid progenitor cells to mature cells ready for release into the blood stream. These pathophysiological hallmarks of CIA imply that the bone marrow is not only deprived of iron as nutrient but also of erythropoietin as central growth factor for erythropoiesis. Tumor-associated macrophages (TAM) are present in the tumor microenvironment and display altered immune and iron phenotypes. On the one hand, their functions are altered by adjacent tumor cells so that they promote rather than inhibit the growth of malignant cells. As consequences, TAM may deliver iron to tumor cells and produce reduced amounts of cytotoxic mediators. Furthermore, their ability to stimulate adaptive anti-tumor immune responses is severely compromised. On the other hand, TAM are potential off-targets of therapeutic interventions against CIA. Red blood cell transfusions, intravenous iron preparations, erythropoiesis-stimulating agents and novel treatment options for CIA may interfere with TAM function and thus exhibit secondary effects on the underlying malignancy. In this Hypothesis and Theory, we summarize the pathophysiological hallmarks, clinical implications and treatment strategies for CIA. Focusing on TAM, we speculate on the potential intended and unintended effects that therapeutic options for CIA may have on the innate immune response and, consequently, on the course of the underlying malignancy.

Suppression of NLRP3 Inflammasome by Erythropoietin via the EPOR/JAK2/STAT3 Pathway Contributes to Attenuation of Acute Lung Injury in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. An excessive inflammatory response results in the progression of ALI/ARDS, and the NLRP3 inflammasome is a key participant in inflammation. Erythropoietin (EPO), which is clinically used for anemia, reportedly exerts pleiotropic effects in ALI. However, whether EPO could protect against lipopolysaccharide (LPS)-induced ALI by regulating the NLRP3 inflammasome and its underlying mechanisms remain poorly elucidated. This study aimed to explore whether the therapeutic effects of EPO rely on the suppression of the NLRP3 inflammasome and the specific mechanisms in an LPS-induced ALI mouse model. ALI was induced in C57BL/6 mice by intraperitoneal (i.p.) injection of LPS (15 mg/kg). EPO was administered intraperitoneally at 5 U/g after LPS challenge. The mice were sacrificed 8 h later. Our findings indicated that application of EPO markedly diminished LPS-induced lung injury by restoring histopathological changes, lessened lung wet/dry (W/D) ratio, protein concentrations in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) levels. Meanwhile, EPO evidently decreased interleukin-1β (IL-1β) and interleukin-18 (IL-18) secretion, the expression of NLRP3 inflammasome components including pro-IL-1β, NLRP3, and cleaved caspase-1 as well as phosphorylation of nuclear factor-κB (NF-κB) p65, which may be associated with activation of EPO receptor (EPOR), phosphorylation of Janus-tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). However, all the beneficial effects of EPO on ALI and modulation NLRP3 inflammasome were remarkably abrogated by the inhibition of EPOR/JAK2/STAT3 pathway and knockout (KO) of NLRP3 gene. Taken together, this study indicates that EPO can effectively attenuate LPS-induced lung injury in mice by suppressing the NLRP3 inflammasome, which is dependent upon activation of EPOR/JAK2/STAT3 signaling and inhibition of the NF-κB pathway.

Ventilatory and Autonomic Regulation in Sleep Apnea Syndrome: A Potential Protective Role for Erythropoietin?

Obstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and is associated with wide array of cardiovascular morbidities. It has been proposed that during OSA, the respiratory control center (RCC) is affected by exaggerated afferent signals coming from peripheral/central chemoreceptors which leads to ventilatory instability and may perpetuate apnea generation. Treatments focused on decreasing hyperactivity of peripheral/central chemoreceptors may be useful to improving ventilatory instability in OSA patients. Previous studies indicate that oxidative stress and inflammation are key players in the increased peripheral/central chemoreflex drive associated with OSA. Recent data suggest that erythropoietin (Epo) could also be involved in modulating chemoreflex activity as functional Epo receptors are constitutively expressed in peripheral and central chemoreceptors cells. Additionally, there is some evidence that Epo has anti-oxidant/anti-inflammatory effects. Accordingly, we propose that Epo treatment during OSA may reduce enhanced peripheral/central chemoreflex drive and normalize the activity of the RCC which in turn may help to abrogate ventilatory instability. In this perspective article we discuss the potential beneficial effects of Epo administration on ventilatory regulation in the setting of OSA.

Significance of Erythropoietin Receptor Antagonist EMP9 in Cancers

We have clarified that cancer cells express their own erythropoietin (Epo) and its receptor (EpoR) mRNA levels, and the respective proteins, which are under the control of Epo-EpoR signaling. Then we explored to inhibit the Epo-EpoR signaling with an EpoR antagonist Epo mimetic peptide 9 (EMP9) that is a derivative of an Epo-mimicking peptide EMP1. In the study of the cancer cell lines in vitro, rhEpo accelerated the cancer cell growth, whereas the EMP9 inhibited the cell growth along with the inhibition of STAT5 tyrosine phosphorylation. Moreover, in vitro study of surgically resected histoculture of lung cancers revealed that EMP9 diminishes the expression of myoglobin in the cancer cells and destroys the feeding vessels. Additionally, in the xenografts of lung cancer histoculture, the EMP9 destroyed the xenografts by inducing apoptosis and suppressing proliferation of cancer cells in concomitant with macrophage accumulation. Furthermore, two types of perforations were detected in their cytoplasm: the one is mediated by nNOS in the cancer cells and the other one is by iNOS in the innate immune cells. These findings suggest that the inhibition of the Epo-EpoR signaling by EMP9 induces the cancer cell death that is mediated by the apoptosis and calcification of the cancer cells as well as the oxygen deficiency through the feeding vessels. Taken together, EMP9-based therapy may be a promising strategy to treat cancer patients.

Short-term exposure of erythropoietin impairs endothelial function through inhibition of nitric oxide production and eNOS mRNA expression in the rat pulmonary artery

BACKGROUND

Administration of recombinant erythropoietin (rEPO) is often associated with systemic and pulmonary arterial hypertension in animals and human. The present study was conducted to determine whether one-week rEPO-treatment can produce any effect on pulmonary vasomotor function.

METHODS

Male Wistar rats were injected with rEPO (400IU/kg sc) or saline every other day for one week. Tension, biochemical and Real-Time PCR experiments were conducted on left and right branches of pulmonary artery and main pulmonary artery isolated from the rats.

RESULTS

ACh-induced relaxation was significantly (p<0.05) reduced in rEPO-treated rats in comparison to control animals. Relaxation to the NO donor SNP was not different between the groups. EDHF-induced relaxation was remarkably higher in rEPO-treated group in comparison to control. Phenylephrine-induced contraction was significantly (p <0.05) reduced in rings from rEPO-treated rats at the second and third lowest concentrations of phenylephrine and its potency was not significantly reduced. No significant difference was observed in CaCl₂-induced contraction between the groups. Nitric oxide production was significantly reduced in rEPO-treated rats in comparison to control animals. Real-time PCR studies demonstrated a significant decrease (p<0.05) of eNOS transcript. However, peNOS activity was not altered with rEPO treatment.

CONCLUSION

The present study suggests that EPO-treatment for one week attenuates ACh-stimulated NO production. It does not affect the vasodilatory action of SNP. It showed up-regulation of EDHF and decreased potency of phenylephrine. Thus elevated EPO may diversely affect the vasomotor function of pulmonary artery. Clinically, it is important to observe the use of EPO in hypertensive condition.

A review of the effects of some endocrinological factors on respiratory mechanics

CONTEXT

Endocrinological factors have been recently described to affect respiratory mechanics.

OBJECTIVE

To review recent literature data, most of all obtained by the end-inflation occlusion method, describing the effects of molecules of endocrinological interest such as endothelin, erythropoietin and renin-angiotensin, on respiratory mechanics parameters.

METHODS

The papers considered in this review were found by inserting in Pubmed/Medline the following indexing terms: hormones, endothelin, erythropoietin, angiotensin and respiratory mechanics.

RESULTS

It was found that the above cited molecules, beside their well known physiological main effects, exhibit influences on respiratory mechanics, most of all on the airflow resistance, which was described to be increased by endothelin and angiotensin, and decreased by erythropoietin.

CONCLUSIONS

A number of molecules of biological interest exhibit unexpected influences on respiratory mechanics. The clinical effects depend on the consequences of modified inspiratory pressure values the respiratory muscles have to perform for a given breathing pattern.

Erythropoietin Receptor Antagonist Suppressed Ectopic Hemoglobin Synthesis in Xenografts of HeLa Cells to Promote Their Destruction

The aim of this study is to explore a cause-oriented therapy for patients with uterine cervical cancer that expresses erythropoietin (Epo) and its receptor (EpoR). Epo, by binding to EpoR, stimulates the proliferation and differentiation of erythroid progenitor cells into hemoglobin-containing red blood cells. In this study, we report that the HeLa cells in the xenografts expressed ε, γ, and α globins as well as myoglobin (Mb) to produce tetrameric α2ε2 and α2γ2 and monomeric Mb, most of which were significantly suppressed with an EpoR antagonist EMP9. Western blotting revealed that the EMP9 treatment inhibited the AKT-pAKT, MAPKs-pMAPKs, and STAT5-pSTAT5 signaling pathways. Moreover, the treatment induced apoptosis and suppression of the growth and inhibited the survival through disruption of the harmonized hemoprotein syntheses in the tumor cells concomitant with destruction of vascular nets in the xenografts. Furthermore, macrophages and natural killer (NK) cells with intense HIF-1α expression recruited significantly more in the degenerating foci of the xenografts. These findings were associated with the enhanced expressions of nNOS in the tumor cells and iNOS in macrophages and NK cells in the tumor sites. The treated tumor cells exhibited a substantial number of perforations on the cell surface, which indicates that the tumors were damaged by both the nNOS-induced nitric oxide (NO) production in the tumor cells as well as the iNOS-induced NO production in the innate immune cells. Taken together, these data suggest that HeLa cells constitutively acquire ε, γ and Mb synthetic capacity for their survival. Therefore, EMP9 treatment might be a cause-oriented and effective therapy for patients with squamous cell carcinoma of the uterine cervix.

Association of erythropoietin gene rs576236 polymorphism and risk of adrenal tumors in a Chinese population

Erythropoietin (EPO) is a circulating glycosylated protein hormone and has been implicated in the development and progression of non-hematopoietic tissue tumors. The objective of the present study was to determine if the EPO rs576236 polymorphism was associated with the risk of adrenal tumors. We genotyped the EPO rs576236 polymorphism in a case-control study of 288 adrenal tumor patients and 456 cancer-free controls by using the TaqMan method, and assessed the association between the polymorphism and the adrenal tumor risk by logistic regression. Furthermore, 95% confidence interval (CI) was used to assess the genetic association between the polymorphism and the risk of adrenal tumor. Compared with the TT genotype, the TC genotype had a significantly increased risk of adrenal tumor [adjusted odds ratio (OR)  =  1.24, 95% CI  =  1.12–2.22]. Furthermore a significantly increased risk of adrenal tumor was found in the combined variant genotypes TC+CC compared with the TT genotype (adjusted OR  =  1.17, 95% CI  =  1.12–2.21). Our present study suggests that the rs576236 polymorphism of EPO confers susceptibility to adrenal tumor in the Chinese population.

Erythropoietin upregulation in pulmonary arterial hypertension

The pathophysiologic alterations of patients with pulmonary arterial hypertension (PAH) are diverse. We aimed to determine novel pathogenic pathways from circulating proteins in patients with PAH. Multianalyte profiling (MAP) was used to measure 90 specifically selected antigens in the plasma of 113 PAH patients and 51 control patients. Erythropoietin (EPO) functional activity was assessed via in vitro pulmonary artery endothelial cell networking and smooth muscle cell proliferation assays. Fifty-eight patients had idiopathic PAH, whereas 55 had other forms of PAH; 5 had heritable PAH, 18 had connective tissue disease (15 with scleroderma and 3 with lupus erythematosis), 13 had portopulmonary hypertension, 6 had PAH associated with drugs or toxins, and 5 had congenital heart disease. The plasma-antigen profile of PAH revealed increased levels of several novel biomarkers, including EPO. Immune quantitative and histochemical studies revealed that EPO not only was significantly elevated in the plasma of PAH patients but also promoted pulmonary artery endothelial cell network formation and smooth muscle cell proliferation. MAP is a hypothesis-generating approach to identifying novel pathophysiologic pathways in PAH. EPO is upregulated in the circulation and lungs of patients with PAH and may affect endothelial and smooth muscle cell proliferation.

Erythropoietin receptor expression is a potential prognostic factor in human lung adenocarcinoma

Recombinant human erythropoietins (rHuEPOs) are used to treat cancer-related anemia. Recent preclinical studies and clinical trials, however, have raised concerns about the potential tumor-promoting effects of these drugs. Because the clinical significance of erythropoietin receptor (EPOR) signaling in human non-small cell lung cancer (NSCLC) also remains controversial, our aim was to study whether EPO treatment modifies tumor growth and if EPOR expression has an impact on the clinical behavior of this malignancy. A total of 43 patients with stage III–IV adenocarcinoma (ADC) and complete clinicopathological data were included. EPOR expression in human ADC samples and cell lines was measured by quantitative real-time polymerase chain reaction. Effects of exogenous rHuEPOα were studied on human lung ADC cell lines in vitro. In vivo growth of human ADC xenografts treated with rHuEPOα with or without chemotherapy was also assessed. In vivo tumor and endothelial cell (EC) proliferation was determined by 5-bromo-2’-deoxy-uridine (BrdU) incorporation and immunofluorescent labeling. Although EPOR mRNA was expressed in all of the three investigated ADC cell lines, rHuEPOα treatment (either alone or in combination with gemcitabine) did not alter ADC cell proliferation in vitro. However, rHuEPOα significantly decreased tumor cell proliferation and growth of human H1975 lung ADC xenografts. At the same time, rHuEPOα treatment of H1975 tumors resulted in accelerated tumor endothelial cell proliferation. Moreover, in patients with advanced stage lung ADC, high intratumoral EPOR mRNA levels were associated with significantly increased overall survival. This study reveals high EPOR level as a potential novel positive prognostic marker in human lung ADC.

Exposure to ethinyl estradiol prenatally and/or after sexual maturity induces endometriotic and precancerous lesions in uteri and ovaries of mice

Unrecognizable exposure to estrogenic substance may cause estrogen-dependent diseases, endometriosis and cancer. Pregnant mice (ICR/Jcl, CLEA) were exposed to 0.01 mg ethinyl estradiol (EE2 )/kg per day or vehicle (olive oil) through oral intubation from day 11 to 17 of gestation. They delivered their offspring and raised them. When the experimental female F1 mice were at 8 weeks of age, they were not exposed to EE2 or to the same dose of EE2 or to vehicle twice a week until 20 weeks of age. The control female F1 mice were exposed to the same dose of EE2 or vehicle alone, similarly. All mice were killed at 28 weeks of age. The resected uteri and ovaries were processed for microscopic examinations and for determination of the aromatase mRNA levels and aromatase protein through quantitative RT-PCR and Western blotting, respectively. Adenomyosis and adenocarcinomatous changes were significantly discernible in the EE2 -exposed uteri, and incidence of ectopic glands and serous cysts were significantly increased in the prenatally EE2 -exposed ovaries as compared with respective controls. Significant upregulation of the aromatase mRNA was seen in the prenatally EE2 -exposed uteri and in the EE2 -exposed ovaries. The aromatase protein was identified in all ovaries examined, and in EE2 -exposed uteri but not in controls and confirmed its localization in eutopic and ectopic glands, abnormally proliferated lesions and the lining of the cysts. Taken together, continuous EE2 exposure may cause endometriotic and precancerous lesions due to excessive estrogen synthesis in both target organs.

Erythropoietin acutely decreases airway resistance in the rat

While some experimental data suggest that erythropoietin (EPO) influences respiratory mechanics, reports on scientific trials are lacking. In the present work, respiratory mechanics were measured using the end-inflation occlusion method in control and EPO treated anaesthetised and positive-pressure ventilated rats. Causing an abrupt inspiratory flow arrest, the end-inflation occlusion method makes it possible to measure the ohmic airway resistance and the respiratory system elastance. It was found that EPO induces a significant decrement in the ohmic airway resistance, not noted in control animals, 20 and 30 min after intraperitoneal EPO injection. The elastic characteristics of the respiratory system did not vary. Hypotheses about the mechanism (s) explaining these results were addressed. In particular, additional experiments have indicated that the decrement in airway resistance could be related to an increase in nitric oxide production induced by EPO. Spontaneous increments in plasmatic erythropoietin levels, such as those that take place in association with hypoxia and/or blood loss, appear to be related to the decrement in airway resistance, allowing pulmonary ventilation to increase without altering respiratory mechanics leading to deleterious increments in energy dissipation during breathing.