Effect of prolonged physical exercise on the fibrinolytic system

The effect of a test marathon race on plasma fibrinolytic activity (FA) was studied in 16 endurance athletes before, immediately after, 3 h, and 31 h after the run. Tissue plasminogen activator (t-PA) activity increased about 31-fold immediately after the run. Similar increases were found in t-PA antigen concentration. Plasminogen activator inhibitor (PAI) was not detectable immediately after the race and was significantly decreased 3 h (P less than 0.05) and 31 h (P less than 0.01) later. B beta 15-42 peptide increased by 0.63 pmol.ml-1 (P less than 0.001), D-dimer by 68.3 ng.ml-1 (P less than 0.05). Euglobulin lysis time (ELT) was reduced from 109 to 18 min (P less than 0.001). The increased t-PA activity and t-PA antigen concentration disappeared in the course of the first 3 h after exertion. ELT also reached its pre-exercise levels at this time. Thirty-one hours after the race ELT and t-PA antigen levels were slightly but significantly reduced (P less than 0.05), whereas B beta 15-42 peptide remained increased (P less than 0.05). t-PA activity was unchanged compared with pre-exercise values. It seems that the exercise-induced FA is mainly caused by the marked increase of t-PA antigen and t-PA activity.     

Reticulocyte changes after experimental anemia and erythropoietin treatment of horses.

Availability of recombinant human erythropoietin (EPO) has facilitated use to enhance red blood cell production, and therefore aerobic performance, in human and equine athletes. Recombinant human EPO promotes growth and differentiation of equine erythroid precursor cells, but in some horses repeat administration induces immune interference with endogenous EPO resulting in fatal anemia. Although blood reticulocyte parameters acquire unique changes in humans treated with EPO, with manual enumeration methods, horses were not considered to release reticulocytes from the bone marrow into circulation, even under severe erythropoietic stress. The goals of this study were to determine whether reticulocytes could be detected and characterized in horses that are anemic or have been treated with EPO using a modern hematology analyzer. Anemia was induced in six horses by removal of 30 ml of blood/kg of body wt over 24 h. After 28 days, the horses were treated twice with 55 U/kg of EPO (Eprex), and after 65 days they were treated thrice with 73 U/kg of EPO. Blood samples were analyzed with the ADVIA120 instrument every 3-5 days and bone marrow samples 7 days after anemia and EPO treatments. Analysis of blood reticulocyte parameters by ANOVA in a randomized complete block design determined that anemia and EPO induced significant (P < or = 0.05) increases in red cell distribution width and reticulocyte mean cell volume. Parameters changed only after EPO treatment were cellular hemoglobin concentration mean, mean cell volume, reticulocyte concentration, proportion of macrocytic reticulocytes, and reticulocyte cellular hemoglobin. These findings indicate that horses under erythropoietic stress and after EPO treatment release reticulocytes with unique characteristics into circulation.     

Changes in kidney tissue and effects of erythropoietin after acute heart failure

Impairment of cardiac function causes renal damage. Renal failure after heart failure is attributed to hemodynamic derangement including reduced renal perfusion and increased venous pressure. One mechanism involves apoptosis and is defined as cardiorenal syndrome type 1. Erythropoietin (EPO) is a cytokine that induces erythropoiesis under hypoxic conditions. Hypoxia inducible factor 1 alpha (HIF-1α) plays a regulatory role in cellular response to hypoxia. Protective effects of EPO on heart, kidney and nervous system are unrelated to red blood cell production. We investigated early changes in and effects of EPO on renal tissues of rats with myocardial infarction by morphology and immunohistochemistry. Coronary artery ligation was used to induce myocardial infarction in Wistar rats. Group 1 comprised sham operated rats; groups 2, 3 and 4 included rats after coronary artery ligation that were sacrificed 6 h after ligation and that were treated with saline, 5,000 U/kg EPO or 10,000 U/kg EPO, respectively; group 5 included rats sacrificed 1 h after ligation. Group 2 showed increased renal tubule damage. Significantly less tubule damage was observed in EPO treated groups. EPO and EPO receptor (EPO-R) immunostaining intensities increased slightly for group 5 and became more intense for group 2. EPO and EPO-R immunostaining was observed in the interstitial area, glomerular cells and tubule epithelial cells of EPO treated groups. HIF-1α immunostaining was observed in collecting tubules in the medulla only in group 2. Caspase-3 immunostaining is an indicator of apoptosis. Caspase-3 staining intensity decreased in renal medulla of EPO treated groups. EPO treatment may exert a protective effect on the renal tissues of patients with cardiorenal syndrome.     

Erythropoietin non-viral gene therapy does not affect motility,viability, morphology or concentration of rabbit sperm

Erythropoietin (EPO) gene therapy can be used for several purposes; however, its effects on reproductive performance are unknown. The aim of this study was to evaluate the toxicological effects of non-viral (EPO) gene transfer on sperm motility, viability, morphology and concentration. Rabbit EPO cDNA was cloned into a pTarget mammalian expression vector. Rabbits were administered with: (1) pTarget/EPO vector, (2) recombinant human EPO (rHuEpo) and (3) saline (control). Both pTarget/EPO and rHuEpo significantly increased (P < 0.05) hematocrit levels 1 week after injection and they remained significantly higher than the control for up to 5 weeks (P < 0.05), showing that both EPO treatments were effective in stimulating the production of red blood cells in rabbits. The EPO gene transfer or rHuEPO administration had no significant effect (P > 0.05) on sperm motility, vigor, viability, concentration or morphology in the testis.     

Creatine kinase isoenzyme activity during and after an ultra-distance (200 km) run

It is commonly assumed that creatine kinase (CK) activity in plasma is related to the state of an inflammatory response at 24-48 h, and also it has shown biphasic patterns after a marathon run. No information is available on CK isoenzymes after an ultra-marathon run. The purpose of the present study is to examine the CK isoenzymes after a 200 km ultra-marathon run and during the subsequent recovery. Blood samples were obtained during registration 1 2 h before the 200-km race and during the race at 100 km, 150 km and at the end of 200 km, as well as after a 24 h period of recovery. Thirty-two male ultra-distance runners participated in the study. Serum CPK showed a marked increase throughout the race and 24 h recovery period (p < 0.001). Serum CK during the race occurs mostly in the CK-MM isoform and only minutely in the CK-MB isoform and is unchanged in the CK-BB isoform. High-sensitivity C-reactive protein (hs-CRP), oestradiol, AST and ALT increased significantly from the pre-race value at 100 km and a further increase took place by the end of the 200 km run. The results of our study demonstrate a different release pattern of creatine kinase after an ultra-distance (200 km) run compared to the studies of marathon running and intense eccentric exercise, and changes in several biomarkers, indicative of muscle damage during the race, were much more pronounced during the latter half (100–200 km) of the race. However, the increases in plasma concentration of muscle enzymes may reflect not only structural damage, but also their rate of clearance.     

Selenium and glutathione levels, and glutathione peroxidase activities in blood components of uremic patients on hemodialysis supplemented with selenium and treated with erythropoietin

Patients with chronic renal failure (CRF) often have reduced concentrations of selenium (Se) and lowered activities of glutathione peroxidase (GSH-Px) in blood components. The kidney is a major source of plasma GSH-Px. We measured Se and glutathione levels in blood components and red cell and plasma GSH-Px activities in 58 uremic patients on regular (3 times a week) hemodialysis (HD). The dialyzed patients were divided in 4 subgroups and were supplemented for 3 months with: 1) placebo (bakers yeast), 2) erythropoietin (EPO; 3 times a week with 2,000 U after each HD session), 3) Se-rich yeast (300 μg 3 times a week after each HD), and 4) Se-rich yeast plus EPO in doses as above. The results were compared with those for 25 healthy subjects. The Se concentrations and GSH-Px activities in the blood components of dialyzed uremic patients were significantly lower compared with the control group. Treatment of the HD patients with placebo and EPO only did not change the parameters studied. The treatment with Se as well as with Se and EPO caused an increase in Se levels and red cell GSH-Px activity. Plasma GSH-Px activity, however, increased only slowly or did not change after treatment with Se and with Se plus EPO. In the group treated with Se plus EPO the element concentration in blood components was higher compared with the group supplemented with Se alone. The weak or absence of response in plasma GSH-Px activity to Se supply indicates that the impaired kidney of uremic HD patients has reduced possibilities to synthesize this enzyme.     

Effect of prolonged physical exercise on fluid regulating hormones

Sixteen well-trained young men performed a test marathon to study the behaviour of atrial natriuretic peptide (ANP) and its second messenger cyclic guanosine monophosphate (cGMP) in relation to changes in plasma volume (PV) and plasma proteins, arginine vasopressin (AVP), renin, aldosterone, potassium and sodium. Blood samples were drawn under standardized conditions before and immediately after the run, as well as 3 h and 31 h after the run. Directly after the run, a two-and-a-half fold increase of plasma ANP and a twofold increase of plasma cGMP level were found, whereas PV decreased significantly by 7.4%. At this time renin-, aldosterone- and AVP-secretion were much stimulated. Thirty-one hours after the run, PV was markedly greater (10%) than before the race, whereas plasma proteins had returned to pre-exercise values. The ANP and cGMP were not significantly altered compared to the pre-race values. We have concluded that ANP and the other volume-regulating hormones may play an important role during and immediately after prolonged physical exercise but not in the longer recovery period. It seems that an influx of plasma proteins into the vascular space is responsible for the increased PV at this time.     

Erythrocyte 2,3-diphosphoglycerate concentration before and after a marathon in men

Erythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentration was studied in 23 runners before and after a marathon race. Blood samples were drawn from an antecubital vein the morning before the race (baseline), at 3 p.m. 2 h before the start, on finishing, and 12 and 36 h later. Compared to the baseline values, erythrocyte 2,3-DPG concentration was increased (p less than 0.001) immediately after the marathon from 4.62 +/- 0.14 to 5.56 +/- 0.13 mumol.ml-1 RBC and remained elevated 12 h later (5.45 +/- 0.14 mumol.ml-1 RBC): it returned to prerace values 36 h after completion of the marathon.     

血红蛋白总量在运动员生物护照兴奋剂检测中的意义

目的：观察注射微量重组人促红细胞生成素（rHuEPO）后,受试者在不同时间段血液某些参数指标的变化,为兴奋剂rHuEPO检测运动员生物护照（ABP）提供实验依据。方法：采用单盲方式对14名健康青年男性受试者进行两个阶段随机安慰剂（n=14）和微量rHuEPO（n=14）皮下注射,每阶段7周,每周2次。EPO注射期间给予每天口服铁剂105 mg;在注射前第7日、第一次注射后第3、10、17、24、31、38和45日、以及第7周最后一次注射后第7、14、21日分别采取静脉血测试血液基础参数（红细胞、血红蛋白浓度[Hb]、红细胞压积、网织红细胞）,改良一氧化碳（CO）吸入法测试血红蛋白总量（tHb）以及全血量（BV）、血浆量（PV）的变化情况;分析这些指标在ABP中的使用,观察总量指标和浓度指标在检测中的有效性和时效性。结果：与安慰剂组相比,14名受试者在微量rHuEPO注射后第2周,即开始出现红细胞数量和[Hb]增加,在注射期间第5~6周达到高峰（分别增加9%和10%左右,P<0.01）,一直持续到最后一次注射后3周左右;tHb在注射后1周即开始增加,5周达到最高峰（增加10%左右,P<0.01）并一直持续到最后一次注射后1周才开始逐级恢复到注射前水平;红细胞总量在实验第5周上升至峰值,幅度为10.89%（P<0.01）,总血量（BV）变化不明显,血浆量（PV）出现下降,血液浓缩。结论：7周微量rHuEPO注射可以显著增加血液总量指标和浓度指标,其中血红蛋白总量更加敏感,可以用ABP血红蛋白总量等监测微量EPO注射;在最后一次注射结束后,血液总量指标如血红蛋白总量恢复正常,而浓度指标仍保持较高水平,可能是血液浓缩的结果。     

Erythropoietin responses to progressive blood loss over 10 days in the ovine fetus

Long-term loss of fetal blood can occur with fetomaternal hemorrhage, vasoprevia, or placental previa. Our objective was to determine the effects of progressive fetal blood loss over 10 days on fetal plasma erythropoietin (EPO) concentration and its relationship to arterial PO(2), hematocrit, and the volume of blood loss. Late-gestation fetal sheep (n = 8) were hemorrhaged daily at a rate of 1 ml/min over 10 days. The extent of hemorrhage differed in each fetus and ranged from 30 to 80 ml/day, with the cumulative volume removed ranging from 78 to 236 ml/kg estimated fetal weight. Four fetuses served as time controls. EPO concentration measurements were by radioimmunoassay. Statistical analyses included regression, correlation, and analysis of variance. We found that EPO and arterial PO(2) were unchanged until the cumulative hemorrhage volume exceeded 20-40 ml/kg. Once this threshold was exceeded, plasma EPO concentration increased progressively throughout the study and averaged 14.3 +/- 3.2 times basal values on day 10. EPO concentration, arterial PO(2), and hematocrit changes were related curvilinearly to cumulative hemorrhage volume (P < 0.01), whereas the relationship between plasma EPO and arterial PO(2) was log linear (P < 0.001). We conclude that 1) fetal plasma EPO concentration and arterial PO(2) are insensitive to a slow, mild-to-moderate blood loss over several days; 2) unlike the rapid return of EPO to normal within 48 h after acute hemorrhage, fetal EPO concentration undergoes a progressive increase with moderate-to-severe blood loss over several days; 3) the long-term hemorrhage-induced changes in EPO are best correlated with arterial PO(2); and 4) the fetal EPO response to hemorrhage does not appear to be limited by the fetus's ability to produce EPO.     

Micronucleus formation in cultured fetal liver blood cells using mitomycin C.

Mouse fetal-liver blood cells were cultured and used to investigate micronucleus formation after exposure to mitomycin C (MMC). The isolated fetal cells were incubated in a medium supplemented with erythropoietin (EPO), and the frequency of micronuclei formation was detected in polychromatic erythrocytes (PCE). The effects of four variables were investigated: (1) MMC exposure dose, (2) MMC exposure time, (3) incubation time, and (4) EPO concentration. PCE were formed by proliferation and differentiation of the erythroid cells in culture. Micronucleated PCE (MNPCE) were observed in a dose-dependent manner after exposing the cultured cells with up to 1.0 microgram/ml MMC. The optimum time of MMC exposure and post-exposure incubation was 3 h and 48 h, respectively, and the optimum EPO concentration was 0.25 U/ml. Mouse fetal-liver PCE are sensitive primordial cell targets that can be obtained in relatively large numbers from a single pregnant animal. The procedure is relatively simple and potentially useful in detecting mutagens and carcinogens capable of causing chromosomal damage.     

Changes in plasma volume and red cell formation after a marathon competition

The purpose of this study was to investigate middle-term influences of a marathon race on plasma volume (PV) and red cell production. We performed the following measurements in the blood of 15 male athletes: haemoglobin ([Hb]), haematocrit (Hct), plasma protein concentration ([Prot]), plasma osmolality, sodium concentration ([Na+]), potassium concentration ([K+]), aldosterone concentration ([Aldo]), haptoglobin concentration ([Hpto]), and the reticulocyte count, as well as the calculation of relative changes in PV, 3 days before and on 3-consecutive days after a marathon race. By the 2nd day of recovery PV had increased by 16%. Plasma osmolality and [K+] remained constant, whereas [Na+] had decreased slightly 2 days after the competition and [Aldo] tended to be elevated 1 day after the competition. [Hpto] was low before and 1 day after the competition and increased on the following days. Reticulocyte count was unaffected 1 day after the race, but increased by 106% on the 2nd day and was still elevated after 3 days. The causes for higher post-marathon plasma volumes and reticulocyte counts could be in the complex variations in hormonal regulation, which have not yet been sufficiently investigated.     

Plasma atrial natriuretic peptide and cyclic nucleotide levels before and after a marathon

Plasma alpha-atrial natriuretic peptide (alpha-ANP) concentration and levels of cyclic nucleotides [guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP)] were studied in 23 runners before and after a marathon race. Blood samples were drawn from an antecubital vein the morning before the race (base line), at 3 P.M. (i.e., 2 h before the start), on arrival, and 12 and 36 h and 7 days later. Compared with the base-line values of plasma alpha-ANP (5 pmol/l), cGMP (3.8 nmol/l), and cAMP (15.8 nmol/l), the plasma levels of alpha-ANP, cGMP, and cAMP were increased immediately after the marathon, respectively, to 12.0 pmol/l, 12.7 nmol/l, and 50.5 nmol/l. The increase in the plasma alpha-ANP concentration was related (r = 0.85; P less than 0.001) to the changes in plasma cGMP, plasma lactate, hematocrit, and body weight. The plasma cGMP and cAMP concentrations had returned to the prerace levels 12 h after the marathon, whereas the plasma alpha-ANP concentration was significantly lower (3.1 pmol/l) than the base-line values and increased above the prerace values 36 h (7.5 pmol/l) and 7 days (6.8 pmol/l) after the marathon. The plasma cGMP level was also higher 36 h (5.4 nmol/l) and 7 days (5.0 nmol/l) after the marathon race.     

Salivary cortisol for monitoring adrenal activity during marathon runs

In non-elite male runners (n = 8), changes in adrenal activity were monitored by measurement of salivary cortisol in samples collected at 4-mile intervals during marathon runs. These changes were compared with those in similarly timed samples collected on rest days. Immediately prior to the Cardiff marathon, at 09.00 h, mean salivary cortisol concentrations (21.5 nmol/l) were higher than those in similarly timed rest day samples (14.9 nmol/l). Cortisol concentrations increased during the marathon, and although values at 25 miles were high (79.4 nmol/l), maximum values (87.9 nmol/l) were observed in samples collected 30 min after completion of the run. Some Cardiff marathon runners also participated in the Bristol marathon (n = 4) and a non-competitive event (n = 3). The changing pattern in secretory activity was similar in all events. The easy collection of saliva without cessation of exercise is ideal for monitoring the hormonal response to exercise.     

Multiple Doses of Erythropoietin Impair Liver Regeneration by Increasing TNF-α, the Bax to Bcl-xL Ratio and Apoptotic Cell Death

Background

Liver resection and the use of small-for-size grafts are restricted by the necessity to provide a sufficient amount of functional liver mass. Only few promising strategies to maximize liver regeneration are available. Apart from its erythropoiesis-stimulating effect, erythropoietin (EPO) has meanwhile been recognized as mitogenic, tissue-protective, and anti-apoptotic pleiotropic cytokine. Thus, EPO may support regeneration of hepatic tissue.

Methodology

Rats undergoing 68% hepatectomy received daily either high dose (5000 IU/kg bw iv) or low dose (500 IU/kg bw iv) recombinant human EPO or equal amounts of physiologic saline. Parameters of liver regeneration and hepatocellular apoptosis were assessed at 24 h, 48 h and 5 d after resection. In addition, red blood cell count, hematocrit and serum EPO levels as well as plasma concentrations of TNF-α and IL-6 were evaluated. Further, hepatic Bcl-x_L and Bax protein expression were analyzed by Western blot.

Principal Findings

Administration of EPO significantly reduced the expression of PCNA at 24 h followed by a significant decrease in restitution of liver mass at day 5 after partial hepatectomy. EPO increased TNF-α levels and shifted the Bcl-x_L to Bax ratio towards the pro-apoptotic Bax resulting in significantly increased hepatocellular apoptosis.

Conclusions

Multiple doses of EPO after partial hepatectomy increase hepatocellular apoptosis and impair liver regeneration in rats. Thus, careful consideration should be made in pre- and post-operative recombinant human EPO administration in the setting of liver resection and transplantation.     

Determinants of erythropoietin release in response to short-term hypobaric hypoxia.

We measured blood erythropoietin (EPO) concentration, arterial O(2) saturation (Sa(O(2))), and urine PO(2) in 48 subjects (32 men and 16 women) at sea level and after 6 and 24 h at simulated altitudes of 1,780, 2,085, 2,454, and 2,800 m. Renal blood flow (Doppler) and Hb were determined at sea level and after 6 h at each altitude (n = 24) to calculate renal O(2) delivery. EPO increased significantly after 6 h at all altitudes and continued to increase after 24 h at 2,454 and 2,800 m, although not at 1,780 or 2,085 m. The increase in EPO varied markedly among individuals, ranging from -41 to 400% after 24 h at 2,800 m. Similar to EPO, urine PO(2) decreased after 6 h at all altitudes and returned to baseline by 24 h at the two lowest altitudes but remained decreased at the two highest altitudes. Urine PO(2) was closely related to EPO via a curvilinear relationship (r(2) = 0.99), although also with prominent individual variability. Renal blood flow remained unchanged at all altitudes. Sa(O(2)) decreased slightly after 6 h at the lowest altitudes but decreased more prominently at the highest altitudes. There were only modest, albeit statistically significant, relationships between EPO and Sa(O(2)) (r = 0.41, P < 0.05) and no significant relationship with renal O(2) delivery. These data suggest that 1) the altitude-induced increase in EPO is "dose" dependent: altitudes > or =2,100-2,500 m appear to be a threshold for stimulating sustained EPO release in most subjects; 2) short-term acclimatization may restore renal tissue oxygenation and restrain the rise in EPO at the lowest altitudes; and 3) there is marked individual variability in the erythropoietic response to altitude that is only partially explained by "upstream" physiological factors such as those reflecting O(2) delivery to EPO-producing tissues.     

Treatment of a fatal transplantable erythroleukemia by procedures that lower endogenous erythropoietin

The in vitro growth of primary erythroleukemia cells has been examined in the presence and absence of the hormone erythropoietin (EPO). Although these leukemic cells had previously been considered to be hormone-independent, addition of EPO was found to be essential for maximum growth in culture. Erythroid colonies that grew in the presence of EPO were leukemogenic when returned to mice. Influence of EPO on the in vivo growth of leukemic cells was indicated by our findings that administration of the hormone caused a more severe leukemia and rapid death, and transfusion of red blood cells, which lowers endogenous EPO, led to decreased spleen size and increased survival of leukemic mice. We suggest from our results that hormone-associated therapy might be efficacious in the treatment of this and, perhaps, other leukemias.     

Alterations in plasma-volume-corrected blood components of marathon runners and concomitant relationship to performance

The study was undertaken to determine the effects of running a marathon on concentration of various blood components resulting from phenomena other than fluid loss, and these were related to performance times. Twenty male marathon runners ranging from 20 to 50 years of age participated in the study. Blood samples were collected before and after the subjects ran in a marathon. Blood samples were analyzed for sodium, potassium, glucose, lactate dehydrogenase, creatinine, creatine phosphokinase, triglycerides, cholesterol, hematocrit, hemoglobin, protein, white blood cell number, uric acid, carbon dioxide, and iron. All of the blood parameters increased significantly in concentration with the exceptions of glucose and carbon dioxide which decreased. After accounting for plasma-volume loss (COR), there remained significant increases in blood serum lactate dehydrogenase, creatinine, creatine phosphokinase, uric acid, iron, and whole-blood white blood cell number. Significant decreases in COR serum sodium, protein, glucose, and carbon dioxide were found. Lactate dehydrogenase and creatine phosphokinase concentration changes support the concept of acute damage to muscle tissue resulting from marathon running. No strong relationship between performance time and other measured variables was found. COR measures were more representative of marathon induced blood changes from physiological dynamics other than plasma volume change than presently reported findings.     

Changes in blood glutathione concentrations, and in erythrocyte glutathione reductase and glutathione S-transferase activity after running training and after participation in contests

Previously sedentary men (n = 23) and women (n = 18) were trained to run a half marathon contest after 40 weeks. Total blood glutathione had increased by 20 weeks of training and had returned to normal after 40 weeks. Erythrocyte glutathione reductase activity had increased by 20 weeks and remained elevated after 40 weeks. This effect was accompanied by decreases in glutathione reductase coefficients, which indicated that increases in the presence of riboflavin may have been responsible for the changes in reductase activity. Erythrocyte glutathione S-transferase activity had increased slightly after 20 weeks of training and a much more marked increase was found after 40 weeks. This may have been indicative of the occurrence of lipid peroxidation in this phase of training. The participants ran a 15-km race after the first 20 weeks of training and a half marathon after 40 weeks. Blood glutathione tended to decrease after the 15-km race and increased after the half marathon. In both cases it had returned to normal values 5 days after the race. Erythrocyte glutathione reductase was elevated 1 day after the races, and had returned to normal after 5 days. This could also have been explained from concurrent changes in the riboflavin content of the erythrocytes. Erythrocyte glutathione S-transferase activity decreased after both races, but was restored 5 days after the half marathon while such was not the case after the 15-km race.     

Erythropoietin-driven proliferation of cells with mutations in the tumor suppressor gene TSC2

Lymphangioleiomyomatosis (LAM) is characterized by cystic lung destruction, resulting from proliferation of smooth-muscle-like cells, which have mutations in the tumor suppressor genes TSC1 or TSC2. Among 277 LAM patients, severe disease was associated with hypoxia and elevated red blood cell indexes that accompanied reduced pulmonary function. Because high red cell indexes could result from hypoxemia-induced erythropoietin (EPO) production, and EPO is a smooth muscle cell mitogen, we investigated effects of EPO in human cells with genetic loss of tuberin function, and we found that EPO increased proliferation of human TSC2-/-, but not of TSC2+/-, cells. A discrete population of cells grown from explanted lungs was characterized by the presence of EPO receptor and loss of heterozygosity for TSC2, consistent with EPO involvement. In LAM cells from lung nodules, EPO was localized to the extracellular matrix, supporting evidence for activation of an EPO-driven signaling pathway. Although the high red cell mass of LAM patients could be related to advanced disease, we propose that EPO, synthesized in response to episodic hypoxia, may increase disease progression by enhancing the proliferation of LAM cells.