Women Are Also Disadvantaged in Accessing Transplant Outside the United States: Analysis of the Spanish Liver Transplantation Registry.

Sex inequities in liver transplantation (LT) have been documented in several, mostly US-based, studies. Our aim was to describe sex-related differences in access to LT in a system with short waiting times. All adult patients registered in the RETH-Spanish Liver Transplant Registry (2000-2022) for LT were included. Baseline demographics, presence of hepatocellular carcinoma, cause and severity of liver disease, time on the waiting list (WL), access to transplantation, and reasons for removal from the WL were assessed. 14,385 patients were analysed (77% men, 56.2 ± 8.7 years). Model for end-stage liver disease (MELD) score was reported for 5,475 patients (mean value: 16.6 ± 5.7). Women were less likely to receive a transplant than men (OR 0.78, 95% CI 0.63, 0.97) with a trend to a higher risk of exclusion for deterioration (HR 1.17, 95% CI 0.99, 1.38), despite similar disease severity. Women waited longer on the WL (198.6 ± 338.9 vs. 173.3 ± 285.5 days, p < 0.001). Recently, women's risk of dropout has reduced, concomitantly with shorter WL times. Even in countries with short waiting times, women are disadvantaged in LT. Policies directed at optimizing the whole LT network should be encouraged to guarantee a fair and equal access of all patients to this life saving resource.

NFAT transcription factors regulate survival, proliferation, migration, and differentiation of neural precursor cells.

The study of factors that regulate the survival, proliferation, and differentiation of neural precursor cells (NPCs) is essential to understand neural development as well as brain regeneration. The Nuclear Factor of Activated T Cells (NFAT) is a family of transcription factors that can affect these processes besides playing key roles during development, such as stimulating axonal growth in neurons, maturation of immune system cells, heart valve formation, and differentiation of skeletal muscle and bone. Interestingly, NFAT signaling can also promote cell differentiation in adults, participating in tissue regeneration. The goal of the present study is to evaluate the expression of NFAT isoforms in NPCs, and to investigate its possible role in NPC survival, proliferation, migration, and differentiation. Our findings indicate that NFAT proteins are active not only in neurogenic brain regions such as hippocampus and subventricular zone (SVZ), but also in cultured NPCs. The inhibition of NFAT activation with the peptide VIVIT reduced neurosphere size and cell density in NPC cultures by decreasing proliferation and increasing cell death. VIVIT also decreased NPC migration and differentiation of astrocytes and neurons from NPCs. In addition, we identified NFATc3 as a predominant NFAT isoform in NPC cultures, finding that a constitutively-active form of NFATc3 expressed by adenoviral infection reduces NPC proliferation, stimulates migration, and is a potent inducer of NPC differentiation into astrocytes and neurons. In summary, our work uncovers active roles for NFAT signaling in NPC survival, proliferation and differentiation, and highlights its therapeutic potential for tissue regeneration.

Results of the implementation of a double-check protocol with point-of-care ultrasound for acute heart failure in the emergency department.

OBJECTIVE: To determine the effectiveness of a double-check protocol using Point-of-Care Ultrasound in the management of patients diagnosed with Acute Heart Failure in an Emergency Department. METHOD: Prospective analytical cross-sectional observational study with patients diagnosed with Acute Heart Failure by the outgoing medical team, who undergo multi-organ ultrasound evaluation including cardiac, pulmonary, and inferior vena cava ultrasound. RESULTS: 96 patients were included. An alternative diagnosis was found in 33% of them. Among the 77% where AHF diagnosis was confirmed, 73.4% had an underlying cause or condition not previously known (Left Ventricular Ejection Fraction less than 40% or moderate-severe valvulopathy). The introduction of the protocol had a clinically relevant impact on 47% of all included patients. CONCLUSIONS: The implementation of a double-check protocol using POCUS, including cardiac, pulmonary, and inferior vena cava assessment in patients diagnosed with Acute Heart Failure, demonstrates a high utility in ensuring accurate diagnosis and proper classification of these patients.

An analysis of the association between breast density and body mass index with breast cancer molecular subtypes in early breast cancer: data from a Spanish population.

PURPOSE: Breast cancer is an important health problem, like obesity and dyslipidemia, with a strong association between body mass index (BMI) and breast cancer incidence and mortality. The risk of breast cancer is also high in women with high mammographic breast density (MBD). The purpose of this study was to analyze the association between BMI and MBD according to breast cancer molecular subtypes. METHODS: This transversal, descriptive, multicenter study was conducted at three Spanish breast cancer units from November 2019 to October 2020 in women with a recent diagnosis of early breast cancer. Data were collected at the time of diagnosis. RESULTS: The study included 162 women with a recent diagnosis of early breast cancer. The median age was 52 years and 49.1% were postmenopausal; 52% had normal weight, 32% overweight, and 16% obesity. There was no association between BMI and molecular subtype but, according to menopausal status, BMI was significantly higher in postmenopausal patients with luminal A (p = 0.011) and HER2-positive (p = 0.027) subtypes. There was no association between MBD and molecular subtype, but there were significant differences between BMI and MBD (p < 0.001), with lower BMI in patients with higher MBD. Patients with higher BMI had lower HDL-cholesterol (p < 0.001) and higher insulin (p < 0.001) levels, but there were no significant differences in total cholesterol or vitamin D. CONCLUSIONS: This study showed higher BMI in luminal A and HER2-positive postmenopausal patients, and higher BMI in patients with low MBD regardless of menopausal status.

NFATc3 promotes Ca(2+) -dependent MMP3 expression in astroglial cells.

Increase in intracellular calcium ([Ca(2+) ]i ) is a key mediator of astrocyte signaling, important for activation of the calcineurin (CN)/nuclear factor of activated T cells (NFAT) pathway, a central mediator of inflammatory events. We analyzed the expression of matrix metalloproteinase 3 (Mmp3) in response to increases in [Ca(2+) ]i and the role of the CN/NFAT pathway in this regulation. Astrocyte Mmp3 expression was induced by overexpression of a constitutively active form of NFATc3, whereas other MMPs and tissue inhibitor of metalloproteinases (TIMP) were unaffected. Mmp3 mRNA and protein expression was also induced by calcium ionophore (Io) and 2'(3')-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (Bz-ATP) and Mmp3 upregulation was prevented by the CN inhibitor cyclosporin A (CsA). Ca(2+) -dependent astrocyte Mmp3 expression was also inhibited by actinomycin D, and a Mmp3 promoter luciferase reporter was efficiently activated by increased [Ca(2+) ]i , indicating regulation at the transcriptional level. Furthermore, Ca(2+) /CN/NFAT dependent Mmp3 expression was confirmed in pure astrocyte cultures derived from neural stem cells (Ast-NSC), demonstrating that the induced Mmp3 expression occurs in astrocytes, and not microglial cells. In an in vivo stab-wound model of brain injury, MMP3 expression was detected in NFATc3-positive scar-forming astrocytes. Because [Ca(2+) ]i increase is an early event in most brain injuries, these data support an important role for Ca(2+) /CN/NFAT-induced astrocyte MMP3 expression in the early neuroinflammatory response. Understanding the molecular pathways involved in this regulation could provide novel therapeutic targets and approaches to promoting recovery of the injured brain.

General infection prevention, mitigation, and control procedures implemented in the university education during the COVID-19 pandemic to achieve classroom attendance: a successful community case study.

Introduction: The COVID-19 pandemic entailed confinement and elimination of face-to-face university classes in Spain. The Francisco de Vitoria University in Madrid (UFV by its Spanish acronym) implemented risk management systems to enable on-campus university activity to avoid a negative impact on students, teachers, and faculties. Methods: A tracking/registry system was implemented to collect data, identify COVID-19-related cases, implement containment measures, and do follow-up in the UFV community (administration/services personnel [ASP], teaching/research personnel [TRP], and students), from September 2020 to April 2022. In addition, a prevention plan was implemented on campus to avoid COVID-19 spreading. Satisfaction with these measures was assessed through an online questionnaire. Results: A total of 7,165 suspected COVID-19 cases (84.7% students, 7.7% ASP, 6.5% TRP) were tracked (62.5% female cases, mean age (±SD) 24.8 years (±9.2 years)), and 45% of them confirmed (82% symptomatic/16% asymptomatic), being the student group that with the highest percentage (38.3% total tracked cases). The source of infection was identified in 50.6% of the confirmed cases (90.2% located off-campus). Nineteen COVID-19 outbreaks were registered (inside-10/outside-9). COVID-19 incidence rates were similar or lower than those reported in the Community of Madrid, except in the last wave, corresponding to Omicron variant. The degree of satisfaction (scale 1-6) with the implemented measures was high (scores 4.48-5.44). Conclusion: During the COVID-19 pandemic, UFV control measures, periodic monitoring, and the effectiveness of the tracking system have contributed to maintaining classroom teaching, guaranteeing health and safety. UFV has adapted to a new reality as an example of good practice for future pandemics or emergency situations.

Clinical Findings and Outcomes From Subjects With COVID-19 Pneumonia in an Intermediate Respiratory Care Unit.

BACKGROUND: Many patients with COVID-19 require respiratory support and close monitoring. Intermediate respiratory care units (IRCU) may be valuable to optimally and adequately implement noninvasive respiratory support (NRS) to decrease clinical failure. We aimed at describing intubation and mortality in a novel facility entirely dedicated to COVID-19 and to establish their outcomes. METHODS: This was a retrospective, observational study performed at one hospital in Spain. We included consecutive subjects age > 18 y, admitted to IRCU with COVID-19 pneumonia, and requiring NRS between December 2020-September 2021. Data collected included mode and usage of NRS, laboratory findings, endotracheal intubation, and mortality at day 30. A multivariable Cox model was used to assess risk factors associated with clinical failure and mortality. RESULTS: A total of 1,306 subjects were included; 64.6% were male with mean age of 54.7 y. During the IRCU stay, 345 subjects clinically failed NRS (85.5% intubated; 14.5% died). Cox model showed a higher clinical failure in IRCU upon onset of symptoms and hospitalization was < 10 d (hazard ratio [HR] 1.59 [95% CI 1.24-2.03], P < .001) and PaO2 /FIO2 < 100 mm Hg (HR 1.59 [95% CI 1.27-1.98], P < .001). These variables were not associated with increased 30-d mortality. CONCLUSIONS: The IRCU was a valuable option to manage subjects with COVID-19 requiring NRS, thus reducing ICU overload. Male sex, gas exchange, and blood chemistry at admission were associated with worse prognosis, whereas older age, gas exchange, and blood chemistry were associated with 30-d mortality. These findings may provide a basis for better understanding outcomes and to improve management of noninvasively ventilated patients with COVID-19.

Regulator of calcineurin 1 (Rcan1) has a protective role in brain ischemia/reperfusion injury.

BACKGROUND: An increase in intracellular calcium concentration [Ca2+]i is one of the first events to take place after brain ischemia. A key [Ca2+]i-regulated signaling molecule is the phosphatase calcineurin (CN), which plays important roles in the modulation of inflammatory cascades. Here, we have analyzed the role of endogenous regulator of CN 1 (Rcan1) in response to experimental ischemic stroke induced by middle cerebral artery occlusion. METHODS: Animals were subjected to focal cerebral ischemia with reperfusion. To assess the role of Rcan1 after stroke, we measured infarct volume after 48 h of reperfusion in Rcan1 knockout (KO) and wild-type (WT) mice. In vitro studies were performed in astrocyte-enriched cortical primary cultures subjected to 3% oxygen (hypoxia) and glucose deprivation (HGD). Adenoviral vectors were used to analyze the effect of overexpression of Rcan1-4 protein. Protein expression was examined by immunohistochemistry and immunoblotting and expression of mRNA by quantitative real-time Reverse-Transcription Polymerase Chain Reaction (real time qRT-PCR). RESULTS: Brain ischemia/reperfusion (I/R) injury in vivo increased mRNA and protein expression of the calcium-inducible Rcan1 isoform (Rcan1-4). I/R-inducible expression of Rcan1 protein occurred mainly in astroglial cells, and in an in vitro model of ischemia, HGD treatment of primary murine astrocyte cultures induced Rcan1-4 mRNA and protein expression. Exogenous Rcan1-4 overexpression inhibited production of the inflammatory marker cyclo-oxygenase 2. Mice lacking Rcan1 had higher expression of inflammation associated genes, resulting in larger infarct volumes. CONCLUSIONS: Our results support a protective role for Rcan1 during the inflammatory response to stroke, and underline the importance of the glial compartment in the inflammatory reaction that takes place after ischemia. Improved understanding of non-neuronal mechanisms in ischemic injury promises novel approaches to the treatment of acute ischemic stroke.

Incidence, risk factors, and evolution of venous thromboembolic events in patients diagnosed with pancreatic carcinoma and treated with chemotherapy on an outpatient basis.

BACKGROUND: Pancreatic carcinoma is one of the tumors associated with a higher risk for thromboembolic events, with incidence rates ranging from 5% to 41% in previous retrospective series. PATIENTS AND METHODS: We conducted a retrospective study in eleven Spanish hospitals that included 666 patients diagnosed with pancreatic carcinoma (any stage) between 2008 and 2011 and treated with chemotherapy. The main objective was to evaluate the incidence of venous thromboembolic events (VTE) in this population, as well as potential risk factors for thrombosis. The impact of VTE on mortality was also assessed. RESULTS: With a median follow-up of 9.3 months, the incidence of VTE was 22.1%; 52% were diagnosed incidentally. Our study was unable to confirm the ability of the Khorana score to discriminate between patients in the intermediate or high risk category for thrombosis. The presence of VTE proved to be an independent prognostic factor associated with increased risk of death (HR 2.39, 95% CI 1.96-2.92). Symptomatic events correlated with higher mortality than asymptomatic events (HR 1.72; 95% CI, 1.21-2.45; p = 0.002), but incidental VTE, including visceral vein thrombosis (VVT), negatively affected survival compared to patients without VTE. Subjects who developed VTE within the first 3 months of diagnosis of pancreatic carcinoma had lower survival rates than those with VTE after 3 months (HR 1.92, 95% CI 1.30-2.84; p<0.001). CONCLUSIONS: Pancreatic carcinoma is associated with a high incidence of VTE, which, when present, correlates with worse survival, even when thrombosis is incidental. Early onset VTE has a particularly negative impact.

RAS Mutational Status in Advanced Colorectal Adenocarcinoma Treated With Anti-angiogenics: Preliminary Experience With Liquid Biopsy.

AIM: To determinate molecular changes in the downstream epidermal growth factor receptor signaling pathway using serial liquid biopsies in patients with metastatic colorectal tumors (mCRC) under anti-angiogenic treatment. PATIENTS AND METHODS: Determination of RAS mutation in primary tissue samples from colorectal tumors was performed in the 23 patients included in the study at diagnosis using quantitative-polymerase chain reaction. Sequential mutations were studied in circulating tumor (ct) DNA obtained from plasma samples. RESULTS: Twenty-three patients with RAS-mutated primary tumors were included. In the first ctDNA determination, 17 of these patients were found to have wild-type RAS status. Remarkably, three out of these 17 wild-type cases changed to RAS-mutated in subsequent ctDNA assays. CONCLUSION: Serial liquid biopsies in patients with mCRC might be a useful tool for identifying changes in the RAS mutation status in patients who had undergone previous anti-angiogenic therapy. The understanding of these changes might help to better define the landscape of mCRC and be the path to future randomized studies.

Inhibition of JAK2 protects renal endothelial and epithelial cells from oxidative stress and cyclosporin A toxicity.

Cyclosporin A is an immunosuppressant drug widely used in solid organ transplantation, but it has nephrotoxic properties that promote oxidative stress. The JAK2/STAT pathway has been implicated in both cell protection and cell injury; therefore, we determined a role of JAK2 in oxidative stress-mediated renal cell injury using pathophysiologically relevant oxidative challenges. The AG490 JAK2 inhibitor and overexpression of a dominant negative JAK2 protein protected endothelial and renal epithelial cells in culture against peroxide, superoxide anion and cyclosporin A induced cell death while reducing intracellular oxidation in cells challenged with peroxide and cyclosporin A. The decrease in Bcl2 expression and caspase 3 activation, induced by oxidative stress, was prevented by AG490. In mouse models of ischemia/reperfusion and cyclosporin A nephrotoxicity, AG490 decreased peritubular capillary and tubular cell injury. Our study shows that JAK2 inhibition is a promising renoprotective strategy defending endothelial and tubular cells from cyclosporin A- and oxidative stress-induced death.

Alkalinization potentiates vascular calcium deposition in an uremic milieu.

BACKGROUND: Vascular calcification is a serious complication of chronic kidney disease. Acid-base balance is a relevant, albeit somewhat forgotten factor in the regulation of calcium deposition. Hemodialysis patients undergo repeated episodes of alkaline loading from the dialysate, resulting in prolonged alkalinization. We have hypothesized that extracellular alkalinization may promote vascular calcification. METHODS: Primary cultures of vascular smooth muscle cells were induced to calcify by the phosphate donor beta-glycerophosphate, in the presence of normal or uremic sera from hemodialysis patients and at different pH conditions. The influence of sodium bicarbonate supplementation for 2 months on aorta calcification was studied in 5/6 nephrectomized uremic rats. RESULTS: Uremic serum increased vascular smooth muscle cell calcification (twofold over nonuremic human serum at day 12, p<0.001). Alkalinization of the extracellular medium also increased vascular smooth muscle cell calcification. Increasing the extracellular pH from 7.42 to 7.53 resulted in a 2.5-fold increase in calcium accumulation at day 12 (p<0.05). In vivo, arterial calcification was significantly higher in alkalinized uremic animals (aorta calcification index, uremic + sodium bicarbonate, 164 +/- 57 units, vs. uremic + vehicle, 56 +/- 14 units; p<0.01). CONCLUSIONS: Alkalinization increases vascular calcification in cultured cells and uremic rats. These data may be used to optimize dialysate composition and the degree of alkalinization in calcification-prone individuals with advanced renal disease.

[Response to hypoxia. A systemic mechanism based on the control of gene expression]. / Respuesta a la hipoxia. Un mecanismo sistemico basado en el control de la expresion genica.

New, critically important data have been recently generated about the response to hypoxia. This response can be schematized in three main systems or functions, ie, detectional or oxygen sensing, regulatory, which controls gene expression and effector. The principal organizer of the regulatory branch is a specific transcription factor, the hypoxia-inducible factor 1 (HIF-1). In the presence of oxygen, the alpha subunit of HIF-1 (HIF-1alpha) is modified by hydroxylases, that represent the central point of the oxygen sensing mechanism. This type of hydroxylation induces HIF-1alpha catabolism by the proteosome. On the contrary, in hypoxia, or in the presence of certain growth factors that increase HIF-1alpha synthesis, HIF-1alpha translocates to the nucleus, where it binds HIF-1beta, and thence acts on transcription of genes carrying hypoxia responsive elements (HRE) on their promoters. These genes regulate the synthesis of an ample series of proteins, which span from respiratory enzymes and transporters to hormones regulating circulation and erythropoiesis. The role of HIF-1alpha is not restricted to the mere induction of adaptation to decreased oxygen: instead, it significantly participates in cell repairing mechanisms. A simple list of some of the stimulatory or inhibitory alterations of pathophysiological importance involving the HIF-1 system, would include: chronic lung disease, smoking adaptation, anemia/hemorrhage, ischemia/reperfusion, growth, vascularization and cell resistance of tumors, preeclampsia and intrauterine growth retardation, retinal hyper o hypovascularization, drug intoxications, bowel inflammatory disease and wound repair. This list illustrates by itself the importance of the mechanism herein reviewed.

Induction of hypoxia-inducible factor 1alpha gene expression by vascular endothelial growth factor.

Transcriptional regulation of vascular endothelial growth factor (VEGF) is critically dependent on hypoxia-inducible factor 1 (HIF-1). However, not only hypoxia, but selected growth factors can induce HIF-1. High levels of both VEGF and HIF-1 coexist in certain conditions, e.g. tumors. Nonetheless, the possibility that the stimulatory relationship between HIF-1 and VEGF may be bi-directional has not been addressed up to date. The present study in endothelial cells analyzed whether HIF-1 is regulated by a product of its own transcriptionally activated genes, namely, VEGF. As a main finding, VEGF-A(165) induced the increase of HIF-1alpha mRNA and HIF-1alpha protein and nuclear translocation. Autologous endothelial cell VEGF mRNA and protein were also increased upon exposure to exogenous VEGF. The signaling implication of reactive oxygen species was examined by comparison with H(2)O(2) and hypoxanthine/xanthine oxidase and by the superoxide dismutase mimetic, MnTMPyP, the Rac1-NAD(P)H oxidase complex inhibitor, apocynin, transfection of a dominant negative Rac1 mutant, and transfection of a p67phox antisense oligonucleotide. Superoxide anion, largely dependent on Rac1-NAD(P)H oxidase complex activity, was the critical signaling element. The transductional functionality of the pathway was confirmed by means of a reporter gene flanked by a transcription site-related VEGF sequence and by quantitative PCR. In summary, the present results reveal a previously undescribed action of VEGF on the expression of its own transcription factor, HIF-1, and on VEGF itself. This effect is principally mediated by superoxide anion, therefore identifying a new, potentially relevant role of reactive oxygen species in VEGF signaling.

Mechanisms of endothelial cell protection by blockade of the JAK2 pathway.

Inhibition of the JAK2/STAT pathway has been implicated recently in cytoprotective mechanisms in both vascular smooth muscle cells and astrocytes. The advent of JAK2-specific inhibitors provides a practical tool for the study of this pathway in different cellular types. An interest in finding methods to improve endothelial cell (EC) resistance to injury led us to examine the effect of JAK2/STAT inhibition on EC protection. Furthermore, the signaling pathways involved in JAK2/STAT inhibition-related actions were examined. Our results reveal, for the first time, that blockade of JAK2 with the tyrosine kinase inhibitor AG490 strongly protects cultured EC against cell detachment-dependent death and serum deprivation and increases reseeding efficiency. Confirmation of the specificity of the effects of JAK2 inhibition was attained by finding protective effects on transfection with a dominant negative JAK2. Furthermore, AG490 blocked serum deprivation-induced phosphorylation of JAK2. In terms of mechanism, treatment with AG490 induces several relevant responses, both in monolayer and detached cells. These mechanisms include the following: 1) Increase and nuclear translocation of the active, dephosphorylated form of beta-catenin. In functional terms, this translocation is transcriptionally active, and its protective effect is further supported by the stimulation of EC cytoprotection by transfectionally induced excess of beta-catenin. 2) Increase of platelet endothelial cell adhesion molecule (PECAM)/CD31 levels. 3) Increase in total and phosphorylated AKT. 4) Increase in phosphorylated glycogen synthase kinase (GSK)3alpha/beta. The present findings imply potential practical applications of JAK2 inhibition on EC. These applications affect not only EC in the monolayer but also circulating detached cells and involve mechanistic interactions not previously described.

Tumor-induced endothelial cell activation: role of vascular endothelial growth factor.

Proangiogenic, proliferative effects of tumors have been extensively characterized in subconfluent endothelial cells (EC), but results in confluent, contact-inhibited EC are critically lacking. The present study examined the effect of tumor-conditioned medium (CM) of the malignant osteoblastic cell line MG63 on monolayer, quiescent bovine aorta EC. MG63-CM and MG63-CM + CoCl(2) significantly increased EC survival in serum-starved conditions, without inducing EC proliferation. Furthermore, MG63-CM and MG63-CM + CoCl(2), both containing high amounts of vascular endothelial growth factor (VEGF), induced relevant phenotypic changes in EC (all P < 0.01) involving increase of nucleoli/chromatin condensations, nucleus-to-cytosol ratio, capillary-like vacuolated structures, vessel-like acellular areas, migration through Matrigel, growth advantage in reseeding, and factor VIII content. All these actions were significantly inhibited by VEGF and VEGF receptor (VEGFR2) blockade. Of particular importance, a set of similar effects were detected in a human microvascular endothelial cell line (HMEC). With regard to gene expression, incubation with MG63-CM abolished endogenous VEGF mRNA and protein but induced a clear-cut increase in VEGFR2 mRNA expression in EC. In terms of mechanism, MG63-CM activates protein kinase B (PKB)/Akt, p44/p42-mitogen-activated protein kinase (MAPK)-mediated pathways, as suggested by both inhibition and phosphorylation experiments. In conclusion, tumor cells activate confluent, quiescent EC, promoting survival, phenotypic, and gene expression changes. Of importance, VEGF antagonism converts MG63-CM from protective to EC-damaging effects.

Respuesta a la hipoxia: un mecanismo sistemico basado en el control de la expresion genica / Response to hypoxia: a systemic mechanism based on the control of gene expression

La respuesta hipóxica, sobre la que se dispone de nuevos datos críticamente importantes, puede esquematizarse en tres sistemas, vg. de detección o sensor de oxígeno, de regulación, que controla la expresión génica y efector. El elemento principal de organización del sistema regulador es un factor de transcripción específico, el factor inducible por hipoxia 1 (HIF-1). En presencia de oxígeno, la subunidad α del HIF-1 (HIF-1α) se modifica por las hidroxilasas, que constituyen el punto central del mecanismo sensor, induciendo su catabolismo por el proteosoma. Por el contrario, en hipoxia, o en presencia de algunos factores de crecimiento que incrementan su síntesis, el HIF-1α se transloca al núcleo, donde, unido al HIF-1β, actúa como factor transcripcional de genes con elementos de respuesta hipóxica (HRE) en su promotor. Estos regulan lasíntesis de una amplia serie de proteínas, que abarcan desde enzimas respiratorias y transportadores hasta hormonas involucradas en la regulación a escala del organismo de la circulación y la eritropoyesis. El papel del HIF-1 no se restringe a la mera inducción de una respuesta adaptativa a la falta de oxígeno, sino que participa significativamente en los mecanismos de reparación celular. Una simple lista de algunas alteraciones de importância fisiopatológica, tanto estimulatorias como inhibitorias, que involucran al sistema de HIF-1, incluiría: enfermedad pulmonar crónica, adaptación al tabaco/humo, anemia/hemorragia, isquemia/reperfusión, crecimiento, vascularización y resistencia celular de los tumores, preeclampsia y crecimiento intrauterino retardado, hiper o hipovascularización retiniana, sobredosis de fármacos, enfermedad inflamatoria intestinal y curación de heridas. Esta sola enumeración ilustra la importancia de este mecanismo. .

New, critically important data have been recently generated about the response to hypoxia. This response can be schematized in three main systems or functions, ie, detectional or oxygen sensing, regulatory, which controls gene expression and effector. The principal organizer of the regulatory branch is a specific transcription factor, the hypoxia-inducible factor 1 (HIF-1). In the presence of oxygen, the α subunit of HIF-1 (HIF-1α) is modified by hydroxylases, that represent the central point of the oxygen sensing mechanism. This type of hydroxylation induces HIF-1α catabolism by the proteosome. On the contrary, in hypoxia, or in the presence of certain growth factors that increase HIF-1α synthesis, HIF-1α translocates to the nucleus, where it binds HIF-1β, and thence acts on transcription of genes carrying hypoxia responsive elements (HRE) on their promoters. These genes regulate the synthesis of an ample series of proteins, which span from respiratory enzymes and transporters to hormones regulating circulation and erythropoiesis. The role of HIF-1α is not restricted to the mere induction of adaptation to decreased oxygen: instead, it significantly participates in cell repairing mechanisms. A simple list of some of the stimulatory or inhibitory alterations of pathophysiological importance involving the HIF-1 system, would include: chronic lung disease, smoking adaptation, anemia/hemorrhage, ischemia/reperfusion, growth, vascularization and cell resistance of tumors, preeclampsia and intrauterine growth retardation, retinal hyper ohypovascularization, drug intoxications, bowel inflammatory disease and wound repair. This list illustrates by itself the importance of the mechanism herein reviewed.