Pharmacological approaches in either intermittent or permanent hypoxia: A tale of two exposures.

Hypoxia induces several responses at cardiovascular, pulmonary and reproductive levels, which may lead to chronic diseases. This is relevant in human populations exposed to high altitude (HA), in either chronic continuous (permanent inhabitants) or intermittent fashion (HA workers, tourists and mountaineers). In Chile, it is estimated that 1.000.000 people live at highlands and more than 55.000 work in HA shifts. Initial responses to hypoxia are compensatory and induce activation of cardioprotective mechanisms, such as those seen under intermittent hypobaric (IH) hypoxia, events that could mediate preconditioning. However, whenever hypoxia is prolonged, the chronic activation of cellular responses induces long-lasting modifications that may result in acclimatization or produce maladaptive changes with increase in cardiovascular risk. HA exposure during pregnancy induces hypoxia and oxidative stress, which in turn may promote cellular responses and epigenetic modifications resulting in severe impairment in growth and development. Sadly, this condition is accompanied with an increased fetal and neonatal morbi-mortality. Further, developmental hypoxia may program cardio-pulmonary circulations later in postnatal life, ending in vascular structural and functional alterations with augmented risk on pulmonary and cardiovascular failure. Additionally, permanent HA inhabitants have augmented risk and prevalence of chronic hypoxic pulmonary hypertension, right ventricular hypertrophy and cardiopulmonary remodeling. Similar responses are seen in adults that are intermittently exposed to chronic hypoxia (CH) such as shift workers in HA areas. The mechanisms involved determining the immediate, short and long-lasting effects are still unclear. For several years, the study of the responses to hypoxic insults and pharmacological targets has been the motivation of our group. This review describes some of the mechanisms underlying hypoxic responses and potential therapeutic approaches with antioxidants such as melatonin, ascorbate, omega 3 (Ω3) or compounds that increase the nitric oxide (NO) bioavailability.

Transfusion-Related Acute Lung Injured (TRALI): Current Concepts.

Transfusion-related acute lung injury (TRALI) is a life-threatening intervention that develops within 6 hours of transfusion of one or more units of blood, and is an important cause of morbidity and mortality resulting from transfusion. It is necessary to dismiss other causes of acute lung injury (ALI), like sepsis, acute cardiogenic edema, acute respiratory distress syndrome (ARDS) or bacterial infection. There are two mechanisms that lead to the development of this syndrome: immune-mediated and no immune- mediated TRALI. A common theme among the experimental TRALI models is the central importance of neutrophils in mediating the early immune response, and lung vascular injury. Central clinical symptoms are dyspnea, tachypnea, tachycardia, cyanosis and pulmonary secretions, altogether with other hemodynamic alterations, such as hypotension and fever. Complementary to these clinical findings, long-term validated animal models for TRALI should allow the determination of the cellular targets for TRALI-inducing alloantibodies as well as delineation of the underlying pathogenic molecular mechanisms, and key molecular mediators of the pathology. Diagnostic criteria have been established and preventive measures have been implemented. These actions have contributed to the reduction in the overallnumber of fatalities. However, TRALI still remains a clinical problem. Any complication suspected of TRALI should immediately be reported.

Pathophysiological Approaches of Acute Respiratory Distress syndrome: Novel Bases for Study of Lung Injury.

Experimental approaches have been implemented to research the lung damage related-mechanism. These models show in animals pathophysiological events for acute respiratory distress syndrome (ARDS), such as neutrophil activation, reactive oxygen species burst, pulmonary vascular hypertension, exudative edema, and other events associated with organ dysfunction. Moreover, these approaches have not reproduced the clinical features of lung damage. Lung inflammation is a relevant event in the develop of ARDS as component of the host immune response to various stimuli, such as cytokines, antigens and endotoxins. In patients surviving at the local inflammatory states, transition from injury to resolution is an active mechanism regulated by the immuno-inflammatory signaling pathways. Indeed, inflammatory process is regulated by the dynamics of cell populations that migrate to the lung, such as neutrophils and on the other hand, the role of the modulation of transcription factors and reactive oxygen species (ROS) sources, such as nuclear factor kappaB and NADPH oxidase. These experimental animal models reproduce key components of the injury and resolution phases of human ALI/ARDS and provide a methodology to explore mechanisms and potential new therapies.

Cellular mechanisms against ischemia reperfusion injury induced by the use of anesthetic pharmacological agents.

Ischemia-reperfusion (IR) cycle in the myocardium is associated with activation of an injurious cascade, thus leading to new myocardial challenges, which account for up to 50% of infarct size. Some evidence implicates reactive oxygen species (ROS) as a probable cause of myocardial injury in prooxidant clinical settings. Damage occurs during both ischemia and post-ischemic reperfusion in animal and human models. The mechanisms that contribute to this damage include the increase in cellular calcium (Ca(2+)) concentration and induction of ROS sources during reperfusion. Pharmacological preconditioning, which includes pharmacological strategies that counteract the ROS burst and Ca(2+) overload followed to IR cycle in the myocardium, could be effective in limiting injury. Currently widespread evidence supports the use of anesthetics agents as an important cardioprotective strategy that act at various levels such as metabotropic receptors, ion channels or mitochondrial level. Their administration before a prolonged ischemic episode is known as anesthetic preconditioning, whereas when given at the very onset of reperfusion, is termed anesthetic postconditioning. Both types of anesthetic conditioning reduce, albeit not to the same degree, the extent of myocardial injury. This review focuses on cellular and pathophysiological concepts on the myocardial damage induced by IR and how anesthetic pharmacological agents commonly used could attenuate the functional and structural effects induced by oxidative stress in cardiac tissue.