Hypoxic signal transduction in critical illness

Tsantan Sumtang attenuated chronic hypoxia-induced right ventricular structure remodeling and fibrosis by equilibrating local ACE-AngII-AT1R/ACE2-Ang1-7-Mas axis in rat

ETHNOPHARMACOLOGICAL RELEVANCE

Tsantan Sumtang, which consists of Choerospondias axillaris (Roxb.) Burtt et Hill, Myristica fragrans Houtt and Santalum album L, is a traditional and common prescription of Tibetan medicine. Tsantan Sumtang originates from Four Tantra with properties of nourishing heart and has been used as a folk medicine for cardiovascular diseases and heart failure in Qinghai, Tibet and Inner Mongolia. Our previous studies found that Tsantan Sumtang showed beneficial effects on right ventricular structure in hypoxia rats, while the underling mechanism remains unclear.

AIM OF THE STUDY

To elucidate the underlying mechanisms of Tsantan Sumtang attenuated right ventricular (RV) remodeling and fibrosis of chronic hypoxia-induced pulmonary arterial hypertension (HPAH) rats.

MATERIALS AND METHODS

Fifty male Sprague Dawley (SD) rats (170 ± 20 g) were randomly divided into control group, hypoxia group, and hypoxia + Tsantan Sumtang groups (1.0 g· kg^-1·day^-1, 1.25 g· kg^-1·day^-1, 1.5 g ·kg^-1·day^-1). Rats in the hypoxia group and hypoxia + Tsantan Sumtang groups were maintained in a hypobaric chamber by adjusting the inner pressure and oxygen content to simulate an altitude of 4500 m for 28 days. The mean pulmonary arterial pressure (mPAP), right ventricle hypertrophy index (RVHI), the ratio of RV weight to tibia length (TL) (RV/TL), heart rate (HR) and RV systolic pressure (RVSP) was determined. Histomorphological assay of RV structure was evaluated by hematoxylin and eosin (HE) staining. RV tissue fibrosis was assessed by collagen proportion area (CPA), collagen I, collagen III and hydroxyproline content. CPA was obtained by picro-sirius red staining (PSR). The expression of collagen I and collagen III were detected by immunohistochemistry and western blotting. The hydroxyproline content was detected by alkaline hydrolysis. In addition, the level of angiotensin II (AngII) and angiotensin 1-7 (Ang1-7) in RV tissue was tested by enzyme-linked immune sorbent assay (ELISA). Protein expression of angiotensin-converting enzyme (ACE), AngII, AngII type 1 receptor (AT1R), angiotensin-converting enzyme 2 (ACE2), Mas receptor (Mas) were determined by immunohistochemistry and western blotting. mRNA level of ACE, AT1R, ACE2, Mas were tested by qPCR. The chemical profile of Tsantan Sumtang was revealed by UHPLC-Q-Exactive hybrid quadrupole-orbitrap mass analysis.

RESULTS

Our results showed that RVHI, RV/TL and RVSP were significantly increased in HPAH rat. Furthermore, levels of collagen I, collagen III and hydroxyproline were up-regulated in RV tissue under hypoxia. We found that RV hypertrophy and fibrosis were associated with increased expression of ACE, AngII, AT1R as well as decreased expression of ACE2, Ang1-7 and Mas. RV remodeling and fibrosis were attenuated after Tsantan Sumtang administration by up-regulating ACE2 and Mas level as well as down-regulating ACE, AngII and AT1R levels in RV tissue. 35 constituents in Tsantan Sumtang were identified.

CONCLUSION

Tsantan Sumtang attenuated RV remodeling and fibrosis in rat exposed to chronic hypoxia. The pharmacological effect of Tsantan Sumtang was based on equilibrating ACE-AngII-AT1R and ACE2-Ang1-7-Mas axis of RV tissue in HPAH rat.

Bone Failure in Critical Illness

OBJECTIVES

The origin of systemic inflammatory response syndrome and multiple organ dysfunction syndrome is poorly understood but remains a fundamental concern in the ICU. This paper provides a critical appraisal on whether bone failure may represent an unrecognized component of systemic inflammatory response syndrome/multiple organ dysfunction syndrome.

DATA SOURCES, DATA SELECTION, AND DATA EXTRACTION

Search of the PubMed database and manual review of selected articles investigating bone pathophysiology in critical illness.

DATA SYNTHESIS

Bone hyperresorption is highly prevalent among critically ill patients. Bone breakdown releases numerous systemically active cytokines and bone-sequestered toxins, with the capacity to fuel inflammatory hypercytokinaemia and metabolic toxaemia. Anti-resorptive medication inhibits bone break down and preadmission anti-resorptive use is associated with superior survival among critically ill patients.

CONCLUSIONS

We propose that hyperresorptive bone failure is an unrecognised component of systemic inflammatory response syndrome/multiple organ dysfunction syndrome that is causal to critical illness progression. If this hypothesis is valid, bone preservative strategies could reduce the risk of osteoporosis/fractures among ICU survivors, as well as decreasing critical illness mortality.

Skeletal muscle oxygenation in severe trauma patients during haemorrhagic shock resuscitation

Introduction

Early alterations in tissue oxygenation may worsen patient outcome following traumatic haemorrhagic shock. We hypothesized that muscle oxygenation measured using near-infrared spectroscopy (NIRS) on admission could be associated with subsequent change in the SOFA score after resuscitation.

Methods

The study was conducted in two Level I trauma centres and included 54 consecutive trauma patients with haemorrhagic shock, presenting within 6 hours of injury. Baseline tissue haemoglobin oxygen saturation (StO2) in the thenar eminence muscle and StO2 changes during a vascular occlusion test (VOT) were determined at 6 hours (H6) and 72 hours (H72) after the admission to the emergency room. Patients showing an improved SOFA score at H72 (SOFA improvers) were compared to those for whom it was unchanged or worse (SOFA non-improvers).

Results

Of the 54 patients, 34 patients were SOFA improvers and 20 SOFA non-improvers. They had comparable injury severity scores on admission. SOFA improvers had higher baseline StO2 values and a steeper StO2 desaturation slope at H6 compared to the SOFA non-improvers. These StO2 variables similarly correlated with the intra-hospital mortality. The StO2 reperfusion slope at H6 was similar between the two groups of patients.

Conclusions

Differences in StO2 parameters on admission of traumatic haemorrhagic shock were found between patients who had an improvement in organ failure in the first 72 hours and those who had unchanged or worse conditions. The use of NIRS to guide the initial management of trauma patients with haemorrhagic shock warrants further investigations.

Low-volume binary drug therapy for the treatment of hypovolemia

The selective regulation of total peripheral circulation in hypovolemic crisis offers a unique approach for treating and preventing hemorrhagic shock. Ideally, such a therapeutic intervention would require targeting of the striated muscle vascular beds without altering the vascular resistance in vital organ vascular beds. We discovered that a combination of cannabinoid receptor agonist, THC (Δ-tetrahydrocannabinol), and cyclooxygenase 2 inhibitor, NS-398, caused selective microvascular constriction in the mouse cremaster muscle manifested by a pronounced and significant 27.4% ± 7.9% decrease in vessel diameter relative to control (P < 0.01). This observation, and the reported lack of microvascular response in the mesentery and brain, led us to hypothesize that the drug combination could favorably redistribute blood volume in hypovolemia and prolong survival. To test the hypothesis, male Sprague-Dawley rats were subjected to a pressure-controlled hemorrhage (mean arterial pressure reduced to 30 ± 13.73 mmHg) then randomly assigned to one of six treatment groups (n = 6 per group). The untreated, NS-398-treated, and THC-treated groups manifested an insignificant difference in survival between groups after shock. The group treated with a combination of THC and NS-398 manifested a significant increase in mean survival from 53 ± 12 to 227 ± 23 min after shock (P < 0.001). The drug combination significantly reduced IL-1α, IL-1β, IFN-γ, and IL-10 production compared with the group resuscitated with normal saline. In addition, histological evaluation indicated that the therapy protects the lungs and liver against hemorrhagic shock-induced damage. The combination of cannabinoid receptor agonist and cyclooxygenase 2 inhibitor represents a potentially new approach to low-volume therapeutic intervention for hypovolemia.

High-altitude physiology and pathophysiology: implications and relevance for intensive care medicine

Cellular hypoxia is a fundamental mechanism of injury in the critically ill. The study of human responses to hypoxia occurring as a consequence of hypobaria defines the fields of high-altitude medicine and physiology. A new paradigm suggests that the physiological and pathophysiological responses to extreme environmental challenges (for example, hypobaric hypoxia, hyper-baria, microgravity, cold, heat) may be similar to responses seen in critical illness. The present review explores the idea that human responses to the hypoxia of high altitude may be used as a means of exploring elements of the pathophysiology of critical illness.

Pathophysiology of intensive care unit-acquired anemia

The formation of red blood cells (RBCs) in the bone marrow is regulated by erythropoietin in response to a cascade of events. Anemia in the intensive care unit can be caused by a host of factors. Patients in the intensive care unit may have decreased RBC production and a blunted response to erythropoietin. Administration of recombinant human erythropoietin may stimulate erythropoiesis, increase hematocrit levels and hemoglobin concentration, and reduce the need for RBC transfusions.

Multiple organ failure in patients with cardiogenic shock is associated with high plasma levels of interleukin-6

OBJECTIVE

In patients with septic shock, multiple organ failure (MOF) is associated with high levels of interleukin-6 (IL-6). Although organ failure is also a common complication of cardiogenic shock (CS), IL-6 levels have been reported to be lower in patients with CS than in patients with septic shock. We studied IL-6 plasma levels in patients with CS with respect to organ failure.

SETTING

Eight-bed intensive care unit at a university hospital.

PATIENTS

Fifty-one patients with CS, 26 patients with septic shock, and 11 noncritically ill controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with CS had higher IL-6 levels than noncritically ill controls ( p<.001) but lower levels than patients with septic shock ( p=.003). CS patients with MOF at the time of blood sampling exhibited, however, higher IL-6 levels than CS patients without organ failure, and IL-6 levels in patients with CS correlated to the total Sepsis-related Organ Failure Assessment score at the time of blood sampling ( r=.57, <.001). No significant differences in IL-6 levels were found when comparing CS patients with MOF at the time of blood sampling with patients with septic shock. Furthermore, CS patients who developed MOF during ICU stay exhibited significantly higher IL-6 levels than CS patients who never did develop MOF. An IL-6 level of >200 pg/mL had a 93% specificity and 100% sensitivity for the prediction of MOF in patients with CS.

CONCLUSIONS

Once MOF is present, patients with CS exhibit similarly high IL-6 levels as patients with septic shock. High IL-6 levels in CS patients are associated with a progression to MOF.