A fully integrated wearable ultrasound system to monitor deep tissues in moving subjects.

Recent advances in wearable ultrasound technologies have demonstrated the potential for hands-free data acquisition, but technical barriers remain as these probes require wire connections, can lose track of moving targets and create data-interpretation challenges. Here we report a fully integrated autonomous wearable ultrasonic-system-on-patch (USoP). A miniaturized flexible control circuit is designed to interface with an ultrasound transducer array for signal pre-conditioning and wireless data communication. Machine learning is used to track moving tissue targets and assist the data interpretation. We demonstrate that the USoP allows continuous tracking of physiological signals from tissues as deep as 164 mm. On mobile subjects, the USoP can continuously monitor physiological signals, including central blood pressure, heart rate and cardiac output, for as long as 12 h. This result enables continuous autonomous surveillance of deep tissue signals toward the internet-of-medical-things.

Enteral administration of the protease inhibitor gabexate mesilate preserves vascular function in experimental trauma/hemorrhagic shock.

Preserving vascular function is crucial for preventing multiorgan failure and death in ischemic and low-pressure states such as trauma/hemorrhagic shock (T/HS). It has recently been reported that inhibiting circulating proteases released from the bowel to the circulation during T/HS may preserve vascular function and improve outcomes following T/HS. This study aimed to evaluate the role of the serine protease inhibitor gabexate mesilate (GM) in preserving vascular function during T/HS when given enterally. We studied the vascular reactivity of mesenteric arteries from male Wistar rats treated with enteral GM (10 mg/kg) (GM-treated, n = 6) or control (Shock-control, n = 6) following (T/HS) using pressure myography. Concentration-response curves of endothelial-dependent and endothelial-independent agonists (e.g., acetylcholine, sodium nitroprusside) ranging from 10-10 to 10-5 M were performed. In a second set of experiments, ex-vivo arteries from healthy rats were perfused with plasma from shocked animals from both groups and vascular performance was similarly measured. Arteries from the GM-treated group demonstrated a preserved concentration-response curve to the α1 adrenergic agonist phenylephrine compared to arteries from Shock-control animals (- logEC50: - 5.73 ± 0.25 vs. - 6.48 ± 0.2, Shock-control vs. GM-treated, p = 0.04). When perfused with plasma from GM-treated rats, healthy arteries exhibited an even greater constriction and sensitivity to phenylephrine (- logEC50: - 6.62 ± 0.21 vs. - 7.13 ± 0.21, Shock-control vs. GM-treated, p = 0.02). Enteral GM also preserved the endothelium-dependent vascular response to agonists following T/HS and limited syndecan-1 shedding as a marker of glycocalyx compromise (41.84 ± 9 vs. 17.63 ± 3.97 ng/mL, Shock-control vs. GM-treated, p = 0.02). Syndecan-1 cleavage was correlated with plasma trypsin-like activity (r2 = 0.9611). Enteral gabexate mesilate was able to maintain vascular function in experimental T/HS, which was reflected by improved hemodynamics (mean arterial pressure 50.39 ± 7.91 vs. 64.95 ± 3.43 mmHg, Shock-control vs. GM treated, p = 0.0001). Enteral serine protease inhibition may be a potential therapeutic intervention in the treatment of T/HS.

Enteral gabexate mesilate improves volume requirements and autonomic cardiovascular function after experimental trauma/hemorrhagic shock in the absence of blood reperfusion.

The standard of care for fluid resuscitation of trauma/hemorrhagic shock (T/HS) is the infusion of blood. However, in many instances, blood product transfusion may not be feasible. Consequently, crystalloid solutions may be utilized as temporizing cost-effective resuscitation fluids. In this study, we explored an alternative therapeutic strategy of enteral protease inhibition adjunctive to intravenous Lactated Ringer's (LR) reperfusion after T/HS. Male Wistar rats underwent midline laparotomy (trauma) and an enteral catheter was inserted orally and positioned post-pyloric for the infusion of vehicle (Golytely®) with or without the serine protease inhibitor gabexate mesilate (GM) (n=8/group). Hemorrhagic shock was induced by blood removal to reduce the mean arterial blood pressure (MAP) to 35-40 mmHg for 90 minutes, before resuscitation with LR. Animals treated with enteral GM required significantly less crystalloid volume to achieve hemodynamic stability and displayed improvements in both blood pressure and autonomic function (via increased baroreflex sensitivity to vasopressors, heightened vascular sympathetic modulation, elevated levels of circulating catecholamines, and increased α1-adrenergic receptor density) compared to untreated (control) shocked animals. Resistance arteries isolated from healthy donor animals and perfused with plasma from untreated T/HS animals revealed impaired vascular response to the α1 adrenergic agonist phenylephrine and decreased reactivity to sodium nitroprusside that was preserved in the GM-treated group. These findings suggest that blockade of serine proteases within the intestinal lumen in non-blood resuscitated experimental T/HS preserves and enhances peripheral sympathetic modulation, improving hemodynamics. Enteral infusion of gabexate mesilate may be a new and promising approach to the management of trauma/hemorrhagic shock.

Efficacy of Tranexamic Acid in Blood Versus Crystalloid-Resuscitated Trauma/Hemorrhagic Shock.

INTRODUCTION: Whole blood (WB) or blood products are not always immediately available for repletion of lost intravascular volume in trauma/hemorrhagic shock (T/HS), and thus, resuscitation with crystalloid solutions is often necessary. Recently, we have shown enteral tranexamic acid (TXA) to be effective as a mild protease inhibitor in blood-resuscitated T/HS by counteracting proteolytic activity in and leaking from the gut with resultant preservation of systemic vascular integrity. We hypothesized that enteral TXA would improve hemodynamic stability after T/HS in the absence of blood reperfusion. METHODS: We directly compared resuscitation with enteral TXA versus intravenous (IV) TXA in conjunction with lactated Ringer's solution (LR) or WB reperfusion in an experimental T/HS model. Rats were subjected to laparotomy and exsanguinated to a mean arterial blood pressure of 35-40 mm Hg for 90 min, followed by LR or WB reperfusion and monitored for 120 min. TXA was administered via IV (10 mg/kg) or enteral infusion (150 mM) 20 min after establishment of hemorrhage for 150 min. RESULTS: Animals resuscitated with LR were unable to restore or maintain a survivable mean arterial blood pressure (>65 mm Hg), regardless of TXA treatment route. In contrast, rats reperfused with WB and given TXA either enterally or IV displayed hemodynamic improvements superior to WB controls. CONCLUSIONS: Results suggest that the beneficial hemodynamic responses to enteral or IV TXA after experimental T/HS depend upon reperfusion of WB or components present in WB as TXA, regardless of delivery mode, does not have appreciable hemodynamic effects when paired with LR reperfusion.

Continuous enteral protease inhibition as a novel treatment for experimental trauma/hemorrhagic shock.

PURPOSE: Trauma and hemorrhagic shock (T/HS) is a major cause of morbidity and mortality. Existing treatment options are largely limited to source control and fluid and blood repletion. Previously, we have shown that enteral protease inhibition improves outcomes in experimental models of T/HS by protecting the gut from malperfusion and ischemia. However, enteral protease inhibition was achieved invasively, by laparotomy and direct injection of tranexamic acid (TXA) into the small intestine. In this study, we tested a minimally invasive method of enteral protease inhibitor infusion in experimental T/HS that can be readily adapted for clinical use. METHODS: Wistar rats were exsanguinated to a mean arterial blood pressure (MABP) of 40 mmHg, with laparotomy to induce trauma. Hypovolemia was maintained for 120 min and was followed by reperfusion of shed blood. Animals were monitored for an additional 120 min. A modified orogastric multi-lumen tube was developed to enable rapid enteral infusion of a protease inhibitor solution while simultaneously mitigating risk of reflux aspiration into the airways. The catheter was used to deliver TXA (T/HS + TXA) or vehicle (T/HS) continuously into the proximal small intestine, starting 20 min into the ischemic period. RESULTS: Rats treated with enteral protease inhibition (T/HS + TXA) displayed improved outcomes compared to control animals (T/HS), including significantly improved MABP (p = 0.022) and lactate (p = 0.044). Mass spectrometry-based analysis of the plasma peptidome after T/HS indicated mitigation of systemic proteolysis in T/HS + TXA. CONCLUSION: Minimally invasive, continuous enteral protease inhibitor delivery improves outcomes in T/HS and is readily translatable to the clinical arena.

Plasma enzymatic activity, proteomics and peptidomics in COVID-19-induced sepsis: A novel approach for the analysis of hemostasis.

Introduction: Infection by SARS-CoV-2 and subsequent COVID-19 can cause viral sepsis. We investigated plasma protease activity patterns in COVID-19-induced sepsis with bacterial superinfection, as well as plasma proteomics and peptidomics in order to assess the possible implications of enhanced proteolysis on major protein systems (e.g., coagulation). Methods: Patients (=4) admitted to the intensive care units (ICUs) at the University of California, San Diego (UCSD) Medical Center with confirmed positive test for COVID-19 by real-time reverse transcription polymerase chain reaction (RT-PCR) were enrolled in a study approved by the UCSD Institutional Review Board (IRB# 190699, Protocol #20-0006). Informed consent was obtained for the collection of blood samples and de-identified use of the data. Blood samples were collected at multiple time points and analyzed to quantify a) the circulating proteome and peptidome by mass spectrometry; b) the aminopeptidase activity in plasma; and c) the endopeptidase activity in plasma using fluorogenic substrates that are cleaved by trypsin-like endopeptidases, specific clotting factors and plasmin. The one patient who died was diagnosed with bacterial superinfection on day 7 after beginning of the study. Results: Spikes in protease activity (factor VII, trypsin-like activity), and corresponding increases in the intensity of peptides derived by hydrolysis of plasma proteins, especially of fibrinogen degradation products and downregulation of endogenous protease inhibitors were detected on day 7 for the patient who died. The activity of the analyzed proteases was stable in survivors. Discussion: The combination of multiomics and enzymatic activity quantification enabled to i) hypothesize that elevated proteolysis occurs in COVID-19-induced septic shock with bacterial superinfection, and ii) provide additional insight into malfunctioning protease-mediated systems, such as hemostasis.

Involvement of Toll-Like Receptor 4 in Decreased Vasopressor Response Following Trauma/Hemorrhagic Shock.

Refractory vascular failure due to the inability of vascular smooth muscle to respond to vasoconstrictors such as phenylephrine is a final common pathway for severe circulatory shock of any cause, including trauma/hemorrhagic shock. Increased inflammation, Toll-like receptor 4 activation, and decreased response of the alpha-1 adrenergic receptors which control vascular tone have been reported in trauma/hemorrhagic shock. HYPOTHESIS: In trauma/hemorrhagic shock, Toll-like receptor 4 activation contributes to vascular failure via decreased bioavailability of adrenergic receptors. DESIGN AND MEASUREMENTS: Trauma/hemorrhagic shock was induced in Wistar rats (laparotomy combined with mean arterial pressure at 40 mm Hg for 90 min followed by 2 hr resuscitation with Lactated Ringers solution). To inhibit Toll-like receptor 4, resatorvid (TAK-242) and resveratrol were used, and plasma was collected. Smooth muscle cells were incubated with lipopolysaccharide (10 ng/mL) or plasma. Inflammatory cytokines were screened using dot-blot. Toll-like receptor 4 and nuclear factor κB activation and cellular localization of the alpha-1 adrenergic receptor were measured by immunofluorescence imaging and Western blot analysis. Clustered regularly interspaced short palindromic repeats/Cas9 was used to knock out Toll-like receptor 4, and calcium influx following stimulation with phenylephrine was recorded. MAIN RESULTS: Trauma/hemorrhagic shock caused a decreased response to phenylephrine, whereas Toll-like receptor 4 inhibition improved blood pressure. Trauma/hemorrhagic shock plasma activated the Toll-like receptor 4/nuclear factor κB pathway in smooth muscle cells. Double labeling of Toll-like receptor 4 and the alpha-1 adrenergic receptor showed that these receptors are colocalized on the cell membrane. Activation of Toll-like receptor 4 caused cointernalization of both receptors. Calcium influx was impaired in cells incubated with trauma/hemorrhagic shock plasma but restored when Toll-like receptor 4 was knocked out or inhibited. CONCLUSIONS: Activation of the Toll-like receptor 4 desensitizes vascular smooth muscle cells to vasopressors in experimental trauma/hemorrhagic shock by reducing the levels of membrane alpha-1 adrenergic receptor.

Continuous monitoring of deep-tissue haemodynamics with stretchable ultrasonic phased arrays.

Stretchable wearable devices for the continuous monitoring of physiological signals from deep tissues are constrained by the depth of signal penetration and by difficulties in resolving signals from specific tissues. Here, we report the development and testing of a prototype skin-conformal ultrasonic phased array for the monitoring of haemodynamic signals from tissues up to 14 cm beneath the skin. The device allows for active focusing and steering of ultrasound beams over a range of incident angles so as to target regions of interest. In healthy volunteers, we show that the phased array can be used to monitor Doppler spectra from cardiac tissues, record central blood flow waveforms and estimate cerebral blood supply in real time. Stretchable and conformal skin-worn ultrasonic phased arrays may open up opportunities for wearable diagnostics.

Resuscitation from hemorrhagic shock after traumatic brain injury with polymerized hemoglobin.

Traumatic brain injury (TBI) is often accompanied by hemorrhage, and treatment of hemorrhagic shock (HS) after TBI is particularly challenging because the two therapeutic treatment strategies for TBI and HS often conflict. Ischemia/reperfusion injury from HS resuscitation can be exaggerated by TBI-induced loss of autoregulation. In HS resuscitation, the goal is to restore lost blood volume, while in the treatment of TBI the priority is focused on maintenance of adequate cerebral perfusion pressure and avoidance of secondary bleeding. In this study, we investigate the responses to resuscitation from severe HS after TBI in rats, using fresh blood, polymerized human hemoglobin (PolyhHb), and lactated Ringer's (LR). Rats were subjected to TBI by pneumatic controlled cortical impact. Shortly after TBI, HS was induced by blood withdrawal to reduce mean arterial pressure (MAP) to 35-40 mmHg for 90 min before resuscitation. Resuscitation fluids were delivered to restore MAP to ~ 65 mmHg and animals were monitored for 120 min. Increased systolic blood pressure variability (SBPV) confirmed TBI-induced loss of autoregulation. MAP after resuscitation was significantly higher in the blood and PolyhHb groups compared to the LR group. Furthermore, blood and PolyhHb restored diastolic pressure, while this remained depressed for the LR group, indicating a loss of vascular tone. Lactate increased in all groups during HS, and only returned to baseline level in the blood reperfused group. The PolyhHb group possessed lower SBPV compared to LR and blood groups. Finally, sympathetic nervous system (SNS) modulation was higher for the LR group and lower for the PolyhHb group compared to the blood group after reperfusion. In conclusion, our results suggest that PolyhHb could be an alternative to blood for resuscitation from HS after TBI when blood is not available, assuming additional testing demonstrate similar favorable results. PolyhHb restored hemodynamics and oxygen delivery, without the logistical constraints of refrigerated blood.

Resuscitation After Hemorrhagic Shock in the Microcirculation: Targeting Optimal Oxygen Delivery in the Design of Artificial Blood Substitutes.

Microcirculatory preservation is essential for patient recovery from hemorrhagic shock. In hemorrhagic shock, microcirculatory flow and pressure are greatly reduced, creating an oxygen debt that may eventually become irreversible. During shock, tissues become hypoxic, cellular respiration turns to anaerobic metabolism, and the microcirculation rapidly begins to fail. This condition requires immediate fluid resuscitation to promote tissue reperfusion. The choice of fluid for resuscitation is whole blood; however, this may not be readily available and, on a larger scale, may be globally insufficient. Thus, extensive research on viable alternatives to blood has been undertaken in an effort to develop a clinically deployable blood substitute. This has not, as of yet, achieved fruition, in part due to an incomplete understanding of the complexities of the function of blood in the microcirculation. Hemodynamic resuscitation is acknowledged to be contingent on a number of factors other than volume expansion. The circulation of whole blood is carefully regulated to optimize oxygen delivery to the tissues via shear stress modulation through blood viscosity, inherent oxygen-carrying capacity, cell-free layer variation, and myogenic response, among other variables. Although plasma expanders can address a number of these issues, hemoglobin-based oxygen carriers (HBOCs) introduce a method of replenishing the intrinsic oxygen-carrying capacity of blood. There continue to be a number of issues related to HBOCs, but recent advances in the next-generation HBOCs show promise in the preservation of microcirculatory function and limiting toxicities. The development of HBOCs is now focused on viscosity and the degree of microvascular shear stress achieved in order to optimize vasoactive and oxygen delivery responses by leveraging the restoration and maintenance of physiological responses to blood flow in the microcirculation. Blood substitutes with higher viscous properties tend to improve oxygen delivery compared to those with lower viscosities. This review details current concepts in blood substitutes, particularly as they relate to trauma/hemorrhagic shock, with a specific focus on their complex interactions in the microcirculation.

Gut Ischemia Reperfusion Injury Induces Lung Inflammation via Mesenteric Lymph-Mediated Neutrophil Activation.

Gut ischemia/reperfusion (I/R) injury is a common clinical problem associated with significant mortality and morbidities that result from systemic inflammation and remote organ dysfunction, typically acute lung injury. The mechanisms underlying the dissemination of gut-derived harmful mediators into the circulation are poorly understood. The objective of our study was to determine the role of mesenteric lymphatic circulation in the systemic and pulmonary inflammatory response to gut I/R. Using a murine intestinal I/R model, we evaluated whether and how blocking mesenteric lymph flow affects the inflammatory response in local tissues (gut) and remote organs (lungs). We further explored the mechanisms of post-I/R lymph-induced systemic inflammation by examining neutrophil activity and interaction with endothelial cells in vitro. Mice subjected to intestinal I/R displayed a significant inflammatory response in local tissues, evidenced by neutrophil infiltration into mucosal areas, as well as lung inflammation, evidenced by increased myeloperoxidase levels, neutrophil infiltration, and elevated microvascular permeability in the lungs. Mesenteric lymph duct ligation (MLDL) had no effect on gut injury per se, but effectively attenuated lung injury following gut I/R. Cell experiments showed that lymph fluid from post-I/R animals, but not pre-I/R, increased neutrophil surface CD11b expression and their ability to migrate across vascular endothelial monolayers. Moreover, post-I/R lymph upregulated neutrophil expression of pro-inflammatory cytokines and chemokines, which was mediated by a mechanism involving nuclear factor (NF)-κB signaling. Consistently, gut I/R activated NF-κB in lung neutrophils, which was alleviated by MLDL. In conclusion, all these data indicate that mesenteric lymph circulation contributes to neutrophil activation and lung inflammation following gut I/R injury partly through activating NF-κB.

High-Resolution Mass Spectrometry-Based Approaches for the Detection and Quantification of Peptidase Activity in Plasma.

Proteomic technologies have identified 234 peptidases in plasma but little quantitative information about the proteolytic activity has been uncovered. In this study, the substrate profile of plasma proteases was evaluated using two nano-LC-ESI-MS/MS methods. Multiplex substrate profiling by mass spectrometry (MSP-MS) quantifies plasma protease activity in vitro using a global and unbiased library of synthetic peptide reporter substrates, and shotgun peptidomics quantifies protein degradation products that have been generated in vivo by proteases. The two approaches gave complementary results since they both highlight key peptidase activities in plasma including amino- and carboxypeptidases with different substrate specificity profiles. These assays provide a significant advantage over traditional approaches, such as fluorogenic peptide reporter substrates, because they can detect active plasma proteases in a global and unbiased manner, in comparison to detecting select proteases using specific reporter substrates. We discovered that plasma proteins are cleaved by endoproteases and these peptide products are subsequently degraded by amino- and carboxypeptidases. The exopeptidases are more active and stable in plasma and therefore were found to be the most active proteases in the in vitro assay. The protocols presented here set the groundwork for studies to evaluate changes in plasma proteolytic activity in shock.

A longitudinal study highlights shared aspects of the transcriptomic response to cardiogenic and septic shock.

BACKGROUND: Septic shock (SS) and cardiogenic shock (CS) are two types of circulatory shock with a different etiology. Several studies have described the molecular alterations in SS patients, whereas the molecular factors involved in CS have been poorly investigated. We aimed to assess in the whole blood of CS and SS patients, using septic patients without shock (SC) as controls, transcriptomic modifications that occur over 1 week after ICU admission and are common to the two types of shock. METHODS: We performed whole blood RNA sequencing in 21 SS, 11 CS, and 5 SC. In shock patients, blood samples were collected within 16 h from ICU admission (T1), 48 h after ICU admission (T2), and at day 7 or before discharge (T3). In controls, blood samples were available at T1 and T2. Gene expression changes over time have been studied in CS, SS, and SC separately with a paired analysis. Genes with p value < 0.01 (Benjamini-Hochberg multiple test correction) were defined differentially expressed (DEGs). We used gene set enrichment analysis (GSEA) to identify the biological processes and transcriptional regulators significantly enriched in both types of shock. RESULTS: In both CS and SS patients, GO terms of inflammatory response and pattern recognition receptors (PRRs) were downregulated following ICU admission, whereas gene sets of DNA replication were upregulated. At the gene level, we observed that alarmins, interleukin receptors, PRRs, inflammasome, and DNA replication genes significantly changed their expression in CS and SS, but not in SC. Analysis of transcription factor targets showed in both CS and SS patients, an enrichment of CCAAT-enhancer-binding protein beta (CEBPB) targets in genes downregulated over time and an enrichment of E2F targets in genes with an increasing expression trend. CONCLUSIONS: This pilot study supports, within the limits of a small sample size, the role of alarmins, PRRs, DNA replication, and immunoglobulins in the pathophysiology of circulatory shock, either in the presence of infection or not. We hypothesize that these genes could be potential targets of therapeutic interventions in CS and SS. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02141607. Registered 19 May 2014.

Enteral Tranexamic Acid Decreases Proteolytic Activity in the Heart in Acute Experimental Hemorrhagic Shock.

The mechanisms for cardiac injury after hemorrhagic shock (HS) are unresolved. We hypothesize that remote organ damage can be caused by uncontrolled pancreatic proteolytic activity, as enteral protease inhibition improves outcomes in experimental HS. Uncontrolled proteolysis in the heart may disrupt cardiac metabolism and adrenergic control with subsequent deleterious outcomes. To test this hypothesis, the heart rate-pressure product (RPP) as an index of myocardial oxygen consumption and the levels of fatty acid transporter proteins CD36 and FATP6 as surrogates for metabolic activity in the heart were measured in rats subjected to experimental HS (n = 6/group) with and without the enteral protease inhibitor tranexamic acid (TXA). Plasma troponin I and heart fatty acid-binding protein (HFABP) concentrations were measured as indices of myocardial damage. Expression of the adrenergic receptors ß1, α1D, and ß2 was also measured in the heart to determine the possible effects of shock with and without enteral TXA on the adrenergic control of heart function. Hemorrhagic shock was induced by reduction in mean arterial blood pressure to 35 mm Hg for 2 hours before reperfusion of shed blood. The RPP was maintained in shocked animals treated enterally with TXA but not in those subjected to HS alone; this group also demonstrated decreased HFABP and plasma troponin I levels. Serine protease (trypsin, chymotrypsin, and elastase) and matrix metalloproteinase (MMP)-2 and MMP-9 activity was elevated in cardiac tissue and plasma after HS and abrogated by enteral TXA. Levels of CD36, FATP6, ß1, α1D, and ß2 were also increased after HS in cardiac tissue, and the increases were mitigated by TXA treatment. These results suggest that increased proteolytic activity may contribute to cardiac injury after HS. Enteral TXA prevents these changes, indicating a potential therapeutic option in the management of shock with resultant cardiac injury.

Cleavage of the leptin receptor by matrix metalloproteinase-2 promotes leptin resistance and obesity in mice.

Obesity and related morbidities pose a major health threat. Obesity is associated with increased blood concentrations of the anorexigenic hormone leptin; however, obese individuals are resistant to its anorexigenic effects. We examined the phenomenon of reduced leptin signaling in a high-fat diet-induced obesity model in mice. Obesity promoted matrix metalloproteinase-2 (Mmp-2) activation in the hypothalamus, which cleaved the leptin receptor's extracellular domain and impaired leptin-mediated signaling. Deletion of Mmp-2 restored leptin receptor expression and reduced circulating leptin concentrations in obese mice. Lentiviral delivery of short hairpin RNA to silence Mmp-2 in the hypothalamus of wild-type mice prevented leptin receptor cleavage and reduced fat accumulation. In contrast, lentiviral delivery of Mmp-2 in the hypothalamus of Mmp-2-/- mice promoted leptin receptor cleavage and higher body weight. In a genetic mouse model of obesity, transduction of cleavage-resistant leptin receptor in the hypothalamus reduced the rate of weight gain compared to uninfected mice or mice infected with the wild-type receptor. Immunofluorescence analysis showed that astrocytes and agouti-related peptide neurons were responsible for Mmp-2 secretion in mice fed a high-fat diet. These results suggest a mechanism for leptin resistance through activation of Mmp-2 and subsequent cleavage of the extracellular domain of the leptin receptor.

Severity of Acute Kidney Injury in the Post-Lung Transplant Patient Is Associated With Higher Healthcare Resources and Cost.

OBJECTIVE: Perioperative risk factors and the clinical impact of acute kidney injury (AKI) and failure after lung transplantation are not well described. The incidences of AKI and acute renal failure (ARF), potential perioperative contributors to their development, and postdischarge healthcare needs were evaluated. DESIGN: Retrospective. SETTING: University hospital. PARTICIPANTS: Patients undergoing lung transplantation between January 1, 2011 and December 31, 2015. MEASURED DATA: The incidences of AKI and ARF, as defined using the Risk, Injury, Failure, Loss, End-Stage Renal Disease criteria, were measured. Perioperative events were analyzed to identify risk factors for renal compromise. A comparison of ventilator days, intensive care unit (ICU) and hospital lengths of stay (LOS), 1-year readmissions, and emergency department visits was performed among AKI, ARF, and uninjured patients. MEASUREMENTS AND MAIN RESULTS: Ninety-seven patients underwent lung transplantation; 22 patients developed AKI and 35 patients developed ARF. Patients with ARF had significantly longer ICU LOS (12 days v 4 days, p < 0.001); ventilator days (4.5 days v 1 day, p < 0.001); and hospital LOS (22.5 days v 14 days, p < 0.001) compared with uninjured patients. Patients with AKI also had significantly longer ICU and hospital LOS. Patients with ARF had significantly more emergency department visits and hospital readmissions (2 v 1 readmissions, p = 0.002) compared with uninjured patients. A univariable analysis suggested that prolonged surgical time, intraoperative vasopressor use, and cardiopulmonary bypass use were associated with the highest increased risk for AKI. Intraoperative vasopressor use and cardiopulmonary bypass mean arterial pressure <60 mmHg were identified as independent risk factors by multivariable analysis for AKI. CONCLUSION: The severity of AKI was associated with an increase in the use of healthcare resources after surgery and discharge. Certain risk factors appeared modifiable and may reduce the incidence of AKI and ARF.

Enteral tranexamic acid attenuates vasopressor resistance and changes in α1-adrenergic receptor expression in hemorrhagic shock.

BACKGROUND: Irreversible hemorrhagic shock is characterized by hyporesponsiveness to vasopressor and fluid therapy. Little is known, however, about the mechanisms that contribute to this phenomenon. Previous studies have shown that decreased intestinal perfusion in hemorrhagic shock leads to proteolytically mediated increases in gut permeability, with subsequent egress of vasoactive substances systemically. Maintenance of blood pressure is achieved in part by α1 receptor modulation, which may be affected by vasoactive factors; we thus hypothesized that decreases in hemodynamic stability and vasopressor response in shock can be prevented by enteral protease inhibition. METHODS: Rats were exposed to experimental hemorrhagic shock (35 mm Hg mean arterial blood pressure for 2 hours, followed by reperfusion for 2 hours) and challenged with phenylephrine (2 µg/kg) at discrete intervals to measure vasopressor responsiveness. A second group of animals received enteral injections with the protease inhibitor tranexamic acid (TXA) (127 mM) along the small intestine and cecum 1 hour after induction of hemorrhagic shock. RESULTS: Blood pressure response (duration and amplitude) to phenylephrine after reperfusion was significantly attenuated in animals subjected to hemorrhagic shock compared with baseline and control nonshocked animals and was restored to near baseline by enteral TXA. Arteries from shocked animals also displayed decreased α1 receptor density with restoration to baseline after enteral TXA treatment. In vitro, rat shock plasma decreased α1 receptor density in smooth muscle cells, which was also abrogated by enteral TXA treatment. CONCLUSION: Results from this study demonstrate that experimental hemorrhagic shock leads to decreased response to the α1-selective agonist phenylephrine and decreased α1 receptor density via circulating shock factors. These changes are mitigated by enteral TXA with correspondingly improved hemodynamics. Proteolytic inhibition in the lumen of the small intestine improves hemodynamics in hemorrhagic shock, possibly by restoring α1 adrenergic functionality necessary to maintain systemic blood pressure and perfusion.

Peptidomic Analysis of Rat Plasma: Proteolysis in Hemorrhagic Shock.

It has been previously shown that intestinal proteases translocate into the circulation during hemorrhagic shock and contribute to proteolysis in distal organs. However, consequences of this phenomenon have not previously been investigated using high-throughput approaches. Here, a shotgun label-free quantitative proteomic approach was utilized to compare the peptidome of plasma samples from healthy and hemorrhagic shock rats to verify the possible role of uncontrolled proteolytic activity in shock. Plasma was collected from rats after hemorrhagic shock (HS) consisting of 2-h hypovolemia followed by 2-h reperfusion, and from healthy control (CTRL) rats. A new two-step enrichment method was applied to selectively extract peptides and low molecular weight proteins from plasma, and directly analyze these samples by tandem mass spectrometry. One hundred twenty-six circulating peptides were identified in CTRL and 295 in HS animals. Ninety-six peptides were present in both conditions; of these, 57 increased and 30 decreased in shock. In total, 256 peptides were increased or present only in HS confirming a general increase in proteolytic activity in shock. Analysis of the proteases that potentially generated the identified peptides suggests that the larger relative contribution to the proteolytic activity in shock is due to chymotryptic-like proteases. These results provide quantitative confirmation that extensive, system-wide proteolysis is part of the complex pathologic phenomena occurring in hemorrhagic shock.

Autodigestion: Proteolytic Degradation and Multiple Organ Failure in Shock.

There is currently no effective treatment for multiorgan failure following shock other than supportive care. A better understanding of the pathogenesis of these sequelae to shock is required. The intestine plays a central role in multiorgan failure. It was previously suggested that bacteria and their toxins are responsible for the organ failure seen in circulatory shock, but clinical trials in septic patients have not confirmed this hypothesis. Instead, we review here evidence that the digestive enzymes, synthesized in the pancreas and discharged into the small intestine as requirement for normal digestion, may play a role in multiorgan failure. These powerful enzymes are nonspecific, highly concentrated, and fully activated in the lumen of the intestine. During normal digestion they are compartmentalized in the lumen of the intestine by the mucosal epithelial barrier. However, if this barrier becomes permeable, e.g. in an ischemic state, the digestive enzymes escape into the wall of the intestine. They digest tissues in the mucosa and generate small molecular weight cytotoxic fragments such as unbound free fatty acids. Digestive enzymes may also escape into the systemic circulation and activate other degrading proteases. These proteases have the ability to clip the ectodomain of surface receptors and compromise their function, for example cleaving the insulin receptor causing insulin resistance. The combination of digestive enzymes and cytotoxic fragments leaking into the central circulation causes cell and organ dysfunction, and ultimately may lead to complete organ failure and death. We summarize current evidence suggesting that enteral blockade of digestive enzymes inside the lumen of the intestine may serve to reduce acute cell and organ damage and improve survival in experimental shock.