Pulmonary Apoptosis After Supraceliac Aorta Clamping in a Rat Model1

Fingolimod attenuates renal ischemia/reperfusion-induced acute lung injury by inhibiting inflammation and apoptosis and modulating S1P metabolism

Objective

This study examined whether the immunomodulator fingolimod (FTY720) could alleviate renal ischemia/reperfusion (I/R)-induced lung injury and explored the potential mechanisms.

Methods

Renal I/R was established in a rat model, and FTY720 (0.5, 1, or 2 mg/kg) was injected intraperitoneally after 15 minutes of ischemia. Pro-inflammatory cytokine levels, oxidative stress, apoptosis, and the mRNA expression of the sphingosine-1-phosphate (S1P)-related signaling pathway genes sphingosine kinase-1 (SphK1) and sphingosine kinase-2 were analyzed in lung tissue.

Results

Increased pro-inflammatory cytokine levels; decreased total superoxide dismutase, catalase, and glutathione peroxidase levels; increased apoptosis; and increased S1P lyase and SphK1 expression were observed following renal I/R. FTY720 reversed renal I/R-induced changes and effectively attenuated lung injury.

Conclusion

FTY720 protected against acute lung injury in rats subjected to renal I/R by decreasing pulmonary inflammation and apoptosis, increasing oxidative stress, and modulating S1P metabolism.

Open surgical repair of juxtarenal abdominal aortic aneurysms in the elderly is not associated with increased thirty-day mortality compared with fenestrated endovascular grafting

OBJECTIVE

Endovascular repair of juxtarenal abdominal aortic aneurysms (JAAAs) with fenestrated grafts (fenestrated endovascular aneurysm repair [FEVAR]) has been reported to decrease operative mortality and morbidity compared with open surgical repair (OSR). However, previous comparisons of OSR and FEVAR have not necessarily included patients with comparable clinical profiles and aneurysm extent. Although FEVAR has often been chosen as the first-line therapy for high-risk patients such as the elderly, many patients will not have anatomy favorable for FEVAR. At present, a paucity of data has examined the operative outcomes of OSR in elderly patients for JAAAs relative to FEVAR. Therefore, we chose to perform a propensity-matched comparison of OSR and FEVAR for JAAA repair in patients aged ≥70 years.

METHODS

Patients aged ≥70 years who had undergone elective nonruptured JAAA repairs from 2012 to 2018 were identified in the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) targeted endovascular aneurysm repair (EVAR) and AAA databases. Patients who had undergone FEVAR were identified in the targeted EVAR database as those who had received the Cook Zenith Fenestrated endograft (Cook Medical, Bloomington, Ind). Because our study specifically examined JAAAs, those patients who had undergone OSR with supraceliac proximal clamping or concomitant renal/visceral revascularization were excluded. A 1:1 propensity-match algorithm matched the OSR and FEVAR patients by preoperative clinical and demographic characteristics, operative indications, and aneurysm extent. The 30-day outcomes, including mortality, major adverse cardiovascular events, and pulmonary and renal complications, were compared between the propensity-matched OSR and FEVAR groups.

RESULTS

A 1:1 propensity match was achieved, and the final analysis included 136 OSR patients and 136 FEVAR patients. No significant differences were found in 30-day mortality (4.4% vs 3.7%; odds ratio [OR], 1.21; 95% confidence interval [CI], 0.36-4.06; P = .759) between the OSR and FEVAR groups. OSR was associated with a higher incidence of major adverse cardiovascular events compared with FEVAR; however, the trend was not statistically significant (8.1% vs 3.7%; OR, 2.31; 95% CI, 0.78-6.82; P = .131). Compared with FEVAR, the OSR group had significantly greater rates of pulmonary complications (19.1% vs 3.7%; OR, 6.19; 95% CI, 2.30-16.67; P < .001) and renal complications (8.1% vs 2.2%; OR, 3.90; 95% CI, 1.06-14.31; P = .040).

CONCLUSIONS

In the samples assessed in the present study, the results with OSR of JAAAs in the elderly did not differ from those of FEVAR with respect to 30-day mortality despite a greater incidence of pulmonary and renal complications. Although FEVAR should remain the first-line therapy for JAAAs in elderly patients, OSR might be an acceptable alternative for select patients with anatomy unfavorable for FEVAR.

Thirty-day outcomes of open abdominal aortic aneurysm repair by proximal clamp level in patients with normal and impaired renal function

OBJECTIVE

Open surgical repair (OSR) of abdominal aortic aneurysms (AAAs) has often been reserved in contemporary practice for complex aneurysms requiring a suprarenal or supraceliac proximal clamp level. The present study investigated the associated 30-day outcomes of different proximal clamp levels in OSR of complex infrarenal/juxtarenal AAA in patients with normal renal function and those with chronic renal insufficiency (CRI).

METHODS

All patients undergoing elective OSR of infrarenal and juxtarenal AAA were identified in the American College of Surgeons National Surgical Quality Improvement Program-targeted AAA database from 2012 to 2018. The patients were stratified into two cohorts (normal renal function [estimated glomerular filtration rate, ≥60 mL/min] and CRI [estimated glomerular filtration rate, <60 mL/min and no dialysis]) before further substratification into groups by the proximal clamp level (infrarenal, inter-renal, suprarenal, and supraceliac). The 30-day outcomes, including mortality, renal and pulmonary complications, and major adverse cardiovascular event rates, were compared within each renal function cohort between proximal clamp level groups using the infrarenal clamp group as the reference. Supraceliac clamping was also compared with suprarenal clamping.

RESULTS

A total of 1284 patients with normal renal function and 524 with CRI were included in the present study. The proximal clamp levels for the 1808 patients were infrarenal for 1080 (59.7%), inter-renal for 337 (18.6%), suprarenal for 279 (15.4%), and supraceliac for 112 (6.2%). In the normal renal function cohort, no difference was found in 30-day mortality with any clamp level. Increased 30-day acute renal failure was only observed in the supraceliac vs infrarenal clamp level comparison (5.9% vs 1.5%; adjusted odds ratio [aOR], 3.97; 95% confidence interval [CI], 1.04-5.18; P = .044). In the CRI cohort, supraceliac clamping was associated with an increased rate of renal composite complications (22.7% vs 5.6%; aOR, 8.81; 95% CI, 3.17-24.46; P < .001) and ischemic colitis (13.6% vs 3.0%; aOR, 4.78; 95% CI, 1.38-16.62; P = .014) compared with infrarenal clamping and greater 30-day mortality (13.6% vs 2.4%; aOR, 6.00; 95% CI, 1.14-31.55; P = .034) and renal composite complications (22.7% vs 10.8%; aOR, 2.87; 95% CI, 1.02-8.13; P = .047) compared with suprarenal clamping. Suprarenal clamping was associated with greater renal dysfunction (10.8% vs 5.6%; aOR, 2.77; 95% CI, 1.08-7.13; P = .035) compared with infrarenal clamping, with no differences in mortality. No differences were found in 30-day mortality or morbidity for inter-renal clamping compared with infrarenal clamping in either cohort. No differences were found in major adverse cardiovascular events with higher clamp levels in either cohort.

CONCLUSIONS

In elective OSR of infrarenal and juxtarenal AAAs for patients with CRI, this study found a heightened mortality risk with supraceliac clamping and increased renal morbidity with suprarenal clamping, though these effects were not present for patients with normal renal function. Every effort should be made to keep the proximal clamp level as low as possible, especially in patients with CRI.

A 30-Minute Supraceliac Aortic Clamping in the Rat Causes Death Due to an Inflammatory Response and Pulmonary Lesions

BACKGROUND

The treatment of thoracoabdominal aortic aneurysms through an open approach has general and pulmonary consequences of multiple etiologies. Our assumption was that the supraceliac aortic clamping needed for this operation causes a systemic inflammatory response associated with a pulmonary attack.

METHODS

We developed a model of 30-min supraceliac aortic clamping in Wistar rats weighing 300 g. After 90 min of reperfusion, the rats were sacrificed. The effects on the digestive tract wall were analyzed by measurement of the mucosal thickness/total thickness ratio. The effects on the mesenteric endothelial function were determined by an ex situ measurement of the arterial pressure/volume curves (third branch). The systemic consequences of the procedure were analyzed by dosing tumor necrosis factor alpha (TNFα), interleukin (IL)1β, and IL10 in the blood. The pulmonary consequences were analyzed by the measurement of macrophages, polymorphonuclear neutrophils (PNs), T lymphocyte infiltration, pulmonary apoptosis (TUNEL) and active caspase 3. The experimental scheme included 20 rats with ischemia-reperfusion (IR) and 20 control rats. An analysis of survival was carried out on 20 other rats (10 IR and 10 controls).

RESULTS

The results were expressed as average ± standard error of the mean. The statistical tests were Student's t-test and Mann-Whitney test. This visceral IR model decreased the ratio of the thickness of the intestinal mucosa compared with that of the control rats (0.77 ± 0.008 vs. 0.82 ± 0.009 [P < 0.001]). This local effect was not accompanied by any mesenteric endothelial dysfunction (P = 0.91). On a systemic level, IR increased TNFα (37.9 ± 1.5 vs. 28.2 ± 0.6 pg/mL; P < 0.0001), IL1β (67.1 ± 9.8 vs. 22.5 ± 5.6 pg/mL; P < 0.001), and IL10 (753.3 ± 96 vs. 3.7 ± 1.7 pg/mL; P < 0.0001). As regards the lungs, IR increased the parenchymal cellular infiltration by macrophages (6.8 ± 0.8 vs. 4.5 ± 0.4 cells per field; P < 0.05) and PNs (7.4 ± 0.5 vs. 6.2 ± 03 cells per field; P < 0.05). There was no increase in the pulmonary cellular apoptosis measured by TUNEL (P = 0.77) or in the caspase 3 activity (P = 0.59). The mortality of the visceral IR rats was 100% at 36 hr vs. 0% in the animals without IR.

CONCLUSIONS

This work showed that the inflammatory response to visceral IR had systemic and pulmonary effects which always results in the death in the rat.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Ischaemic preconditioning prevents the liver inflammatory response to lung ischaemia/reperfusion in a swine lung autotransplant model

OBJECTIVES

Lung ischaemia/reperfusion (IR) induces a systemic inflammatory response that causes damage to remote organs. The liver is particularly sensitive to circulating inflammatory mediators that occur after IR of remote organs. Recently, remote ischaemic preconditioning has been proposed as a surgical tool to protect several organs from IR. The present study was designed to investigate a possible protective effect of lung ischaemic preconditioning (IP) against the liver inflammatory response to lung IR.

METHODS

Two groups [IP and control (CON)] of 10 Large White pigs underwent lung autotransplants (left pneumonectomy, ex situ cranial lobectomy and caudal lobe reimplantation). Before pneumonectomy was performed in the study group, IP was induced with two 5-min cycles of left pulmonary arterial occlusion and a 5-min interval of reperfusion between the two occlusions. Five animals underwent sham surgery. Liver biopsies were obtained during surgery at (i) prepneumonectomy, (ii) prereperfusion, (iii) 10 min after reperfusion of the implanted lobe and (iv) 30 min after reperfusion. The expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-1, IL-10 and inducible form of nitric oxide synthase (iNOS) was analysed by western blotting. The expression of mRNA for TNF-α, IL1, IL-10, monocyte chemoattractant protein-1 (MCP-1), nuclear factor kappa beta and iNOS was analysed by reverse transcription-polymerase chain reaction. Caspase-3 activity was determined by enzyme-linked immunosorbent assay. Non-parametric tests were used to compare differences between and within groups.

RESULTS

Lung IR markedly increased expression of TNF-α (P = 0.0051) and IL-1 (P = 0.0051) and caspase-3 activity (P = 0.0043) in the CON group compared with the prepneumonectomy levels. A decrease of IL-10 mRNA expression was observed in the CON group after lung reperfusion. In the IP group, TNF-α (P = 0.0011) and IL-1 (P = 0.0001) expression and caspase-3 activity (P < 0.0009) were lower after reperfusion than in the CON group. IP caused reversion of the observed decrease of IL-10 mRNA expression (P = 0.016) induced in liver tissue by lung IR. Lung IR markedly increased the expression of mRNA MCP-1 after 10 min (P = 0.0051) and 30 min (P = 0.0051) of reperfusion. These increases were not observed in the IP or sham groups.

CONCLUSIONS

IP prevented liver injury induced by lung IR through the reduction of proinflammatory cytokines and hepatocyte apoptosis.

Milk fat globule-EGF factor VIII in sepsis and ischemia-reperfusion injury

Sepsis and ischemia-reperfusion (I/R) injury are among the leading causes of death in critically ill patients at the surgical intensive care unit setting. Both conditions are marked by the excessive inflammatory response which leads to a lethal disease complex such as acute lung injury, systemic inflammatory response syndrome and multiple organ dysfunction syndrome. Despite the advances in the understanding of the pathophysiology of those conditions, very little progress has been made toward therapeutic interventions. One of the key aspects of these conditions is the accumulation of apoptotic cells that have the potential to release toxic and proinflammatory contents due to secondary necrosis without appropriate clearance by phagocytes. Along with the prevention of apoptosis, that is reported to be beneficial in sepsis and I/R injury, thwarting the development of secondary necrosis through the active removal of apoptotic cells via phagocytosis may offer a novel therapy. Milk fat globule-EGF factor VIII (MFG-E8), which is mainly produced by macrophages and dendritic cells, is an opsonin for apoptotic cells and acts as a bridging protein between apoptotic cells and phagocytes. Recently, we have shown that MFG-E8 expression is decreased in experimental sepsis and I/R injury models. Exogenous administration of MFG-E8 attenuated the inflammatory response as well as tissue injury and mortality through the promotion of phagocytosis of apoptotic cells. In this review, we describe novel information available about the involvement of MFG-E8 in the pathophysiology of sepsis and I/R injury, and the therapeutic potential of exogenous MFG-E8 treatment for those conditions.

Morphological and apoptotic changes in the intestinal mucosa and lung parenchyma after ischaemic/reperfusion injury of the jejunum

Ischaemic/reperfusion (IR) injury of the small intestine may lead to the development of multiple organ failure. Little is known about the morphological changes occurring in the organs during the subacute course of this syndrome. The objective of this study was to observe histopathological features and the role of apoptosis in the jejunal mucosa and lung parenchyma after intestinal IR injury in a long-term experiment. Wistar rats (n = 36) were divided into 4 experimental groups (IR(10), IR(20), IR(30), S). Groups IR(10), IR(20) and IR(30) (each n = 10) were subjected to 1-hour ischaemia of the cranial mesenteric artery followed by 10, 20 or 30 days of reperfusion, respectively. The control group S (n = 6) was not subjected to ischaemia. The jejunal mucosa remained intact after all periods of reperfusion. Apoptotic cells were found particularly in the lamina propria, with the most significant difference observed in the IR(30) group (P < 0.01). The lung parenchyma had lower regenerative capacity, which was confirmed by a high index of histological damage after 30 days of reperfusion (P < 0.01) and by the presence of an increased number of apoptotic cells, especially in the pulmonary interstitium. The number of apoptotic cells was ten times higher than in the control group (P < 0.001).

Milk fat globule epidermal growth factor 8 attenuates acute lung injury in mice after intestinal ischemia and reperfusion

RATIONALE

Milk fat globule epidermal growth factor 8 (MFG-E8) is a potent opsonin for the clearance of apoptotic cells and is produced by mononuclear cells of immune competent organs including the spleen and lungs. It attenuates chronic and acute inflammation such as autoimmune glomerulonephritis and bacterial sepsis by enhancing apoptotic cell clearance. Ischemia-reperfusion (I/R) injury of the gut results in severe inflammation, apoptosis, and remote organ damage, including acute lung injury (ALI).

OBJECTIVES

To determine whether MFG-E8 attenuates intestinal and pulmonary inflammation after gut I/R.

METHODS

Wild-type (WT) and MFG-E8(-/-) mice underwent superior mesenteric artery occlusion for 90 minutes, followed by reperfusion for 4 hours. A group of WT mice was treated with 0.4 microg/20 g recombinant murine MFG-E8 (rmMFG-E8) at the beginning of reperfusion. Four hours after reperfusion, MFG-E8, cytokines, myeloperoxidase activity, apoptosis, and histopathology were assessed. A 24-hour survival study was conducted in rmMFG-E8- and vehicle-treated WT mice.

MEASUREMENTS AND MAIN RESULTS

Mesenteric I/R caused severe widespread injury and inflammation of the small intestines and remote organs, including the lungs. MFG-E8 levels decreased in the spleen and lungs by 50 to 60%, suggesting impaired apoptotic cell clearance. Treatment with rmMFG-E8 significantly suppressed inflammation (TNF-alpha, IL-6, IL-1beta, and myeloperoxidase) and injury of the lungs, liver, and kidneys. MFG-E8-deficient mice suffered from greatly increased inflammation and potentiated ALI, whereas treatment with rmMFG-E8 significantly improved the survival in WT mice.

CONCLUSIONS

MFG-E8 attenuates inflammation and ALI after gut I/R and may represent a novel therapeutic agent.

Human adrenomedullin combined with human adrenomedullin binding protein-1 is protective in gut ischemia and reperfusion injury in the rat

Previous studies have demonstrated that co-administration of rat adrenomedullin (AM) and human AM binding protein-1 (AMBP-1) has various beneficial effects following adverse circulatory conditions. In order to reduce rat proteins to elicit possible immune responses in humans, we determined the effect of human AM combined with human AMBP-1 after intestinal ischemia and reperfusion (I/R). Intestinal ischemia was induced in the rat by occluding the superior mesenteric artery for 90 min. At 60 min after the beginning of reperfusion, human AM/AMBP-1 at 3 different dosages was administered intravenously over 30 min. At 240 min after the treatment, blood and tissue samples were harvested and measured for pro-inflammatory cytokines (i.e., TNF-alpha and IL-6), myeloperoxidase activities in the gut and lungs, and cleaved caspase-3 expression in the lungs, as well as serum levels of hepatic enzymes and lactate. In additional groups of animals, a 10-day survival study was conducted. Results showed that administration of human AM/AMBP-1 reduced pro-inflammatory cytokines, attenuated organ injury, and improved the survival rate in a seemingly dose-response fashion. Co-administration of the highest dose of human AM/AMBP-1 in this study had the optimal therapeutic effect in the rat model of intestinal I/R.

Lung injury after ischemia-reperfusion of small intestine in rats involves apoptosis of type II alveolar epithelial cells mediated by TNF-alpha and activation of Bid pathway

Although ischemia-reperfusion (I/R) of small intestine is known to induce lung cell apoptosis, there is little information on intracellular and extracellular molecular mechanisms. Here, we investigated the mechanisms of apoptosis including the expression of Fas, Fas ligand (FasL), Bid, Bax, Bcl-2, cytochrome c, and activated caspase-3 in the rat lung at various time-points (0-24 h) of reperfusion after 1-h ischemia of small intestine. As assessed by TUNEL, the number of apoptotic epithelial cells, which were subsequently identified as type II alveolar epithelial cells by electron microscopy and immunohistochemical double-staining, increased at 3 h of reperfusion in the lung. However, intravenous injections of anti-TNF-alpha antibody decreased the number of TUNEL-positive cells, indicating involvement of tumor necrosis factor-alpha (TNF-alpha) in the induction of lung cell apoptosis. Western blotting and/or immunohistochemistry revealed a marked up-regulation of Fas, FasL, Bid, Bax, cytochrome c and activated caspase-3 and down-regulation of Bcl-2 in lung epithelial and stromal cells at 3 h of reperfusion. Our results indicate that I/R of small intestine results in apoptosis of rat alveolar type II cells through a series of events including systemic TNF-alpha, activation of two apoptotic signaling pathways and mitochondrial translocation of Bid.

L-Lactate After Embolization of the Superior Mesenteric Artery

BACKGROUND

Plasma markers for intestinal ischemia have not proven to be accurate. The value of L-lactate is unclear. Experimental models based on open surgery confound the effects of surgical trauma with that of ischemia. The aim was to create an endovascular model for acute superior mesenteric artery thromboembolism, and then to study L-lactate and lactate dehydrogenase (LD) activity in plasma and peritoneal fluid in pigs with extensive, high-grade intestinal ischemia.

MATERIALS AND METHODS

Nine pigs underwent full superior mesenteric artery embolization with 4 h of intended intestinal ischemia, whereas six were control animals. Sampling of central venous and arterial blood was performed throughout the experiment, ending with laparotomy to collect peritoneal fluid and segmental intestinal biopsies. A pathologist, blinded to the performed interventions, graded the ischemic lesions.

RESULTS

There were no differences in plasma L-lactate (P = 0.61) or LD activity levels (P = 0.69), measured at different time points from baseline to end of study, between animals with extensive, high-grade intestinal ischemia and sham. Intraperitoneal L-Lactate (P = 0.005) and LD activity (P = 0.018) levels were elevated compared with sham. There were differences in grades of ischemia in the duodenum (P = 0.003), small intestine (P < 0.001), proximal (P < 0.001), and sigmoid (P = 0.032) colon between experimental animals and sham. The grade of small bowel ischemia (n = 15) correlated to intraperitoneal fluid L-lactate (r = 0.80; P < 0.001) and LD activity levels (r = 0.72; P = 0.003).

CONCLUSIONS

This endovascular study in a porcine model showed that L-lactate and LD activity levels in peritoneal fluid, not in plasma, reflect intestinal ischemia. The study suggests that plasma L-lactate not is a useful early marker in patients with suspicion of intestinal ischemia.