Intestinal preconditioning ameliorates ischemia-reperfusion induced acute lung injury in rats: an experimental study

Mitochondrial DNA Release Contributes to Intestinal Ischemia/Reperfusion Injury

Mitochondria release many damage-associated molecular patterns (DAMPs) when cells are damaged or stressed, with mitochondrial DNA (mtDNA) being. MtDNA activates innate immune responses and induces inflammation through the TLR-9, NLRP3 inflammasome, and cGAS-STING signaling pathways. Released inflammatory factors cause damage to intestinal barrier function. Many bacteria and endotoxins migrate to the circulatory system and lymphatic system, leading to systemic inflammatory response syndrome (SIRS) and even damaging the function of multiple organs throughout the body. This process may ultimately lead to multiple organ dysfunction syndrome (MODS). Recent studies have shown that various factors, such as the release of mtDNA and the massive infiltration of inflammatory factors, can cause intestinal ischemia/reperfusion (I/R) injury. This destroys intestinal barrier function, induces an inflammatory storm, leads to SIRS, increases the vulnerability of organs, and develops into MODS. Mitophagy eliminates dysfunctional mitochondria to maintain cellular homeostasis. This review discusses mtDNA release during the pathogenesis of intestinal I/R and summarizes methods for the prevention or treatment of intestinal I/R. We also discuss the effects of inflammation and increased intestinal barrier permeability on drugs.

Phospholipases A2 as biomarkers in ARDS

Acute respiratory distress syndrome (ARDS) is a multifactorial life-threatening lung injury, characterized by diffuse lung inflammation and increased alveolocapillary barrier permeability. The different stages of ARDS have distinctive biochemical and clinical profiles. Despite the progress of our understanding on ARDS pathobiology, the mechanisms underlying its pathogenesis are still obscure. Herein, we review the existing literature about the implications of phospholipases 2 (PLA2s), a large family of enzymes that catalyze the hydrolysis of fatty acids at the sn-2 position of glycerophospholipids, in ARDS-related pathology. We emphasize on the versatile way of participation of different PLA2s isoforms in the distinct ARDS subgroup phenotypes by either potentiating lung inflammation and damage or by preserving the normal lung. Current research supports that PLA2s are associated with the progression and the outcome of ARDS. We herein discuss the transcellular communication of PLA2s through secreted extracellular vesicles and suggest it as a new mechanism of PLA2s involvement in ARDS. Thus, the elucidation of the spatiotemporal features of PLA2s expression may give new insights and provide valuable information about the risk of an individual to develop ARDS or advance to more severe stages, and potentially identify PLA2 isoforms as biomarkers and target for pharmacological intervention.

Higher mini-BAL total protein concentration in early ARDS predicts faster resolution of lung injury measured by more ventilator-free days

The protein concentration of alveolar edema fluid in acute respiratory distress syndrome (ARDS) is dynamic. It reflects alveolar flooding during acute injury, as well as fluid and protein clearance over time. We hypothesized that among ARDS patients treated with low tidal volume ventilation, higher concentrations of protein in mini-bronchoalveolar lavage (mBAL) samples would predict slower resolution of lung injury and worse clinical outcomes. Total protein and IgM concentrations in day 0 mBAL samples from 79 subjects enrolled in the aerosolized albuterol (ALTA) ARDS Network Albuterol Trial were measured by colorimetric assay and ELISA, respectively. Linear regression models were used to test the association of mBAL proteins with clinical outcomes and measures of length of illness, including ventilator-free days (VFDs). Median mBAL total protein concentration was 1,740 μg/ml [interquartile range (IQR): 890-3,170]. Each 500 μg/ml increase in day 0 mBAL total protein was associated with an additional 0.8 VFDs [95% confidence interval (CI): 0.05-1.6, P value = 0.038]. Median mBAL IgM concentration was 410 ng/ml (IQR: 340-500). Each 50 ng/ml increase in mBAL IgM was associated with an additional 1.1 VFDs (95% CI 0.2-2.1, P value = 0.022). These associations remained significant and were not attenuated in multivariate models adjusted for age, serum protein concentration, and vasopressor use in the 24 h before enrollment. Thus, higher mBAL total protein and IgM concentrations at day 0 are associated with more VFDs in patients with ARDS and may identify patients with preserved alveolar epithelial mechanisms for net alveolar fluid clearance.

Impact of remote ischaemic preconditioning on cerebral oxygenation during total knee arthroplasty

Background: Ischaemic reperfusion injury (IRI) after tourniquet release during total knee arthroplasty (TKR) is related to postoperative cerebral complications. Remote ischaemic preconditioning (RIPC) is known to minimise IRI in previous studies. Thus, we evaluated the effect of RIPC on regional cerebral oxygenation after tourniquet release during TKR. Methods: Patients undergoing TKR were randomly allocated to not receive RIPC (control group) and to receive RIPC (RIPC group). Regional cerebral oxygenation and pulmonary oxygenation were assessed up to 24 h postoperatively. The changes in serum cytokine and lactate dehydrogenase (LDH) levels were assessed and arterial blood gas analysis was performed. Total transfusion amounts and postoperative bleeding were also examined. Results: In total, 72 patients were included in the final analysis. Regional cerebral oxygenation (P < 0.001 in the left side, P = 0.003 in the right side) with pulmonary oxygenation (P = 0.001) was significantly higher in the RIPC group. The serum LDH was significantly lower in the RIPC group at 1 h and 24 h postoperatively (P < 0.001). The 24 h postoperative transfusion (P = 0.002) and bleeding amount (P < 0.001) were significantly lower in the RIPC group. Conclusions: RIPC increased cerebral oxygenation after tourniquet release during TKR by improving pulmonary oxygenation. Additionally, RIPC decreased the transfusion and bleeding amount with the serum LDH level.

Ischemic preconditioning modifies mortality and inflammatory response

PURPOSE

To evaluate the effect of ischemic preconditioning on mortality, inflammatory mediators and oxidative stress after intestinal ischemia and reperfusion.

METHODS

Male Wistar rats were allocated according to the period of ischemia with or without ischemic preconditioning which consist on clamping the superior mesenteric artery for 10 minutes followed by reperfusion for 10 minutes before the sustained ischemia period. Mortality was assessed in Phase 1 study, and the CINC-1, CINC-2 and MDA levels in the lungs were analyzed in Phase 2.

RESULTS

Mortality was lower in the ischemic preconditioning group subjected to 90 minutes of ischemia compared to the group without ischemic preconditioning (I-90: 50% and IPC-90: 15%, p=0.018), and it was lower in the ischemic preconditioning group as a whole compared to the groups without ischemic preconditioning (IPC-14% and I=30%, p=0.006). Lower levels of MDA, CINC-1, and CINC-2 were observed in the animals that were subjected to ischemic preconditioning compared to the animals that were not (MDA: I-45=1.23 nmol/mg protein, and IPC-45=0.62 nmol/mg protein, p=0.0333; CINC-1: I-45=0.82 ng/mL and IPC-45=0.67 ng/mL, p=0.041; CINC-2: I-45=0.52 ng/mL and IPC-45=0.35 ng/mL, p=0.032).

CONCLUSION

Ischemic preconditioning reduces mortality, inflammatory process and oxidative stress in rats subjected to intestinal ischemia and reperfusion.

Protective effect of intestinal ischemic preconditioning on ischemia reperfusion-caused lung injury in rats

Intestinal ischemia reperfusion (IR) causes injury of distant critical organs. Remote intestinal ischemic preconditioning (IP) may confer the cytoprotection in critical organs including lung. The authors hypothesized that intestinal IP would be a prophylactic factor in the prevention of distant lung injury induced by IR. Rats were randomly divided into IR, IP, and Sham (S) group. Compared with IR group in the serum and lung tissue, MPO, MDA, TNF-α, and IL-1 levels were significantly decreased in the IP group. Following the same pattern, NO level in the serum and lung tissue was significantly increased in the IP group. And intestinal IP markedly abolished lung injury scores in contrast to IR group. Moreover, intestinal IP significantly attenuated caspase-3 expression, leading to the low expression of Bax and the high expression of Bcl-2. The present study showed that intestinal IP ameliorates the capacity of anti-oxygen free radical, inhibits the release of pro-inflammatory cytokines and alleviates apoptosis in IR-induced lung injury in rats. Intestinal IP may provide a novel prophylactic strategy for treatment of IR-induced lung injury.

Ischemic preconditioning ameliorates intestinal injury induced by ischemia-reperfusion in rats

AIM: To evaluate preventative effects of ischemic preconditioning (IP) in a rat model of intestinal injury induced by ischemia-reperfusion (IR).

METHODS: Male Sprague-Dawley rats (250-300 g) were fasted for 24 h with free access to water prior to the operation. Eighteen rats were randomly divided into three experimental groups: S group (n = 6), rats were subjected to isolation of the superior mesenteric artery (SMA) for 40 min, then the abdomen was closed; IR group (n = 6), rats were subjected to clamping the SMA 40 min, and the abdomen was closed followed by a 4-h reperfusion; IP group (n = 6) rats underwent three cycles of 5 min ischemia and 5 min reperfusion, then clamping of the SMA for 40 min, then the abdomen was closed and a 4-h reperfusion followed. All animals were euthanized by barbiturate overdose (150 mg/kg pentobarbital sodium, i.v.) for tissue collection, and the SMA was isolated via median abdominal incision. Intestinal histologic injury was observed. Malondialdehyde (MDA), myeloperoxidase (MPO) and tumor necrosis factor (TNF)-α concentrations in intestinal tissue were measured. Intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 expression, as well as nuclear factor (NF)-κB activity and expression in intestinal tissue were also determined.

RESULTS: Compared with the IR group, IP reduced IR-induced histologic injury of the intestine in rats (2.00 ± 0.71 vs 3.60 ± 0.84, P < 0.05). IP significantly inhibited the increase in MDA content (5.6 ± 0.15 μmol/L vs 6.84 ± 0.18 μmol/L, P < 0.01), MPO activity (0.13 ± 0.01 U/L vs 0.24 ± 0.01 U/L, P < 0.01), and TNF-α levels (7.79 ± 2.35 pg/mL vs 10.87 ± 2.48 pg/mL, P < 0.05) in the intestinal tissue of rats. IP also markedly ameliorated the increase in ICAM-1 (204.67 ± 53.27 vs 353.33 ± 45.19, P < 0.05) and VCAM-1 (256.67 ± 58.59 vs 377.33 ± 41.42, P < 0.05) protein expression in the intestinal tissues. Additionally, IP remarkably decreased NF-κB activity (0.48 ± 0.16 vs 0.76 ± 0.22, P < 0.05) and protein expression (320.23 ± 38.16 vs 520.76 ± 40.53, P < 0.01) in rat intestinal tissue.

CONCLUSION: IP may protect against IR-induced intestinal injury by attenuation of the neutrophil-endothelial adhesion cascade via reducing ICAM-1 and VCAM-1 expression and TNF-α-induced NF-κB signaling pathway activity.

Pivotal role of mast cell carboxypeptidase A in mediating protection against small intestinal ischemia-reperfusion injury in rats after ischemic preconditioning

AIM OF THE STUDY

Mast cell (MC) degranulation contributes to the protection mediated by ischemic preconditioning (IPC); however, the precise mechanisms underlying this protection remain largely unknown. Mast cell carboxypeptidase A (MC-CPA) is released solely from MCs and plays a critical role in degrading toxins and endothelin 1 (ET-1). The present study sought to explore whether MC-CPA is involved in the process of IPC in a rodent model of small intestinal ischemia reperfusion (IIR) injury.

MATERIALS AND METHODS

IIR injuries were induced in Sprague-Dawley rats by clamping the superior mesenteric artery for 60 min followed by reperfusion for 2 h. One cycle of 10 min intestinal ischemia and 10 min of reperfusion was used in the IPC group, and the MC stabilizer cromolyn sodium and MC potato carboxypeptidase inhibitor were administered before the start of IPC. At the end of experiment, intestine tissue was obtained for assays of the MC-CPA3, tumor necrosis factor-α, interleukin-6, and ET-1 contents and myeloperoxidase activities. Intestinal histologic injury scores and MC degranulation were assessed. Apoptosis indices and cleaved caspase- 3 protein expressions were quantified.

RESULTS

IIR resulted in severe injury, as evidenced by significant increases in injury scores and MC-CPA3, tumor necrosis factor-α, interleukin-6, and ET-1 contents that were accompanied with concomitant elevations in cleaved caspase 3 expression, apoptosis indices, and myeloperoxidase activities. IPC induced a significant increase in MC-CPA3, induced MC degranulation, and attenuated IIR injury by downregulating IIR-induced biochemical changes, whereas cromolyn sodium and potato carboxypeptidase inhibitor abolished the IPC-mediated changes.

CONCLUSIONS

These data suggest that IPC protected against IIR injury via the MC degranulation-mediated release of MC-CPA.

Ischemic preconditioning attenuates remote pulmonary inflammatory infiltration of diabetic rats with an intestinal and hepatic ischemia-reperfusion injury

PURPOSE

To assess ischemic preconditioning (IPC) effects in pulmonary lesion in intestinal and hepatic ischemia-reperfusion (IR) injury models using diabetic rats.

METHODS

Diabetes (DM) was induced in 28 male Wistar rats by alloxan (42 mg/kg, IV). After 28 days, severe DM rats were submitted to intestinal or hepatic IR injury with or without IPC. Intestinal IR (30 min of mesenteric artery occlusion and 30 min of reperfusion; n=6) and IPC groups (10 min ischemia, 10 min reperfusion, followed by intestinal IR; n=6), and Hepatic IR (30 min of hepatic pedicle occlusion and 30 min of reperfusion; n=5) and IPC groups (10 min ischemia, 10 min reperfusion, followed by hepatic IR; n=5), were compared to DM rats group (n=6). Plasmatic lactate, glycemia were measured before and after IR injury. Histomorphology of lung was performed counting inflammatory cells. Data was expressed in mean± SE. P<0.05.

RESULTS

Glycemia and lactate were similar among groups. IPC did not interfere in these parameters. On histological evaluation, IR increased inflammatory cells infiltration in pulmonary parenchyma compared to control in both IR injury models. IPC attenuated inflammatory infiltration in lungs.

CONCLUSION

Ischemic preconditioning protects against remote ischemia-reperfusion injury in lung on intestinal or hepatic ischemia-reperfusion model with acute diabetes.

Alterations of epithelial layer after ischemic preconditioning of small intestine in rats

Ischemic-reperfusion (IR) injury of the small intestine makes a serious complications associated with various surgical procedures and is related to changes in motility, secretory activity and structural alterations. Preconditioning can reduce range of this damage. The aim of the experimental study was to determine the influence of ischemic preconditioning (IPC) on IR injury on jejunal epithelial layer. Wistar rats (n = 56) were divided in two experimental groups. IR group was subjected to 60 min ischemia of cranial mesenteric artery and followed by reperfusion periods: 1,4,8,24 h (IR1, IR4, IR8, IR24). Group with ischemic preconditioning (IPC+IR) was subjected to two subsequent ischemic attacks (12 min) with 10 min of reperfusion between them, and after 2nd attack ischemia was induced for 60 min followed by relevant reperfusion period. IPC showed the protective impact on the jejunal tissue architecture after 1 h reperfusion, when in IR1 group the highest and significant damage was observed (p < 0.001) in contrast to IPC+IR1 group. Histopathological damage of the intestine in pretreated groups was postponed to 4 h of reperfusion. Protective effect of IPC together with later accumulation of injury signs were confirmed by weaker impact on goblet cell (p < 0.001) and Paneth cell populations (p < 0.05).The increased cells proliferation in preconditioned groups came later, but stronger after 8 h of reperfusion (p < 0.001) and after 24 h of reperfusion still remained at the high activity level (p < 0.001). Our experimental results on the histopathological changes in the jejunum during ischemic preconditioning proved that IPC may have a positive effect on maintaining intestinal barrier function.

TLR4 mediates lung injury and inflammation in intestinal ischemia-reperfusion

BACKGROUND

Splanchnic ischemia is common in critically ill patients, and it can result in injury not only of the intestine but also in distant organs, particularly in the lung. Local inflammatory changes play a pivotal role in the development of acute lung injury after intestinal ischemia, but the underlying molecular mechanisms are not fully understood. We sought to examine the role of Toll-like receptor 4 (TLR4) in the mouse model of intestinal ischemia-reperfusion (I/R)-induced lung injury and inflammation.

MATERIALS AND METHODS

Adult male TLR4 mutant (C3H/HeJ) mice and TLR4 wild-type (WT) (C3H/HeOuJ) mice were subjected to 40 min of intestinal ischemia by clamping the superior mesenteric artery followed by 6 h of reperfusion. Lung histology was assessed and parameters of pulmonary microvascular permeability, inflammatory cytokine expression, and neutrophil infiltration were measured. Activation of mitogen-activated protein kinases (MAPKs) and the transcription factors nuclear factor κB (NF-κB) and activator protein-1 (AP-1) in the lungs were also detected.

RESULTS

After intestinal I/R, lungs from TLR4 mutant mice demonstrated a significantly lower histological injury, a marked reduction of epithelial apoptosis associated with the decreased level of cleaved caspase-3 and the increased ratio of Bcl-xL to Bax proteins, and a large reduction in pulmonary vascular permeability and myeloperoxidase (MPO) activity in comparison with WT mice. TLR4 mutant mice also displayed marked decreases in tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2) expression. Following intestinal I/R, phosporylation of p38 MAPK and activation of NF-κB and AP-1 were significantly inhibited in lung tissue from TLR4 mutant mice compared with WT controls.

CONCLUSIONS

These data suggest that TLR4 plays an important role in the pathogenesis of intestinal I/R-induced acute lung injury and inflammation and that p38 kinase and NF-κB may be involved in TLR4 signaling-mediated lung inflammatory processes during intestinal I/R.

Phospholipase A2 subclasses in acute respiratory distress syndrome

Phospholipases A2 (PLA2) catalyse the cleavage of fatty acids esterified at the sn-2 position of glycerophospholipids. In acute lung injury-acute respiratory distress syndrome (ALI-ARDS) several distinct isoenzymes appear in lung cells and fluid. Some are capable to trigger molecular events leading to enhanced inflammation and lung damage and others have a role in lung surfactant recycling preserving lung function: Secreted forms (groups sPLA2-IIA, -V, -X) can directly hydrolyze surfactant phospholipids. Cytosolic PLA2 (cPLA2-IVA) requiring Ca2+ has a preference for arachidonate, the precursor of eicosanoids which participate in the inflammatory response in the lung. Ca(2+)-independent intracellular PLA2s (iPLA2) take part in surfactant phospholipids turnover within alveolar cells. Acidic Ca(2+)-independent PLA2 (aiPLA2), of lysosomal origin, has additionally antioxidant properties, (peroxiredoxin VI activity), and participates in the formation of dipalmitoyl-phosphatidylcholine in lung surfactant. PAF-AH degrades PAF, a potent mediator of inflammation, and oxidatively fragmented phospholipids but also leads to toxic metabolites. Therefore, the regulation of PLA2 isoforms could be a valuable approach for ARDS treatment.