Lung inflammation is induced by renal ischemia and reperfusion injury as part of the systemic inflammatory syndrome

NaHS protects brain, heart, and lungs as remote organs from renal ischemia/reperfusion-induced oxidative stress in male and female rats

Acute Kidney Injury (AKI) is frequently observed in hospitalized patients in intensive care units, often caused by renal ischemia-reperfusion injury (IRI). IRI disrupts the function of various 'remote organs' such as the lungs, pancreas, intestine, liver, heart, and brain through inflammation, oxidative stress, apoptosis, leukocyte infiltration, and increased urea and creatinine levels. Gender differences in renal IRI-induced injury are noted. H2S, an endogenous gaseous modulator, shows potential in vasodilation, bronchodilation, and hypotension and can regulate apoptosis, inflammation, angiogenesis, metabolism, and oxidative stress. This study aims to investigate the protective effects of NaHS on brain, heart, and lung injuries following renal IR and to assess the oxidative system status as a potential mechanism in male and female rats.Forty-eight Wistar rats were randomly divided into eight groups (n = 6): Control/Saline, Sham/Saline, IR/Saline, and IR/NaHS in both sexes. Forty-five minutes of bilateral renal ischemia followed by 24-hour reperfusion was induced in the IR groups. NaHS (100µM/Kg, IP) was administered 10 min before clamp release in treated groups. BUN, SCr, BUN/SCr, albuminuria, histopathology, and oxidative stress biomarkers of the brain, heart, and lung were assessed as remote organs. IR increased serum markers of renal function, albuminuria, malondialdehyde levels, and tissue injury scores while reducing nitrite levels and superoxide dismutase and glutathione peroxidase activities. NaHS treatment reversed the adverse effects of IR in remote organs in both sexes, although it showed limited improvement in renal function. Our findings demonstrate that NaHS has a beneficial effect on remote organ injury following renal IR by mitigating oxidative stress, with noted tissue-specific and gender-specific differences in response. These findings suggest NaHS as a potential therapeutic agent for mitigating multi-organ injury after renal IR, with effects varying by tissue and gender.

Sevoflurane protects against ischemia-reperfusion injury in mice after total knee arthroplasty via facilitating RASD1-mediated protein kinase A pathway activation

This study aimed to explore effects of Sevoflurane on ischemia-reperfusion (I/R) injury after total knee arthroplasty (TKA). To explore potential molecular mechanism, Ras related dexamethasone induced 1 (RASD1), a Protein kinase A (PKA) activator, frequently associated with various models of I/R injury, was also investigated. In vivo mouse models with I/R injury after TKA and in vitro cell models with I/R injury were induced. Contents of creatinine kinase (CK), lactic dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA), serum levels of inflammatory factors, expression of PKA pathway-related genes and cell proliferation and apoptosis were measured. RASD1 was altered and PKA pathway was inhibited in mice and cells to elucidate the involvement of RASD1 and PKA pathway in Sevoflurane treatment on I/R injury. RASD1 was upregulated in I/R injury after TKA. Sevoflurane treatment or silencing RASD1 reduced RASD1 expression, CK, LDH and MDA contents, inflammation, apoptosis, but increased proliferation, SOD content, cAMP expression, and extents of PKA and cAMP responsive element binding protein (CREB) phosphorylation in skeletal muscle cells of I/R injury. Additionally, PKA pathway activation potentiated the therapeutic effect of Sevoflurane on I/R injury after TKA. Altogether, Sevoflurane treatment confines I/R injury after TKA via RASD1-mediated PKA pathway activation.

Identifying pathophysiological bases of disease in COVID-19

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus that can affect lung physiology encompassing a wide spectrum of severities, ranging from asymptomatic and mild symptoms to severe and fatal cases; the latter including massive neutrophil infiltration, stroke and multiple organ failure. Despite many recents findings, a clear mechanistic description underlying symptomatology is lacking. In this article, we thoroughly review the available data involving risk factors, age, gender, comorbidities, symptoms of disease, cellular and molecular mechanisms and the details behind host/pathogen interaction that hints at the existence of different pathophysiological mechanisms of disease. There is clear evidence that, by targeting the angiotensin-converting enzyme II (ACE2) -its natural receptor-, SARS-CoV-2 would mainly affect the renin-angiotensin-aldosterone system (RAAS), whose imbalance triggers diverse symptomatology-associated pathological processes. Downstream actors of the RAAS cascade are identified, and their interaction with risk factors and comorbidities are presented, rationalizing why a specific subgroup of individuals that present already lower ACE2 levels is particularly more susceptible to severe forms of disease. Finally, the notion of endotype discovery in the context of COVID-19 is introduced. We hypothesize that COVID-19, and its associated spectrum of severities, is an umbrella term covering different pathophysiological mechanisms (endotypes). This approach should dramatically accelerate our understanding and treatment of disease(s), enabling further discovery of pathophysiological mechanisms and leading to the identification of specific groups of patients that may benefit from personalized treatments.

Electroacupuncture pre‑conditioning protects from lung injury induced by limb ischemia/reperfusion through TLR4 and NF‑κB in rats

Limb ischemia/reperfusion (I/R) can induce inflammation, causing acute lung injury. The Toll-like receptor 4 (TLR4)/NF-κB pathway plays an important role in acute and chronic inflammatory disorders. Several studies have demonstrated the efficacy of acupuncture in lung inflammatory injury. The aim of the present study was to elucidate the mechanism underlying the protective effect of electroacupuncture (EA) against lung injury induced by limb I/R. EA applied at the Zusanli and Sanyinjiao acupoints attenuated lung injury and decreased the secretion of inflammatory factors such as tumor necrosis factor-α, interleukin (IL)-1, IL-6 and myeloperoxidase. Moreover, the expression levels of TLR4 and NF-κB were suppressed by EA. Thus, the present findings suggested that EA can reduce pulmonary inflammation induced by limb I/R injury, possibly via the inhibition of the TLR4/NF-κB pathway.

Propofol post-conditioning lessens renal ischemia/reperfusion-induced acute lung injury associated with autophagy and apoptosis through MAPK signals in rats

Renal Ischemia/Reperfusion (rI/R)-induced acute lung injury (ALI) is a major problem in rI/R. The objective of the current study was to explore the defensive roles of propofol (Pro), an intravenous anesthetic, on rI/R-induced ALI through mitogen-activated protein kinase (MAPK) signaling. Rats were divided into Sham, Pro (10 mg/kg), rI/R, rI/R + Pro (5 mg/kg), and rI/R + Pro (10 mg/kg) groups. Rats were treated with Pro at 1 h after rI/R treatment. Serum and lung tissues at 24 h after rI/R were collected to evaluate morphological changes and the expression of myeloperoxidase (MPO), inflammatory cytokines, and crucial proteins in the MAPK pathway. Pro attenuated the production of mediators, resulting in reduced levels of autophagy and apoptosis by restricting the MAPK pathway in rI/R-induced ALI model. Pro represses rI/R-induced pulmonary autophagy and apoptosis by decreasing the production of inflammatory molecules, and the effects of Pro are involved in the inhibition of the MAPK pathway.

Inflammation in Renal Diseases: New and Old Players

Inflammation, a process intimately linked to renal disease, can be defined as a complex network of interactions between renal parenchymal cells and resident immune cells, such as macrophages and dendritic cells, coupled with recruitment of circulating monocytes, lymphocytes, and neutrophils. Once stimulated, these cells activate specialized structures such as Toll-like receptor and Nod-like receptor (NLR). By detecting danger-associated molecules, these receptors can set in motion major innate immunity pathways such as nuclear factor ĸB (NF-ĸB) and NLRP3 inflammasome, causing metabolic reprogramming and phenotype changes of immune and parenchymal cells and triggering the secretion of a number of inflammatory mediators that can cause irreversible tissue damage and functional loss. Growing evidence suggests that this response can be deeply impacted by the crosstalk between the kidneys and other organs, such as the gut. Changes in the composition and/or metabolite production of the gut microbiota can influence inflammation, oxidative stress, and fibrosis, thus offering opportunities to positively manipulate the composition and/or functionality of gut microbiota and, consequentially, ameliorate deleterious consequences of renal diseases. In this review, we summarize the most recent evidence that renal inflammation can be ameliorated by interfering with the gut microbiota through the administration of probiotics, prebiotics, and postbiotics. In addition to these innovative approaches, we address the recent discovery of new targets for drugs long in use in clinical practice. Angiotensin II receptor antagonists, NF-ĸB inhibitors, thiazide diuretics, and antimetabolic drugs can reduce renal macrophage infiltration and slow down the progression of renal disease by mechanisms independent of those usually attributed to these compounds. Allopurinol, an inhibitor of uric acid production, has been shown to decrease renal inflammation by limiting activation of the NLRP3 inflammasome. So far, these protective effects have been shown in experimental studies only. Clinical studies will establish whether these novel strategies can be incorporated into the arsenal of treatments intended to prevent the progression of human disease.

PRR34-AS1 overexpression promotes protection of propofol pretreatment against ischemia/reperfusion injury in a mouse model after total knee arthroplasty via blockade of the JAK1-dependent JAK-STAT signaling pathway

Long noncoding RNAs have been documented to be protective against ischemia/reperfusion (I/R) injury. However, few research works have focused on the protective effects of PRR34-AS1 on I/R injury after total knee arthroplasty (TKA). The objective of the present study was to investigate the possible effect of PRR34-AS1 on I/R injury after TKA. A mouse model with I/R injury after TKA was established. The interaction between PRR34-AS1 and Janus kinase 1 (JAK1) was examined and thoroughly investigated. Next, the effects of PRR34-AS1 on the expression of apoptosis-related proteins, JAS-signal transducer and activator of transcription (STAT) signaling pathways, and inflammation-related genes, chondrocyte proliferation, and apoptosis were analyzed after gain- and loss-of-function experiments. Attenuated symptoms were observed in mice pretreated with propofol, which was evidenced by decreased positive expression rate of JAK1 protein and superoxide dismutase content along with increased malondialdehyde content and IL-10 levels. PRR34-AS1 was poorly expressed in mice with I/R injury after TKA. JAK1 was a target of PRR34-AS1. Upregulated PRR34-AS1 diminished expression of JAK1, STAT1, JAK2, and STAT3 as well as cell apoptosis, while enhancing cell proliferation in vitro. Furthermore, JAK1 silencing could reverse the suppressed cell proliferation and enhanced cell apoptosis of chondrocytes imposed by silencing PRR34-AS1. Upregulation of PRR34-AS1 can potentially relieve I/R injury after TKA in mice pretreated with propofol through inhibition of the JAS-STAT signaling pathway by targeting JAK1.

The aquaporin 5 -1364A/C promoter polymorphism impacts on resolution of acute kidney injury in pneumonia evoked ARDS

Background

Aquaporin 5 (AQP5) expression impacts on cellular water transport, renal function but also on key mechanisms of inflammation and immune cell migration that prevail in sepsis and ARDS. Thus, the functionally relevant AQP5 -1364A/C promoter single nucleotide polymorphism could impact on the development and resolution of acute kidney injury (AKI). Accordingly, we tested the hypothesis that the AQP5 promoter -1364A/C polymorphism is associated with AKI in patients suffering from pneumonia evoked ARDS.

Methods

This prospective study included 136 adult patients of Caucasian ethnicity with bacterially evoked pneumonia resulting in ARDS. Blood sampling was performed within 24 hours of ICU admission and patients were genotyped for the AQP5 promoter -1364A/C single nucleotide polymorphism. The development of an AKI and the cumulative net fluid balance was described over a 30-day observation period and compared between the AA and AC/CC genotypes, and between survivors and non-survivors.

Results

Incidence of an AKI upon admission did not differ in AA (58%) and AC/CC genotype carriers (60%; p = 0.791). However, on day 30, homozygous AA genotypes (57%) showed an increased prevalence of AKI compared to AC/CC genotypes (24%; p = 0.001). Furthermore, the AA genotype proved to be a strong, independent risk factor for predicting AKI persistence (odds-ratio: 3.35; 95%-CI: 1.2–9.0; p = 0.017). While a negative cumulative fluid balance was associated with increased survival (p = 0.001) the AQP5 promoter polymorphism had no impact on net fluid balance (p = 0.96).

Conclusions

In pneumonia evoked ARDS, the AA genotype of the AQP5 promoter polymorphism is associated with a decreased recovery rate from AKI and this is independent of fluid balance. Consequently, the role of AQP5 in influencing AKI likely rests in factors other than fluid balance.

Effect of Combined Treatment of Ketorolac and Remote Ischemic Preconditioning on Renal Ischemia-Reperfusion Injury in Patients Undergoing Partial Nephrectomy: Pilot Study

We evaluated postoperative renal function in patients with/without combined therapy of ketorolac and remote ischemic preconditioning during partial nephrectomy. Sixteen patients were randomly allocated to either the ketorolac combined with RIPC group (KI, n = 8) or control group (n = 8). The KI group received both remote ischemic preconditioning before surgery and intravenous ketorolac of 1 mg/kg before renal artery clamping. Renal parameters were measured before induction, after anesthesia induction, and 2, 12, 24, 48, and 72 h after renal artery declamping. Acute kidney injury was assessed by Acute Kidney Injury Network criteria. The estimated glomerular filtration rate decreased in both groups, but then increased significantly at 48 h and 72 h after declamping only in the KI group compared to 24 h (p = 0.001 and p = 0.016). Additionally, it was higher at 48 h and 72 h after declamping in the KI group compared to the control group (p = 0.025 and p = 0.044). The incidence of acute kidney injury was significantly reduced in the KI group (13%) compared to the control group (83%) (p = 0.026). FE_Na was markedly increased at 2 h after declamping, and recovered in both groups, but it was more significant at 12 h after declamping in the KI group (p = 0.022). Urinary N-acetyl-1-β-D-glucosoaminidase and serum neutrophil gelatinase-associated lipocalin were similar (p = 0.291 and p = 0.818). There is a possibility that combined therapy of ketorolac and remote ischemic preconditioning prior to ischemia may alleviate renal dysfunction and reduce the incidence of acute kidney injury in patients undergoing partial nephrectomy.

Nephrogenic acute respiratory distress syndrome: A narrative review on pathophysiology and treatment

The kidneys have a close functional relationship with other organs especially the lungs. This connection makes the kidney and the lungs as the most organs involved in the multi-organ failure syndrome. The combination of acute lung injury (ALI) and renal failure results a great clinical significance of 80% mortality rate. Acute kidney injury (AKI) leads to an increase in circulating cytokines, chemokines, activated innate immune cells and diffuse of these agents to other organs such as the lungs. These factors initiate pathological cascade that ultimately leads to ALI and acute respiratory distress syndrome (ARDS). We comprehensively searched the English medical literature focusing on AKI, ALI, organs cross talk, renal failure, multi organ failure and ARDS using the databases of PubMed, Embase, Scopus and directory of open access journals. In this narrative review, we summarized the pathophysiology and treatment of respiratory distress syndrome following AKI. This review promotes knowledge of the link between kidney and lung with mechanisms, diagnostic biomarkers, and treatment involved ARDS induced by AKI.

Lipid emulsion mitigates impaired pulmonary function induced by limb I/R in rats through attenuation of local cellular injury and the subsequent systemic inflammatory response/inflammation

Background

Limb ischemia/reperfusion causes inflammation and elicits oxidative stress that may lead to local tissue damage and remote organ such as lung injury. This study investigates pulmonary function after limb ischemia/reperfusion and the protective effect of a lipid emulsion (Intralipid).

Methods

Twenty-four rats were divided into three groups: sham operation group (group S), ischemia/reperfusion group (group IR), and lipid emulsion treatment group (group LE). limb ischemia/reperfusion was induced through occlusion of the infrarenal abdominal aorta for 3 h. The microvascular clamp was removed carefully and reperfusion was provided for 3 h.

Results

The mean arterial pressure in group LE was higher than group IR during the reperfusion period (P = 0.024). The heart rate of both group LE and IR are significantly higher than group S during the ischemia period(P < 0.001, P < 0.001, respectively). The arterial oxygen pressure of group LE was significantly higher than group IR (P = 0.003), the arterial carbon dioxide pressure of group LE were lower than that of group IR (P = 0.005). The concentration of plasma interleukin-6, tumor necrosis factor-α and malondialdehyde in group LE were significantly lower than group IR (P < 0.001, P = 0.009 and 0.029, respectively). The plasma superoxide dismutase activity in group LE was significantly higher than group IR (P = 0.029). The myeloperoxidase activity in lung tissues of group LE was significantly less than group IR (P = 0.046). Both muscle and lung in group IR were damaged seriously, whereas lipid emulsion (Intralipid) effectively reversed the damage. In summary, Intralipid administration resulted in several beneficial effects as compared to group IR, such as the pulmonary gas exchange and inflammatory.

Conclusions

The ischemic/reperfusion injury of limb muscles with resultant inflammatory damage to lung tissue can be mitigated by administration of a lipid emulsion (Intralipid, 20%, 5 ml/kg). The mechanisms attenuating such a physiological may be attributed to reduction of the degree of limb injury through a decrease in the release of local inflammatory mediators, a reduction of lipid peroxidation, and a blunting of the subsequent remote inflammatory response.

Renal ischemia/reperfusion against nephrectomy for induction of acute lung injury in rats

PURPOSE

Acute kidney injury (AKI) induces acute lung injury (ALI) through releasing injurious mediators or impairing clearance of systemic factors. To determine the links between AKI and ALI, pulmonary and blood variables were evaluated following induction of AKI via different experimental models of bilateral renal ischemia/reperfusion (BIR: renal ischemia with uremia), unilateral renal ischemia/reperfusion (UIR: renal ischemia without uremia), bilateral nephrectomy (BNX: uremia without renal ischemia), and unilateral nephrectomy (UNX: without uremia and renal ischemia).

METHODS

Ninety male Sprague-Dawley rats were divided into six groups. Animals had 1-h bilateral or 2-h unilateral renal ischemia followed by 24-h reperfusion in the BIR and UIR groups, respectively, and 24-h period following bilateral or unilateral nephrectomy in the BNX and UNX groups, respectively. There were also sham and control groups with and without sham-operation, respectively.

RESULTS

Plasma malondialdehyde and nitric oxide were elevated by BIR more than UIR, but not changed by UNX and BNX. UIR slightly increased plasma creatinine, whereas BIR and BNX largely increased plasma creatinine, urea, K⁺and osmolality and decreased arterial HCO₃^-, pH, and CO₂. UNX and UIR did not affect lung, but BIR and BNX induced ALI with equal capillary leak and macrophages infiltration. However, there were more prominent lung edema and vascular congestion following BNX and more severe neutrophils infiltration and P_aO₂/F_iO₂ reduction following BIR.

CONCLUSION

Acutely accumulated systemic mediators following renal failure in the absence of kidneys vary from those due to combined renal failure with ischemic-reperfused kidneys and consequently they induce ALI with distinct characteristics.

Analysis of the effects of topical renal hypothermia on lung tissue after kidney ischemia and reperfusion in rats

PURPOSE

To evaluate whether topical renal hypothermia (TRH) at different levels of temperature has protective effects on lung tissue after renal I/R, through an analysis of organ histology and inflammatory markers in lung tissue.

METHODS

Twenty-eight male Wistar rats were randomly allocated across four groups and subjected to renal ischemia at different levels of topical renal temperature: normothermia (no cooling, 37°C), mild hypothermia (26°C), moderate hypothermia (15°C), and deep hypothermia (4°C). To induce I/R, the vessels supplying the left kidney of each animal were clamped for 40 minutes, followed by reperfusion. After four hours, another procedure was performed to harvest the tissues of interest. TNF-α, IL-1β and myeloperoxidase activity were measured in lung tissue. Histological analysis was performed in hematoxylin and eosin-stained lung specimens.

RESULTS

Induction of renal I/R under deep topical hypothermia resulted in a significant decrease in lung concentrations of TNF-α compared with normothermic I/R (p<0.05). A trend toward significant correlation was found between lung IL-1β concentration and intensity of hypothermia (Spearman r=-0.37; p=0.055). No difference was found in myeloperoxidase activity or histologic injury between groups.

CONCLUSION

Topical renal hypothermia reduces activation of the inflammatory cascade in the lung parenchyma. However, tissue-protective effects were not observed.

Distant effects of unilateral renal ischemia/reperfusion on contralateral kidney but not lung in rats: the roles of ROS and iNOS

Acute kidney injury is usually associated with distant organ dysfunction. The roles of inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) in this phenomenon were investigated following 2 h unilateral renal ischemia and 24 h reperfusion. There were 3 groups of rats subjected to either unilateral ischemia/reperfusion (UIR group), unilateral nephrectomy (UNX group), or sham operation. Two further groups were given α-tocopherol and aminoguanidine with UIR (treated-UIR group) and UNX (treated-UNX group). Plasma nitrite/nitrate and malondialdehyde were elevated only in the UIR group. Creatinine clearance and blood flow increased in non-ischemic kidney of the UIR, but not to the same extent as remnant kidney of the UNX group, while they had equal compensatory rises in absolute Na(+) and K(+) excretion and urine flow. Non-ischemic kidney of the treated-UIR group, but not remnant kidney of the treated-UNX group, showed more elevation in blood flow, whereas both kidneys had reductions in absolute Na(+) excretion and urine flow. Respiratory functional variable were not different between all groups. Therefore, 2 h unilateral renal ischemia and 24 h reperfusion did not affect lung but had distant effects on contralateral kidney partly mediated by ROS and NO-derived from iNOS to dampen compensatory increases in renal hemodynamics and to decrease tubular reabsorption.

Effects of atrial natriuretic peptide on inter-organ crosstalk among the kidney, lung, and heart in a rat model of renal ischemia-reperfusion injury

Background

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury and a frequent occurrence in critically ill patients. Renal IRI releases proinflammatory cytokines within the kidney that induce crosstalk between the kidney and other organ systems. Atrial natriuretic peptide (ANP) has anti-inflammatory as well as natriuretic effects and serves important functions as a regulator of blood pressure, fluid homeostasis, and inflammation. The objective of the present study was to elucidate whether ANP post-treatment attenuates kidney-lung-heart crosstalk in a rat model of renal IRI.

Methods

In experiment I, a rat model of unilateral renal IRI with mechanical ventilation was prepared by clamping the left renal pedicle for 30 min. Five minutes after clamping, saline or ANP (0.2 μg/kg/min) was infused. The hemodynamics, arterial blood gases, and plasma concentrations of lactate and potassium were measured at baseline and at 1, 2, and 3 h after declamping. The mRNA expression and localization of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in the kidney, lung, and heart were examined. In experiment II, a rat model of bilateral renal IRI without mechanical ventilation was prepared by clamping bilateral renal pedicles for 30 min. Thirty minutes after clamping, lactated Ringer's (LR) solution or ANP (0.2 μg/kg/min) was infused. Plasma concentrations of TNF-α, IL-6, and IL-1β were determined at baseline and at 3 h after declamping.

Results

In unilateral IRI rats with mechanical ventilation, ANP inhibited the following changes induced by IRI: metabolic acidosis; pulmonary edema; increases in lactate, creatinine, and potassium; and increases in the mRNA expression of TNF-α, IL-1β, and IL-6 in the kidney and lung and IL-1β and IL-6 in the heart. It also attenuated the histological localization of TNF-α, IL-6, and nuclear factor (NF)-κB in the kidney and lung. In bilateral IRI rats without mechanical ventilation, ANP attenuated the IRI-induced increases of the plasma concentrations of potassium, IL-1β, and IL-6.

Conclusions

Renal IRI induced injury in remote organs including the lung and the contralateral kidney. ANP post-treatment ameliorated injuries in these organs by direct tissue protective effect and anti-inflammatory effects, which potentially inhibited inter-organ crosstalk.

Hyper-inflammation and skin destruction mediated by rosiglitazone activation of macrophages in IL-6 deficiency

Injury initiates recruitment of macrophages to support tissue repair; however, excessive macrophage activity may exacerbate tissue damage causing further destruction and subsequent delay in wound repair. Here we show that the peroxisome proliferation–activated receptor-γ agonist, rosiglitazone (Rosi), a medication recently reintroduced as a drug to treat diabetes and with known anti-inflammatory properties, paradoxically generates pro-inflammatory macrophages. This is observed in both IL-6-deficient mice and control wild-type mice experimentally induced to produce high titers of auto-antibodies against IL-6, mimicking IL-6 deficiency in human diseases. IL-6 deficiency when combined with Rosi-mediated upregulation of suppressor of cytokine signaling 3 leads to an altered ratio of nuclear signal transducer and activator of transcription 3/NF-κB that allows hyper-induction of inducible nitric oxide synthase (iNOS). Macrophages activated in this manner cause de novo tissue destruction, recapitulating human chronic wounds, and can be reversed in vivo by recombinant IL-6, blocking macrophage infiltration, or neutralizing iNOS. This study provides insight into an unanticipated paradoxical role of Rosi in mediating hyper-inflammatory macrophage activation significant for diseases associated with IL-6 deficiency.

Celastrol protects kidney against ischemia-reperfusion-induced injury in rats

BACKGROUND

Ischemia-reperfusion (IR) causes various damages in renal tissues, which is exacerbated by hypoxia-induced excessive inflammation and deteriorates the prognosis of patients after kidney surgery. Celastrol is a potent inflammation inhibitor that has little toxicity. In this report, we investigated whether celastrol protects against IR-induced renal injury in rats.

MATERIALS AND METHODS

Renal IR injury was induced by occlusion of the bilateral renal pedicles for 45 min followed by reperfusion for 6 h. Celastrol or vehicle solution was intraperitoneally injected 30 min before renal ischemia, respectively. Renal histology, function, and pro-inflammatory cytokines and mediators were assessed. The effect of celastrol on nuclear translocation of nuclear factor kappa B (NF-κB) was also measured.

RESULTS

Celastrol significantly suppressed elevation of the renal function markers and the lipid peroxidation level, alleviated renal tubular damage, and decreased the levels of tumor necrosis factor-α, interleukin-1β, and monocyte chemotactic protein-1 (MCP-1) messenger RNA in kidney caused by IR. Moreover, celastrol prevented IR-induced expression of pro-inflammatory mediators, which was associated with suppression of nuclear translocation of NF-κB subunit p65.

CONCLUSIONS

Celastrol ameliorated the acute kidney injury caused by IR, which was associated with inhibiting local NF-κB activation and inflammation. Our findings suggest that celastrol could be useful for preventing IR-induced renal injury.

Atrial natriuretic peptide attenuates kidney-lung crosstalk in kidney injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury after cardiovascular surgery, which in turn deteriorates oxygenation. Atrial natriuretic peptide (ANP) has natriuretic, diuretic, and anti-inflammatory effects. To elucidate whether renal IRI induces inflammation in the kidney and lung and ANP attenuates kidney-lung crosstalk.

MATERIALS AND METHODS

The rats were anesthetized, tracheostomized, mechanically ventilated, and randomized to four groups: saline + IRI (n = 12), ANP + IRI (n = 12), ANP + sham (n = 6), and saline + sham (n = 6). Saline (6 mL/kg/h) or ANP (0.2 μg/kg/min) at the rate of 6 mL/kg/h was started 5 min before clamping, respectively. Renal IRI was induced by clamping the left renal pedicle for 30 min. The hemodynamics, arterial blood gases, and plasma concentrations of creatinine and lactate were measured at baseline and 1, 2, and 3 h after declamping. Lung wet-to-dry ratio was measured. The mRNA expression of tumor necrosis factor (TNF)-α, interleukin (IL) 1β, and IL-6 and histologic localization of TNF-α in the kidney and lung were measured.

RESULTS

Renal IRI induced metabolic acidosis, pulmonary edema, increases in plasma concentrations of creatinine and lactate, and augmentation of the cytokine mRNA expression and histologic localization of TNF-α in the kidney and Renal IRI induced lung. ANP prevented IRI-induced metabolic acidosis, pulmonary edema, increases in creatinine, lactate, and the cytokine mRNA expression, attenuated histologic localization of TNF-α in the kidney and lung, and increased oxygenation.

CONCLUSIONS

ANP has renoprotective and anti-inflammatory effects on the kidney and lung in a rat model of renal IRI, suggesting that ANP attenuates kidney-lung crosstalk.

Antecedent acute kidney injury worsens subsequent endotoxin-induced lung inflammation in a two-hit mouse model

Acute kidney injury (AKI) contributes greatly to morbidity and mortality in critically ill adults and children. Patients with AKI who subsequently develop lung injury are known to suffer worse outcomes compared with patients with lung injury alone. Isolated experimental kidney ischemia alters distal lung water balance and capillary permeability, but the effects of such an aberration on subsequent lung injury are unknown. We present a clinically relevant two-hit murine model wherein a proximal AKI through bilateral renal ischemia (30 min) is followed by a subsequent acute lung injury (ALI) via intratracheal LPS endotoxin (50 μg at 24 h after surgery). Mice demonstrated AKI by elevation of serum creatinine and renal histopathological damage. Mice with ALI and preexisting AKI had increased lung neutrophilia in bronchoalveolar lavage fluid and by myeloperoxidase activity over Sham-ALI mice. Additionally, lung histopathological damage was greater in ALI mice with preexisting AKI than Sham-ALI mice. There was uniform elevation of monocyte chemoattractant protein-1 in kidney, serum, and lung tissue in animals with both AKI and ALI over those with either injury alone. The additive lung inflammation after ALI with antecedent AKI was abrogated in MCP-1-deficient mice. Taken together, our two-hit model demonstrates that kidney injury may prime the lung for a heightened inflammatory response to subsequent injury and MCP-1 may be involved in this model of kidney-lung cross talk. The model holds clinical relevance for patients at risk of lung injury after ischemic injury to the kidney.