LIPOCALIN-2 is a major acute-phase protein in a rat and mouse model of sterile abscess. Shock. 2012;37:191-196. [PMID: 22249220 DOI: 10.1097/shk.0b013e31823918c2]

Lipocalin-2 as a prognostic biomarker and its association with systemic inflammation in small cell lung cancer

BACKGROUND

Systemic inflammation is believed to contribute to small cell lung cancer (SCLC) progression, but the underlying relationship remains unclear. Lipocalin-2, a potential biomarker of inflammation, has been implicated in various cancers but its prognostic value in SCLC is underexplored.

METHODS

We retrospectively analyzed 191 patients with SCLC (72 with limited-stage [LD] and 119 with extensive-stage) treated using platinum-based chemotherapy. Lipocalin-2 expression was evaluated using immunohistochemistry. Optimal cutoff values for lipocalin-2 and neutrophil-to-lymphocyte ratio (NLR) were determined using time-dependent receiver operating characteristic curve analysis. The pectoralis muscle index was used to assess sarcopenia.

RESULTS

In LD-SCLC, high lipocalin-2 expression was associated with worse progression-free survival (PFS; median: 7.0 vs. 15.9 months, p = 0.015) and overall survival (OS; median: 12.9 vs. 30.3 months, p = 0.035) compared with low lipocalin-2 expression. Patients were stratified into three prognostic groups by combining lipocalin-2 with NLR: low lipocalin-2/low NLR, high lipocalin-2/low NLR or low lipocalin-2/high NLR, and high lipocalin-2/high NLR (median PFS: 17.3 vs. 11.0 vs. 6.3 months, p = 0.004; median OS: 30.5 vs. 17.3 vs. 8.6 months, p = 0.002). Similar trends were observed when combining lipocalin-2 with the pectoralis muscle index. High lipocalin-2 expression was also associated with lower complete response rates (18.9% vs. 34.3%, p = 0.035). No significant prognostic implications were found for lipocalin-2 in extensive-stage SCLC.

CONCLUSIONS

High lipocalin-2 expression is potentially associated with poorer survival in LD-SCLC. Combining lipocalin-2 with other inflammation-related markers could improve prognostic stratification.

RAGE is a critical factor of sex-based differences in age-induced kidney damage

Introduction: Advanced glycation end products (AGEs) are a heterogeneous group of molecules with potential pathophysiological effects on the kidneys. Fibrosis together with the accumulation of AGEs has been investigated for its contribution to age-related decline in renal function. AGEs mediate their effects in large parts through their interactions with the receptor for AGEs (RAGE). RAGE is a transmembrane protein that belongs to the immunoglobulin superfamily and has the ability to interact with multiple pro-inflammatory/pro-oxidative ligands. The role of RAGE in aging kidneys has not been fully characterized, especially for sex-based differences. Methods: Therefore, we analyzed constitutive RAGE knockout (KO) mice in an age- and sex-dependent manner. Paraffin-embedded kidney sections were used for histological analysis and protein expression of fibrosis and damage markers. RNA expression analysis from the kidney cortex was done by qPCR for AGE receptors, kidney damage, and early inflammation/fibrosis factors. FACS analysis was used for immune cell profiling of the kidneys. Results: Histological analysis revealed enhanced infiltration of immune cells (positive for B220) in aged (>70 weeks old) KO mice in both sexes. FACS analysis revealed a similar pattern of enhanced B-1a cells in aged KO mice. There was an age-based increase in pro-fibrotic and pro-inflammatory markers (IL-6, TNF, TGF-β1, and SNAIL1) in KO male mice that presumably contributed to renal fibrosis and renal damage (glomerular and tubular). In fact, in KO mice, there was an age-dependent increase in renal damage (assessed by NGAL and KIM1) that was accompanied by increased fibrosis (assessed by CTGF). This effect was more pronounced in male KO mice than in the female KO mice. In contrast to the KO animals, no significant increase in damage markers was detectable in wild-type animals at the age examined (>70 weeks old). Moreover, there is an age-based increase in AGEs and scavenger receptor MSR-A2 in the kidneys. Discussion: Our data suggest that the loss of the clearance receptor RAGE in male animals further accelerates age-dependent renal damage; this could be in part due to an increase in AGEs load during aging and the absence of protective female hormones. By contrast, in females, RAGE expression seems to play only a minor role when compared to tissue pathology.

Deletion of the P2Y2 receptor aggravates internal elastic lamina calcification in chronic kidney disease mice through upregulation of alkaline phosphatase and lipocalin-2

Calcification of the medial layer, inducing arterial stiffness, contributes significantly to cardiovascular mortality in patients with chronic kidney disease (CKD). Extracellular nucleotides block the mineralization of arteries by binding to purinergic receptors including the P2Y₂ receptor. This study investigates whether deletion of the P2Y₂ receptor influences the development of arterial media calcification in CKD mice. Animals were divided into: (i) wild type mice with normal renal function (control diet) (n = 8), (ii) P2Y₂ R^-/- mice with normal renal function (n = 8), (iii) wild type mice with CKD (n = 27), and (iv) P2Y₂ R^-/- mice with CKD (n = 22). To induce CKD, animals received an alternating (0.2-0.3%) adenine diet for 7 weeks. All CKD groups developed a similar degree of chronic renal failure as reflected by high serum creatinine and phosphorus levels. Also, the presence of CKD induced calcification in the heart and medial layer of the aortic wall. However, deletion of the P2Y₂ receptor makes CKD mice more susceptible to the development of calcification in the heart and aorta (aortic calcium scores (median ± IQR), CKD-wild type: 0.34 ± 4.3 mg calcium/g wet tissue and CKD-P2Y₂ R^-/- : 4.0 ± 13.2 mg calcium/g wet tissue). As indicated by serum and aortic mRNA markers, this P2Y₂ R^-/- mediated increase in CKD-related arterial media calcification was associated with an elevation of calcification stimulators, including alkaline phosphatase and inflammatory molecules interleukin-6 and lipocalin 2. The P2Y₂ receptor should be considered as an interesting therapeutic target for tackling CKD-related arterial media calcification.

ST2 and the alteration of cobalt, sodium, potassium and calcium concentration in acute inflammation

INTRODUCTION

ST2 is the receptor for interleukin (IL)-33, the last discovered member of the IL-1 cytokine family. Acute inflammation is an early response of vascularized tissue to injury, in which alteration of micro- and macro-elements occurs. This study aimed to examine the alteration of cobalt, sodium, potassium, and calcium concentration at the site of acute inflammation and the role of ST2 in these alterations.

MATERIAL AND METHODS

Wild-type (WT) and ST2 knockout (ST2-/-) mice were divided into groups: WT control group (WT-C), ST2 knockout control group (KO-C), WT inflammatory group (WT-I), and ST2 knockout inflammatory group (KO-I). We induced acute inflammation by intramuscular injection of turpentine oil or saline in the case of the control group. After 12 h, we anesthetized mice and collected treated tissues for histopathological analysis and determination of cobalt, sodium, potassium, and calcium concentration by atomic absorption spectrometer.

RESULTS

Histopathological analysis showed the inflammatory infiltrate and cell necrosis in the treated tissue in WT-I and KO-I. The concentration of sodium was significantly lower in WT-I than in WT-C. The concentration of potassium and cobalt was significantly lower in WT-I and KO-I when compared to WT-C and KO-C, respectively. However, the concentration of potassium and cobalt in the tissue was significantly lower in WT-I than in KO-I. The concentration of calcium in the tissue did not significantly differ between groups.

CONCLUSION

We reported, to our knowledge for the first time, that ST2 is involved in decreasing sodium, potassium, and cobalt concentration at the site of acute inflammation.

RNA adenosine deaminase (ADAR1) alleviates high-fat diet-induced nonalcoholic fatty liver disease by inhibiting NLRP3 inflammasome

Nonalcoholic fatty liver disease (NAFLD) is a chronic inflammatory disease in which nucleotide-binding domain of leucine-rich repeat protein 3 (NLRP3) inflammasome plays an important role. The present research was aimed to explore the protective function of ADAR1, an RNA editing enzyme, against inflammatory damages in high-fat diet (HFD)-induced NAFLD through inhibiting NLRP3 inflammasome and subsequent inflammation. A total of 30 patients with NAFLD were investigated, and ADAR1 mRNA expression in peripheral blood monocytes surveyed. The in vivo study used lentivirus to explore the function of ADAR1 overexpression in the HFD-induced mouse model of NAFLD. The in vitro study used lentivirus and siRNA to explore the function of ADAR1 on the NLRP3 inflammasome activation in THP-1 cells. Results shown that the ADAR1 expression was upregulated in NAFLD patients in comparison to healthy controls. In vivo, the upregulation of ADAR1 impaired NLRP3 inflammasome activation and alleviated liver disease in HFD mice in comparison to the control group. Moreover, ADAR1 overexpression attenuated NLRP3 inflammasome in lipopolysaccharide (LPS)+ palmitic acid (PA)-induced THP-1 cells, while ADAR1 knockdown increased the NLRP3 inflammasome activation. Furthermore, we speculated that c-Jun may participate in ADAR1's inhibition of NLRP3 inflammasome. Our results suggested that ADAR1 is a potential treatment target for NAFLD via regulating the activation of NLRP3 inflammasome.

Review of immunological plasma markers for longitudinal analysis of inflammation and infection in rat models

Disease or trauma of orthopedic tissues, including osteomyelitis, osteoporosis, arthritis, and fracture, results in a complex immune response, leading to a change in the concentration and milieu of immunological cells and proteins in the blood. While C-reactive protein levels and white blood cell counts are used to track inflammation and infection clinically, controlled longitudinal studies of disease/injury progression are limited. Thus, the use of clinically-relevant animal models can enable a more in-depth understanding of disease/injury progression and treatment efficacy. Though longitudinal tracking of immunological markers has been performed in rat models of various inflammatory and infectious diseases, currently there is no consensus on which markers are sensitive and reliable for tracking levels of inflammation and/or infection. Here, we discuss the blood markers that are most consistent with other outcome measures of the immune response in the rat, by reviewing their utility for longitudinal tracking of infection and/or inflammation in the following types of models: localized inflammation/arthritis, injury, infection, and injury + infection. While cytokines and acute phase proteins such as haptoglobin, fibrinogen, and α₂ -macroglobulin demonstrate utility for tracking immunological response in many inflammation and infection models, there is likely not a singular superior marker for all rat models. Instead, longitudinal characterization of these models may benefit from evaluation of a collection of cytokines and/or acute phase proteins. Identification of immunological plasma markers indicative of the progression of a pathology will allow for the refinement of animal models for understanding, diagnosing, and treating inflammatory and infectious diseases of orthopedic tissues.

Interleukin-6-Production Is Responsible for Induction of Hepatic Synthesis of Several Chemokines as Acute-Phase Mediators in Two Animal Models: Possible Significance for Interpretation of Laboratory Changes in Severely Ill Patients

Simple Summary

The release of acute-phase proteins and cytokine storms are considered critical parameters for the progression of COVID-19 disease. The increase in the serum levels of cytokines such as IL6 and IL8 observed in patients primarily infected with the SARS-CoV-2 virus has been used to determine the severity of clinical conditions resulting from infection and for prognostic purposes. Animal models have been used to understand the mechanisms of the changes in homeostasis observed under pathological conditions. In the present study, we therefore report the changes in serum levels and hepatic gene expression of cytokines and chemokines in two different animal models of acute-phase responses. The acute-phase response is a transient emergency response aimed at preserving life and bringing about the changes necessary to reduce and repair tissue damage after the removal of damaging noxious agents. Our data suggest that the liver may be responsible for the increase in the serum levels of cytokines and chemokines as part of the body’s defense response to tissue damage. It is therefore doubtful that inhibiting this response at any stage after infection could improve the prognosis of patients. These results may help to interpret the laboratory changes observed in critically ill patients, as may be the case following SARS-CoV-2 infection.

Abstract

A mild to moderate increase in acute-phase proteins (APPs) and a decrease in serum albumin levels are detected in hospitalized COVID-19 patients. A similar trend is also observed for acute-phase cytokines (APC), mainly IL6, besides chemokines (e.g., CXCL8 and CCL2). However, the source of the chemokines in these patients at different stages of disease remains to be elucidated. We investigated hepatic gene expression of CXC- and CC-chemokines in a model of a localized extrahepatic aseptic abscess and in a model of septicemia produced by the intramuscular injection of turpentine oil (TO) into each hindlimb or lipopolysaccharide (LPS) intraperitoneally (i.p.) in rats and mice (wild-type (WT) and IL6-KO). Together with a striking increase in the serum IL6 level, strong serum CXCL2 and CXCL8 concentrations were detected. Correspondingly, rapid (2 h) upregulation of CXCL1, CXCL2, CXCL5, and CXCL8 was observed in rat liver after intramuscular TO injection. The induction of the gene expression of CXCL1 and CXCL8 was the fastest and strongest. The hepatic CXC-chemokines behaved like positive APPs that depend on IL6 production by activated macrophages recruited to extrahepatic damaged tissue. Chemokine upregulation was greatly reduced in IL6-KO mice. However, IL6 was dispensable in the LPS–APR model, as massive induction of hepatic chemokines studied was measured in IL6-KO mice.

Universal Accessible Biomarkers of Drug-Induced Tissue Injury and Systemic Inflammation in Rat: Performance Assessment of TIMP-1, A2M, AGP, NGAL and Albumin

The ability to monitor for general drug-induced tissue injury (DITI) or systemic inflammation in any tissue using blood-based accessible biomarkers would provide a valuable tool in early exploratory animal studies to understand potential drug liabilities. Here we describe the evaluation of four biomarkers of tissue remodeling and inflammation [α2-macroglobin (A2M), α1-acid glycoprotein (AGP), neutrophil gelatinase-associated lipocalin (NGAL) and tissue inhibitor of metalloproteinases (TIMP-1)] as well as the traditional serum parameter albumin as potential blood-based biomarkers of DITI and systemic inflammatory response (SIR). Biomarker performance was assessed in 51 short-term rat in vivo studies with various end-organ toxicities or SIR and receiver operator characteristic (ROC) curves were generated to compare relative performances. All four biomarkers performed well in their ability to detect DITI and SIR with an area under the curve (AUC) of 0.82 - 0.78, however TIMP-1 achieved the best sensitivity (at 95% specificity) of 61%; AGP, NGAL, and A2M sensitivity was 51-52%. AUC for albumin was 0.72 with sensitivity of 39%. A2M was the best performer in studies with only SIR (AUC 0.91). In the subset of studies with drug-induced vascular injury, TIMP-1 performed best with an AUC of 0.96. Poor performance of all tested biomarkers was observed in samples with CNS toxicity. In summary, TIMP-1, A2M, AGP and NGAL demonstrated performance as sensitive accessible biomarkers of DITI and SIR, supporting their potential application as universal accessible tissue toxicity biomarkers to quickly identify dose levels associated with drug-induced injury in early exploratory rat safety and other studies.

Lipocalin-2: a role in hepatic gluconeogenesis via AMP-activated protein kinase (AMPK)

PURPOSE

Evidence is accumulating that lipocalin2 (LCN2) is implicated in insulin resistance and glucose homeostasis, but the underlying possible mechanisms remain unclear. This study is to investigate the possible linkage between LCN2 and AMP-activated protein kinase (AMPK) or forkhead transcription factor O1 (FoxO1), which influences insulin sensitivity and gluconeogenesis in liver.

METHODS

LCN2 knockout (LCN2KO) mice and wild-type littermates were used to evaluate the effect of LCN2 on insulin sensitivity and hepatic gluconeogenesis through pyruvate tolerance test (PTT), glucose tolerance test (ipGTT), insulin tolerance test (ITT), and hyperinsulinemic-euglycemic clamps, respectively. LCN2KO mice and WT mice in vivo, and in vitro HepG2 cells were co-transfected with adenoviral FoxO1-siRNA (Ad-FoxO1-siRNA) or adenovirus expressing constitutively active form of AMPK (Ad-CA-AMPK), or dominant negative adenovirus AMPK (Ad-DN-AMPK), the relative mRNA and protein levels of two key gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6P) were measured.

RESULTS

Improved insulin sensitivity and inhibited gluconeogenesis in the LCN2KO mice were confirmed by pyruvate tolerance tests and hyperinsulinemic-euglycemic clamps. Nuclear FoxO1 and its downstream genes PEECK and G6P were decreased in the livers of the LCN2KO mice, and AMPK activity was stimulated and directly phosphorylated FoxO1. In vitro, AMPK activity was inhibited in HepG2 cells overexpressing LCN2 leading to a decrease in phosphorylated FoxO1 and an increase in nuclear FoxO1.

CONCLUSION

The present study demonstrates that LCN2 regulates insulin sensitivity and glucose metabolism through inhibiting AMPK activity, and regulating FoxO1 and its downstream genes PEPCK/G6P, which regulate hepatic gluconeogenesis.

Lipocalin 2 increases after high-intensity exercise in humans and influences muscle gene expression and differentiation in mice

Lipocalin 2 (LCN2) is an adipokine that accomplishes several functions in diverse organs. However, its importance in muscle and physical exercise is currently unknown. We observed that following acute high‐intensity exercise (“Gran Sasso d'Italia” vertical run), LCN2 serum levels were increased. The Wnt pathway antagonist, DKK1, was also increased after the run, positively correlating with LCN2, and the same was found for the cytokine Interleukin 6. We, therefore, investigated the involvement of LCN2 in muscle physiology employing an Lcn2 global knockout (Lcn2^−/−) mouse model. Lcn2^−/− mice presented with smaller muscle fibres but normal muscle performance (grip strength metre) and muscle weight. At variance with wild type (WT) mice, the inflammatory cytokine Interleukin 6 was undetectable in Lcn2^−/− mice at all ages. Intriguingly, Lcn2^−/− mice did not lose gastrocnemius and quadriceps muscle mass and muscle performance following hindlimb suspension, while at variance with WT, they lose soleus muscle mass. In vitro, LCN2 treatment reduced the myogenic differentiation of C2C12 and primary mouse myoblasts and influenced their gene expression. Treating myoblasts with LCN2 reduced myogenesis, suggesting that LCN2 may negatively affect muscle physiology when upregulated following high‐intensity exercise.

Acute phase response to exertional heat stroke in mice

NEW FINDINGS

What is the central question of this study? Exertional heat stroke is accompanied by a marked inflammatory response. In this study, we explored the time course of acute phase proteins during recovery from severe heat stress in mice and the potential role of skeletal muscles as their source. What is the main finding and its importance? Exertional heat stroke transiently increased expression of acute phase proteins in mouse liver and plasma and depleted liver and plasma fibrinogen, a typical response to severe trauma. In contrast, skeletal muscle fibrinogen production was stimulated by heat stroke, which can provide an additional reservoir for fibrinogen supply to maintain the clotting potential throughout the body and locally within the muscle.

ABSTRACT

Exertional heat stroke (EHS), the most severe manifestation of heat illness, is accompanied by a marked inflammatory response. The release of acute phase proteins (APPs) is an important component of inflammation, which can assist in tissue survival/repair. The time course of APPs in recovery from EHS is unknown. Furthermore, skeletal muscles produce APPs during infection, but it is unknown whether they can produce APPs after EHS. Our objective was to determine the time course of representative APPs in liver, plasma and skeletal muscle during recovery from EHS. Male C57BL6/J mice ran in a forced running wheel at 37.5°C, 40% relative humidity until symptom limitation. Exercise control (EXC) mice ran for the same duration and intensity at 22.5°C. Samples were collected (n = 6-12 per group) over 14 days of recovery. Protein abundance was quantified using immunoblots. Total and phosphorylated STAT3 (pSTAT3) at Tyr705, responsible for APP activation, increased in liver at 0.5 h after EHS compared with EXC, (P < 0.05 and P < 0.001, respectively). In contrast, in tibialis anterior (TA) muscle, total STAT3 increased at 3 h (P < 0.05) but pSTAT3 (Tyr705) did not. Liver serum amyloid A1 (SAA1) increased at 3 and 24 h after EHS (P < 0.05), whereas plasma SAA1 increased only at 3 h (P < 0.05). SAA1 was not detected in TA muscle. In liver and plasma, fibrinogen decreased at 3 h (P < 0.01) and increased in TA muscle (P < 0.05). Lipocalin-2 was undetectable in liver or TA muscle. Recovery from EHS is characterized by a transient acute phase response in both liver and skeletal muscle. However, APP expression profiles and subtypes differ between skeletal muscle and liver.

Sex Differences in Diabetes- and TGF-β1-Induced Renal Damage

While females are less affected by non-diabetic kidney diseases compared to males, available data on sex differences in diabetic nephropathy (DN) are controversial. Although there is evidence for an imbalance of sex hormones in diabetes and hormone-dependent mechanisms in transforming growth factor β1 (TGF-β1) signaling, causes and consequences are still incompletely understood. Here we investigated the influence of sex hormones and sex-specific gene signatures in diabetes- and TGF-β1-induced renal damage using various complementary approaches (a db/db diabetes mouse model, ex vivo experiments on murine renal tissue, and experiments with a proximal tubular cell line TKPTS). Our results show that: (i) diabetes affects sex hormone concentrations and renal expression of their receptors in a sex-specific manner; (ii) sex, sex hormones and diabetic conditions influence differences in expression of TGF-β1, its receptor and bone morphogenetic protein 7 (BMP7); (iii) the sex and sex hormones, in combination with variable TGF-β1 doses, determine the net outcome in TGF-β1-induced expression of connective tissue growth factor (CTGF), a profibrotic cytokine. Altogether, these results suggest complex crosstalk between sex hormones, sex-dependent expression pattern and profibrotic signals for the precise course of DN development. Our data may help to better understand previous contradictory findings regarding sex differences in DN.

Chronic Carbon Tetrachloride Applications Induced Hepatocyte Apoptosis in Lipocalin 2 Null Mice Through Endoplasmic Reticulum Stress and Unfolded Protein Response

The lack of Lipocalin (LCN2) provokes overwhelming endoplasmic reticulum (ER) stress responses in vitro and in acute toxic liver injury models, resulting in hepatocyte apoptosis. LCN2 is an acute phase protein produced in hepatocytes in response to acute liver injuries. In line with these findings we investigated ER stress responses of Lcn2^−/− mice in chronic ER stress using a long-term repetitive carbon tetrachloride (CCl₄) injection model. We found chronic CCl₄ application to enhance ER stress and unfolded protein responses (UPR), including phosphorylation of eukaryotic initiation factor 2α (eIF2α), increased expression of binding immunoglobulin protein (BiP) and glucose-regulated protein 94 (GRP94). IRE1α/TRAF2/JNK signaling enhanced mitochondrial apoptotic pathways, and showed slightly higher in Lcn2^−/− mice compared to the wild type counterparts, leading to increased hepatocyte apoptosis well evidenced by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Hepatocyte injuries were confirmed by significant high serum alanine transaminase (ALT) levels in CCl₄-treated Lcn2^−/− mice. Lcn2^−/− mice furthermore developed mild hepatic steatosis, supporting our finding that ER stress promotes lipogenesis. In a previous report we demonstrated that the pharmacological agent tunicamycin (TM) induced ER stress through altered protein glycosylation and induced high amounts of C/EBP-homologous protein (CHOP), resulting in hepatocyte apoptosis. We compared TM-induced ER stress in wild type, Lcn2^−/−, and Chop null (Chop^−/−) primary hepatocytes and found Chop^−/− hepatocytes to attenuate ER stress responses and resist ER stress-induced hepatocyte apoptosis through canonical eIF2α/GADD34 signaling, inhibiting protein synthesis. Unexpectedly, in later stages of TM incubation, Chop^−/− hepatocytes resumed activation of IRE1α/JNK/c-Jun and p38/ATF2 signaling, leading to late hepatocyte apoptosis. This interesting observation indicates Chop^−/− mice to be unable to absolutely prevent all types of liver injury, while LCN2 protects the hepatocytes by maintaining homeostasis under ER stress conditions.

Early Hepatic Oxidative Stress and Mitochondrial Changes Following Western Diet in Middle Aged Rats

To assess the effect of 4 weeks of high fat-high fructose feeding on whole body composition, energy balance, specific markers of oxidative stress and inflammation, and insulin sensitivity in the liver of middle-aged rats, rats (1 year) were fed a diet rich in saturated fatty acids and fructose (HFF rats), mimicking the “Western diet”, and compared with rats of the same age that were fed a low fat diet (LF rats). HFF rats exhibited a significant increase in the gain of body weight, energy, and lipids compared to LF rats. HFF rats also showed hepatic insulin resistance, together with an increase in plasma triglycerides, cholesterol, and tumor necrosis factor alpha. Hepatic lipids, triglycerides and cholesterol were higher in HFF rats, while a significant decrease in Stearoyl-CoA desaturase activity was found in this tissue. A marked increase in the protein amount of complex I, concomitant to a decrease in its contribution to mitochondrial respiration, was found in HFF rats. Lipid peroxidation and Nitro-Tyrosine content, taken as markers of oxidative stress, as well as NADPH oxidase activity, were significantly higher in HFF rats, while the antioxidant enzyme catalase decreased in these rats. Myeloperoxidase activity and lipocalin content increased, while peroxisome proliferator activated receptor gamma decreased in HFF rats. The present results provide evidence that middle-aged rats show susceptibility to a short-term “Western diet”, exhibiting altered redox homeostasis, insulin resistance, and early mitochondrial alterations in the liver. Therefore, this type of dietary habits should be drastically limited to pursue a “healthy aging”.

Liver parenchymal cells lacking Lipocalin 2 (LCN2) are prone to endoplasmic reticulum stress and unfolded protein response

Unfolded protein response (UPR) is an adaptive mechanism allowing the endoplasmic reticulum (ER) to react to an accumulation of unfolded proteins in its lumen, also known as ER stress. The UPR is interconnected with inflammation through several pathways such as reactive oxygen species (ROS) production resulting from the protein folding or alternatively, activation of nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) via IRE1, or induction of acute phase response (APR). Lipocalin 2 (LCN2) is one of the APR proteins induced under inflammatory conditions and up-regulated during ER stress. Upon incubation of Lcn2^-/- and wild type (wt) primary hepatocytes with tunicamycin (TM) or thapsigargin (TG) we found the Lcn2^-/- hepatocytes to react with strong UPR to the ER stress, as evidenced by significantly increased levels of Grp94, Bip and Chop mRNA and protein compared to the wt. TM and TG-treated hepatocytes activated p65 NF-κB and JNK, the pathways that respond to stress stimuli and playing a central role in inflammation and apoptosis, respectively. ER stress further activated and cleaved full-length CREBH/CREB3L3, the hepatocyte specific transcription factor to induce systemic inflammatory responses. Upregulation of the C/EBP homologous protein (CHOP) was very prominent in Lcn2^-/- hepatocytes and sustained until 48 h, resulting in hepatocyte apoptosis as evidenced by increased cleaved caspase 3. We also explored the UPR of the Lcn2 null mouse livers in acute intoxication and inflammation stages with a single application of lipopolysaccharide (LPS) or carbon tetrachloride (CCl₄). The Lcn2 null mice clearly developed stronger UPR in LPS- and CCl₄-induced ER stress compared to the wt. Our findings indicate that the upregulation of LCN2 during ER stress-induced inflammatory responses protects hepatocytes from being overwhelmed by UPR upon liver injury.

The Role of Adipokines in Surgical Procedures Requiring Both Liver Regeneration and Vascular Occlusion

Liver regeneration is a perfectly calibrated mechanism crucial to increase mass recovery of small size grafts from living donor liver transplantation, as well as in other surgical procedures including hepatic resections and liver transplantation from cadaveric donors. Regeneration involves multiple events and pathways in which several adipokines contribute to their orchestration and drive hepatocytes to proliferate. In addition, ischemia-reperfusion injury is a critical factor in hepatic resection and liver transplantation associated with liver failure or graft dysfunction post-surgery. This review aims to summarize the existing knowledge in the role of adipokines in surgical procedures requiring both liver regeneration and vascular occlusion, which increases ischemia-reperfusion injury and regenerative failure. We expose and discuss results in small-for-size liver transplantation and hepatic resections from animal studies focused on the modulation of the main adipokines associated with liver diseases and/or regeneration published in the last five years and analyze future perspectives and their applicability as potential targets to decrease ischemia-reperfusion injury and improve regeneration highlighting marginal states such as steatosis. In our view, adipokines means a promising approach to translate to the bedside to improve the recovery of patients subjected to partial hepatectomy and to increase the availability of organs for transplantation.

Adipose Tissue Dysfunction Occurs Independently of Obesity in Adipocyte-Specific Oncostatin Receptor Knockout Mice

OBJECTIVE

This study examined the phenotypic effects of adipocyte-specific oncostatin M receptor (OSMR) loss in chow-fed mice.

METHODS

Chow-fed adipocyte-specific OSMR knockout (FKO) mice and littermate OSMR^fl/fl controls were studied. Tissue weights, insulin sensitivity, adipokine production, and stromal cell immunophenotypes were assessed in epididymal fat (eWAT); serum adipokine production was also assessed. In vitro, adipocytes were treated with oncostatin M, and adipokine gene expression was assessed.

RESULTS

Body weights, fasting blood glucose levels, and eWAT weights did not differ between genotypes. However, the eWAT of OSMR^FKO mice was modestly less responsive to insulin stimulation than that of OSMR^fl/fl mice. Notably, significant increases in adipokines, including C-reactive protein, lipocalin 2, intercellular adhesion molecule-1, and insulinlike growth factor binding protein 6, were observed in the eWAT of OSMR^FKO mice. In addition, significant increases in fetuin A and intercellular adhesion molecule-1 were detected in OSMR^FKO serum. Flow cytometry revealed a significant increase in leukocyte number and modest, but not statistically significant, increases in B cells and T cells in the eWAT of OSMR^FKO mice.

CONCLUSIONS

The chow-fed OSMR^FKO mice exhibited adipose tissue dysfunction and increased proinflammatory adipokine production. These results suggest that intact adipocyte oncostatin M-OSMR signaling is necessary for adipose tissue immune cell homeostasis.

Reabsorption of iron into acutely damaged rat liver: A role for ferritins

AIM

To studied iron metabolism in liver, spleen, and serum after acute liver-damage, in relation to surrogate markers for liver-damage and repair.

METHODS

Rats received intraperitoneal injection of the hepatotoxin thioacetamide (TAA), and were sacrificed regularly between 1 and 96 h thereafter. Serum levels of transaminases and iron were measured using conventional laboratory assays. Liver tissue was used for conventional histology, immunohistology, and iron staining. The expression of acute-phase cytokines, ferritin light chain (FTL), and ferritin heavy chain (FTH) was investigated in the liver by qRT-PCR. Western blotting was used to investigate FTL and FTH in liver tissue and serum. Liver and spleen tissue was also used to determine iron concentrations.

RESULTS

After a short initial decrease, iron serum concentrations increased in parallel with serum transaminase (aspartate aminotransferase and alanine aminotransferase) levels, which reached a maximum at 48 h, and decreased thereafter. Similarly, after 48 h a significant increase in FTL, and after 72h in FTH was detected in serum. While earliest morphological signs of inflammation in liver were visible after 6 h, increased expression of the two acute-phase cytokines IFN-γ (1h) and IL-1β (3h) was detectable earlier, with maximum values after 12-24 h. Iron concentrations in liver tissue increased steadily between 1 h and 48 h, and remained high at 96 h. In contrast, spleen iron concentrations remained unchanged until 48 h, and increased mildly thereafter (96 h). Although tissue iron staining was negative, hepatic FTL and FTH protein levels were strongly elevated. Our results reveal effects on hepatic iron concentrations after direct liver injury by TAA. The increase of liver iron concentrations may be due to the uptake of a significant proportion of the metal by healthy hepatocytes, and only to a minor extent by macrophages, as spleen iron concentrations do not increase in parallel. The temporary increase of iron, FTH and transaminases in serum is obviously due to their release by damaged hepatocytes.

CONCLUSION

Increased liver iron levels may be the consequence of hepatocyte damage. Iron released into serum by damaged hepatocytes is obviously transported back and stored via ferritins.

Anti-Obesity Effect of the Above-Ground Part of Valeriana dageletiana Nakai ex F. Maek Extract in High-Fat Diet-Induced Obese C57BL/6N Mice

Valeriana dageletiana Nakai ex F. Maek (VD) has been used as traditional medicine for the treatment of restlessness and sleeping disorders. However, it is still unclear whether obesity in mice can be altered by diet supplementation with VD. In this study, we first investigated the influences of VD on the accumulation of lipid content in 3T3-L1 cells; and the results showed that the above-ground VD extracts (VDAE) suppressed the differentiation of 3T3-L1 preadipocytes in a concentration-dependent manner without cytotoxicity. Thus, the effects of VDAE on preventing obesity were then studied in the C57BL/6N mice for 10 weeks (n = 6): normal-fat diet, high-fat diet (HFD), HFD supplemented with 1% (10 g/kg) Garcinia combogia extract (positive control), and HFD supplemented with 1% (10 g/kg) VDAE. The results showed that VDAE reduced food efficiency ratio, body weight, epididymal adipose and hepatic tissue weight, hepatic lipid metabolites, and triacylglycerol and cholesterol serum levels compared to the high-fat diet group. Moreover, VD significantly inhibited the expression of adipogenic genes, such as PPAR-γ, C/EBP-α, and aP2, and lipogenic genes, such as SREBP-1c, FAS, SCD-1, and CD36, in epididymal adipose tissue and hepatic tissue. These findings indicate anti-adipogenic and anti-lipogenic effects of VDAE and suggest that it could be a potent functional food ingredient for the prevention of high-fat diet-induced obesity.

Macrophage inflammatory protein-2 as mediator of inflammation in acute liver injury

Macrophage inflammatory protein (MIP)-2 is one of the CXC chemokines and is also known as chemokine CXC ligand (CXCL2). MIP-2 affects neutrophil recruitment and activation through the p38 mitogen-activated-protein-kinase-dependent signaling pathway, by binding to its specific receptors, CXCR1 and CXCR2. MIP-2 is produced by a variety of cell types, such as macrophages, monocytes, epithelial cells, and hepatocytes, in response to infection or injury. In liver injury, activated Kupffer cells are known as the major source of MIP-2. MIP-2-recruited and activated neutrophils can accelerate liver inflammation by releasing various inflammatory mediators. Here, we give a brief introduction to the basic molecular and cellular sources of MIP-2, and focus on its physiological and pathological functions in acute liver injury induced by concanavalin A, lipopolysaccharides, irradiation, ischemia/reperfusion, alcohol, and hypoxia, and hepatectomy-induced liver regeneration and tumor colorectal metastasis. Further understanding of the regulatory mechanisms of MIP-2 secretion and activation may be helpful to develop MIP-2-targeted therapeutic strategies to prevent liver inflammation.

Long-Term Ethanol Exposure Decreases the Endotoxin-Induced Hepatic Acute Phase Response in Rats

BACKGROUND

Long-term excessive alcohol intake predisposes to infectious diseases. The hepatic acute-phase response is a component of the innate immune system and is part of the first line of defense against invading pathogens, which may be compromised by alcohol. We aimed to investigate whether an induced acute-phase response is impaired in long-term ethanol (EtOH)-fed rats.

METHODS

For 6 weeks, rats were either fed a Lieber-DeCarli EtOH-containing (36% as calories) liquid diet ad libitum or calorically pair-fed. Then, the rats were injected intraperitoneally with a low dose of lipopolysaccharide (LPS) (0.5 mg/kg) to induce an acute-phase response. Two hours after LPS, we measured the plasma concentrations of an array of inflammatory cytokines. Twenty-four hours after LPS, we measured the hepatic mRNA expression and serum concentrations of prominent rat acute-phase proteins.

RESULTS

EtOH-fed rats showed either no liver histopathological changes or varying degrees of steatosis. EtOH feeding decreased the spontaneous liver mRNA expression of the prevailing acute-phase protein alpha-2-macroglobulin (α2M) by 30% (p < 0.01). LPS immediately increased plasma tumor necrosis factor-alpha and interleukin-6 more than 100-fold in both feeding groups (p < 0.001, all) and approximately twice as much in the EtOH-fed rats (p < 0.05 and p = 0.08, respectively). LPS also induced a variable but marked amplification of (α2M), haptoglobin, alpha-1-acid glycoprotein, and lipocalin-2 liver mRNA expression levels and serum concentrations in both feeding groups (p ≤ 0.01 to 0.001). However, the LPS-induced increases in serum (α2M) and haptoglobin were less pronounced in the EtOH-fed rats, averaging approximately 60% of the concentrations in the pair-fed rats (p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

Long-term EtOH exposure in rats reduces the spontaneous hepatic mRNA expression of (α2M) and markedly impairs the hepatic acute-phase response to endotoxin, despite higher pro-inflammatory cytokine release. The same phenomenon may contribute to the increased susceptibility to infections observed in humans with long-term excessive alcohol intake.

Activation of innate immune genes in caprine blood leukocytes after systemic endotoxin challenge

Background

Sepsis is a serious health problem associated with a range of infectious diseases in animals and humans. Early events of this syndrome can be mimicked by experimental administration of lipopolysaccharides (LPS). Compared with mice, small ruminants and humans are highly sensitive to LPS, making goats valuable in inflammatory models. We performed a longitudinal study in eight Norwegian dairy goats that received LPS (0.1 μg/kg, Escherichia coli O26:B6) intravenously. A control group of five goats received corresponding volumes of sterile saline. Clinical examinations were performed continuously, and blood samples were collected throughout the trial.

Results

Characteristic signs of acute sepsis, such as sickness behavior, fever, and leukopenia were observed within 1 h of LPS administration. A high-throughput longitudinal gene expression analysis of circulating leukocytes was performed, and genes associated with the acute phase response, type I interferon signaling, LPS cascade and apoptosis, in addition to cytokines and chemokines were targeted. Pro-inflammatory genes, such as IL1B, CCL3 and IL8, were significantly up-regulated. Interestingly, increased mRNA levels of seven interferon stimulated genes (ISGs) were observed peaking at 2 h, corroborating the increasing evidence that ISGs respond immediately to bacterial endotoxins. A slower response was manifested by four extrahepatic acute phase proteins (APP) (SAA3, HP, LF and LCN2) reaching maximum levels at 5 h.

Conclusions

We report an immediate induction of ISGs in leukocytes in response to LPS supporting a link between the interferon system and defense against bacterial infections. The extrahepatic expression of APPs suggests that leukocytes contribute to synthesis of these proteins at the beginning of a systemic inflammation. Taken together, these findings provide insights into the dynamic regulation of innate immune genes, as well as raising new questions regarding the importance of ISGs and extrahepatic APPs in leukocytes after systemic endotoxin challenge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0870-x) contains supplementary material, which is available to authorized users.

Effects of IL-33/ST2 pathway in acute inflammation on tissue damage, antioxidative parameters, magnesium concentration and cytokines profile

AIM

The aim of this study was to examine the role of IL-33/ST2 pathway in a pathogenesis of acute inflammation and its effects on tissue damage, antioxidative capacity, magnesium concentration and cytokine profile in acutely inflamed tissue.

MATERIAL AND METHODS

Male mice were randomly divided in four groups: wild-type control group (WT-C), ST2 knockout control group (KO-C), wild-type inflammatory group (WT-I), and ST2 knockout inflammatory group (KO-I). Acute inflammation was induced in WT-I and KO-I by intramuscular injection of turpentine oil, while mice in WT-C and KO-C were treated with saline. After 12h, animals were euthanized, and blood was collected for determination of creatine kinase (CK) and aspartate transaminase (AST) activity. The treated tissue was used for histopathological analysis, determination of volume density of inflammatory infiltrate (Vdii) and necrotic fiber (Vdnf), gene expression of interleukin (IL)-33, ST2, tumor necrosis factor alpha (TNF-alpha), IL-6, IL-12p35, and transforming growth factor beta (TGF-beta), concentration of magnesium (Mg), copper (Cu), selenium (Se), manganese (Mn) and reduced glutathione (GSH), and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity.

RESULTS

Presence of inflammatory infiltration and necrosis in the treated tissue was histopathologically confirmed in WT-I and KO-I. Vdii was significantly higher in WT-I when compared to KO-I, whereas Vdnf did not significantly differ between WT-I and KO-I. CK and AST significantly increased in both inflammatory groups when compared to corresponding control groups. However, the values of CK and AST were significantly higher in WT-I than in KO-I. Mg in the treated tissue was significantly lower in WT-I in comparison to WT-C and KO-I, while there was no significant difference between KO-C and KO-I. There was no significant difference in Cu, Se, and Mn in the treated tissue between WT-C, KO-C, WT-I and KO-I. Gene expression of IL-33 in the treated tissue increased in both inflammatory groups when compared to the corresponding control groups, but it was significantly higher in KO-I than in WT-I. Gene expression of ST2 in the treated tissue was significantly higher in WT-I than in WT-C. Gene expression of TNF-alpha, IL-6, and IL-12p35 in the treated tissue was significantly higher in WT-I and KO-I than in the corresponding control groups, and IL-6 was significantly higher in KO-C than in WT-C. TGF-beta gene expression in the treated tissue was significantly higher in KO-I when compared to WT-I, while there was no difference between WT-C and KO-C. SOD activity decreased at the site of acute inflammation in both inflammatory groups, while the GPx activity increased. GSH in the treated tissue was significantly higher in KO-I than in KO-C or WT-I.

CONCLUSION

The results of our study have indicated, to our knowledge for the first time, that IL-33/ST2 pathway plays a role in enhancing inflammation and tissue damage at the site of acute inflammation by affecting the concentration of magnesium and GSH, important for antioxidative capacity, as well as gene expression of anti-inflammatory cytokine TGF-beta.

Induction of Lipocalin2 in a Rat Model of Lung Irradiation

Previously, we showed that lipocalin2 (LCN2) serum levels increased after liver irradiation and during acute-phase conditions. Here, we evaluate LCN2 expression and serum levels after single-dose lung irradiation with 25 Gy, percutaneously administered to the lung of randomly-paired male Wistar rats. Due to the concave anatomy of the lung recesses, the irradiation field included the upper part of the liver. No rat died due to irradiation. In control tissue, lung immunohistochemistry showed a high constitutive expression of LCN2+ granulocytes. LCN2 mRNA levels in lung tissue increased up to 24 h (9 ± 2.3-fold) after irradiation. However, serum LCN2 levels remained undetectable after lung irradiation. LCN2 expression in the upper part of the liver increased up to 4.2-fold after lung irradiation, but the lower liver showed an early decrease. Acute-phase cytokines (IL-1β and TNF-α) showed a significant increase on transcript level in both lung and upper liver, whilst the lower liver did not show any considerable increase. In conclusion, constitutive expression of LCN2 in local immune cells demonstrates its local role during stress conditions in the lung. The absence of LCN2 in the serum strengthens our previous findings that the liver is the key player in secreting LCN2 during stress conditions with liver involvement.

Lipocalin 2 drives neutrophilic inflammation in alcoholic liver disease

BACKGROUND & AIMS

Alcoholic steatohepatitis (ASH) is characterised by neutrophil infiltration that contributes to hepatic injury and disease. Lipocalin-2 (LCN2) was originally identified as siderophore binding peptide in neutrophils, which exerted tissue protective effects in several disease models. Here we investigate the role of LCN2 in the pathogenesis of alcohol-induced liver injury.

METHODS

We compared hepatic LCN2 expression in ASH patients, alcoholic cirrhosis patients without evidence of ASH and patients with non-alcoholic fatty liver disease (NAFLD; i.e. simple steatosis). To mechanistically dissect LCN2 function in alcohol-induced liver injury, we subjected wild-type (WT) and Lcn2-deficient (Lcn2(-/-)) mice to the Lieber-DeCarli diet containing 5% ethanol (EtOH) or isocaloric maltose. Adoptive transfer experiments were performed to track neutrophil migration. Furthermore, we tested the effect of antibody-mediated LCN2 neutralisation in an acute model of ethanol-induced hepatic injury.

RESULTS

Patients with ASH exhibited increased hepatic LCN2 immunoreactivity compared to patients with alcoholic cirrhosis or simple steatosis, which mainly localised to neutrophils. Similarly, ethanol-fed mice exhibited increased LCN2 expression that mainly localised to leukocytes and especially neutrophils. Lcn2(-/-) mice were protected from alcoholic liver disease (ALD) as demonstrated by reduced neutrophil infiltration, liver injury and hepatic steatosis compared to WT controls. Adoptive transfers revealed that neutrophil-derived LCN2 critically determines hepatic neutrophil immigration and persistence during chronic alcohol exposure. Antibody-mediated neutralisation of LCN2 protected from hepatic injury and neutrophilic infiltration after acute alcohol challenge.

CONCLUSIONS

LCN2 drives ethanol-induced neutrophilic inflammation and propagates the development of ALD. Despite a critical role for LCN2 in immunity and infection, pharmacological neutralisation of LCN2 might be of promise in ALD.

Effects of Il-33/St2 pathway on alteration of iron and hematological parameters in acute inflammation

AIM

The aim of this study was to examine the role of the IL-33/ST2 pathway in pathogenesis of acute inflammation by investigating its possible role in alteration of iron and hematological parameters in experimental model of acute inflammation.

MATERIAL AND METHODS

Wild-type and ST2 knockout BALB/c mice were divided into four groups: wild-type control group, ST2-/- control group, wild-type inflammatory group, and ST2-/- inflammatory group. Acute inflammation was induced by intramuscular injection of turpentine oil, while control groups were injected with saline. After 12h animals were anesthetized, and the treated tissue, blood and spleen were collected. Iron concentration in the treated tissue, hemoglobin blood concentration, mean corpuscular hemoglobin (MCH), hematocrit, erythrocyte, neutrophil and lymphocyte blood count, and erythrocytes percentage in spleen were determined.

RESULTS

Iron concentration in the treated tissue was significantly higher in wild-type inflammatory group (WT-I) when compared to both, the wild-type control group (WT-C) and ST2-/- inflammatory group (KO-I). There was no significant difference in iron concentration between ST2-/- control group (KO-C) and the KO-I. MCH had significantly decreased in WT-I when compared to WT-C, while there was no significant difference between KO-C and KO-I. Hemoglobin blood concentration significantly increased in KO-I in comparison to KO-C, while it did not significantly differ between WT-I and KO-I. Erythrocyte count and hematocrit had significantly increased, while the percentage of erythrocytes in spleen decreased in both inflammatory groups when compared to their controls. Neutrophil count significantly decreased in WT-I, when compared to WT-C. Lymphocyte count decreased in both inflammatory groups when compared to their controls.

CONCLUSION

Results of this study indicate that the IL-33/ST2 axis could have a role in the alteration of iron in acute inflammation, namely in an increase of iron concentration at the site of acute inflammation and a decrease of blood mean corpuscular hemoglobin.

Liver is the major source of elevated serum lipocalin-2 levels after bacterial infection or partial hepatectomy: a critical role for IL-6/STAT3

Lipocalin-2 (LCN2) was originally isolated from human neutrophils and termed neutrophil gelatinase-associated lipocalin (NGAL). However, the functions of LCN2 and the cell types that are primarily responsible for LCN2 production remain unclear. To address these issues, hepatocyte-specific Lcn2 knockout (Lcn2(Hep-/-)) mice were generated and subjected to bacterial infection (with Klesbsiella pneumoniae or Escherichia coli) or partial hepatectomy (PHx). Studies of Lcn2(Hep-/-) mice revealed that hepatocytes contributed to 25% of the low basal serum level of LCN2 protein (∼ 62 ng/mL) but were responsible for more than 90% of the highly elevated serum LCN2 protein level (∼ 6,000 ng/mL) postinfection and more than 60% post-PHx (∼ 700 ng/mL). Interestingly, both Lcn2(Hep-/-) and global Lcn2 knockout (Lcn2(-/-)) mice demonstrated comparable increases in susceptibility to infection with K. pneumoniae or E. coli. These mice also had increased enteric bacterial translocation from the gut to the mesenteric lymph nodes and exhibited reduced liver regeneration after PHx. Treatment with interleukin (IL)-6 stimulated hepatocytes to produce LCN2 in vitro and in vivo. Hepatocyte-specific ablation of the IL-6 receptor or Stat3, a major downstream effector of IL-6, markedly abrogated LCN2 elevation in vivo. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed that STAT3 was recruited to the promoter region of the Lcn2 gene upon STAT3 activation by IL-6.

CONCLUSION

Hepatocytes are the major cell type responsible for LCN2 production after bacterial infection or PHx, and this response is dependent on IL-6 activation of the STAT3 signaling pathway. Thus, hepatocyte-derived LCN2 plays an important role in inhibiting bacterial infection and promoting liver regeneration.

Morg1 heterozygous deficiency ameliorates hypoxia-induced acute renal injury

Acute kidney injury is a common complication of critically ill patients and may occur as a result of various factors and coexisting previous illnesses. Some pathophysiological responses seen in critical illness can be similar to the human physiological response to extreme environmental challenges, such as hypoxia from reduced oxygen availability at high altitudes (systemic hypoxia). Due to oxygen deficiency, mammalian cells activate the transcriptional factor hypoxia-inducible factor (HIF); its degradation is regulated by prolyl hydroxylase 3 (PHD3) in interaction with the scaffold protein MAPK organizer 1 (Morg1). While homozygous Morg1(-/-) mice are embryonically lethal, the kidneys of heterozygous Morg1(+/-) mice reveal elevated HIF protein levels and increased serum erythropoietin compared with wild-type Morg1(+/+) mice. In this study, we exposed wild-type and Morg1(+/-) mice to 10% oxygen in a hypoxic chamber for 3 days. This reduced oxygen concentration leads to a deterioration of renal function, an increase in renal inflammation, and significantly more tubular damage and apoptosis in the kidneys of wild-type (Morg1(+/+)) mice. In sharp contrast, Morg1(+/-) kidneys were protected against systemic hypoxia. They show significantly less renal lesions, reduced or no inflammation, and less tubular damage and apoptosis. Thus short-term systemic and subsequently renal hypoxia which may occur in many patients in the intensive care unit induces in wild-type mice renal injury, which is ameliorated by Morg1 deficiency. Our findings suggest that therapeutical manipulation of Morg1 may be an interesting novel target to prevent hypoxia-associated renal damage.

Neutrophil gelatinase-associated lipocalin in cancer

Neutrophil gelatinase-associated lipocalin (NGAL), also known as lipocalin-2, is a 178-amino acid protein which exists in three molecular forms, including a 25-kDa monomer, a 45-kDa homodimer, and a 135-kDa heterodimer complexed with matrix metalloproteinase 9 (MMP-9). Polymorphonuclear neutrophils and tubular cells of the kidney are the most representative cellular sources. As such, NGAL is now considered the biochemical gold standard for early diagnosis of acute kidney injury. Recent evidence suggests, however, that ectopic or enhanced expression of NGAL may occur in many other pathologic conditions including cancer. Several epidemiologic studies, as reviewed in this chapter, showed that a variety of malignant tumors consistently overexpressed NGAL with increased concentration in blood, urine, and other biologic fluids. In addition, NGAL was frequently associated with tumor size, stage, and invasiveness. These features thus make it a potential biomarker for malignancy. A number of experimental studies also demonstrated that the ability to bind MMP-9, to scavenge iron into cancer cells along with the effect on subcellular localization of transmembrane proteins such as cadherins and catenins, confers this protein the potential to enhance can cer aggressiveness and makes it an appealing target of future anticancer research.

Lipocalin-2 test in distinguishing acute lung injury cases from septic mice without acute lung injury

OBJECTIVE

To explore whether the amount of lipocalin-2 in the biofluid could reflect the onset of sepsis-induced acute lung injury (ALI) in mice.

METHODS

Lipopolysaccharide (LPS, 10 mg/kg) injection or cecal ligation and puncture (CLP) was performed to induce severe sepsis and ALI in C57 BL/6 male mice randomly divided into 5 groups (n=10 in each group): group A (intraperitoneal LPS injection), group B (intravenous LPS injection via tail vein), group C (CLP with 25% of the cecum ligated), group D (CLP with 75% of the cecum ligated), and the control group (6 sham-operation controls plus 4 saline controls). All the mice received volume resuscitation. Measurements of pulmonary morphological and functional alterations were used to identify the presence of experimental ALI. The expressions of lipocalin-2 and interleukin (IL)-6 in serum, bronchoalveolar lavage fluid (BALF), and lung tissue were quantified at both protein and mRNA levels. The overall abilities of lipocalin-2 and IL-6 tests to diagnose sepsis-induced ALI were evaluated by generating receiver operator characteristic curves (ROC) and computing area under curve (AUC).

RESULTS

In both group B and group D, most of the main features of experimental ALI were reproduced in mice, while group A and group C showed septic syndrome without definite evidence for the presence of ALI. Compared with septic mice without ALI (group A+group C), lipocalin-2 protein expression in septic mice with ALI (group B+group D) was significantly up-regulated in BALF (P<0.01) and in serum (P<0.01), and mRNA expression boosted in lung tissues (all P<0.05). Lipocalin-2 tests performed better than IL-6 tests in recognizing sepsis-induced ALI cases, evidenced by the larger AUC of the former (BALF tests, 0.8800 versus 0.6625; serum tests, 0.8500 versus 0.7000). Using a dual cutoff system to diagnose sepsis-induced ALI, BALF lipocalin-2 test exhibited the highest positive likelihood ratio (13.000) and the lowest negative likelihood ratio (0.077) among the tests of lipocalin-2 and IL-6 in blood and BALF. A statistically significant correlation was found between lipocalin-2 concentration in BALF and that in serum (Spearman r=0.8803, P<0.0001).

CONCLUSIONS

Lipocalin-2 expression is significantly up-regulated in septic ALI mice compared with those without ALI. Lipocalin-2 tests with a dual cutoff system could be an effective tool in distinguishing experimental ALI cases.

Diet high in fructose leads to an overexpression of lipocalin-2 in rat fatty liver

AIM: To explore lipocalin-2 (LCN-2) expression and its possible role and mechanism(s) of production in rat models of diet-inducible fatty liver.

METHODS: Fatty liver was triggered in male Sprague-Dawley rats fed either with liquid Lieber-DeCarli (LDC) or LDC + 70% cal fructose (L-HFr) diet for 4 or 8 wk. Chow-nourished animals served as controls. Hepatic expression of LCN-2 and other metabolic and inflammatory mediators was assessed by quantitative reverse transcription polymerase chain reaction and Western blotting. Serum LCN-2, fasting leptin, and lipid profile were evaluated via Enzyme-Linked Immunosorbent Assay, Radioimmunoassay, and colorimetric assays, respectively. The localization of LCN-2 in the liver was detected by using immunofluorescence staining. Furthermore, HE stain was used to evaluate hepatic fat degeneration and inflammation.

RESULTS: Both LDC-fed and L-HFr-fed rat histologically featured fatty liver. In the liver, mRNA transcriptions of Mcp-1, a2-m, Il-8 and Glut5 were increased in the L-HFr group at both time points (P < 0.001), while the transcription of Tlr4, Inos, and Tnf-α was significantly up-regulated at week 4. Interestingly, hepatic Lcn-2 expression was 90-fold at week 4 and 507-fold at week 8 higher in L-HFr-subjected rats vs control (P < 0.001). In contrast to HDL-cholesterol, systemic levels of LCN-2, fasting leptin and triglycerides were elevated in the L-HFr regimen (P < 0.001). Moreover, protein expression of hepatic LCN-2, CD14, phospho-MAPK, caspase-9, cytochrome c and 4-hydroxynonenal was increased in the L-HFr group. Conversely, the hepatic expression of PGC-1α (a mitochondrial-biogenic protein) was reduced in the L-HFr category at week 8. The localization of LCN-2 in the liver was predominantly restricted to MPO⁺ granulocytes.

CONCLUSION: Fructose diet up-regulates hepatic LCN-2 expression, which correlates with the increased indicators of oxidative stress and mitochondrial dysfunction. The LCN-2 may be involved in liver protection.

Ferritin L is the sole serum ferritin constituent and a positive hepatic acute-phase protein

Ferritin L (FTL) and ferritin H (FTH) subunits are responsible for intracellular iron storage. Serum ferritin levels are not only dependant on body iron stores. Aims of the present study are to demonstrate nature, source, and major regulatory mediators of serum ferritin in an animal model of acute-phase (AP) response. Animals (rats, wild-type [WT] mice, and interleukin [IL]-6ko mice) were injected with turpentine oil (TO) intra-muscularity to induce a sterile abscess and sacrificed at different time points afterward. Rat hepatocytes were isolated for cell culture and, after reaching confluence, stimulated with major AP cytokines to induce AP conditions. We found a significantly increased expression of both ferritin subunits in liver at mRNA and protein levels during AP response. In the serum of both control and TO-injected rats, only FTL was detectable by Western blotting, whereas no increase in serum FTL was measured by Western blot or enzyme-linked immunosorbent assay. An increase in protein expression of FTL and FTH was observed in lysates of rat hepatocytes after treatment with IL-6, IL-1β, and tumor necrosis factor-α; however, only FTL was increasingly released into supernatant. In both TO-injected rats and WT mice, a dramatic increase in serum IL-6 levels was observed, along with an increased amount of hepatic ferritin subunits. However, an increase of hepatic FTL but not of FTH protein expression was observed in IL-6ko mice after TO injection. Our data demonstrate that FTL is the only rat serum ferritin whose release into circulation from the hepatocytes is increased by the effect of AP cytokines (e.g., IL-6). In contrast, FTH expression is intracellular in both under physiological and AP conditions.

Immune-induced expression of lipocalin-2 in brain endothelial cells: relationship with interleukin-6, cyclooxygenase-2 and the febrile response

Interleukin (IL)-6 is critical for the febrile response to peripheral immune challenge. However, the mechanism by which IL-6 enables fever is still unknown. To characterise the IL-6-dependent fever generating pathway, we used microarray analysis to identify differentially expressed genes in the brain of lipopolysaccharide (LPS)-treated IL-6 wild-type and knockout mice. Mice lacking IL-6 displayed a two-fold lower expression of the lipocalin-2 gene (lcn2), and this difference was confirmed by real-time reverse transcriptase-polymerase chain reaction. Conversely, the induction of lipocalin-2 protein was observed in brain vascular cells following i.p. administration of recombinant IL-6, suggesting a direct relationship between IL-6 and lipocalin-2. Immunohistochemical analysis also revealed that LPS-induced lipocalin-2 is expressed by brain endothelial cells and is partly co-localised with cyclooxygenase-2 (Cox-2), the rate-limiting enzyme for the production of inflammatory induced prostaglandin E(2) (PGE(2) ), which is the key mediator of fever. The direct role of lipocalin-2 in fever was examined in LPS-challenged lipocalin-2 knockout mice. In both male and female mice, normal fever responses were observed at near-thermoneutral conditions (29-30 °C) but when recorded at normal room temperature (19-20 °C), the body temperature of lipocalin-2 knockout female mice displayed an attenuated fever response compared to their wild-type littermates. This difference was reflected in significantly attenuated mRNA expression of Cox-2 in the brain of lipocalin-2 knockout female mice, but not of male mice, following challenge with peripheral LPS. Our findings suggest that IL-6 influences the expression of lipocalin-2, which in turn may be involved in the control of the formation of Cox-2, and hence central PGE(2) -production. We have thus identified lipocalin-2 as a new factor in the pathway of inflammatory IL-6 signalling. However, the effect of lipocalin-2 on fever is small, being sex-dependent and ambient temperature-specific, and thus lipocalin-2 cannot be considered as a major mediator of the IL-6-dependent fever generating pathway.

Serum Lipocalin2 is a potential biomarker of liver irradiation damage

BACKGROUND/AIM

IL-6 - IL-1- lipocalin2 (LCN2) - liver irradiation - oxidative stress - TNF-a Lipocalin2 (LCN2) is an acute phase protein. The source of its increased serum level in oxidative stress conditions (ROS) remains still unknown. We prospectively evaluate the serum LCN2 increase after single dose liver irradiation along with hepatic LCN2 gene and protein expression.

METHODS

A single dose of 25 Gray was administered percutaneously to the liver of randomly paired rats after a planning CT scan. Male Wistar rats were sacrificed 1, 3, 6, 12, 24 and 48 h after irradiation along with sham-irradiated controls. ELISA, RT-PCR, Western blot and immunofluorescence staining was performed. Furthermore, hepatocytes, myofibroblasts and Kupffer cells were isolated from the liver of healthy rats and irradiated ex-vivo.

RESULTS

After liver irradiation, LCN2 serum levels increased significantly up to 2.7 μg/ml within 6 h and stayed elevated over 24 h. LCN2 specific transcripts increased significantly up to 552 ± 109-fold at 24 h after liver irradiation, which was further confirmed at protein level. α2-macroglobulin and hemoxygenase-1 also showed an increase, but the magnitude was less as compared to LCN2. LCN2+ granulocytes were detected within 1 h after irradiation around central and portal fields and remained high during the course of study. Ex-vivo irradiated hepatocytes (2.4 ± 0.6-fold) showed a higher LCN2 gene expression as compared to myofibroblasts and Kupffer cells. IL-1β treatment further increased LCN2 gene expression in cultured hepatocytes.

CONCLUSIONS

Single dose liver irradiation induces a significant increase in LCN2 serum levels, comparable to the induction of acute phase proteins. We suggest LCN2 as marker for the early phase of radiation-induced tissue damage.

Protective effects of lipocalin-2 (LCN2) in acute liver injury suggest a novel function in liver homeostasis

Lipocalin-2 is expressed under pernicious conditions such as intoxication, infection, inflammation and other forms of cellular stress. Experimental liver injury induces rapid and sustained LCN2 production by injured hepatocytes. However, the precise biological function of LCN2 in liver is still unknown. In this study, LCN2(-/-) mice were exposed to short term application of CCl4, lipopolysaccharide and Concanavalin A, or subjected to bile duct ligation. Subsequent injuries were assessed by liver function analysis, qRT-PCR for chemokine and cytokine expression, liver tissue Western blot, histology and TUNEL assay. Serum LCN2 levels from patients suffering from liver disease were assessed and evaluated. Acute CCl4 intoxication showed increased liver damage in LCN2(-/-) mice indicated by higher levels of aminotransferases, and increased expression of inflammatory cytokines and chemokines such as IL-1β, IL-6, TNF-α and MCP-1/CCL2, resulting in sustained activation of STAT1, STAT3 and JNK pathways. Hepatocytes of LCN2(-/-) mice showed lipid droplet accumulation and increased apoptosis. Hepatocyte apoptosis was confirmed in the Concanavalin A and lipopolysaccharide models. In chronic models (4weeks bile duct ligation or 8weeks CCl4 application), LCN2(-/-) mice showed slightly increased fibrosis compared to controls. Interestingly, serum LCN2 levels in diseased human livers were significantly higher compared to controls, but no differences were observed between cirrhotic and non-cirrhotic patients. Upregulation of LCN2 is a reliable indicator of liver damage and has significant hepato-protective effect in acute liver injury. LCN2 levels provide no correlation to the degree of liver fibrosis but show significant positive correlation to inflammation instead.

Lipocalin 2 deficiency dysregulates iron homeostasis and exacerbates endotoxin-induced sepsis

Various states of inflammation, including sepsis, are associated with hypoferremia, which limits iron availability to pathogens and reduces iron-mediated oxidative stress. Lipocalin 2 (Lcn2; siderocalin, 24p3) plays a central role in iron transport. Accordingly, Lcn2-deficient (Lcn2KO) mice exhibit elevated intracellular labile iron. In this study, we report that LPS induced systemic Lcn2 by 150-fold in wild-type mice at 24 h. Relative to wild-type littermates, Lcn2KO mice were markedly more sensitive to endotoxemia, exhibiting elevated indices of organ damage (transaminasemia, lactate dehydrogenase) and increased mortality. Such exacerbated endotoxemia was associated with substantially increased caspase-3 cleavage and concomitantly elevated immune cell apoptosis. Furthermore, cells from Lcn2KO mice were hyperresponsive to LPS ex vivo, exhibiting elevated cytokine secretion. Additionally, Lcn2KO mice exhibited delayed LPS-induced hypoferremia despite normal hepatic hepcidin expression and displayed decreased levels of the tissue redox state indicators cysteine and glutathione in liver and plasma. Desferroxamine, an iron chelator, significantly protects Lcn2KO mice from LPS-induced toxicity, including mortality, suggesting that Lcn2 may act as an antioxidant in vivo by regulating iron homeostasis. Thus, Lcn2-mediated regulation of labile iron protects the host against sepsis. Its small size and simple structure may make Lcn2 a deployable treatment for sepsis.