Extracellular CIRP dysregulates macrophage bacterial phagocytosis in sepsis.

In sepsis, macrophage bacterial phagocytosis is impaired, but the mechanism is not well elucidated. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that causes inflammation. However, whether eCIRP regulates macrophage bacterial phagocytosis is unknown. Here, we reported that the bacterial loads in the blood and peritoneal fluid were decreased in CIRP-/- mice and anti-eCIRP Ab-treated mice after sepsis. Increased eCIRP levels were correlated with decreased bacterial clearance in septic mice. CIRP-/- mice showed a marked increase in survival after sepsis. Recombinant murine CIRP (rmCIRP) significantly decreased the phagocytosis of bacteria by macrophages in vivo and in vitro. rmCIRP decreased the protein expression of actin-binding proteins, ARP2, and p-cofilin in macrophages. rmCIRP significantly downregulated the protein expression of ßPIX, a Rac1 activator. We further demonstrated that STAT3 and ßPIX formed a complex following rmCIRP treatment, preventing ßPIX from activating Rac1. We also found that eCIRP-induced STAT3 phosphorylation was required for eCIRP's action in actin remodeling. Inhibition of STAT3 phosphorylation prevented the formation of the STAT3-ßPIX complex, restoring ARP2 and p-cofilin expression and membrane protrusion in rmCIRP-treated macrophages. The STAT3 inhibitor stattic rescued the macrophage phagocytic dysfunction induced by rmCIRP. Thus, we identified a novel mechanism of macrophage phagocytic dysfunction caused by eCIRP, which provides a new therapeutic target to ameliorate sepsis.

Human adrenomedullin and its binding protein attenuate tissue injury and inflammation following hepatic ischemia reperfusion in rabbits.

BACKGROUND: Liver injury caused by ischemia reperfusion (I/R) during surgical procedures, such as liver resection or liver transplantation, is a major cause of liver damage and graft failure. The current method of treatment is mostly preventative (i.e., ischemic preconditioning). While a number of pharmacological modalities have been studied to reduce hepatic I/R injury, none have been entirely successful. It has been demonstrated that the administration of adrenomedullin (AM) in combination with AM-binding protein (AM/AMBP-1) exerts significant protective effects in various pathological conditions. In an effort to develop AM/AMBP-1 as a novel therapeutic for hepatic I/R injury, the present study examined the effect of a low dose of human AM, which does not induce hypotension, in combination with human AMBP-1 in a rabbit model of hepatic I/R (i.e., non-rodent species). METHODS: Ischemia of 70% of the liver was induced by placing a microvascular clip across the hilum of the left and median lobes for 60 min. The clip was then removed to commence reperfusion. At 15 min following clip removal (i.e., reperfusion), human AM/AMBP-1 was administered intravenously via the ear marginal vein continuously for 30 min. At 20 h, blood and tissue samples were collected for various measurements. RESULTS: The serum levels of liver enzymes (alanine aminotransferase and aspartate aminotransferase) and lactate dehydrogenase, were elevated following hepatic I/R. The administration of AM/AMBP-1 significantly decreased these levels by 58, 44, 41%, respectively. Hepatic I/R increased the direct and total bilirubin levels, whereas treatment with human AM/AMBP-1 decreased these levels by 60% and 69%, respectively. Treatment with AM/AMBP-1 also inhibited interleukin-6 gene expression by 95%. There were no changes in tumor necrosis factor-α (TNF-α) gene expression and myeloperoxidase activity (MPO), lactate and Suzuki scores after treatment. The treatment, however, reduced apoptosis post-hepatic I/R in the ischemic portion of the liver. CONCLUSION: Additional experiments with AM and AMBP-1 alone are needed to completely interpret the experimental results in this non-rodent species of hepatic I/R injury. The present study suggests that human AM/AMBP-1 may be developed as a novel therapeutic to attenuate hepatic I/R associated inflammation and liver injury.

Extracellular CIRP induces macrophage endotoxin tolerance through IL-6R-mediated STAT3 activation.

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern, whose effect on macrophages is not entirely elucidated. Here we identified that eCIRP promotes macrophage endotoxin tolerance. Septic mice had higher serum levels of eCIRP; this was associated with a reduced ex vivo immune response of their splenocytes to LPS. Pretreatment of macrophages with recombinant murine CIRP (rmCIRP) resulted in a tolerance to LPS stimulation as demonstrated by a reduction of TNF-α production. We found that eCIRP increased phosphorylated STAT3 (p-STAT3) in macrophages. A STAT3 inhibitor, Stattic, rescued macrophages from rmCIRP-induced tolerance by restoring the release of TNF-α in response to LPS stimulation. We discovered strong binding affinity between eCIRP and IL-6 receptor (IL-6R) as revealed by Biacore, fluorescence resonance energy transfer (FRET), and their colocalization in macrophages by immunostaining assays. Blockade of IL-6R with its neutralizing Ab inhibited eCIRP-induced p-STAT3 and restored LPS-stimulated TNF-α release in macrophages. Incubation of macrophages with rmCIRP skewed them toward an M2 phenotype, while treatment with anti-IL-6R Ab prevented rmCIRP-induced M2 polarization. Thus, we have demonstrated that eCIRP activates p-STAT3 via a novel receptor, IL-6R, to promote macrophage endotoxin tolerance. Targeting eCIRP appears to be a new therapeutic option to correct immune tolerance in sepsis.

MFG-E8-derived peptide attenuates inflammation and injury after renal ischemia-reperfusion in mice.

BACKGROUND: Renal ischemia-reperfusion (renal I/R) injury may lead to acute kidney injury (AKI). After renal I/R, proinflammatory mediators cause immune cell infiltration and further injury. Milk fat globule-epidermal growth factor-factor 8 (MFG-E8) is a protein involved in cell-cell and cell-matrix interactions. MSP68 is an MFG-E8-derived peptide that inhibits neutrophil adhesion and migration. Here, we evaluated whether MSP68 attenuates renal I/R injury. MATERIALS AND METHODS: Adult C57BL/6 mice were subjected to bilateral renal ischemia for 30 min followed by reperfusion and intraperitoneal administration of saline (vehicle) or MSP68 (5 mg/kg). Sham animals underwent laparotomy without renal I/R. The blood collected and studied for BUN, creatinine, and LDH by colorimetry. The kidneys were analyzed for IL-6 and TNFα by qPCR, ELISA, histological injury, and apoptosis by TUNEL. RESULTS: At 24 h after surgery, serum levels of BUN, creatinine, and LDH were markedly higher in vehicle-treated renal I/R mice than in sham mice, but significantly lower in MSP68-treated renal I/R mice. Similarly, compared to sham, renal levels of IL-6 mRNA and protein and TNFα protein were markedly higher in vehicle-treated renal I/R mice, but significantly lower in MSP68-treated renal I/R mice. Vehicle-treated renal I/R mice also had severe renal tubular histological injury, which was significantly lower in MSP68-treated renal I/R mice. Additionally, the kidneys of vehicle-treated renal I/R mice had a 93-fold increase in TUNEL-positive cells, which were reduced by 35% in mice treated with MSP68. CONCLUSION: MSP68 has the potential to be developed as novel therapeutic agent for patients with AKI.

Deficiency of cold-inducible ribonucleic acid-binding protein reduces renal injury after ischemia-reperfusion.

BACKGROUND: Renal ischemia-reperfusion injury, commonly caused by major operation and shock, leads to acute kidney injury and is associated with high morbidity and mortality. Cold-inducible ribonucleic acid-binding protein, a cold shock protein, has recently been identified as a damage-associated molecular pattern. We hypothesized that cold-inducible ribonucleic acid-binding protein exacerbates severity of injury in renal ischemia-reperfusion. METHODS: Renal ischemia was induced in an 8-week-old male C57BL/6 wild-type mice and Cirp(-/-) mice via bilateral clamping of renal pedicles for 30 minutes, followed by reperfusion for 5 or 24 hours and harvest of blood and renal tissue for analysis. Anti-cold-inducible ribonucleic acid-binding protein antibody or non-immunized immunoglobulin G (IgG) was injected intravenously (10 mg/kg body weight) at time of reperfusion. RESULTS: After renal ischemia-reperfusion, Cirp(-/-) mice demonstrated a reduction of blood urea nitrogen and creatinine of 53% and 60%, respectively, compared with wild-type mice. Serum IL-6 levels were reduced significantly: 70% in Cirp(-/-) mice compared with wild-type mice after renal ischemia-reperfusion. Levels of nitrotyrosine, an oxidatively modified protein marker, and cyclooxygenase-2, an inflammatory mediator, also were significantly decreased in the kidneys of the Cirp(-/-) mice compared with wild-type mice after renal ischemia-reperfusion. Renal caspase-3 activity was decreased in Cirp(-/-) mice compared with wild-type mice after renal ischemia-reperfusion, which corresponded to the reduction of apoptotic cells determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. Injection of neutralizing anti-cold-inducible ribonucleic acid-binding protein antibody into wild-type mice led to an 82% reduction in blood urea nitrogen compared with the vehicle after renal ischemia-reperfusion. CONCLUSION: Deficiency of cold-inducible ribonucleic acid-binding protein results in less renal injury after renal ischemia-reperfusion by attenuating inflammation and oxidative stress. Furthermore, blockade of cold-inducible ribonucleic acid-binding protein shows a protective effect, indicating cold-inducible ribonucleic acid-binding protein as a target in the treatment of renal ischemia-reperfusion.

Combined Administration of Human Ghrelin and Human Growth Hormone Attenuates Organ Injury and Improves Survival in Aged Septic Rats.

Sepsis is a major healthcare concern, especially in the elderly population. The use of an animal model closely resembling clinical conditions in this population may provide a better prediction in translating bench studies to the bedside. Ghrelin inhibits sympathetic nerve activity and inflammation in young septic animals; however, aged animals become hyporesponsive to ghrelin. In this study, we evaluated the efficacy of combined human ghrelin and growth hormone (GH) for sepsis treatment in the elderly utilizing a clinically relevant animal model of sepsis. Male Fischer 344 rats 22 to 24 months old were subjected to cecal ligation and puncture (CLP). Human ghrelin plus GH or vehicle (normal saline) was administered subcutaneously at 5 h after CLP. At 20 h after CLP, blood and tissue samples were collected for various analyses. Combined treatment attenuated serum levels of lactate, lactate dehydrogenase, creatinine, blood urea nitrogen, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in aged septic rats. The integrity of the microscopic structure in the lungs, liver and kidneys was well preserved after treatment. Expression of IL-6, TNF-α, macrophage inflammatory protein-2 and keratinocyte-derived chemokine as well as myeloperoxidase activity and caspase-3 activation were significantly reduced in the lungs and liver of treated rats. Moreover, treated rats showed an improvement in cardiovascular function and increased expression of ghrelin receptor and c-fos in the brainstem. Finally, the 10-d survival of aged septic rats was increased from 29% to 64% after combined treatment and was associated with less body weight loss. Our findings warrant the development of combined human ghrelin and GH for sepsis treatment in the geriatric population.

A deficiency in cold-inducible RNA-binding protein accelerates the inflammation phase and improves wound healing.

Chronic or non-healing wounds are a major concern in clinical practice and these wounds are mostly associated with diabetes, and venous and pressure ulcers. Wound healing is a complex process involving overlapping phases and the primary phase in this complex cascade is the inflammatory state. While inflammation is necessary for wound healing, a prolonged inflammatory phase leads to impaired healing. Cold-inducible RNA-binding protein (CIRP) belongs to a family of cold-shock proteins that are expressed in high levels under stress conditions. Recently, we demonstrated that a deficiency in CIRP led to decreased inflammation and mortality in an experimental model of hemorrhagic shock. Thus, we hypothesized that a deficiency in CIRP would accelerate the inflammatory phase and lead to an improvement in cutaneous wound healing. In this study, to examine this hypothesis, a full-thickness wound was created on the dorsum of wild-type (WT) and CIRP-/- mice. The wound size was measured every other day for 14 days. The wound area was significantly decreased in the CIRP-/- mice by day 9 and continued to decrease until day 14 compared to the WT mice. In a separate cohort, mice were sacrificed on days 3 and 7 after wounding and the skin tissues were harvested for histological analysis and RNA measurements. On day 3, the mRNA expression of tumor necrossis factor (TNF)-α in the skin tissues was increased by 16-fold in the WT mice, whereas these levels were increased by 65-fold in the CIRP-/- mice. Of note on day 7, while the levels of TNF-α remained high in the WT mice, these levels were significantly decreased in the CIRP-/- mice. The histological analysis of the wounded skin tissue indicated an improvement as early as day 3 in the CIRP-/- mice, whereas in the WT mice, infiltrated immune cells were still present on day 7. On day 7 in the CIRP-/- mice, Gr-1 expression was low and CD31 expression was high, whereas in the WT mice, Gr-1 expression was high and CD31 expression was low, indicating that the CIRP-/- mice have already moved into the angiogenesis and tissue formation phase, whereas the WT mice were still in the inflammatory state. These data collectively suggest that a deficiency in CIRP accelerates the wound healing process.