Model of polymicrobial peritonitis that induces the proinflammatory and immunosuppressive phases of sepsis

Nicotinamide Mononucleotide Administration Triggers Macrophages Reprogramming and Alleviates Inflammation During Sepsis Induced by Experimental Peritonitis

Peritonitis and subsequent sepsis lead to high morbidity and mortality in response to uncontrolled systemic inflammation primarily mediated by macrophages. Nicotinamide adenine dinucleotide (NAD+) is an important regulator of oxidative stress and immunoinflammatory responses. However, the effects of NAD+ replenishment during inflammatory activation are still poorly defined. Hence, we investigated whether the administration of β-nicotinamide mononucleotide (β-NMN), a natural biosynthetic precursor of NAD+, could modulate the macrophage phenotype and thereby ameliorate the dysregulated inflammatory response during sepsis. For this purpose, C57BL6 mice were subjected to the cecal ligation and puncture (CLP) model to provoke sepsis or were injected with thioglycolate to induce sterile peritonitis with recruitment and differentiation of macrophages into the inflamed peritoneal cavity. β-NMN was administered for 4 days after CLP and for 3 days post thioglycolate treatment where peritoneal macrophages were subsequently analyzed. In the CLP model, administration of β-NMN decreased bacterial load in blood and reduced clinical signs of distress and mortality during sepsis. These results were supported by transcriptomic analysis of hearts and lungs 24 h post CLP-induction, which revealed that β-NMN downregulated genes controlling the immuno-inflammatory response and upregulated genes involved in bioenergetic metabolism, mitochondria, and autophagy. In the thioglycolate model, a significant increase in the proportion of CD206 macrophages, marker of anti-inflammatory M2 phenotype, was detected on peritoneal exudate macrophages from β-NMN-administered mice. Transcriptomic signature of these macrophages after bacterial stimulation confirmed that β-NMN administration limited the pro-inflammatory M1 phenotype and induced the expression of specific markers of M2 type macrophages. Furthermore, our data show that β-NMN treatment significantly impacts NAD + metabolism. This shift in the macrophage phenotype and metabolism was accompanied by a reduction in phagolysosome acidification and secretion of inflammatory mediators in macrophages from β-NMN-treated mice suggesting a reduced pro-inflammatory activation. In conclusion, administration of β-NMN prevented clinical deterioration and improved survival during sepsis. These effects relied on shifts in the metabolism of organs that face up an increased energy requirement caused by bacterial infection and in innate immunity response, including reprogramming of macrophages from a highly inflammatory phenotype to an anti-inflammatory/pro-resolving profile.

Curcumol Targeting PAX8 Inhibits Ovarian Cancer Cell Migration and Invasion and Increases Chemotherapy Sensitivity of Niraparib

Objective. To investigate the effects of Curcumol on invasion, migration and epithelial-mesenchymal transformation of IGROV-1 and OVCAR-3 cells in ovarian cancer and its potential mechanism. Meanwhile, the effect of Curcumol on the antitumor activity of Niraparib was analyzed. Methods. Cell Counting Kit 8 (CCK-8) was used to detect the effects of Curcumol on the activity of IGROV-1 and OVCAR 3 cells. In vitro invasion assay (Transwell) was used to test the invasiveness of cells. Cell migration was detected by scratch assay. The inhibitory effect of Curcumol on PAX8 was detected by QRT-PCR. To evaluate the antitumor effect of Curcumol in subcutaneous tumor-bearing animal model. Results. Knockdown of PAX8 could inhibit the proliferation, invasion and migration of ovarian cancer cells. After Curcumol treated IGROV-1 and OVCAR-3 cells, the cell proliferation ability was decreased, the number of invasive cells was significantly reduced, and the scratch closure rate was significantly reduced, in a dose-dependent manner. Mechanism studies showed that Curcumol increased the antitumor activity of Niraparib by inhibiting PAX8. Conclusion. Curcumol can inhibit the invasion, migration and epithelial-mesenchymal transformation of IGROV-1 and OVCAR-3 cells in ovarian cancer, and its mechanism is related to the targeted inhibition of PAX8. Curcumol also increased the sensitivity of Niraparib chemotherapy by inhibiting PAX8.

The microbial composition of the initial insult can predict the prognosis of experimental sepsis

We hypothesized that the composition of sepsis-inducing bacterial flora influences the course of fecal peritonitis in rodents. Saline or fecal suspensions with a standardized dose range of bacterial colony-forming units (CFUs) were injected intraperitoneally into Sprague–Dawley rats. The qualitative composition of the initial inoculum and the ascites was analyzed separately by MALDI-TOF mass spectrometry. Invasive monitoring was conducted in separate anesthetized groups (n = 12–13/group) after 12, 24, 48 and 72 h to determine rat-specific organ failure assessment (ROFA) scores. Death and ROFA scores peaked at 24 h. At this time, 20% mortality occurred in animals receiving a monomicrobial E. coli suspension, and ROFA scores were significantly higher in the monomicrobial subgroup than in the polymicrobial one (median 6.5; 5.0–7.0 and 5.0; 4.75–5.0, respectively). ROFA scores dropped after 48 h, accompanied by a steady decrease in ascites CFUs and a shift towards intra-abdominal monomicrobial E. coli cultures. Furthermore, we found a relationship between ascites CFUs and the evolving change in ROFA scores throughout the study. Hence, quantitatively identical bacterial loads with mono- or polymicrobial dominance lead to a different degree of sepsis severity and divergent outcomes. Initial and intraperitoneal microbiological testing should be used to improve translational research success.

Protective Effect of Curcumin on Bone Trauma in a Rat Model via Expansion of Myeloid Derived Suppressor Cells

BACKGROUND Bone fracture, a common injury to bones leads to various biophysiological changes and pathological responses in the body. The current study investigated curcumin for treatment of bone fracture in a rat model of bone trauma, and evaluated the related mechanism. MATERIAL AND METHODS The rats were separated randomly into 3 groups; sham, model, and curcumin treatment groups. The fracture rat model was established by transverse osteotomy in the right femur bone at the mid-shaft. The osteoblast count was determined using hematoxylin and eosin staining. Vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) expression were measured by western blotting. RESULTS The rpS6-phosphorylation was suppressed and light chain 3 (LC3II) expression elevated in the curcumin treated group of the fracture rat model. In the curcumin-treated group, mineralization of fracture calluses was markedly higher on day 14 of fracture. The formation of osteoblasts was observed at a greater rate in the curcumin treated group compared to the model rat group. Treatment of rats with curcumin significantly (P<0.05) promoted expression of PCNA and VEGF. The decrease in CD11b+/Gr-1+ cell expansion in rats with bone trauma was alleviated significantly by curcumin treatment. A marked increase in arginase-1 expression in rats with bone trauma was caused by curcumin treatment. CONCLUSIONS In summary, curcumin activates autophagy and inhibits mTOR activation in bone tissues of rats with trauma. The curcumin promoted myeloid-derived suppressor cell (MDSC) proliferation and increased expansion of MDSCs in a rat model of trauma. Therefore, curcumin may have beneficial effect in patients with bone trauma and should be evaluated further for development of treatment.

Essential Role of Visfatin in Lipopolysaccharide and Colon Ascendens Stent Peritonitis-Induced Acute Lung Injury

Acute lung injury (ALI) is a life-threatening syndrome characterized by acute and severe hypoxemic respiratory failure. Visfatin, which is known as an obesity-related cytokine with pro-inflammatory activities, plays a role in regulation of inflammatory cytokines. The mechanisms of ALI remain unclear in critically ill patients. Survival in ALI patients appear to be influenced by the stress generated by mechanical ventilation and by ALI-associated factors that initiate the inflammatory response. The objective for this study was to understand the mechanisms of how visfatin regulates inflammatory cytokines and promotes ALI. The expression of visfatin was evaluated in ALI patients and mouse sepsis models. Moreover, the underlying mechanisms were investigated using human bronchial epithelial cell lines, BEAS-2B and NL-20. An increase of serum visfatin was discovered in ALI patients compared to normal controls. Results from hematoxylin and eosin (H&E) and immunohistochemistry staining also showed that visfatin protein was upregulated in mouse sepsis models. Moreover, lipopolysaccharide (LPS) induced visfatin expression, activated the STAT3/NFκB pathway, and increased the expression of pro-inflammatory cytokines, including IL1-β, IL-6, and TNF-α in human bronchial epithelial cell lines NL-20 and BEAS-2B. Co-treatment of visfatin inhibitor FK866 reversed the activation of the STAT3/NFκB pathway and the increase of pro-inflammatory cytokines induced by LPS. Our study provides new evidence for the involvement of visfatin and down-stream events in acute lung injury. Further studies are required to confirm whether the anti-visfatin approaches can improve ALI patient survival by alleviating the pro-inflammatory process.

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis

Sepsis is associated with thrombocytopenia and microvascular thrombosis. Studies have described platelets implication in this pathology but their kinetics of activation and behavior remain poorly known. We show in a mouse model of peritonitis, the appearance of platelet-rich thrombi in organ microvessels and organ damage. Complementary methods are necessary to characterize platelet activation during sepsis as circulating soluble markers and platelet-monocyte aggregates revealed early platelet activation, while surface activation markers were detected at later stage. A microfluidic based ex-vivo thrombosis assay demonstrated that platelets from septic mice have a prothrombotic behavior at shear rate encountered in microvessels. Interestingly, we found that even though phosphoinositide-3-kinase β-deficient platelet mice formed less thrombi in liver microcirculation, peritoneal sepsis activates a platelet alternative pathway to compensate the otherwise mandatory role of this lipid-kinase to form stable thrombi at high shear rate. Platelets are rapidly activated during sepsis. Thrombocytopenia can be attributed in part to platelet-rich thrombi formation in capillaries and platelet-leukocytes interactions. Platelets from septic mice have a prothrombotic phenotype at a shear rate encountered in arterioles. Further studies are necessary to unravel molecular mechanisms leading to this prothrombotic state of platelets in order to guide the development of future treatments of polymicrobial sepsis.

Polymicrobial sepsis and non-specific immunization induce adaptive immunosuppression to a similar degree

Sepsis is frequently complicated by a state of profound immunosuppression, in its extreme form known as immunoparalysis. We have studied the role of the adaptive immune system in the murine acute peritonitis model. To read out adaptive immunosuppression, we primed post-septic and control animals by immunization with the model antigen TNP-ovalbumin in alum, and measured the specific antibody-responses via ELISA and ELISpot assay as well as T-cell responses in a proliferation assay after restimulation. Specific antibody titers, antibody affinity and plasma cell counts in the bone marrow were reduced in post-septic animals. The antigen-induced splenic proliferation was also impaired. The adaptive immunosuppression was positively correlated with an overwhelming general antibody response to the septic insult. Remarkably, antigen “overload” by non-specific immunization induced a similar degree of adaptive immunosuppression in the absence of sepsis. In both settings, depletion of regulatory T cells before priming reversed some parameters of the immunosuppression. In conclusion, our data show that adaptive immunosuppression occurs independent of profound systemic inflammation and life-threatening illness.

Full activation of CD4+ T cells early during sepsis requires specific antigen

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During sepsis, CD4⁺ T cells express activation markers within the first 24 h. In the present study, the mechanisms of T-cell activation and its consequences were addressed in an acute peritonitis model in mice. The response of CD4⁺ T cells to sepsis induction was compared between OTII mice, characterized by ovalbumin-specific T-cell receptor–transgenic T cells, and C57BL/6 controls (wild type [WT] mice). Because ovalbumin was absent during peritonitis, the OTII CD4⁺ T cells could not be activated by canonical antigen recognition. In both OTII and WT control mice, CD4⁺ T effector cells and CD4⁺ Foxp3⁺ regulatory T cells (Tregs) expressed the activation marker CD69 early after sepsis onset. However, full activation with upregulation of CD25 and proliferation took place only in the presence of the antigen. Besides this, the fraction of Tregs was lower in OTII than that in WT mice. Sepsis mortality was increased in OTII mice. Our data show that, in sepsis, partial activation of CD4⁺ T cells is induced by a T-cell receptor–independent pathway, whereas full stimulation and proliferation require a specific antigen. Antigen-dependent T-cell effector functions as well as Treg activity may contribute to sepsis survival.

Alcohol extract of Schinu sterebinthifolius raddi (anacardiaceae) as a local antimicrobial agent in severe autogenously fecal peritonitis in rats

PURPOSE

To develop an alcoholic extract of the inner bark of the Schinus terebinthifolius raddi and to test its impact on autogenously fecal peritonitis in Wistar rats.

METHODS

The inner bark of the Schinus terebinthifolius raddi was kept for seven days in 70% ethanol alcohol. The total elimination of the solvent was performed in a rotary evaporator under reduced pressure at 55-60°C. Four milliliter of this extract was injected, after 24 h, into the abdominal cavity of six out of eight survival rats that underwent autogenously fecal peritonitis with five milliliter of 10% filtered fecal suspension. They were clinically followed up for 45 days when they were euthanized. The necropsy findings (inventory) of the abdominal and thorax cavities were inspected and the main findings were recorded and photographed. The investigation was approved by the Ethics Committee.

RESULTS

Two out of six survival rats that were critically ill after 24 h died within the 12 h after the extract injection into the abdominal cavity. Four rats that were also critically ill recovered and gradually became healthy, eating well, regaining weight and moving normally in the cage. At 45 days post severe peritonitis the necropsy findings revealed few signs of residual infection on the abdominal and thorax cavities. There were no bowel adhesions.

CONCLUSION

The impact of alcoholic extract of the inner bark of the Schinus terebinthifolius raddi was considered very positive and promising as natural local antiseptic against very severe peritonitis in Wistar rats.

TRAIL induces neutrophil apoptosis and dampens sepsis-induced organ injury in murine colon ascendens stent peritonitis

TNF-related apoptosis inducing ligand (TRAIL) influences several inflammatory reactions by partially still unknown mechanisms. TRAIL is produced and expressed by several cells of the immune system. Murine Colon Ascendens Stent Peritonitis (CASP) represents a hyperinflammatory model of diffuse peritonitis. As we have shown previously, TRAIL strongly improves survival in murine CASP. This is accompanied by a significantly reduced infiltration of neutrophils in the associated lymphoid tissue. Additionally, it is known that TRAIL induces apoptosis in neutrophils and acceleration of neutrophil apoptosis enhances resolution of inflammatory reactions. In this study, we investigated the correlation of the protective effect of TRAIL in sepsis and its influence on neutrophils. We found that neutrophils infiltrating the lymphoid organs express the TRAIL-receptor DR5 at high density. Furthermore, we demonstrated that TRAIL-treatment enhances apoptosis of neutrophils in the spleen, lung and liver and decreases organ injury during sepsis. To further examine a role for neutrophils in TRAIL-mediated protection in CASP, we have depleted neutrophils 24 hours prior to CASP. In these depleted mice, administration of TRAIL was ineffective. We conclude that TRAIL induces apoptosis in tissue-infiltrating neutrophils thereby protecting organs from sepsis-induced injury.

Severity of sepsis-induced acute kidney injury in a novel mouse model is age dependent

OBJECTIVE

Despite extensive research, the mortality rate of patients with sepsis-induced acute kidney injury (AKI) is unacceptably high, especially in the elderly. Current sepsis models have difficulties in reproducing AKI. This study aimed to develop a novel, clinically relevant mouse model for sepsis-induced AKI by uterine ligation and inoculation of bacteria. In addition, the age dependency of the severity of sepsis and sepsis-induced AKI was studied by validating this model in three different age categories.

DESIGN

Experimental animal investigation.

SETTING

University research laboratory.

SUBJECTS

Young (12-14 wks), aged (46-48 wks), and old (70-72 wks) C57BL/6 female mice were used as models for adolescent, adult premenopausal, and elderly postmenopausal women, respectively.

INTERVENTIONS

Uterine ligation and inoculation with 10 colony forming unit Escherichia coli or saline (sham) was performed; in vivo imaging with a luminescent Escherichia coli strain documented the course of infection.

MEASUREMENTS AND MAIN RESULTS

All mice had established Escherichia coli sepsis at 48 hrs postinfection, with higher mortality rate in old (43%) compared to aged (23%) or young (9%) mice. Infected mice had elevated serum or plasma cytokine, chemokine (tumor necrosis factor, interleukin-6, keratinocyte-derived chemokine, monocyte chemoattractant protein 1, and interleukin-10), and NOx concentrations compared to sham mice. AKI was confirmed by renal histology. Serum creatinine concentrations at 48 hrs increased with age (mean ± SEM; controls 0.18 ± 0.03 mg/dL, young 0.28 ± 0.03 mg/dL, aged 0.38 ± 0.05 mg/dL, and old 0.44 ± 0.06 mg/dL).

CONCLUSION

The uterine ligation and inoculation model for sepsis-induced AKI starts from a real infectious focus and shows an age-dependent severity of septic AKI that resembles AKI in humans.

Evaluation of peritoneal reinfection after fecal peritonitis

PURPOSE

To investigate the role of a previous abdominal infection on peritonitis.

METHODS

Twenty-seven adult female Wistar rats were submitted to fecal peritonitis by an intraperitoneal injection of a solution of rat feces. The animals were divided into three groups (n = 9 each): Group 1 - control - intraperitoneal injection of an amount of fecal solution known to be lethal (10 ml/kg), Group 2 - reinfection - intraperitoneal injection of an amount of fecal solution known not to be lethal (2 ml/kg) followed by an injection of fecal solution (10 ml/kg) 30 days later, Group 3 - late reinfection - intraperitoneal injection of 2 ml/kg feces followed by an injection of 10 ml/kg four months later.

RESULTS

All animals in Group 1 died within seven days after injection of the fecal solution. In contrast, in the pre-infected Group 2 only one animal died 24 hours after injection of the fecal solution (10 ml/kg). In Group 3, eight of the nine animals in each subgroup died over a period of seven days. The difference in survival time between groups 1, 2 and 3 was for p = 0.0042 (logrank test).

CONCLUSIONS

Milder peritoneal sepsis due to fecal infection raises the organic resistance to a new more intense fecal contamination occuring after a short period of time. However, this protection did not persist over a prolonged period of time.

Ageing-associated changes in cellular immunity based on the SENIEUR protocol

To investigate ageing-associated changes in cellular immunity, we recruited three groups of healthy subjects based on SENIEUR protocol criteria. In addition, 10 subjects were randomly selected from each group to isolate their T cells from peripheral blood mononuclear cells; T cell proliferation after phytohemagglutinin (PHA) stimulation was determined by methyl thiazolyl tetrazolium assays. There were no marked differences in the absolute numbers of peripheral blood T cells, NK cells or B cells among the three groups (P > 0.05). Also, no significant differences were noted in the numbers of CD4+ cells, CD8+ cells, or the CD4+/CD8+ ratios (P > 0.05). After PHA stimulation, T cell proliferation was markedly increased, with the highest level in group C and the lowest level in group A (P < 0.05). Cytokine-induced killer tumouricidal activities were also dramatically increased, with the highest activity in group C and the lowest activity in group A (P < 0.05). Our findings suggest that the number of immune cells remains unchanged with advanced age. However, there is a trend for decreased cellular immunity with an increase in age.

Hepatic Fibrosis in a Long-term Murine Model of Sepsis

Chronic sequelae of sepsis represent a major, yet underappreciated clinical problem, contributing to long-term mortality and quality-of-life impairment. In chronic liver disease, inflammation perpetuates fibrogenesis, but development of fibrosis in the post-acute phase of systemic inflammation has not been studied. Therefore, a mouse model of post-acute sequelae of sepsis was established based on polymicrobial peritonitis under antibiotic protection. Survival decreased to approximately 40% within 7 days and remained constant until day 28 (post-acute phase). In survivors, clinical recovery was observed within 1 week, whereas white blood cell and platelet count, as well as markers of liver injury, remained elevated until day 28. Macroscopically, inflammation and abscess formation were detected in the peritoneal space and on/in the liver. Microscopically, acute-chronic inflammation with ductular proliferation, focal granuloma formation in the parenchyma, and substantial hepatic fibrosis were observed. Increased numbers of potentially pathogenetic macrophages and α-smooth muscle actin-positive cells, presumably activated hepatic stellate cells, were detected in the vicinity of fibrotic areas. Fibrosis was associated with the presence of elastin and an augmented production/deposition of collagen types I and III. Microarray analyses revealed early activation of canonical and noncanonical pathways of hepatic stellate cell transdifferentiation. Thus, chronic sequelae of experimental sepsis were characterized by abscess formation, persistent inflammation, and substantial liver injury and fibrosis, the latter associated with increased numbers of macrophages/α-smooth muscle actin-positive cells and deposition of collagen types I and III. This suggests persistent activation of stellate cells, with consecutive fibrosis-a hallmark of chronic liver disease-as a result of acute life-threatening infection.

Hypothermia predicts the prognosis in colon ascendens stent peritonitis mice

BACKGROUND

The mortality rate of severe sepsis remains unacceptably high. It is difficult to make advances in the treatment of this problematic and increasingly frequent medical condition. In severe sepsis, hypothermia can be recognized as an important feature. The present study investigated the role of hypothermia in the prognosis of the colon ascendens stent peritonitis (CASP) model.

METHODS

We employed the CASP model for wild-type C57BL/6 mice. We compared physiologic indices in survivor and non-survivor groups after CASP to test whether low temperature might be a helpful predictor in sepsis. To certify this hypothesis, we examined the survival rate, peritoneal leukocytes, and organ damage. We also measured the bacterial burden and inflammatory cytokine levels at different times.

RESULTS

The temperature varied dramatically in the survivors' group compared with the non-survivors' group at 18 h. We divided the CASP models into a mild group and a severe group, based on temperatures above or below 32°C at 18 h. Mice in the severe group had a lower survival rate (0% versus 87.5%), more peritoneal leukocytes, more bacterial culture results, higher expressions of cytokines, and more classical features in pathology compared with the mild group.

CONCLUSIONS

Hypothermia (below 32°C at 18 h) might be a predictor of prognosis in CASP-induced sepsis.

Endogenous glucocorticoids promote the expansion of myeloid-derived suppressor cells in a murine model of trauma

Stress-dose of glucocorticoid has been demonstrated to be beneficial for trauma patients in clinical studies. Recently, a heterogeneous population of myeloid cells with immunosuppressive activity named myeloid-derived suppressor cells (MDSCs) has been found to accumulate in the trauma host and can be induced by glucocorticoids in vitro. In order to explore the effect of endogenous glucocorticoids on MDSCs under trauma conditions, we blocked the glucocorticoid signal in a murine trauma model using the antagonist of the glucocorticoid receptor RU486 (mifepristone). We found for the first time that RU486 not only blunted MDSC expansion induced by trauma in the spleen, peripheral blood and bone marrow especially at 6 h after traumatic stress but also decreased the survival rate from 100 to 20% in traumatic mice within 7 days. Moreover, neither MDSCs producing arginase-1 nor the morphological characterization of trauma-induced MDSCs was affected by the blockage of the glucocorticoid receptor. Our results suggest that endogenous glucocorticoids may promote MDSCs expansion in a murine trauma model and MDSCs may be beneficial for the trauma host.