Polymicrobial sepsis models: CLP versus CASP

YIQIFUMAI INJECTION AMELIORATED SEPSIS-INDUCED CARDIOMYOPATHY BY INHIBITION OF FERROPTOSIS VIA XCT/GPX4 AXIS

ABSTRACT

Sepsis-induced cardiomyopathy ( SIC ) is a distinct form of myocardial injury that disrupts tissue perfusion and stands as the significant cause of mortality among sepsis patients. Currently, effective preventive or treatment strategies for SIC are lacking. YiQiFuMai injection (YQFM), composed of Panax ginseng C.A. Mey., Ophiopogon japonicus (Thunb.) Ker Gawl., and Schisandra chinensis (Turcz.) Baill., is widely used in China to treat cardiovascular diseases, such as coronary heart disease, heart failure, and SIC . Research has shown that YQFM can improve cardiac function and alleviate heart failure through multiple pathways. Nevertheless, the mechanisms through which YQFM exerts its effects on SIC remain to be fully elucidated. In this study, we firstly investigated the therapeutic effects of YQFM on a SIC rat model and explored its effects on myocardial ferroptosis in vivo. Then, LPS-induced myocardial cell death model was used to evaluate the effects of YQFM on ferroptosis and xCT/GPX4 axis in vitro . Furthermore, using GPX4 inhibitors, we aimed to verify whether YQFM improved cardiomyocyte ferroptosis through the xCT/GPX4 axis. The results showed that YQFM was effective in alleviating myocardial injury in septic model rats. Besides, the concentrations of iron and the levels of lipid peroxidation-related factors (ROS, MDA, and 4-HNE) were significantly decreased and the expression of xCT/GPX4 axis was upregulated in SIC rats after YQFM treatment. In vitro studies also showed that YQFM alleviated iron overload and lipid peroxidation and activated xCT/GPX4 axis in LPS-induced myocardial cell death model. Moreover, GPX4 inhibitor could abolish the effects above. In summary, the study highlights the regulatory effect of YQFM in mitigating myocardial injury. It probably achieves this ameliorative effect by enhancing xCT/GPX4 axis and further reducing ferroptosis.

Translational medicine for acute lung injury

Acute lung injury (ALI) is a complex disease with numerous causes. This review begins with a discussion of disease development from direct or indirect pulmonary insults, as well as varied pathogenesis. The heterogeneous nature of ALI is then elaborated upon, including its epidemiology, clinical manifestations, potential biomarkers, and genetic contributions. Although no medication is currently approved for this devastating illness, supportive care and pharmacological intervention for ALI treatment are summarized, followed by an assessment of the pathophysiological gap between human ALI and animal models. Lastly, current research progress on advanced nanomedicines for ALI therapeutics in preclinical and clinical settings is reviewed, demonstrating new opportunities towards developing an effective treatment for ALI.

LCZ696 attenuates sepsis-induced liver dysfunction in rats; the role of oxidative stress, apoptosis, and JNK1/2-P38 signaling pathways

AIM

Sepsis is a serious inflammatory response to infection with an annual incidence rate of >48 million cases and 11 million fatalities worldwide. Furthermore, sepsis remains the world's fifth-greatest cause of death. For the first time, the current study aims to evaluate the possible hepatoprotective benefits of LCZ696, a combination of an angiotensin receptor blocker (valsartan) and a neprilysin inhibitor prodrug (sacubitril), on cecal ligation and puncture (CLP)-induced sepsis in rats.

MAIN METHODS

CLP was employed to induce sepsis. Hepatic malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), interleukin-6 (IL-6), IL-1β, tumor necrosis factor-alpha (TNF-α), and caspase 3 were assessed using ELISA. Serum alanine transaminase (ALT) and aspartate transaminase (AST) were also measured. Western blot assay was used to determine the expression of JNK1/2 and P38 proteins. The histology of liver tissues was also examined.

KEY FINDINGS

CLP resulted in significant elevation of AST, ALT, MDA, IL-6, IL-1β, TNF-α, and caspase 3 levels, and up-regulation of p/t JNK1/2, and p/t P38 proteins, as compared to the sham group. However, level of GSH, and SOD activity were reduced in CLP group. LCZ696 significantly improved all the previously mentioned biochemical and histological abnormalities better than using valsartan alone.

SIGNIFICANCE

LCZ696 substantially ameliorated CLP-induced liver damage, compared to valsartan, by reducing proinflammatory mediators, inhibiting the JNK1/2 and P38 signaling pathway, and attenuating apoptosis.

Currently Used Methods to Evaluate the Efficacy of Therapeutic Drugs and Kidney Safety

Kidney diseases with kidney failure or damage, such as chronic kidney disease (CKD) and acute kidney injury (AKI), are common clinical problems worldwide and have rapidly increased in prevalence, affecting millions of people in recent decades. A series of novel diagnostic or predictive biomarkers have been discovered over the past decade, enhancing the investigation of renal dysfunction in preclinical studies and clinical risk assessment for humans. Since multiple causes lead to renal failure, animal studies have been extensively used to identify specific disease biomarkers for understanding the potential targets and nephropathy events in therapeutic insights into disease progression. Mice are the most commonly used model to investigate the mechanism of human nephropathy, and the current alternative methods, including in vitro and in silico models, can offer quicker, cheaper, and more effective methods to avoid or reduce the unethical procedures of animal usage. This review provides modern approaches, including animal and nonanimal assays, that can be applied to study chronic nonclinical safety. These specific situations could be utilized in nonclinical or clinical drug development to provide information on kidney disease.

Protocol for a Sepsis Model Utilizing Fecal Suspension in Mice: Fecal Suspension Intraperitoneal Injection Model

Background

Various animal models of sepsis have been developed to optimize sepsis treatment. However, therapeutic agents that were successful in animal models were rarely effective in human clinical trials. The cecal ligation and puncture (CLP) model is currently the gold standard for sepsis studies. However, its limitations include the high variability among researchers and the difficulty in comparing animals with different cecum shapes and sizes. In this study, we established a protocol for the creation of a simple and accessible sepsis rodent model using fecal suspensions that minimized differences in technical effects among researchers and individual differences in animals.

Methods

A mouse model of sepsis using fecal suspension intraperitoneal injection (FSI) was created using fresh stool excreted within 24 h. The collected fresh stool was dissolved in saline solution and filtered. The obtained fecal suspension was injected intraperitoneally into the mice. Moreover, fecal suspensions with different concentrations were prepared, and the survival rates were compared among the fecal suspensions for each concentration. To assess the validity of the FSI as a sepsis model, CLP and FSI with similar mortality rates were compared pathologically, physiologically, immunologically, and bacteriologically. Histopathological comparison was evaluated by hematoxylin-eosin and Gram staining of the parenchymal organs. Physiological evaluation was performed by comparing the respiratory rate, body temperature, and blood gas analysis results. Immunological assessment was performed using multiplex analysis. Bacteriological comparisons were performed by culturing ascites fluid.

Results

The FSI model increased mortality in proportion to the fecal suspension concentration. The mortality rate was reduced with antibiotic administration. In various comparative experiments conducted using the FSI and CLP models, both models showed findings consistent with sepsis. Furthermore, the FSI model showed less variability among the individuals in each test.

Conclusion

This is the first detailed and accurate report of a protocol for creating a sepsis model using fecal suspension. The FSI model is a minimally invasive and accessible sepsis rodent model. Its clinical validity as a sepsis model was proven via histological, physiological, microbiological, and immunological evaluation methods. The FSI model minimizes individual differences between mice and helps to conduct accurate studies after the onset of sepsis.

Metabolic syndrome improves cardiovascular dysfunction and survival during cecal ligation and puncture-induced mild sepsis in mice

AIMS

Sepsis is a potentially fatal systemic inflammatory response and its underlying pathophysiology is still poorly understood. Studies suggest that obesity, a component of metabolic syndrome (MS), is associated with sepsis survival. Therefore, this study focused on investigating the influence of MS on mortality and cardiovascular dysfunction induced by sublethal cecal ligation and puncture (SL-CLP).

MAIN METHODS

Newborn Swiss mice received monosodium glutamate (MSG) (4 mg kg^-1 day^-1, s.c.) during the first 5 d of life for MS induction, while the control pups received equimolar saline solution. On the 75th day, SL-CLP was used to induce mild sepsis (M-CLP) in the MS (MS-M-CLP) and control (SAL-M-CLP) mice. The effect of MS on sepsis in mice was assessed by determining the survival rate and quantification of nitric oxide (NO) in the plasma, and associating this data with hematological and cardiovascular parameters.

KEY FINDINGS

MS improved the survival of septic mice, preventing impairment to hematological and cardiovascular parameters. In addition, MS attenuated plasmatic NO increase, which is a typical feature of sepsis.

SIGNIFICANCE

These findings provide new insights into the relationship between obesity and mild sepsis in mice, thus revealing an approach in favor of the "obesity paradox."

β-Lapachone Increases Survival of Septic Mice by Regulating Inflammatory and Oxidative Response

Sepsis is characterized by a dysregulated immune response to infection characterized by an early hyperinflammatory and oxidative response followed by a subsequent immunosuppression phase. Although there have been some advances in the treatment of sepsis, mortality rates remain high, urging for the search of new therapies. β-Lapachone (β-Lap) is a natural compound obtained from Tabebuia avellanedae Lorentz ex Griseb. with several pharmacological properties including bactericidal, anti-inflammatory, and antioxidant activity. Thus, the aim of this study was to evaluate the effects of β-Lap in a mouse sepsis model. To this, we tested two therapeutic protocols in mice submitted to cecal ligation and puncture- (CLP-) induced sepsis. First, we found that in pretreated animals, β-Lap reduced the systemic inflammatory response and improved bacterial clearance and mouse survival. Moreover, β-Lap also decreased lipid peroxidation and increased the total antioxidant capacity in the serum and peritoneal cavity of septic animals. In the model of severe sepsis, the posttreatment with β-Lap was able to increase the survival of animals and maintain the antioxidant defense function. In conclusion, the β-Lap was able to increase the survival of septic animals by a mechanism involving immunomodulatory and antioxidant protective effects.

Vendor effects on murine gut microbiota influence experimental abdominal sepsis

BACKGROUND

Experimental animal models are indispensable components of preclinical sepsis research. Reproducible results highly rely on defined and invariant baseline conditions. Our hypothesis was that the murine gut microbiota varies among different distributors of laboratory animals and that these variations influence the phenotype of abdominal sepsis derived from a bacterial inoculum model (intraperitoneal stool injection).

MATERIALS AND METHODS

Male C57BL/6 mice (8-wk old) purchased from Charles River (CR), Janvier (J), and Harlan (H) were sacrificed, and the bacterial composition of feces was analyzed using CHROMagar orientation medium. Stool was injected intraperitoneally into CR mice, followed by clinical observation and gene expression analysis. Experiments were repeated 16 mo later under the same conditions.

RESULTS

Stool analysis revealed profound intervendor differences in bacterial composition, mainly regarding Staphylococcus aureus and Bacillus licheniformis. Mice challenged with CR as well as H feces developed significantly higher severity of disease and died within the observation period, whereas stool from J mice did not induce any of these symptoms. Real-time polymerase chain reaction revealed corresponding results with significant upregulation of proinflammatory cytokines and vascular leakage-related mediators in CR and H injected animals. Sixteen months later, the bacterial fecal composition had significantly shifted. The differences in clinical phenotype of sepsis after intraperitoneal stool injection had vanished.

CONCLUSIONS

We are the first to demonstrate vendor and time effects on the murine fecal microbiota influencing sepsis models of intraabdominal stool contamination. The intestinal microbiota must be defined and standardized when designing and interpreting past and future studies using murine abdominal sepsis models.

Evaluation of 5-HT7 Receptor Trafficking on In Vivo and In Vitro Model of Lipopolysaccharide (LPS)-Induced Inflammatory Cell Injury in Rats and LPS-Treated A549 Cells

This study aimed to investigate the effects of the 5-HT7 receptor agonist (LP44) and antagonist (SB269970) on LPS-induced in vivo tissue damage and cell culture by molecular methods. This study was conducted in two steps. For in vivo studies, 24 female rats were divided into four groups. Group I: healthy; II (2nd h): LPS 5 mg/kg administered intraperitoneally (i.p.); III (4th h): LPS 5 mg/kg administered i.p.; IV (8th h): LPS 5 mg/kg administered i.p. For in vitro studies, we used the A549 cell line. Groups: I control (healthy) (2-4 h); II LPS: 1 µg/ml E. Coli O55:B5 strain (2-4 h); III agonist (LP44) 10^-9 M (2-4 h); IV antagonist (SB269970) 10^-9 M (2-4 h); V LPS+agonist 10^-9 M (LP44 1 µg/ml) (2-4 h); VI LPS+antagonist 10^-9 M (2-4 h). In molecular analyses, we determined increased TNF-α, IL-1β, NF-κB, and 5-HT7 mRNA expressions in rat lung tissues and increased TNF-α, iNOS, and 5-HT7 mRNA expressions in the A549 cell line. In in vitro parameters, LP44 agonist administration-related decrease was observed. Our study showed that lung 5-HT7 receptor expression is increased in LPS-induced endotoxemia. All this data suggest that 5-HT7 receptor overexpression is an important protective mechanism during LPS-induced sepsis-related cell damage.

Differential Paradigms in Animal Models of Sepsis

Sepsis is a serious clinical problem involving complex mechanisms which requires better understanding and insight. Animal models of sepsis have played a major role in providing insight into the complex pathophysiology of sepsis. There have been various animal models of sepsis with different paradigms. Endotoxin, bacterial infusion, cecal ligation and puncture, and colon ascendens stent peritonitis models are the commonly practiced methods at present. Each of these models has their own advantages and also confounding factors. We have discussed the underlying mechanisms regulating each of these models along with possible reasons why each model failed to translate into the clinic. In animal models, the timing of development of the hemodynamic phases and the varied cytokine patterns could not accurately resemble the progression of clinical sepsis. More often, the exuberant and transient pro-inflammatory cytokine response is only focused in most models. Immunosuppression and apoptosis in the later phase of sepsis have been found to cause more damage than the initial acute phase of sepsis. Likewise, better understanding of the existing models of sepsis could help us create a more relevant model which could provide solution to the currently failed clinical trials in sepsis.

Intraperitoneal adipose tissue is strongly related to survival rate in a mouse cecal ligation and puncture model

Cecal ligation and puncture (CLP) models exhibiting polymicrobial sepsis are considered as the gold standard in sepsis research. However, despite meticulous research being conducted in this field, only few treatment drugs are available, indicating that CLP sepsis models do not completely mimic human sepsis models. The greatest flaw in CLP models is abscess formation because the localization of inflammation caused by abscess formation increases the survival rate. Therefore, by resecting intraperitoneal adipose tissue, we developed a mouse CLP model wherein abscess formation was unlikely. Survival rates at 7 days postoperatively were compared using the Kaplan–Meier method for an intraperitoneal adipose tissue resection group (resection group, n=34), an intraperitoneal adipose tissue non-resection group (non-resection group, n=35) and a sham group (n=10). Results indicated that the survival rate was significantly higher in the non-resection group compared with the resection group. Intraperitoneal macroscopic findings in the non-resection group revealed the localization of inflammation caused by abscesses formation covered in adipose tissue. The survival rate for the sham group was 100%. Measurement of interleukin 6 (IL-6) indicated that during the 12 h after the creation of the CLP model, the median level of IL-6 was 1300 (552–3000) pg ml⁻¹ in the non-resection group (n=19) and 3000 (1224–8595) pg ml⁻¹ in the resection group (n=19). Meanwhile, for the sham group, IL-6 values were below measurement sensitivity in most cases (9/10 mice). Thus our results suggest that, in CLP models, intraperitoneal adipose tissue has an important role in abscess formation and is strongly related to the survival rate.

Refinement of animal models of sepsis and septic shock

This report aims to facilitate the implementation of the Three Rs (replacement, reduction, and refinement) in the use of animal models or procedures involving sepsis and septic shock, an area where there is the potential of high levels of suffering for animals. The emphasis is on refinement because this has the greatest potential for immediate implementation. Specific welfare issues are identified and discussed, and practical measures are proposed to reduce animal use and suffering as well as reducing experimental variability and increasing translatability. The report is based on discussions and submissions from a nonregulatory expert working group consisting of veterinarians, animal technologists, and scientists with expert knowledge relevant to the field.