Therapeutic Targets in Sepsis: Past, Present, and Future

Applications of peptides in nanosystems for diagnosing and managing bacterial sepsis

Sepsis represents a critical medical condition stemming from an imbalanced host immune response to infections, which is linked to a significant burden of disease. Despite substantial efforts in laboratory and clinical research, sepsis remains a prominent contributor to mortality worldwide. Nanotechnology presents innovative opportunities for the advancement of sepsis diagnosis and treatment. Due to their unique properties, including diversity, ease of synthesis, biocompatibility, high specificity, and excellent pharmacological efficacy, peptides hold great potential as part of nanotechnology approaches against sepsis. Herein, we present a comprehensive and up-to-date review of the applications of peptides in nanosystems for combating sepsis, with the potential to expedite diagnosis and enhance management outcomes. Firstly, sepsis pathophysiology, antisepsis drug targets, current modalities in management and diagnosis with their limitations, and the potential of peptides to advance the diagnosis and management of sepsis have been adequately addressed. The applications have been organized into diagnostic or managing applications, with the last one being further sub-organized into nano-delivered bioactive peptides with antimicrobial or anti-inflammatory activity, peptides as targeting moieties on the surface of nanosystems against sepsis, and peptides as nanocarriers for antisepsis agents. The studies have been grouped thematically and discussed, emphasizing the constructed nanosystem, physicochemical properties, and peptide-imparted enhancement in diagnostic and therapeutic efficacy. The strengths, limitations, and research gaps in each section have been elaborated. Finally, current challenges and potential future paths to enhance the use of peptides in nanosystems for combating sepsis have been deliberately spotlighted. This review reaffirms peptides' potential as promising biomaterials within nanotechnology strategies aimed at improving sepsis diagnosis and management.

A cytokine/PTX3 prognostic index as a predictor of mortality in sepsis

Background

Early prognostic stratification of patients with sepsis is a difficult clinical challenge. Aim of this study was to evaluate novel molecules in association with clinical parameters as predictors of 90-days mortality in patients admitted with sepsis at Humanitas Research Hospital.

Methods

Plasma samples were collected from 178 patients, diagnosed based on Sepsis-3 criteria, at admission to the Emergency Department and after 5 days of hospitalization. Levels of pentraxin 3 (PTX3), soluble IL-1 type 2 receptor (sIL-1R2), and of a panel of pro- and anti-inflammatory cytokines were measured by ELISA. Cox proportional-hazard models were used to evaluate predictors of 90-days mortality.

Results

Circulating levels of PTX3, sIL-1R2, IL-1β, IL-6, IL-8, IL-10, IL-18, IL-1ra, TNF-α increased significantly in sepsis patients on admission, with the highest levels measured in shock patients, and correlated with SOFA score (PTX3: r=0.44, p<0.0001; sIL-1R2: r=0.35, p<0.0001), as well as with 90-days mortality. After 5 days of hospitalization, PTX3 and cytokines, but not sIL-1R2 levels, decreased significantly, in parallel with a general improvement of clinical parameters. The combination of age, blood urea nitrogen, PTX3, IL-6 and IL-18, defined a prognostic index predicting 90-days mortality in Sepsis-3 patients and showing better apparent discrimination capacity than the SOFA score (AUC=0.863, 95% CI: 0.780−0.945 vs. AUC=0.727, 95% CI: 0.613-0.840; p=0.021 respectively).

Conclusion

These data suggest that a prognostic index based on selected cytokines, PTX3 and clinical parameters, and hence easily adoptable in clinical practice, performs in predicting 90-days mortality better than SOFA. An independent validation is required.

Epidemiology of intravenous immune globulin in septic shock: a retrospective cohort analysis of the Premier Healthcare Database

PURPOSE

Intravenous immune globulin (IVIG) may improve survival in people with septic shock. Current utilization patterns of IVIG are unknown. We sought to characterize adult patients with septic shock requiring vasopressors who received IVIG, describes IVIG regimens, and evaluate determinants of IVIG use in patients with septic shock.

METHODS

We conducted a retrospective database study of adult patients with septic shock admitted to US hospitals in the Premier Healthcare Database (from July 2010 to June 2013). We described the proportion of patients with septic shock receiving IVIG, examined IVIG regimens across sites and employed random-effects multivariable regression techniques to identify predictors of IVIG use.

RESULTS

Intravenous immune globulin was administered to 0.3% (n = 685) of patients with septic shock; with a median [interquartile range (IQR)] dose of 1 [0.5-1.8] g·kg-1 for a median [IQR] of 1 [1-2] day. Receipt of IVIG was less likely for Black patients (odds ratio [OR], 0.54; 95% confidence interval [CI] 0.41 to 0.72) and patients without private insurance (Medicare OR, 0.73; 95% CI 0.59 to 0.90; Medicaid OR, 0.41; 95% CI 0.30 to 0.57) and more likely for patients with immunocompromise (OR, 6.83; 95% CI 5.47 to 8.53), necrotizing fasciitis (OR, 9.78; 95% CI 6.97 to 13.72), and toxic shock (OR, 56.9; 95% CI 38.7 to 83.7).

CONCLUSIONS

Intravenous immune globulin is used infrequently across the US in patients with septic shock. Regimens of IVIG in septic shock may be less intensive than those associated with a survival benefit in meta-analyses. Observed infrequent use supports apparent clinical equipoise, perhaps secondary to limitations of the primary literature. A clinical trial evaluating the role of IVIG in septic shock is needed.

Intravenous immune globulin in septic shock: a Canadian national survey of critical care medicine and infectious disease specialist physicians

PURPOSE

This national survey evaluated the perceived efficacy and safety of intravenous immune globulin (IVIG) in septic shock, self-reported utilization patterns, barriers to use, the population of interest for further trials and willingness to participate in future research of IVIG in septic shock.

METHODS

We conducted a cross-sectional survey of critical care and infectious diseases physicians across Canada. We summarized categorical item responses as counts and proportions. We developed a multivariable logistic regression model to identify physician-level predictors of IVIG use in septic shock.

RESULTS

Our survey was disseminated to 674 eligible respondents with a final response rate of 60%. Most (91%) respondents reported having prescribed IVIG to patients with septic shock at least once, 86% for septic shock due to necrotizing fasciitis, 52% for other bacterial toxin-mediated causes of septic shock, and 5% for undifferentiated septic shock. The majority of respondents expressed uncertainty regarding the impact of IVIG on mortality (97%) and safety (95%) in septic shock. Respondents were willing to participate in further IVIG research with 98% stating they would consider enrolling their patients into a trial of IVIG in septic shock. Familiarity with published evidence was the single greatest predictor of IVIG use in septic shock (odds ratio, 10.2; 95% confidence interval, 3.4 to 30.5; P < 0.001).

CONCLUSIONS

Most Canadian critical care and infectious diseases specialist physicians reported previous experience using IVIG in septic shock. Respondents identified inadequacy of existing research as the greatest barrier to routine use of IVIG in septic shock. Most respondents support the need for further studies on IVIG in septic shock, and would consider enrolling their own patients into a trial of IVIG in septic shock.

Emerging therapeutic targets for sepsis

Introduction: Sepsis is characterized by a dysregulated host response to infection. Sepsis-associated morbidity/mortality demands concerted research efforts toward therapeutic interventions which are reliable, broadly effective, and etiologically based. More intensive and extensive investigations on alterations in cellular signaling pathways, gene targeting as a means of modifying the characteristic hyper and/or hypo-immune responses, prevention through optimization of the microbiome, and the molecular pathways underlying the septic immune response could improve outcomes.] Areas covered: The authors discuss key experimental mammalian models and clinical trials. They provide an evaluation of evolving therapeutics in sepsis and how they have built upon past and current treatments. Relevant literature was derived from a PubMed search spanning 1987-2020.Expert opinion: Given the complex nature of sepsis and the elicited immune response, it is not surprising that a single cure-all therapeutic intervention, which is capable of effectively and reliably improving patient outcomes has failed to emerge. Innovative approaches seek to address not only the disease process but modify underlying patient factors. A true improvement in sepsis-associated morbidity/mortality will require a combination of unique therapeutic modalities.

Immunological Endotyping of Chronic Critical Illness After Severe Sepsis

Improved management of severe sepsis has been one of the major health care accomplishments of the last two decades. Due to enhanced recognition and improved management of severe sepsis, in-hospital mortality has been reduced by up to 40%. With that good news, a new syndrome has unfortunately replaced in-hospital multi-organ failure and death. This syndrome of chronic critical illness (CCI) includes sepsis patients who survive the early "cytokine or genomic storm," but fail to fully recover, and progress into a persistent state of manageable organ injury requiring prolonged intensive care. These patients are commonly discharged to long-term care facilities where sepsis recidivism is high. As many as 33% of sepsis survivors develop CCI. CCI is the result, at least in part, of a maladaptive host response to chronic pattern-recognition receptor (PRR)-mediated processes. This maladaptive response results in dysregulated myelopoiesis, chronic inflammation, T-cell atrophy, T-cell exhaustion, and the expansion of suppressor cell functions. We have defined this panoply of host responses as a persistent inflammatory, immune suppressive and protein catabolic syndrome (PICS). Why is this important? We propose that PICS in survivors of critical illness is its own common, unique immunological endotype driven by the constant release of organ injury-associated, endogenous alarmins, and microbial products from secondary infections. While this syndrome can develop as a result of a diverse set of pathologies, it represents a shared outcome with a unique underlying pathobiological mechanism. Despite being a common outcome, there are no therapeutic interventions other than supportive therapies for this common disorder. Only through an improved understanding of the immunological endotype of PICS can rational therapeutic interventions be designed.

Overexpression of Gilz Protects Mice Against Lethal Septic Peritonitis

Sepsis in humans and experimental animals is characterized by an acute inflammatory response. glucocorticoids (GCs) are widely used for the treatment of many inflammatory disorders, yet their effectiveness in sepsis is debatable. One of the major anti-inflammatory proteins induced by GCs is glucocorticoid-induced leucine zipper (GILZ, coded by the TSC22D3 gene). We found that TSC22D3 mRNA expression is downregulated in white blood cells of human sepsis patients. Interestingly, transgenic GILZ-overexpressing mice (GILZ-tg) showed better survival rates in the cecal ligation and puncture (CLP) model of mouse sepsis. To our surprise, GILZ had only mild anti-inflammatory effects in this model, as the systemic proinflammatory response was not significantly reduced in GILZ-tg mice compared with control mice. During CLP, we observed reduced bacterial counts in blood of GILZ-tg mice compared with control mice. We found increased expression of Tsc22d3 mRNA specifically in peritoneal exudate cells in the CLP model, as well as increased capacity for bacterial phagocytosis of CD45 GILZ-tg cells compared with CD45 GILZ-wt cells. Hence, we believe that the protective effects of GILZ in the CLP model can be linked to a more efficient phagocytosis.

Recombinant human milk fat globule-EGF factor VIII (rhMFG-E8) as a therapy for sepsis after acute exposure to alcohol

BACKGROUND

Alcohol intake predisposes to infections and sepsis. Alcohol and sepsis inhibit the expression of milk fat globule epidermal growth factor-factor VIII (MFG-E8), a glycoprotein essential for optimal efferocytosis, resulting in the release of proinflammatory molecules and increased sepsis severity. We previously reported that recombinant mouse (rm) MFG-E8 attenuates sepsis-induced organ injury in rats with acute alcohol intoxication. In order to develop a therapy that can be safely used in humans, we have produced recombinant human (rh) MFG-E8 and evaluated its efficacy to ameliorate sepsis after acute exposure to alcohol.

METHODS

We induced acute alcohol intoxication with a bolus injection of alcohol (1.75 g/kg BW) followed by an intravenous infusion of 300 mg/kg/h alcohol for 10 h. Sepsis was then induced by cecal ligation and puncture (CLP). At -10, 0, and 10 h relative to CLP, rats received MFG-E8 or vehicle (albumin) intravenously. Animals were euthanized at 20 h after CLP for blood and tissue collection. Additional groups of animals were used for a survival study.

RESULTS

Compared to vehicle, rhMFG-E8 treatment ameliorated blood levels of proinflammatory cytokines (% improvement: TNF-α 49.8%, IL-6 34.7%) and endotoxin (61.7%), as well as of transaminases (AST 36.2%, ALT 40.1%) and lactate (18.4%). Rats treated with rhMFG-E8 also had a significant histological attenuation of the acute lung injury, as well as a reduction in the number of apoptotic cells in the thymus (43.4%) and cleaved caspase 3 (38.7%) in the spleen. In addition, rhMFG-E8 improved the 10-day sepsis survival rate from 45 to 80% CONCLUSION: rhMFG-E8 significantly ameliorated sepsis in rats with acute alcohol exposure, demonstrating rhMFG-E8's potential to be developed as an effective therapy for sepsis in alcohol abusers.

Identification of risk factors for sepsis-associated mortality by gene expression profiling analysis

Sepsis is a common cause of mortality due to systemic infection. Although numerous studies have investigated this life-threatening condition, there remains a lack of suitable markers to evaluate the severity of sepsis. The present study focused on the identification of risk factors for sepsis‑associated mortality by genome‑wide expression profiling. Initially, the GEO2R web tool was used to identify the differentially expressed genes (DEGs) between sepsis survivors and nonsurvivors. It was identified that the upregulated DEGs in the nonsurvivors compared with survivors were highly enriched in the type I interferon (IFN‑I) signaling pathway. Furthermore, the associations of the upregulated genes were analyzed by STRING and the results demonstrated that a set of proteins in IFN‑I signaling pathway closely interacted with each other. To further investigate whether the IFN‑I signaling pathway is dysregulated in a subset of patients with a high risk of mortality due to sepsis, in this case neonates, the DEGs between the cord blood mononuclear cells of neonates and adult peripheral blood mononuclear cells were analyzed. It was identified that DEGs were not enriched in IFN‑I signaling in the blood of untreated neonates and adults; however, IFN‑I signaling was upregulated in the lipopolysaccharide (LPS)‑treated cord blood mononuclear cells of healthy neonates compared with the LPS‑treated peripheral blood mononuclear cells of adults. In addition, these data revealed that the proteins involved in the IFN‑I signaling pathway possessed a higher number of interacting partners. These results indicated that upregulated IFN‑I signaling may be a high-risk factor for mortality due to sepsis.

Vitamin C: The next step in sepsis management?

Sepsis is a life-threatening medical condition, affecting approximately 26 million people worldwide every year. The disease is a continuum, marked by dysregulated inflammation and hemodynamic instability leading to shock, multi-system organ dysfunction, and death. Over the past decades, there has been a focus on the early identification and treatment of sepsis primarily with bundled and goal directed therapy. Despite these advances, morbidity and mortality has remained high, prompting investigation into novel therapies. Vitamin C is a water-soluble vitamin that plays a role in mediating inflammation through antioxidant activities and is also important in the synthesis of cortisol, catecholamines, and vasopressin, which are key mediators in the disease process. Emerging evidence provides cursory data in support of the administration of vitamin C in addition to standard therapy to ameliorate the effects of inflammation and improve hemodynamic stability in patients with sepsis and septic shock; however, further evidence is needed to support this practice. This review discusses the physiologic role of vitamin C as well as the recent literature and evidence for the use of vitamin C in patients presenting with sepsis.

Hydroxysafflor Yellow A Attenuates the Apoptosis of Peripheral Blood CD4+ T Lymphocytes in a Murine Model of Sepsis

Sepsis is generally considered as a severe condition of inflammation that leads to lymphocyte apoptosis and multiple organ dysfunction. Hydroxysafflor yellow A (HSYA) exerts anti-inflammatory and anti-apoptotic effects in infectious diseases. However, the therapeutic effect of HSYA on polymicrobial sepsis remains unknown. This study was undertaken to investigate the therapeutic effects and the mechanisms of action of HSYA on immunosuppression in a murine model of sepsis induced by cecal ligation and puncture (CLP). NIH mice were randomly divided into four groups: control group, sham group, CLP group, and CLP+HSYA group. HSYA (120 mg/kg) was intravenously injected into experimental mice at 12 h before CLP, concurrent with CLP and 12 h after CLP. The levels of circulating inflammatory cytokines, the apoptosis of CD4⁺ and CD8⁺ T lymphocytes, and protein expression of cytochrome C (Cytc), Bax, Bcl-2, cleaved caspase-9, and cleaved caspase-3 were examined. Plasma levels of IL-6, IL-10 and TNF-alpha as well as the apoptosis of CD4⁺ T lymphocytes were increased compared with sham group. These changes were accompanied by increases of pro-apoptotic proteins including Cytc, Bax, cleaved caspase-9, and cleaved caspase-3 and decreases of anti-apoptotic protein Bcl-2 in CD4⁺ T lymphocytes from mice undergoing CLP. In contrast, we fail to observe significant effect of HSYA on the apoptosis of CD8⁺ T lymphocytes in CLP-treated group. Of note, HSYA treatment reversed all above changes observed in CD4⁺ T lymphocytes, and significantly increased the ratio of CD4⁺:CD8⁺ T lymphocytes in CLP-treated mice. In conclusion, HSYA was an effective therapeutic agent in ameliorating sepsis-induced apoptosis of CD4⁺ T lymphocytes probably through its anti-inflammatory and anti-apoptotic effects.

Protective role of cGMP in early sepsis

Septic shock, which is triggered by microbial products, is mainly characterised by inadequate tissue perfusion, which can lead to multiple organ dysfunction and death. An intense release of vasoconstrictors agents occurs in the early stages of shock, which can lead to ischemic injury. In this scenario, cGMP could play a key role in counterbalancing these agents and preventing tissue damage. Sildenafil, which is a phosphodiesterase-5 inhibitor, increases cGMP in smooth muscle cells and promotes vasodilation. Thus, the purpose of this study was to investigate the effect of treatment with sildenafil in the early stages of sepsis. Male rats were submitted to either cecal ligation and puncture (CLP) or a sham procedure. Eight h after the procedure, the CLP and sham groups were randomly assigned to receive sildenafil (10mg/kg, gavage) or vehicle, and twelve or twenty-four h later the inflammatory, biochemical and haemodynamic parameters were evaluated. Sepsis significantly increased levels of plasma nitrate/nitrite (NOx), aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, creatinine, creatine kinase and lactate. Additionally, sepsis led to hypotension, hyporesponsiveness to vasoconstrictor, renal blood flow reduction and also increased lung and kidney myeloperoxidase. Sildenafil increased renal blood flow and reduced the plasma levels of creatinine, lactate and creatine kinase, as well as reducing lung myeloperoxidase. Thus, phosphodiesterase inhibition may be a useful therapeutic strategy if administered at the proper time.

Delivering Prolonged Intensive Care to a Non-human Primate: A High Fidelity Animal Model of Critical Illness

Critical care needs have been rising in recent decades as populations age and comorbidities increase. Sepsis-related admissions to critical care contribute up to 50% of volume and septic shock carries a 35–54% fatality rate. Improvements in sepsis-related care and mortality would have a significant impact of a resource-intensive area of health care delivery. Unfortunately, research has been hampered by the lack of an animal model that replicates the complex care provided to humans in an intensive care unit (ICU). We developed a protocol to provide full ICU type supportive care to Rhesus macaques. This included mechanical ventilation, continuous sedation, fluid and electrolyte management and vasopressor support in response to Ebolavirus-induced septic shock. The animals accurately recapitulated human responses to a full range of ICU interventions (e.g. fluid resuscitation). This model can overcome current animal model limitations by accurately emulating the complexity of ICU care and thereby provide a platform for testing new interventions in critical care and sepsis without placing patients at risk.

Role of the IL-33-ST2 axis in sepsis

Sepsis remains a major clinical problem with high morbidity and mortality. As new inflammatory mediators are characterized, it is important to understand their roles in sepsis. Interleukin 33 (IL-33) is a recently described member of the IL-1 family that is widely expressed in cells of barrier tissues. Upon tissue damage, IL-33 is released as an alarmin and activates various types of cells of both the innate and adaptive immune system through binding to the ST2/IL-1 receptor accessory protein complex. IL-33 has apparent pleiotropic functions in many disease models, with its actions strongly shaped by the local microenvironment. Recent studies have established a role for the IL-33-ST2 axis in the initiation and perpetuation of inflammation during endotoxemia, but its roles in sepsis appear to be organism and model dependent. In this review, we focus on the recent advances in understanding the role of the IL-33/ST2 axis in sepsis.