Influence of the TNF-alpha and TNF-beta polymorphisms upon infectious risk and outcome in surgical intensive care patients

Association between the Lymphotoxin-α A252g Gene Polymorphism and the Risk of Sepsis and Mortality: A Meta-Analysis

Background

The association between the lymphotoxin-α (LTA) A252G polymorphism and sepsis risk has been extensively studied, but the results have been controversial. This study is aimed at investigating the overall association between the LTA A252G polymorphism and the risk of sepsis/septic shock and sepsis-related mortality.

Methods

We searched the PubMed and EMBASE databases to identify studies that investigated the association between the LTA A252G polymorphism and risks of sepsis, septic shock, and mortality. The relevant data were extracted, and statistical analyses were performed using the Revman 5.0 and STATA 12 software.

Results

A total of 32 publications were included in the meta-analysis. The results demonstrated that the LTA A252G polymorphism showed no significant association with sepsis risk (GG+GA vs. AA: OR = 0.92, 95%CI = 0.79–1.07, p = 0.27) or with sepsis shock risk (GG+GA vs. AA: OR = 1.01, 95%CI = 0.84–1.22, p = 0.91). However, in the subgroup analyzed by ethnicity, the LTA A252G polymorphism significantly decreased sepsis risk in the Asian population for the recessive model [GG vs. GA+AA: OR = 0.82, 95%CI = 0.68–0.99, p = 0.04] but not in the Caucasian population. Moreover, comparisons between sepsis patients who survived and those who did not suggested that the LTA A252G polymorphism decreases the risk of mortality [GG+GA vs. AA: OR = 0.57, 95%CI = 0.41–0.80, p < 0.01].

Conclusion

Our results suggested that the A252G polymorphism in the LTA gene decreased the risk of sepsis in Asians and may reduce mortality in septic individuals.

The effects of tumor necrosis factor-α (TNF-α) rs1800629 and rs361525 polymorphisms on sepsis risk

This meta-analysis of 23 eligible articles comprehensively and quantitatively evaluated the effects of tumor necrosis factor-α (TNF-α) rs1800629 and rs361525 polymorphisms on sepsis risk. We found that TNF-α rs1800629 was associated with increased sepsis risk in the overall population in four genetic models, including A vs. G (P<0.001, odds ratio (OR)=1.32), GA vs. GG (P<0.001, OR=1.46), GA+AA vs. GG (P<0.001, OR=1.46), and carrier A vs. carrier G (P<0.001, OR=1.32). Subgroup analyses showed a similar result for Asian patients (all P<0.05, OR>1). TNF-α rs361525 was also associated with increased sepsis risk in Asian patients in the four genetic models (all P<0.05, OR>1). Begg's and Egger's tests excluded large publication bias, and sensitivity analysis indicated stable results. Our results suggest that the G/A genotype of TNF-α rs1800629 and rs361525 increases sepsis risk in an Asian population.

Tumor necrosis factor-α -308 G/A polymorphism and risk of sepsis, septic shock, and mortality: an updated meta-analysis

Background

The -308G/A polymorphism in the gene encoding tumor necrosis factor-α (TNF-α) has been implicated in sepsis risk in many studies but with variable results. This study aimed to comprehensively assess the evidence of association between this polymorphism and risk of sepsis and sepsis-related mortality.

Materials and Methods

PubMed, EMBASE and other databases were searched to identify relevant studies, and data were analyzed using Review Manager 5.0 and STATA 12.0.

Results

Data from 34 publications involving 12,284 subjects were meta-analyzed. Combined analysis revealed an association between TNF-α -308G/A gene polymorphism and risk of sepsis (AA+GA vs. GG, OR 1.35, 95% CI 1.10–1.67, P = 0.005). This association was observed in the Caucasian subgroup (OR 1.50, 95% CI 1.13–2.00, P = 0.006), but not in the Asian subgroup. Across the entire study population, the polymorphism was also significantly related to septic shock risk (OR 1.52, 95% CI 1.18–1.95, P = 0.001) but not to sepsis-related mortality (OR 0.99, 95% CI 0.71–1.40, P = 0.97).

Conclusions

This meta-analysis suggests that the -308G/A gene polymorphism in the TNF-α gene may contribute to risk of sepsis and septic shock, but not risk of mortality.

Cytokine storm and sepsis disease pathogenesis

Infectious diseases are a leading cause of death worldwide. Sepsis is a severe clinical syndrome related to the host response to infection. The severity of infections is due to an activation cascade that will lead to an autoamplifying cytokine production: the cytokine storm. Cytokines are a broad category of relatively small proteins (<40 kDa) that are produced and released with the aim of cell signaling. Our understanding of the processes that trigger this tremendous amount of cytokine production has made dramatic progress over the last decades, but unfortunately, these findings could not translate yet into effective treatments; so far, all clinical trials targeting cytokine production or effects failed. This review aims to summarize the pathophysiology of the cytokine storm; to describe the type, effects, and kinetics of cytokine production; and to discuss the therapeutic challenges of targeting cytokines. New promising therapeutic strategies focusing on the endothelium, as a source and a target of cytokines, are described.

Tumor necrosis factor-α -308G/A and -238G/A polymorphisms are associated with increased risks of sepsis: evidence from an updated meta-analysis

Previous studies have reported the relationship between tumor necrosis factor-α (TNF-α) -308G/A and -238G/A polymorphisms and sepsis risk with inconsistent results. The aim of this study was to estimate the association of the two polymorphisms with risk of sepsis or sepsis-related mortality using a meta-analysis. PubMed, Embase, and Web of Science databases were searched up to June 20 2016. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using fixed or random effect model. Twenty-six studies were included in this meta-analysis. Overall, an increased sepsis risk of TNF-α -308G/A was observed (GA vs GG: OR = 1.43, 95% CI: 1.07-1.92; GA/AA vs GG: OR = 1.42, 95% CI: 1.06-1.89). Subgroup analyses showed that the significant association was found in Asians (GA vs GG: OR = 1.63, 95% CI: 1.01-2.63) and adult patients. Similarly, an increased sepsis risk of TNF-α -238G/A was observed in overall and subgroup analyses. However, no significant association was found between TNF-α -308G/A and -238G/A polymorphisms and sepsis-related mortality. These findings indicate that both TNF-α -308G/A and -238G/A polymorphisms were associated with increased risks of sepsis but not sepsis-related mortality. Further studies with larger sample size are needed to confirm these results.

Predictive Genomics of Adverse Events After Cardiac Surgery

Significant, yet highly individual, thrombotic and inflammatory responses to surgery provide an excellent opportunity for insight into the genomic impact upon a patient's postoperative course. Cardiac surgery elicits the most profound perioperative disturbance and is associated with the highest incidence of adverse outcomes of any elective surgical procedure. Thus, cardiac surgical patients are an ideal population in which to evaluate the influence of complex traits on perioperative morbidity and mortality. This review describes the application of fundamental genetics upon the occurrence of adverse outcomes after cardiac surgery and cardiac transplantation. Specific emphases include a brief primer of the principles of genetics concentrating on the effects of variation within the human genome upon clinical outcomes and the differences between so-called Mendelian traits and complex traits. Four important clinical diseases dealt with in this review as examples of the impact of genetic factors on clinical outcomes are the genetics of heparin-induced thrombocytopenia, heart transplantation rejection and vasculopathy, atrial fibrillation, and infection.

Genetic variation in the TNF gene is associated with susceptibility to severe sepsis, but not with mortality

Background

Tumor necrosis factor (TNF) and TNF receptor superfamily (TNFR)-mediated immune response play an essential role in the pathogenesis of severe sepsis. Studies examining associations of TNF and lymphotoxin-α (LTA) single nucleotide polymorphisms (SNPs) with severe sepsis have produced conflicting results. The objective of this study was to investigate whether genetic variation in TNF, LTA, TNFRSF1A and TNFRSF1B was associated with susceptibility to or death from severe sepsis in Chinese Han population.

Methodology/Principal Findings

Ten SNPs in TNF, LTA, TNFRSF1A and TNFRSF1B were genotyped in samples of patients with severe sepsis (n = 432), sepsis (n = 384) and healthy controls (n = 624). Our results showed that rs1800629, a SNP in the promoter region of TNF, was significantly associated with risk for severe sepsis. The minor allele frequency of rs1800629 was significantly higher in severe sepsis patients than that in both healthy controls (P_adj = 0.00046, odds ratio (OR)_adj = 1.92) and sepsis patients (P_adj = 0.002, OR_adj = 1.56). Further, we investigated the correlation between rs1800629 genotypes and TNF-α concentrations in peripheral blood mononuclear cells (PBMCs) of healthy volunteers exposed to lipopolysaccharides (LPS) ex vivo, and the association between rs1800629 and TNF-α serum levels in severe sepsis patients. After exposure to LPS, the TNF-α concentration in culture supernatants of PBMCs was significantly higher in the subjects with AA+AG genotypes than that with GG genotype (P = 0.007). Moreover, in patients with severe sepsis, individuals with AA+AG genotypes had significantly higher TNF-α serum concentrations than those with GG genotype (P_adj = 0.02). However, there were no significant associations between SNPs in the four candidate genes and 30 day mortality for patients with severe sepsis.

Conclusions/Significance

Our findings suggested that the functional TNF gene SNP rs1800629 was strongly associated with susceptibility to severe sepsis, but not with lethality in Chinese Han population.

Genetic predisposition to respiratory infection and sepsis

Genetic variations, in part, determine individual susceptibility to sepsis and pneumonia. Advances in genetic sequence analysis as well as high throughput platform analysis of gene expression has allowed for a better understanding of immunopathogenesis during sepsis. Differences in genes can also modulate immune and inflammatory response during sepsis thereby translating to differences in clinical outcomes. An increasing number of candidate genes have been implicated to play a role in sepsis susceptibility, most of which are controversial with few exceptions. This does not refute the significance of genetic polymorphisms in sepsis, but rather highlights the difficulties and pitfalls related to genetic association studies. These difficulties include differences in study design such as heterogeneous patient cohorts and differences in pathogenic organisms, linkage disequilibrium, and lack of power for detailed haplotype analysis or examination of gene-gene interactions. There is extensive diversity in the pathways of inflammation and immune response during sepsis making it even harder to prove the functional and clinical significance of one single genetic polymorphism which could be easily masqueraded or compensated by other upstream or downstream events of the pathway involved. The majority of studies have analysed candidate genes in isolation from other possible polymorphisms. It is likely that susceptibility to sepsis is the result of polymorphisms from multiple genes rather than one single mutation. Future studies should aim for multi-centered collaborative approach looking at genome wide association or gene profiling to provide a more complete appraisal of the key genetic players in determining genetic susceptibility to sepsis. This review paper will summarise the prominent candidate gene polymorphisms with known functional changes or those with haplotype data. In addition, a summary of the expanding research in the field of epigenetics and post-sepsis immunosuppression will be discussed.

Association between lymphotoxin-α intron +252 polymorphism and sepsis: a meta-analysis

BACKGROUND

We evaluated the association of lymphotoxin-α (LTA, also known as tumour necrosis factor-β) promoter +252 A/G polymorphism with sepsis.

METHODS

A systematic search was performed in MEDLINE, EMBASE, and Web of Science (for the period January 1966 to June 2010). Two reviewers independently selected studies on the genetic association of LTA +252 A/G polymorphism with sepsis and independently extracted data onto standardized forms.

RESULTS

Twenty-seven studies with 4399 septic patients were included based on predefined inclusion criteria. As compared to AG + GG, the LTA AA genotype was significantly associated with an increased development of sepsis in the overall population (odds ratio (OR) 1.33, 95% confidence interval (CI) 1.09-1.62; p = 0.006). An association between mortality from sepsis and AA genotype was also found in the overall population (OR 1.89, 95% CI 1.27-2.80; p = 0.002). Stratification by ethnicity indicated that the contribution to both sepsis susceptibility and mortality may be stronger in Caucasians (OR 1.44, 95% CI 1.08-1.91 and OR 2.47, 95% CI 1.52-4.00, respectively) than in other ethnicities.

CONCLUSIONS

The LTA +252 A/G polymorphism is associated with both susceptibility to and mortality from sepsis.

Outcome prediction in sepsis combined use of genetic polymorphisms - A study in Japanese population

Genetic polymorphisms have recently been found to be related to clinical outcome in septic patients. The present study investigated to evaluate the influence of genetic polymorphisms in Japanese septic patients on clinical outcome and whether use of genetic polymorphisms as predictors would enable more accurate prediction of outcome. Effects of 16 genetic polymorphisms related to pro-inflammatory mediators and conventional demographic/clinical parameters (age, sex, past medical history, and APACHE II score) on ICU mortality as well as disease severity during ICU stay were examined in the septic patients (n=123) admitted to the ICU between October 2001 and November 2007 by multivariable logistic regression analysis. ICU mortality was significantly associated with TNF -308GA, IL1β -31CT/TT, and APACHE II score. Receiver-operating characteristics (ROC) analysis demonstrated that, compared with APACHE II score alone (ROC-AUC=0.68), use of APACHE II score and two genetic parameters (TNF -308 and IL1β -31) enabled more accurate prediction of ICU mortality (ROC-AUC=0.80). Significant association of two genetic polymorphisms, TNF -308 and IL1β -31, with ICU mortality was observed in septic patients. In addition, combined use of these genetic parameters with APACHE II score may enable more accurate prediction of outcome in septic patients.

Genetic risk of acute pulmonary infections and sepsis

The focus of this review is the genetic influence on pneumonia and sepsis. A large number of polymorphisms in a diverse collection of genes have been identified as potential candidates to explain the genetic variability in susceptibility to acute pulmonary infection and its adverse outcomes. Unfortunately, apart from polymorphisms in mannose-binding lectin, CD14 and the IgG2 receptor, there is little consensus on which polymorphisms are truly important. As well as discussing some of the major published findings, this review will focus on the reasons for failure to make more progress. We will also address the issues for future research, particularly the need to address the limitations of past studies, including the grouping of patients with different pathogens, as the relationship between genotype and phenotype may be highly pathogen dependent. Finally, our approach to reporting genetic studies needs to change to minimize the number of publications of spurious findings.

Ethical considerations in the collection of genetic data from critically ill patients: what do published studies reveal about potential directions for empirical ethics research?

Critical illness trials involving genetic data collection are increasingly commonplace and pose challenges not encountered in less acute settings, related in part to the precipitous, severe and incapacitating nature of the diseases involved. We performed a systematic literature review to understand the nature of such studies conducted to date, and to consider, from an ethical perspective, potential barriers to future investigations. We identified 79 trials enrolling 24 499 subjects. Median (interquartile range) number of participants per study was 263 (116.75-430.75). Of these individuals, 16 269 (66.4%) were Caucasian, 1327 (5.4%) were African American, 1707 (7.0%) were Asian Pacific Islanders and 139 (0.6%) were Latino. For 5020 participants (20.5%), ethnicity was not reported. Forty-eight studies (60.8%) recruited subjects from single centers and all studies examined a relatively small number of genetic markers. Technological advances have rendered it feasible to conduct clinical studies using high-density genome-wide scanning. It will be necessary for future critical illness trials using these approaches to be of greater scope and complexity than those so far reported. Empirical research into issues related to greater ethnic inclusivity, accuracy of substituted judgment and specimen stewardship may be essential for enabling the conduct of such trials.

Future diagnostic and therapeutic approaches in surgical infections

Despite ongoing efforts to standardize therapy and improve management, the morbidity and mortality associated with surgical infections remain high. Continued innovation is required to improve outcomes further, particularly in the face of the increasing prevalence of multidrug resistant organisms. Although they remain in the experimental stages, a number of recent advances have the potential to have significant impact on the management and outcomes of surgical infections. These include novel diagnostic strategies, antimicrobials targeting microbial virulence factors, novel vaccines, and risk stratification based on genetic profiling.

The Genetics of Sepsis: The Promise, the Progress and the Pitfalls

Physicians are used to taking a family history of cardiovascular disease because of the known significant hereditary risk; yet the familial risk of dying from infection is even greater than that for atherosclerotic disease (Sorensen et al. 1988). There is certainly no doubt that genetic differences impact on the risk of developing or dying from infection. Obvious but rare examples include selective immunoglobulin deficiencies, complement deficiencies, and neutrophil function abnormalities. Genetic factors may also be protective, such as with sickle cell trait and malaria or mutations conferring resistance to human immunodeficiency virus infection.

Much more subtle differences in immune responses are now being described, usually as the result of one or more single nucleotide polymorphisms (SNP) in a gene. Rather than causing the failure of production of a protein or the production of a nonfunctional protein, SNPs are usually associated with changes in the rate of transcription, producing a much less severe phenotype than the classical examples of genetic defects mentioned above. It is now being appreciated that for many complex diseases, such as sepsis, the ultimate phenotype is the result of the interaction of genetic differences across many loci, not the dominant effect of a few key mutations.

As seen in Fig. 3.1, since the mid 1990s, an increasing body of literature has focused on the role that gene polymorphisms in key inflammatory genes play in sepsis. Indeed, with advances in knowledge of the human genome, greater understanding of the inflammatory response, and the development of high throughput genotyping technologies, so many genetic associations have been described that discussion of each one is well beyond the scope of this chapter. I will however summarize those findings that have been reported by multiple groups, as well as give an overview of the major groups of genes that have been implicated in genetic predisposition to sepsis and its adverse outcomes.

Cytokine promoter polymorphisms in severe sepsis

The need to develop individualized risk profiles and drug therapy regimens motivates interest in genetic studies of critically ill patients. Gene promoter variants may predict interindividual variability in response to inflammatory stimuli, such as infection and trauma. Genomic variations also may affect gene expression profiles, as well as the structure and production of proteins. The genes involved in inflammation are numerous, as are genomic variations within most of those genes. Cytokine genes involved in inflammatory cascades are important candidate genes that may determine the extent of a person's response to injury. Understanding the genetic determination of the inflammatory process includes the possibility of developing valuable diagnostic tools and new therapeutic approaches in severe sepsis. To date, specific patterns of markers of genomic variation reliably indicating at-risk populations do not exist. Evaluation of possible genomic markers for risk stratification of patients with sepsis and persons at high risk of developing organ failure has begun at a level of well-powered genetic epidemiological research. Cytokine promoter variants may contribute substantially to studies of genetic predisposition of sepsis because they operate in a gene region of high regulatory activity.

TUMOUR NECROSIS FACTOR: IMPLICATIONS FOR SURGICAL PATIENTS

Tumour necrosis factor alpha (TNF-alpha) is an inflammatory cytokine primarily produced by macrophages. It is a unique protein with contradictive properties; it has the ability to induce cellular death by apoptosis and oncosis, but can also induce cellular regeneration and growth. Genetic polymorphisms in TNFA have been associated with poor outcome in some surgical patients and this may provide a useful tool to screen for high-risk patients. Manipulating TNF-alpha levels in vivo may influence the progression of several pathological conditions. TNF-alpha has anti-cancer properties and has been used to treat cancer patients. Treatment with anti-TNF-alpha drugs and antibodies has been successful in rheumatoid arthritis and other autoimmune diseases, but disappointing in the management of patients with sepsis. This review article focuses on the biological activities, genetic polymorphism of TNFA and the role of TNF-alpha and anti-TNF-alpha treatments, based on animal experiments and clinical trials.

Polymorphisms of heat shock protein-70 (HSPA1B and HSPA1L loci) do not influence infection or outcome risk in critically ill surgical patients

Heat shock proteins (HSP) are induced in various stress conditions and have many cytoprotective effects, including formation of protein complexes for antigen presentation, stabilizing intracellular proteins, and facilitating protein folding. The HSP-70 gene exhibits polymorphisms at the HSPA1B and HSPA1L loci that reportedly influence cytokine levels and clinical outcomes in critically ill patients. These HSP variations also have been linked to TNF-beta polymorphisms associated with poor outcomes. This study further evaluated outcomes and risk of infection of HSP polymorphisms in critically ill patients. Seventy-six consecutive surgical intensive care unit uninfected patients with established systemic inflammatory response features were prospectively enrolled. Genomic DNA was isolated from whole blood samples and specific fragments, including the relevant polymorphic sites, were amplified by PCR, and restriction digestions were performed. Genotypes were determined by electrophoresis and all were confirmed by direct sequencing. Plasma cytokine levels for TNF-alpha were assayed in a subset of patients by enzyme-linked immunoabsorbent assay. None of the HSP alleles bore a significant relationship to nosocomial infection rates, organ specific dysfunctions, or mortality. No linkage of HSP genotype to common TNF-alpha or TNF-beta genotypes could be demonstrated, although the HSPA1L CT polymorphism was associated with higher levels of TNF-alpha compared with the TT genotype. These data suggest that polymorphisms of the HSPA1L or HSPA1B loci do not influence infection or other highly morbid outcomes in surgical intensive care unit patients.

Heterogeneity in lipopolysaccharide responsiveness of endothelial cells identified by gene expression profiling: role of transcription factors

Interindividual differences of endothelial cells in response to endotoxins might contribute to the diversity in clinical outcome among septic patients. The present study was conducted to test the hypothesis that endothelial cells (EC) with high and low proinflammatory potential exist and to dissect the molecular basis underlying this phenomenon. Thirty human umbilical vein endothelial cell (HUVEC) lines were stimulated for 24 h with lipopolysaccharide (LPS) and screened for interleukin (IL)-8 production. Based on IL-8 production five low and five high producers, tentatively called types I and II responders, respectively, were selected for genome-wide gene expression profiling. From the 74 genes that were modulated by LPS in all type II responders, 33 genes were not influenced in type I responders. Among the 41 genes that were increased in both responders, 17 were expressed significantly stronger in type II responders. Apart from IL-8, significant differences in the expression of proinflammatory related genes between types I and II responders were found for adhesion molecules [intercellular adhesion molecule (ICAM-1), E-selectin)], chemokines [monocyte chemoattractant protein (MCP-1), granulocyte chemotactic protein (GCP-2)], cytokines (IL-6) and the transcription factor CCAAT/enhancer binding protein-delta (C/EBP-delta). Type I responders also displayed a low response towards tumour necrosis factor (TNF)-alpha. In general, maximal activation of nuclear factor (NF)-kappaB was achieved in type I responders at higher concentrations of LPS compared to type II responders. In the present study we demonstrate that LPS-mediated gene expression differs quantitatively and qualitatively in types I and II responders. Our results suggest a pivotal role for common transcription factors as a low inflammatory response was also observed after TNF-alpha stimulation. Further studies are required to elucidate the relevance of these findings in terms of clinical outcome in septic patients.