Early diagnosis and evaluation of sepsis is very important for the timely treatment of this complex syndrome. Microbiological culture is the gold standard for the differentiation of sepsis from other non-infectious diseases. However, as this technique takes a long time, diagnosis and treatment are delayed. Therefore, several studies have been conducted to determine the ideal biomarker for sepsis.
The studies in the literature that have examined procalcitonin and cytokine levels to evaluate the duration of an antibiotic use in ICU patients with sepsis have not included patients using antibiotic treatment on admission to ICU [11-15]. Taking the above-mentioned literature and meta-analyses into consideration, the patients included in the current study were those being followed up in ICU who developed sepsis and who had not previously received antibiotic treatment, to be able to create a more homogenous standardised group. This study aimed to compare candidate miRNAs with procalcitonin and proinflammatory cytokines in the evaluation of the efficacy of antibiotic treatment in patients being followed up in ICU who were diagnosed with sepsis and started antibiotic treatment within the first 24 hours.
miRNAs have recently been shown to be related to the pathogenesis of inflammation and sepsis . The stimulation of TLRs in the process of sepsis development plays a role in the induction of nuclear factor kappa B (NF-κB) and the expression of mitogen activated protein kinase (MAPK), monocytes, and macrophages in proinflammatory cytokines . miRNAs directly target signal proteins and control NF-κB activity in immune cells, and are therefore defined as regenerators of the immune system . A link between miRNA in particular and NF-κB has been shown in in-vitro studies.
It has been reported that miRNA-146a and miRNA-146b are expressed as a response to the microbial component and proinflammatory cytokines. There is a relationship of miRNA-146a and b with kinase 1 genes related to Il-1 receptor and 3’UTRs of TNF-related factor 6 . In another study, Funahashi et al. showed that miRNA-146a has an anti-inflammatory role and reduced excessive inflammation by regulating IRAK-1 and TRAF6, thereby modulating NF-κB transcriptional activity. In an in-vitro environment, miRNA-146a has been shown to trigger severe sepsis in macrophages and to be correlated with sepsis severity at the cellular level .
In a study of 50 sepsis patients, 30 patients with SIRS, and a control group of 20, Wang et al. found that the serum miRNA-146a and miRNA-223 values were significantly lower in the sepsis group compared to the SIRS group and the healthy control group, but IL-6 and CRP values were significantly high .
In another study that analyzed chemokines and cytokines in sepsis patients, changes in miRNA-146 were shown to be correlated with polymorphonuclear cells in peripheral blood. IL-6, which is an important inflammatory mediator in sepsis, was reported to increase, while miRNA-146 decreased .
The IL-6 level increases more rapidly in sepsis and reaches a peak level at the end of the second hour. The elevated serum level lasts longer than for TNF-α and IL-1 . Procalcitonin (PCT) is produced as a response to endotoxin or through mediators (IL-1, TNF-α, IL-6) expressed as a response to bacterial infections. It is correlated with the severity of bacterial infection [23,24].
In the current study, miRNA-146a was determined to be significantly reduced in the sepsis group compared to the control group at 24 hrs, 72 hrs, and 7 days of treatment, and a significant increase was determined in proinflammatory cytokine and procalcitonin levels, which was consistent with findings in the literature. In addition, a significant decrease was determined in the miRNA-146a levels in the sepsis group at 72 hrs and 7 days compared to the values at 24 hours, and there was a significant decrease in proinflammatory cytokines and procalcitonin levels.
Schmidt WM et al showed in vivo that the miRNA-150 level decreased in peripheral blood leukocytes during acute LPS-related inflammation . Roderburg C et al. compared 138 patients meeting sepsis criteria and 76 healthy control subjects, and reported that the serum miRNA-150 level was slightly reduced in the sepsis group, and was therefore not suitable as a marker for the diagnosis of sepsis. However, a correlation between serum miRNA levels and hepatic and renal function disorders, and low serum miRNA-150 levels were reported to be associated with a poor prognosis . Low miRNA150 levels in the circulation may cause a decrease in genes such as CXCR4 and c-Myb, which are related to both immune activation and prognosis . In a study of 120 sepsis patients and 50 healthy control subjects, Ma et al. showed that miRNA-150 was significantly decreased in the sepsis group compared to the control group, and there was a negative correlation between IL-6, TNF-α, and miRNA-150 values .
In the current study, the miRNA-150 level was observed to be decreased in the sepsis patients compared to the control group, but at 24 hours this decrease was not statistically significant. These differences from previously published results are most probably related to the size and characteristics of the patient groups analyzed in different studies. A statistically significant decrease was seen in the miRNA-150 levels of the sepsis group after 72 hours and 7 days of sepsis treatment compared to the control group. When the sepsis antibiotic treatment was evaluated over time, a significant decrease was determined in the miRNA-150 level of the sepsis group at 72 hrs and 7 days compared to the value at 24 hours. The proinflammatory cytokines and procalcitonin values were seen to be significantly increased at 24 hours when sepsis was diagnosed, and significantly decreased after 72 hrs and 7 days of treatment. Roderburg et al. determined no correlation between serum miRNA-150 levels and markers of bacterial infection and inflammation such as CRP or procalcitonin .
In addition to miRNA-122 being known to be a miRNA associated with the liver, it has also been stated to be a biomarker in the diagnosis and prognosis of sepsis . When coagulation disorder develops during the course of sepsis, the miRNA-122 level has been reported to increase.. In a study of 108 sepsis patients in the first 24 hrs of admission to ICU and 20 control subjects, miRNA-122 expression was seen to be 40-fold higher in sepsis patients with a mortal course compared to the control group, and 6-fold higher in the patients with sepsis who survived .
In the current study, an increase was seen in the miRNA-122 levels at 24 hours following the diagnosis of sepsis compared to the control group, and a decrease was determined after 72 hours and 7 days of treatment. Within the sepsis group, there was a significant decrease in the miRNA-122 levels at 72 hours and 7 days. Moreover, a parallel decrease was seen in proinflammatory cytokines and procalcitonin levels.
In a study by Wang et al of 166 patients diagnosed with sepsis and 24 control subjects, serum samples were taken from the sepsis patients within 24 hours. There was a diagnosis of severe sepsis and septic shock in 123 patients and mild sepsis in 43. The miRNA-223 expression level was reported to be significantly higher, and the miR-499-5p, miR-122, and miR-193b levels significantly lower in the mild sepsis, severe sepsis, and septic shock patients compared to the control group. In addition, the miRNA-223 expression level was statistically slightly elevated in the septic shock and severe sepsis group compared to the mild sepsis group .
In two separate studies of neonatal sepsis patients, Dhas et al. reported a significant decrease in plasma miRNA-223 levels compared to the control group, whereas Benz et al. found no significant difference in miRNA levels [31,32].
In the current study, an increase, but not at a significant level, was seen in the miRNA-223 levels of the sepsis group compared to the control group, a statistically significant decrease was determined after 72 hours of sepsis treatment, and on the 7th day, an increase was seen which was not statistically significant because of the increase in standard deviation.
The identification of miRNAs and their potential target genes may contribute to the understanding of the complex transcriptional programming of the natural immune system triggered by pathogens. Impairment of the mechanisms which regulate the immune system during sepsis may lead to loss of inflammation control resulting in host damage and deep immunosuppression .
In this study, which compared selected miRNAs with procalcitonin and inflammatory cytokines in the diagnosis, treatment follow-up, and prognosis of patients diagnosed with sepsis in ICU, a relationship was determined between miRNA-150, miRNA-146a, and miRNA-223, and proinflammatory cytokines and procalcitonin levels.
Due to the lack of reliable biomarkers of immune system dysfunction associated with sepsis, effective therapeutic interventions cannot be made for septic patients.