The analysis of the levels of plasma inflammation-related cytokines and endotoxins in patients with acute aortic dissection

Abstract

OBJECTIVE:

To investigate the changes in the levels of plasm interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), matrix metalloproteinase-9 (MMP-9) and endotoxins in patients with acute aortic dissection (AAD).

METHODS:

55 AAD patients who were admitted and scheduled to undergo emergency surgery in our hospital from January 2017 to July 2017 were selected and retrospectively analyzed. They were divided into the survival group (n = 40) and the death group (n = 15). The levels of plasma IL-6, TNF-α, CRP, MMP-9 and endotoxins at admission and at 6 h, 12 h and 24 h after admission (T0, T1, T2 and T3) were measured, and the correlations of inflammatory cytokines with endotoxins were analyzed.

RESULTS:

At T1, T2 and T3, the levels of inflammatory cytokines and endotoxins were increased. The levels of plasma IL-6, TNF-α, CRP, MMP-9 and endotoxins in the death group were significantly higher than those in the survival group at each time point (p < 0.05 in all comparisons). Neutrophil and platelet counts in the death group were higher than those in the survival group (p < 0.05). Correlation analyses indicated that the levels of IL-6, TNF-α, CRP and MMP-9 were positively correlated with the level of endotoxin.

CONCLUSION:

Patients with AAD are often accompanied by systemic inflammatory responses, with inflammation-related cytokines (IL-6, TNF-α, CRP and MMP-9) and endotoxins levels significantly elevated. Combined monitoring of dynamic changes in inflammatory cytokines and endotoxins, as well as early interventions, has important clinical implications for evaluating the prognosis of AAD and reducing mortality.

Keywords

Acute aortic dissection IL-6 CRP MMP-9

1 Introduction

Acute aortic dissection (AAD) has rapid onset, rapid progression, high mortality rate and complex pathogenesis [1, 2]. At present, the incidence rate of AD is constantly increased, and the onset age tends to be younger [3, 4]. It is of great importance to explore the reference index of prognostic evaluation of AAD and conduct clinical intervention to reduce the mortality rate of AAD. When AAD occurs, continuous blood flows enter into the false lumen, which constricts the true lumen and causes ischemia and hypoxia in the intestinal tissues and other downstream organs, thus resulting in the increased releases of plasma cytokines and endotoxins [5, 6]. It has been confirmed that tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), interleukin (IL-6), etc. play important roles in the occurrence of AD [7, 8]. In this study, 55 patients with AD who underwent emergency surgery were selected. The changes of plasma inflammatory cytokines and endotoxin levels in patients with death and survival were compared, and their effects on prognosis were evaluated and their clinical value was explored.

2 Materials and methods

2.1 Study objects

According to postoperative prognosis, a total of 55 patients with AAD who were admitted and scheduled to undergo emergency surgery in our hospital from January 2017 to July 2017 were selected and divided into the survival group (n = 40) and the death group (n = 15). Age, gender, systolic and diastolic blood pressures at admission (T0) and other general data of the two groups of patients were compared (p > 0.05). Diagnostic criteria are based on typical clinical symptoms and results of echocardiography and thoracic enhanced computed tomography (CT). All patients signed the informed consent, and the study was approved by the Ethics Committee.

2.2 Research methods

Fasting anticoagulant venous blood was collected in the morning at T0 and at 6 h, 12 h and 24 h after admission (T1, T2 and T3). The supernatant was collected via centrifugation and stored in a refrigerator at – 80°C for standby application.

2.3 Observational indexes

The levels of plasma IL-6, CRP, matrix metallopeptidase-9 (MMP-9) and TNF-α were measured using the EL×800 automatic microplate reader (BioTek, USA). The plasma endotoxin level was determined via spectrophotometry. White blood cell and platelet counts were measured using a coulter automated five-type blood cell analyzer (Beckman, USA).

2.4 Statistical processing

Analysis was performed using statistical product and service solutions (spss) 20.0 software (IBM). Measurement data were expressed as mean±standard deviation. Two groups were compared using the t-test, the analysis of variance was conducted for comparisons among multiple groups, and correlation analyses were performed using Pearson’s correlation analysis. p < 0.05 represented that the difference was statistically significant.

3 Results

3.1 Comparison of inflammatory factors between the two groups at different time points

In the present study, we observed that IL-6, TNF-α, CRP and MMP-9 at T1, T2 and T3 were increased in both groups, in which these levels at T2 and T3 in the survival group and at T1-T3 at the death group were notably higher than those at T0. The levels of plasma IL-6, TNF-α, CRP and MMP-9 in the death group were remarkably higher than those in the survival group at each time point, and the differences were statistically significant (p < 0.05 in all comparisons) (Table 1).

Table 1
Comparisons of TNF-α, IL-6, MMP-9 and CRP levels at different time points between the two groups

Index Group T0 T1 T2 T3

TNF-α (pg·mL^–1) Survival group (n = 40) 21.63±10.65 25.74±11.55 40.72±12.11^# 51.15±13.26^#

Death group (n = 15) 32.23±12.27^* 50.15±4.22^^# 73.61±17.53^^# 100.15±15.38^#

IL-6 (pg·mL^–1) Survival group (n = 40) 6.12±0.98 9.36±2.33 19.25±5.36^# 26.33±5.38^#

Death group (n = 15) 11.33±3.22^ 20.15±7.22^^# 33.36±9.13^# 60.66±15.32^#

MMP-9 (ng·mL^–1) Survival group (n = 40) 31.25±4.35 36.45±6.31 50.55±10.55^# 56.88±9.45^#

Death group (n = 15) 51.25±10.63^ 72.43±11.48^# 81.29±13.18^# 102.36±15.33^#

CRP (mg·mL^–1) Survival group (n = 40) 10.18±5.56 15.65±5.26 25.87±6.98^# 34.98±8.25^#

Death group (n = 15) 22.35±4.74^ 43.65±6.98^^# 51.53±7.87^# 70.24±11.64^*#

Index	Group	T0	T1	T2	T3
TNF-α (pg·mL^–1)	Survival group (n = 40)	21.63±10.65	25.74±11.55	40.72±12.11^#	51.15±13.26^#
	Death group (n = 15)	32.23±12.27^*	50.15±4.22^*^#	73.61±17.53^*^#	100.15±15.38^*#
IL-6 (pg·mL^–1)	Survival group (n = 40)	6.12±0.98	9.36±2.33	19.25±5.36^#	26.33±5.38^#
	Death group (n = 15)	11.33±3.22^*	20.15±7.22^*^#	33.36±9.13^*#	60.66±15.32^*#
MMP-9 (ng·mL^–1)	Survival group (n = 40)	31.25±4.35	36.45±6.31	50.55±10.55^#	56.88±9.45^#
	Death group (n = 15)	51.25±10.63^*	72.43±11.48^*#	81.29±13.18^*#	102.36±15.33^*#
CRP (mg·mL^–1)	Survival group (n = 40)	10.18±5.56	15.65±5.26	25.87±6.98^#	34.98±8.25^#
	Death group (n = 15)	22.35±4.74^*	43.65±6.98^*^#	51.53±7.87^*#	70.24±11.64^*#

Note: ^*p < 0.05 vs. at the same time point in the survival group. ^#p < 0.05 vs. at T0 in the same group.

3.2 Comparisons of endotoxins at different time points between the two groups

This study revealed that the values of endotoxins at T1, T2 and T3 rose up in both groups, in which the values at T2 and T3 in the survival group and at T1-T3 in the death group were significantly higher than those at T0. The differences between the two groups were statistically significant (p < 0.05 in all comparisons) (Fig. 1).

Fig. 1

Comparisons of endotoxin levels between the two groups.

3.3 Comparisons of white blood cell and platelet counts (clinical indexes) between the two groups

White blood cell and platelet counts in the survival group and the death group at T0 were [(10.8±2.2) vs. (13.0±1.9)] and [(145±40) vs. (166±45)], respectively. The neutrophil and platelet counts in the death group were higher than those in the survival group, and there was a significant difference in neutrophils between the two groups (p < 0.05) (Fig. 2).

Fig. 2

Comparisons of white blood cell and platelet counts between the two groups.

3.4 Correlations of inflammatory cytokines with endotoxins in ADD patients

In this study, Pearson’s correlation analysis manifested that the values of IL-6, TNF-α, CRP and MMP-9 were positively correlated with the level of endotoxins (r = 0.9144, 0.7112, 0.7542 and 0.6394, p < 0.05), suggesting that the joint detection of the above-mentioned inflammatory cytokines and endotoxins has reference value in evaluating prognosis (Figs. 3 –6).

Fig. 3

Correlation between TNF-α and endotoxins (r = 0.9144).

Fig. 4

Correlation between IL-6 and endotoxins (r = 0.7112).

Fig. 5

Correlation between MMP-9 and endotoxins (r = 0.7542).

Fig. 6

Correlation between CRP and endotoxins (r = 0.6394).

4 Discussion

AAD is a critically severe cardiovascular disease. Patient anatomical disruption secondary to systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) are the most important and direct causes of poor prognosis and even death [9 –11]. Previous studies have illustrated that increased levels of cytokines and endotoxins can reflect the severity of AD in patients, since the levels of IL-6, CRP, and TNF-α in AD patients are significantly higher than those in healthy people [12, 13].

TNF-α is the earliest initiator of inflammation. IL-6 is considered to be amultifunctional pro-inflammatory factor, and a sustained increase in IL-6 level indicates a poor prognosis of SIRS. IL-6 stimulates hepatocytes to produce acute phase proteins such as CRP, promotes the release of MMPs, thereby increasing the degradation of extracellular matrix in aortic mediators and regulating blood coagulation [14]. A study has confirmed that MMP-9 begins to increase within 1 h after clinical symptoms appear, and it is an important indicator for the rapid diagnosis of AD. Dynamically monitoring the MMP-9 changes can reflect the evolution process of arterial wall injury in AD patients [15]. CRP is a nonspecific acute-term protein that can be elevated in the early stages of inflammation and infection, and has recently been associated with the diagnosis and prognosis of AAD [16]. Foreign scholars [17, 18] detected the expression level of CRP in hundreds of patients with AAD and found that CRP is not only related to the duration of symptoms but also positively associated with the risk of death.

This study indicated that the measured values of inflammatory factors IL-6, TNF-α, CRP, MMP-9 and endotoxins at T1, T2, and T3 in the two groups were increased, and these values at each time point in the death group were markedly higher than those in the survival group. This suggests that patients with AAD are in an inflammatory state at the onset of the disease. Inflammatory mediators act on the aortic medial smooth muscle cells and the extracellular matrix, leading to avascular necrosis of the cells, and the reduction in wall resistance ultimately leads to expansion and rupture of the endometrium. When AAD patients suffer from acute intestinal ischemia, gram-negative bacilli in the intestinal tract rupture and release endotoxins, thus triggering the release of inflammatory cytokines and forming a vicious circle. In this study, Pearson’s correlation analysis revealed that the levels of TNF-α, IL-6, MMP-9 and CRP were positively correlated with the level of endotoxins, suggesting that the joint detection of the above-mentioned inflammatory cytokines and endotoxins provide reference value in evaluating prognosis and guiding treatment. Clinically, these early warning indicators need to be noted that interventions must be carried out early to improve the prognosis of patients. Foreign studies have shown that platelet count [19] has important predictive value in the prognosis of AAD, and increased white blood cells and CRPs are independently related to the hospitalization rate and long-term mortality rate of AD [20]. It was observed in this study that white blood cell and platelet counts in the survival group and the death group at T0 were [(10.8±2.2) vs. (13.0±1.9)] and [(145±40) vs. (166±45)], respectively. Neutrophil and platelet counts in the death group were higher than those in the survival group, displaying a significant difference in neutrophils between the two groups (p < 0.05). When ad occurs, tissue factor released by aortic injury activates the endogenous coagulation pathway, leading to false lumen thrombosis, high platelet activation, and further release of large amounts of inflammatory factors, aggravating the inflammatory process. This indicates that monitoring of platelet and white blood cell counts has a reference value for the prognosis of AD.

5 Conclusion

In summary, patients with AAD are often accompanied with systemic inflammatory responses, and the levels of inflammation-related factors, such as IL-6, TNF-α, CRP and MMP-9, and endotoxins are significantly elevated. Combined monitoring of dynamic changes in inflammatory cytokines and endotoxins, as well as early interventions, has important clinical implications for evaluating the prognosis of AAD and reducing mortality.

Conflict of interest

None.

Footnotes

Acknowledgments

This work was supported by Wei Feng for his technological help (Wei Feng, Professor, Fuwai Hospital, National Heart Centre).

References

, Luo

, Bai

, et al. A canine model of multiple organ dysfunction following acute type-A aortic dissection. Surg Today. 2012;42(9):876.

Hagan

, Nienaber

, Isselbacher

, et al. The International Registry of Acute Aortic Dissection (IRAD): New insights into an old disease. JAMA. 2000;283(7):897–903.

, Yang

, Duan

, et al. Acute aortic dissection in China. Am J Cardiol. 2012;110(7):1056–61.

Aizawa

, Sakano

, Ohki

, et al. Obesity is a risk factor of young onset of acute aortic dissection and postoperative hypoxemia. Kyobu Geka. 2013;66(6):437–44.

Cuschieri

, Bulger

, Schaeffer

, et al. Early elevation in random plasma IL-6 after severe injure is associated with development of organ failure. Shock. 2010;34(4):346.

Sbarouni

, Georgiadou

, Analitis

, et al. High homocysteine and low folate concentrations in acute aortic dissection. Int J Cardiol. 2013;168(1):463–36.

, Guo

, Estrera

, et al. Characterization of the inflammatory and apoptotic cells in the aortas of patients with ascending thoracic aortic aneurysms and dissections. J Thorac Cardiovasc Surg. 2006;131(3):671–8.

del Porto

, Proietta

, Tritapepe

, et al. Inflammation and immune response in acute aortic dissection[J]. Ann Med. 2010;42(8):622–9.

Song JK . Update in acute aortic syndrome: Intramural hematoma and incomplete dissection as new disease entities. J Cardiol. 2014;64(3):153–61.

10.

Kruger

, Weigang

, Hoffmann

, et al. Cerebral protection during surgery for acute aortic dissection type A: Results of the German Registry for Acute Aortic Dissection Type A(GERAADA). Circulation. 2011;124(4):434–43.

11.

Pacini

, Leone

, Belotti

, et al. Acute type A aortic dissection: Significance of multiorgan malperfusion. Eur J Cardiothorac Surg. 2012;43(4):820–6.

12.

Deitch

, Xu

, Kaise

. Role of the gut in the development of injury- and shock induced SIRS and MODS: The gut-lymph hypothesis, a review[J]. Frontiers in Bioscience. 2006;11:520–8.

13.

Wen

, Zhou

, Li

, et al. Plasma concentrations of interleukin-6, C-reactive protein, tumor necrosis factor-α and matrix metalloproteinase-9 in aortic dissection. Clin Chim Acta. 2012;413(1-2):198–202.

14.

Signorelli

, Fiore

, Malaponte

. Inflammation and peripheral arterial disease: The value of circulating biomarkers. Int J Mol Med. 2014;33(4):777–83.

15.

Wen

, Zhou

, Li

, et al. Biomarkers in aortic dissection. Clin Chim Acta. 2011;412(9/10):688–95.

16.

Luo

, Zhou

, Li

, et al. Infl ammatory response is associated with aortic dissection. Ageing Res Rev. 2009;8(1):31–5.

17.

Schillinger

, Domanovits

, Bayegan

, et al. C-reactive protein and mortality in patients with acute aortic disease[J]. Intensive Care Med. 2002;28(6):740–5.

18.

Wen

, Du

, Dong

, et al. Value of D-dimer and C reactive protein in predicting inhospital death in acute aortic dissection[J]. Heart. 2013;99(16):1192–7.

19.

Huang

, Tian

, Fan

, et al. Low admission platelet counts predicts increased risk of in-hospital mortality in patients with type A acute aortic dissection. Int J Cardiol. 2014;172(3):484–6.

20.

Olsson

, Thelin

, Sthle

, et al. Thoracic aortic aneurysm and dissection: Increasing prevalence and improved outcomes reported in a nationwide population-based study of more than 14,000 cases from 1987 to 2002. Circulation. 2006;114(24):2611–8.