Diagnostic value and mechanism of plasma S100A1 protein in acute ischemic stroke: a prospective and observational study

Introduction

According to the latest global burden of disease data, acute ischemic stroke (AIS) was one of the main reasons for the increase in the number of years of life lost and all age disability-adjusted life years in China (Zhou et al., 2019). The prevalence and mortality of the population were as high as 1.6% and 1.1% (Wang et al., 2017). Acute ischemic stroke accounted for 69.6% of all types of stroke and was the leading cause of disability and death in rural and remote areas of China (Wang et al., 2017; Yang et al., 2013; Wang et al., 2015). In addition, there are approximately two million new cerebral infarcts annually, and medical treatment costs are in the tens of billions of dollars (Lopez et al., 2006). According to the American Heart Stroke Association Guidelines for the Early Management of Acute Ischemic Stroke and the AIS Endovascular Treatment Consensus (Sacks et al., 2018; Powers et al., 2018), the effective treatments for AIS mainly include intravenous thrombolysis and endovascular mechanical thrombectomy, but only for some patients within a specific time window. The vast majority of patients can only receive symptomatic treatment, and their prognosis is dismal, which is also the main reason for the high rates of recurrence, disability, and death among AIS patients. In the meantime, the diagnosis of early disease and the determination of its severity are difficult to assess. Multiple instability factors influence a diagnosis. This may also be related to the complex pathophysiological mechanisms of ASI. Therefore, searching for practical biological markers can help diagnose and determine the condition, especially for hospitals in remote areas or those lacking essential equipment.

Inflammation, abnormal coagulation, and atherosclerosis are the pathophysiological basis of ASI. The vital role of the immune-inflammatory response in all pathophysiological stages of AIS is now well recognized, both in the development of AIS and the prognosis of AIS. When an ischemic stroke occurs, the ischemic brain tissue activates glial cells that produce massive biochemical and inflammatory mediators, such as cytokines, chemokines, and pro-inflammatory enzymes (Bonaventura et al., 2016; Maida et al., 2020). S100A1 protein is a recently discovered novel inflammatory marker; it is also a member of the S100 protein family. It can be expressed in endothelial cells and binds to target proteins inside and outside the cell to play a role in signalling and neurotransmitter transmission, as well as being involved in the synthesis of certain enzymes (Gonzalez, Garrie & Turner, 2020; Baudier, Deloulme & Shaw, 2020). Previous studies have shown that S100A1 protein could bind to RyR receptors to form the S100A1RyR complex, thereby regulating intracellular Ca2+ homeostasis and thus participating in the pathophysiological processes of Alzheimer’s disease (Wright et al., 2008). Another member of the S100 protein family, the S100B protein, shares a similar biological phenotype with the S100A1 protein. The study by Ercole et al. (2016) revealed that the S100B protein could effectively predict the severity of acute cerebral infarction and its prognosis. Given that S100A1 and S100B proteins might function in a common signalling pathway in vivo (Ercole et al., 2016; Heizmann, 2019; Afanador et al., 2014), it was acceptable to posit that the S100A1 protein might be utilized in some capacity for disease diagnosis or reaction to the severity of AIS. The S100A1 protein itself was analyzed in terms of inflammation. A study by Yu et al. (2015) found that S100A1 might regulate inflammation and oxidative stress responses in H9C2 cells through the TLR4/NF- κB pathway. Hypoxic cardiomyocytes released endogenous S100A1, which stimulated NF-κB p65 protein by binding to TLR4 receptors, thereby inducing an increase in pro-inflammatory cytokines such as IL-6. In contrast, after eliminating the gene for S100A1 protein by genetic ablation reduced the expression of this protein, a striking finding was observed that intracranial plaque load and number were significantly reduced, as well as the neuroinflammatory response, demonstrating that inhibition of S100A1 protein might be a way to normalize intracranial inflammatory signalling (Afanador et al., 2014). By actively interfering with the S100A1 protein, we discovered that the protein was an indicator of promoting inflammation and exacerbating inflammation, whether from forward or reverse intervention. Therefore, we could think that this protein might be a potential therapeutic indicator. It was rational to speculate that the S100A1 protein might play a role in a similar pathophysiological process in cerebral infarction. To our knowledge, there are no studies on the relevance of S100A1 protein for ischemic cerebral infarction.

In this study, our objective was to determine the level of S100A1 protein in AIS patients early in the disease progression and to test its diagnostic efficacy for the disease. At the same time, the correlation between this protein and the severity of cerebral infarction was judged. Finally, the mechanism of this protein in the pathogenesis of AIS was investigated.

Materials and Methods

Results

Diagnostic efficacy of plasma S100A1 protein for AIS and TIA

The diagnostic efficacy of AIS and TIA was assessed using the receiver operating characteristic curve (ROC) (Fig. 1). The area under the ROC curve (AUC) of plasma S100A1 for the diagnosis of AIS was 0.818 (Fig. 1A) (P < 0.001, 95% confidence interval [CI] 0.749–0.887), when the optimum cutoff value (cut off) was 181.03, its maximum Youden index (Jmax) was 0.578, sensitivity (Se) was 95.0%, and specificity (Sp) was 62.7% (Table 3). The AUC of plasma S100A1 for the diagnosis of TIA was 0.720 (Fig. 1B) (P = 0.001, 95% CI [0.592–0.848]), and when cut off was 150.14, its Jmax was 0.442, Se was 50.0%, and Sp was 94.2% (Table 3).

Comparison of baseline characteristics between groups with different cerebral infarction volumes

Baseline characteristic data for the different cerebral infarction volume groups were summarized in Table 4. A total of 141 patients with acute ischemic stroke were enrolled, including 78 in the small-volume cerebral infarction group (SCI; age, 67.65 ± 10.28; 34.6% female, 65.4% male), 32 in the medium-volume cerebral infarction group (MCI; age, 66.50 ± 13.41; 44.1% female, 55.9% male), and 31 in the large-volume cerebral infarction group (LCI; age, 67.77 ± 11.97; 41.9% female, 58.1% male). There were no significant differences in demographic characteristics, blood routine indexes, and risk factors among the three groups. Admission NIHSS in the LCI group was significantly higher than in the MCI group and SCI group ((11.00; IQR, 4.00–22.00) vs (2.50; IQR, 1.25–4.75) vs (2.00; IQR, 1.00–3.25), P < 0.001). Comparison between the groups suggested no significant difference between the SCI and MCI groups (P > 0.05). ALT and AST count were significantly increased in the LCI group (ALT, (36.00; IQR, 25.00–49.00) vs (24.00; IQR, 19.25–38.00) vs (24.00; IQR, 17.75–34.25), P = 0.002; AST, (29.00; IQR, 25.00–40.00) vs (25.50; IQR, 22.00–29.75) vs (25.00; IQR, 19.75–30.25), P = 0.007). Comparison between groups only suggested that ALT and AST counts in the LCI group were significantly higher than in the SCI group. Systolic BP, diastolic BP, TOAST type, TC, TG, LDL, HDL, creatinine, and homocysteine were similar among the three groups. Laboratory parameters showed statistically significant differences in plasma S100A1, NF-κB P65, and IL-6 among the three groups. Comparison between the groups suggested that the levels of S100A1, NF-κB P65, and IL-6 in the LCI group were significantly higher than those in the MCI and SCI group (S100A1, (254.25 ± 37.07) vs (225.42 ± 30.92) vs (223.98 ± 40.21), P = 0.001; NF-κB p65, (4.41 ± 0.45) vs (3.85 ± 0.64) vs (3.88 ± 0.66), P < 0.001; IL-6, (14.00 ± 1.40) vs (12.77 ± 1.31) vs (13.27 ± 1.65), P = 0.007) (Fig. 2). There was no significant difference between the MCI and SCI groups (P > 0.05).

Table 3:

Diagnostic efficacy of plasma S100A1 protein for AIS and TIA.

	AUC	95% CI	P-value	Jmax	Cut-off	Se (%)	Sp (%)
AIS group	0.818	0.749–0.887	0.000*	0.578	181.03	95.0	62.7
TIA group	0.720	0.592–0.848	0.001*	0.442	150.14	50.0	94.2

DOI: 10.7717/peerj.14440/table-3

Notes:

*S100A1 protein was statistically significant for disease diagnosis (P < 0.05). The higher the value of AUC, the stronger the diagnostic effect.

Table 4:

Comparison of baseline characteristics between groups with different cerebral infarction volumes.

Baseline characteristic data for the different cerebral infarction volume groups are summarized in Table 4. At the same time, whether there was variability between the three groups was compared.

	SCI group (n = 78)	MCI group (n = 32)	LCI group (n = 31)	P-value
Demographics
Age (years)	67.65 ± 10.28	66.50 ± 13.41	67.77 ± 11.97	0.874
Female (n) (%)	27 (34.6)	15 (44.1)	13 (41.9)	0.455
Risk factors
BMI (kg/m2)	24.01 ± 3.19	24.09 ± 2.82	25.07 ± 3.47	0.278
Smoking (n) (%)	30 (38.5)	10 (31.3)	11 (35.5)	0.771
Alcohol drinking (n) (%)	17 (21.8)	6 (18.8)	8 (25.8)	0.793
Hypertension (n) (%)	53 (67.9)	22 (68.8)	21 (67.7)	0.343
Diabetes (n) (%)	22 (28.2)	8 (25.0)	7 (22.6)	0.844
Hyperlipidemia (n) (%)	4 (5.1)	3 (9.4)	2 (6.5)	0.730
AF (n) (%)	11 (14.1)	6 (18.8)	4 (12.9)	0.810
CHD (n) (%)	9 (11.5)	4 (12.5)	4 (12.9)	1.000
Clinical data
Systolic BP(mmHg)	82.96 ± 11.70	84.09 ± 13.57	82.42 ± 10.45	0.846
Diastolic BP(mmHg)	150.09 ± 18.45	147.66 ± 19.68	144.19 ± 13.54	0.293
Admission NIHSS (points)	2.00 (1.00,3.25)	2.50 (1.25,4.75)	11.00 (4.00,22.00)	0.000*(b,c)
TOAST type
LAA (n) (%)	30 (38.5)	12 (37.5)	11 (35.5)	0.972
CE (n) (%)	11 (14.1)	6 (18.8)	4 (12.9)	0.810
SAO (n) (%)	35 (44.9)	14 (43.8)	15 (48.4)	0.947
Others (n) (%)	2 (2.6)	0 (0.0)	1 (3.2)	0.790
Blood routine indexes
BG (mmol/L)	6.00 ± 2.39	2.39 ± 2.60	6.70 ± 1.78	0.212
RBC (1012/L)	5.36 ± 7.37	4.44 ± 0.67	4.58 ± 0.63	0.659
Hematocrit (%)	40.17 ± 6.67	39.09 ± 4.38	39.03 ± 5.34	0.547
Leukocytes (10 $\stackrel{ˆ}{}$9/L)	7.91 ± 6.23	7.77 ± 6.59	7.72 ± 2.64	0.986
Neutrophils (10 $\stackrel{ˆ}{}$9/L)	4.63 ± 2.17	4.45 ± 1.42	5.56 ± 2.70	0.080
Lymphocytes (10 $\stackrel{ˆ}{}$9/L)	1.55 ± 0.73	1.52 ± 0.52	1.35 ± 0.52	0.358
Monocytes (10 $\stackrel{ˆ}{}$9/L)	0.48 ± 0.26	0.52 ± 0.28	0.48 ± 0.19	0.749
RDW (%)	12.82 ± 1.50	12.79 ± 1.26	12.73 ± 1.28	0.950
PLT (10 $\stackrel{ˆ}{}$9/L)	191.81 ± 59.92	179.81 ± 55.87	179.06 ± 61.51	0.471
Biochemical indicators
TC (mmol/L)	4.07 ± 0.85	4.08 ± 0.82	4.20 ± 1.00	0.774
TG (mmol/L)	1.65 ± 0.71	1.84 ± 0.97	1.49 ± 0.89	0.233
LDL (mmol/L)	2.48 ± 0.74	2.36 ± 0.71	2.58 ± 0.78	0.480
HDL (mmol/L)	0.99 ± 0.24	0.98 ± 0.27	1.11 ± 0.38	0.115
Creatinine (umoL/L)	63.80 (52.78,76.23)	64.4 (47.45,78.38)	64.50 (57.90,89.30)	0.448
ALT (u/L)	24.00 (17.75,34.25)	24.00 (19.25,38.00)	36.00 (25.00,49.00)	0.002*(b)
AST(u/l)	25.00 (19.75,30.25)	25.50 (22.00,29.75)	29.00 (25.00,40.00)	0.007*(b)
Homocysteine (umol/L)	9.50 (5.00,14.00)	10.00 (7.00,14.75)	9.00 (8.00,12.00)	0.858
Laboratory parameters
S100A1 (pg/ml)	223.98 ± 40.21	225.42 ± 30.92	254.25 ± 37.07	0.001*(b,c)
NF-κB p65 (ng/ml)	3.88 ± 0.66	3.85 ± 0.64	4.41 ± 0.45	0.000*(b,c)
IL-6 (pg/ml)	13.27 ± 1.65	12.77 ± 1.31	14.00 ± 1.40	0.007*(b,c)

DOI: 10.7717/peerj.14440/table-4

Notes:

Abbreviations

SCI

Small-volume cerebral infarction

MCI

Middle-volume cerebral infarction

LCI

Large-volume cerebral infarction

BMI

Body mass index

AF

Atrial fibrillation

CHD

Coronary heart disease

BP

Blood pressure

NIHSS

National Institutes of Health Stroke Scale

TOAST

Trial of Org 10172 in acute stroke treatment

LAA

Large-artery atherosclerosis

CE

Cardioembolism

SAO

Small-artery occlusion

BG

Blood glucose

RBC

Red blood cell

RDW

Red blood cell distribution width

PLT

Platelet

TC

Total cholesterol

TG

Triglycerides

LDL

Low-density lipoproteins

HDL

High-density lipoproteins

ALT

Alanine transaminase

AST

Aspartate transaminase

NF- κB p65

Nuclear factor kappa-B p65

IL-6

Interleukin-6

*, statistically significant (P < 0.05) between the three groups; a, statistically significant (P < 0.05) between the SCI and MCI groups; b, statistically significant (P < 0.05) between the SCI and LCI groups; c, statistically significant (P < 0.05) between the MCI and LCI groups.

Correlation of cerebral infarct volume with the levels of S100A1 protein, NF-κB p65, and IL-6

Plasma S100A1, NF-κB P65, and IL-6 significantly differed from cerebral infarction volume. There was no significant positive correlation between plasma S100A1 and cerebral infarction volume (R < 0.3), but there was statistical significance (r = 0.259, P = 0.002) (Fig. 3A). There was a positive correlation between NF-κB p65 and cerebral infarction volume with statistical significance (r = 0.316, P < 0.001) (Fig. 3B). There was no significant positive correlation between IL-6 and cerebral infarction volume (R < 0.3), but there was statistical significance (r = 0.177, P = 0.036) (Fig. 3C).

Mechanistic investigation: correlation analysis among the levels of plasma S100A1 protein, NF-κB p65, and IL-6

Statistically significant differences were found between plasma S100A1, NF-κB P65 and IL-6. There was no significant positive correlation between plasma S100A1 and NF-κB p65 (R < 0.3), but there was statistical significance (R = 0.290, P < 0.001) (Fig. 4A). There was a positive correlation between plasma IL-6 and NF-κB P65 with statistical significance (R = 0.313, P < 0.001) (Fig. 4B). There was a positive correlation between plasma S100A1 and IL-6 with statistical significance (R = 0.353, P < 0.001) (Fig. 4C).

Discussion

In this study, we first assessed the diagnostic efficacy of plasma S100A1 protein for AIS and TIA diseases. The results showed that the diagnosis of AIS might be more favorable when S100A1 ≥181.03 pg/ml, while the diagnosis of TIA might be more advantageous when 150.14 pg/ml ≤S100A1 ≤181.03 pg/ml. At the same time, the correlation between plasma S100A1 protein and cerebral infarct volume was proposed in this study, and the results showed that its level could reflect the severity of AIS to some extent. Furthermore, this study also found that plasma S100A1 protein levels and IL-6 and NF-κB p65 correlated with each other. It was reasonably speculated that this protein might mediate inflammatory responses through the NF-κB pathway in the pathophysiological process of AIS.

Inflammation, abnormal coagulation, and atherosclerosis all play important roles in various pathophysiological stages of AIS (Atif et al., 2020; Fani et al., 2020; Li, Qiu & Li, 2021). Both in the development process of AIS and the post-AIS process, it has a crucial significance. S100A1 protein was a novel inflammatory marker and a protein subtype in the S100 family of proteins (Baudier, Deloulme & Shaw, 2020). This protein could usually bind calcium ions and was essentially a type of calcium-binding protein traditionally found only in vertebrates (Chaturvedi et al., 2020). Currently, there are 25 known members of the S100 protein family with a high degree of sequence and structural similarity. They are involved in intracellular and extracellular regulatory activities in various tissues. In the nervous system, intracellular and extracellularly, S100 proteins could stimulate neuronal and glial cell proliferation and cause neuronal death through apoptotic programs, stimulating or inhibiting cellular inflammation (Sreejit et al., 2020). In recent years, S100A1 protein has been well studied in various systemic diseases, including acute myocardial infarction (Fan et al., 2019), heart failure (Soltani, Kheirouri & Enamzadeh, 2021), malignancy (Nakagawa et al., 2022; Li et al., 2021; Wang et al., 2021b), etc. Previous studies have shown that hypoxic cardiomyocytes released endogenous S100A1, which stimulated NF- κB p65 by binding to TLR4, thereby inducing an increase in pro-inflammatory cytokines; either endogenous or exogenous S100A1 significantly enhanced NF-κB phosphorylation in cardiomyocytes, thereby activating the expression of multiple pro-inflammatory cytokines involved in the inflammatory response (e.g., tumour necrosis factor α, chemokines, and interleukin 6) (Yu et al., 2015). This was the theoretical basis of the present study. Therefore, we suspected whether there was also an association between plasma S100A1 protein levels and AIS and the relationship with NF-κB p65 and IL-6 levels downstream of the conduction pathway.

In this study, clinical data were first compared among the AIS, TIA, and PE groups, and statistically significant differences were found in plasma S100A1, NF-κB p65, and IL-6 (P < 0.05). A two-by-two comparison revealed that the levels of the three in the AIS group were significantly higher than in the TIA and PE groups (P < 0.05). At the same time, no statistically significant differences were discovered between the TIA and PE groups. The results were more similar to the findings of Fan et al. (2019) in acute myocardial infarction, which indicated that plasma S100A1 levels were significantly higher in the ST-segment elevation myocardial infarction (STEMI) group than in healthy controls. After multifactorial logistic regression analysis, it was shown that S100A1 was an independent predictor of STEMI and that patients who possessed higher levels of S100A1 protein had a significantly increased risk of STEMI. It was finally concluded that the elevated plasma S100A1 concentration was an essential predictor of STEMI. This was generally consistent with the finding that the S100A1 level in the AIS group was significantly higher than that in the PE group in this study. This study also found that the S100A1 level in the AIS group was also higher than in the TIA group. It was presumed that this might be associated with the different severity of inflammation between the patients in the AIS and TIA groups, where the clinical symptoms of the patients in the TIA group could be rapidly relieved in a short period, and their resulting inflammatory response was relatively mild. Previous studies have shown that transient ischemic symptoms usually last for seconds or minutes and typically last less than an hour (Amarenco, 2020). The new definition of TIA is now “tissue-based”. An ischemic lesion is not visible on brain imaging in a patient with TIA, and a patient with transient symptoms who has even a tiny ischemic brain lesion on imaging is considered to have had a minor ischemic stroke (Amarenco, 2020; Albers et al., 2002; Kleindorfer et al., 2021). Similarly, in the study by Wang et al. (2021a), the overall level of inflammation in TIA patients was generally lower, which might be relevant to the short duration of TIA symptoms. Hence, both from an inflammatory and imaging point of view, TIA patients tended to be more normal in their performance. This nicely explained the insignificant differences in this study’s three detection indexes between the TIA and PE groups. In addition, multivariate logistic regression analysis showed that plasma S100A1 protein might be an independent predictor of disease diagnosis, which was also consistent with the conclusion of Fan et al. (2019). From the diagnostic efficacy of S100A1 protein for AIS and TIA, the diagnostic efficacy of S100A1 protein for AIS was higher than that for TIA (AUC of AIS was 0.818 > AUC of TIA was 0.720). According to the performance of the best Cut-off value, the diagnosis of AIS might be more inclined when S100A1 ≥181.03 pg/ml, while the diagnosis of TIA might be inclined when 150.14 pg/ml ≤S100A1 ≤181.03 pg/ml, and more inclined to normal when S100A1 ≤150.14 pg/ml. Thus, depending on the magnitude of this value, it was then feasible to make a more accurate and standardized diagnosis or differential diagnosis of the disease as early as possible in the development of the disease.

In exploring the differences in plasma S100A1 levels in acute ischemic strokes of different severity, it was found that there was variability in S100A1 levels in patients with different volumes of cerebral infarction. The S100A1 levels in the LCI group were significantly higher than those in the MCI and SCI groups (P < 0.05). At the same time, no statistically significant difference was found between the MCI and SCI groups (P > 0.05). The levels of NF-κB p65 and IL-6 showed similar consequences among the three groups. Plasma S100A1 protein, NF-B p65, and IL-6 were well-established markers for the overall inflammatory status of the patient’s body, according to several earlier research (Rohde et al., 2014; Mizuno et al., 2022; Liu, Chen & Chang, 2022; García-Juárez & Camacho-Morales, 2022). Thus, patients in the LCI group had significantly higher levels of inflammation than those in the MCI and SCI groups. This suggested that larger infarcts might represent higher levels of inflammation. This was similar to the results of Liu, Xiang & Jin (2015) and Wang et al. (2019), overexpression of inflammatory factors in acute cerebral infarction might increase the volume and edema degree of cerebral infarction. Similarly, serum concentrations of inflammatory factor C1q were positively correlated with both infarct volume and NIHSS in patients with AIS in a research by Wang et al. (2020). As was already noted, the size of the infarct determined how much damage to the brain tissue might occur as well as how intensely the inflammatory reaction would be. This study also investigated the relationship between plasma S100A1 and cerebral infarct size, and there was a statistically significant difference between the two (r = 0.259, P < 0.05), but the correlation coefficient was low. This might be due to the fact that plasma S100A1 protein was not released from brain tissue alone. Still, other systemic and local inflammatory responses, including the effects of certain underlying diseases, might also lead to changes in plasma S100A1 levels. Even nevertheless, plasma S100A1 levels in the LCI group were significantly higher than in the MCI and SCI groups with statistically significant differences, suggesting that S100A1 levels might in part reflect the severity of patients at the time of admission during the acute exacerbation. Meanwhile, the present study also compared the relationship between NF-κB p65, IL-6, and cerebral infarct volume, and the results also showed statistically significant but relatively low correlation coefficients. Previous studies have shown a moderate to a high positive correlation between these two factors and cerebral infarct volume (Li & Xin, 2021; Purroy et al., 2021). The limited sample size of the research population may have contributed to the fact that the same conclusion was not achieved in this work. The levels of plasma S100A1, NF-κB p65, and IL-6 were not statistically significantly different between the MCI and SCI groups, and it was conjectured that these inflammatory markers might need to reach a specific volume of cerebral infarction before their differences could be revealed, but the specific boundaries needed to be further investigated.

Additionally, in this study, the correlation between plasma S100A1, NF-κB p65 and IL-6 was also compared. It turned out that there was some correlation between these three. All three were statistically significantly different from each other, with correlation coefficients preserved at around 0.3, showing a low correlation. This might be due to the complex pathophysiological mechanisms of cerebral infarction and the small number of studied samples. As previously indicated, S100A1 might regulate the inflammatory response of H9C2 cells through the TLR4 /NF-κB pathway. Necrosis of hypoxic cardiac tissue released endogenous S100A1 to activate TLR4, which in turn induced IL-6 production by binding to TLR4 and thus stimulating NF-κB p65 (Yu et al., 2015). This same perspective was shown in the research of Rohde et al. (2014). In studies of multiple sclerosis (MS), it was found that the S100A protein similarly induced microglia activity by activating the NF- κB pathway, thereby increasing the expression of inflammatory cytokines (Wu et al., 2018). Along the same lines, in monocytes with primary thrombocytopenia (PT), IL6 decreased NF-κB-mediated expression of S100A protein levels through a negative feedback mechanism in PT (Diklić et al., 2020). In other words, S100A could enhance IL-6 expression by inducing the NF-κB pathway. In summary, it could be hypothesized that the elevated levels of S100A1 in patients with acute cerebral infarction might enhance the expression of the inflammatory factor IL-6 and thus mediated the inflammatory response through the NF-κB pathway, which was also consistent with the conclusions obtained in this paper.

There were several limitations to this report. First of all, an appropriate sample size and single-center study were important methodological defects, which required an expanded sample size and multi-center prospective study in the later period. Second, the time point at which plasma S100A1 protein levels were determined was single, which could not indicate the dynamic changes in this protein’s levels. Therefore, this protein’s dynamic monitoring and long-term follow-up should be strengthened in the future. Third, further grouping tests have to be conducted since it was possible that the experimental results would be impacted by including patients with anterior and posterior circulation cerebral infarction in the research sample. Fourth, whether plasma S100A1 protein actually enhanced the expression of the inflammatory factor IL-6 through the NF-κB pathway in patients with acute cerebral infarction remained further confirmed by animal experiments. Finally, the possibility that other unknown confounders might influence the results could not be completely ruled out.

Conclusions

In summary, our study indicated that the plasma S100A1 protein was significantly correlated with the diagnostic value of AIS and the volume of cerebral infarction. This protein might have a better diagnostic effect for AIS and TIA. The diagnosis of AIS might be more favorable when S100A1 ≥181.03 pg/ml, while the diagnosis of TIA might be more advantageous when 150.14 pg/ml ≤S100A1 ≤181.03 pg/ml. Furthermore, plasma S100A1 protein was associated with infarct volume in AIS, and its level reflected the severity of acute cerebral infarction to a certain extent. Increased levels of this protein might mean more severe damage in AIS patients with larger brain infarct volumes, while patients with lower levels could benefit more. Concurrently, there was a correlation between plasma S100A1 protein levels and IL-6 and NF-κB p65, and it was reasonable to speculate that this protein might mediate the inflammatory response through the NF-κB pathway during the pathophysiology of acute cerebral infarction. Based on our findings and previous studies, plasma S100A1 protein has the potential to serve as an inclusion criterion for future clinical diagnostic trials in AIS, and lowering the level of this protein may be a novel therapeutic target to improve their severity.

Supplemental Information