Transient ischemic attack (TIA) is one of the most common alerting events for ischemic cerebral vascular attacks, with the sudden onset of neurological disorders such as paralysis, paresthesia, and speech, visual, or hearing impairments. These symptoms were temporary and alleviated in 24 h without any sequelae. However, these patients are at a high risk of further ischemic events after TIA. According to a systemic review of several follow-up studies, the approximate proportion of further stroke in patients with a first episode of TIA varied from approximately 8% to 12% in 7 days; however, it varied from 10% to 22% in 90 days (Giles and Rothwell, 2007). Risk levels of TIA which were measured by the ABCD2 score scale exerted pivotal roles in predicting subsequent ischemic stroke of TIA (Giles and Rothwell, 2007; Perry et al., 2021), whereas patients were usually scored depending on their medical histories and characteristic clinical manifestations. In addition to this, we wondered whether any molecular biomarkers could help to evaluate the latent possibility for recurrent cerebral ischemia after TIA.

According to previous studies, inflammation could exacerbate cerebral ischemic stroke by inducing atherosclerosis, facilitating instability of plaque, as well as overactivating platelets and coagulation (Esenwa and Elkind, 2016; Patel et al., 2018). The expression of C-reactive protein (CRP) was upregulated within 24 h after acute stroke and will sustain at a high level for nearly 6 months (Arenillas et al., 2003). Both clinical evidence and laboratory evidence suggested that anti-inflammatory therapies effectively decreased vascular damages and suppressed cerebral ischemic stroke (Kelly et al., 2018). Moreover, a high level of residual inflammatory risk (RIR) was proven to imply patients’ poor prognosis of acute cerebral ischemic stroke (Li et al., 2021a), while high-sensitivity C-reactive protein (hs-CRP), which represented early inflammatory response, was addressed as a decisive factor of RIR (Ridker et al., 2017). Low-level inflammation reflected by hs-CRP indicated recurrent ischemic events independently (Mengozzi et al., 2020; Coveney et al., 2021).

Potassium voltage-gated channel subfamily Q member 1 opposite strand 1 (KCNQ1OT1) is defined as a long non-coding RNA with more than 200 nucleotides. It was the overlapping transcript 1 located on the opposite strand of KCNQ1. KCNQ1OT1 influenced multiple target gene expression and function through epigenetic modifications (Pandey et al., 2008). Previously, we verified that KCNQ1OT1 could accelerate autophagy of neurons, thus exacerbating ischemia and reperfusion (I/R) injury in acute cerebrovascular diseases (Yu et al., 2019). Evidence demonstrated that KCNQ1OT1 activated inflammatory response and promoted apoptosis of microvascular endothelial cells in acute myocardial infarction (Wang et al., 2019; Liao et al., 2020). Moreover, KCNQ1OT1 could aggravate atherosclerosis via regulation of lipid metabolism (Yu et al., 2020). Nevertheless, little has been known about the effects of KCNQ1OT1 on subsequent ischemic stroke after TIA.

In our study, the mounting expression of KCNQ1OT1 was detected in plasma from TIA patients. Moreover, early inflammation illustrated by the serum hs-CRP level was positively associated with KCNQ1OT1 expression. Our findings will provide not only a novel biomarker for the risk of recurrence but also the latent therapeutic target in patients who suffered TIA.

In this study, we proposed that the expression of KCNQ1OT1 was upregulated in further ischemic events and positively associated with the stroke risk levels of TIA for the first time. Moreover, our study indicated that KCNQ1OT1 could be regarded as a predictive factor for subsequent stroke. With the expression level of KCNQ1OT1 over 1.29, the survival rate in 90 days after the first onset of TIA was decreased apparently. In addition, the early inflammatory response detected by hs-CRP was enhanced with an increasing KCNQ1OT1 level.

TIA has been considered the predominant risk factor for further stroke of unreversible neurological impairments. Studies reported that patients possessed 5.4%–14.2% possibility to develop into permanent neurological deficits after their first onset of TIA (Khanevski et al., 2019). Although neurologists strived to prohibit recurring TIA, there were still 25–30% of patients who suffered secondary stroke within 5 years after TIA (Valls et al., 2017). Currently, patients’ age, blood pressure, diabetes history, clinical manifestations, and duration of clinical symptoms are the most acknowledged factors that would influence further stroke after TIA (Wardlaw et al., 2015). Recent research revealed that patients whose systolic blood pressure was over 140 mmHg exposed a higher risk of recurring neurological dysfunction (de Havenon et al., 2021). Moreover, studies also discovered that further stroke was more likely to happen in TIA patients with intracranial atherosclerosis and aberrant inflammatory response (Luijendijk et al., 2011; Colas-Campas et al., 2020; Lindenholz et al., 2020). In the previous study, we have proven that overactivated autophagy and apoptosis of neurons could exacerbate cerebral ischemia–reperfusion injury and aggravated neurological impairments (Yu et al., 2020; Yu et al., 2021). In spite of no neurological deficits left, TIA was also caused by cerebral ischemia. Thus, we further studied the latent factors reflecting the development and prognosis of TIA.

Mounting evidence manifested that lncRNA KCNQ1OT1 participated in regulating cell progression and differentiation among various diseases such as cancer, fracture, and myocardial infarction (Feng et al., 2020; Wang et al., 2020; Li et al., 2021b; Hong et al., 2021). According to the previous study, KCNQ1OT1 was upregulated in the ischemic brain tissue, and its expression was growing with the patients’ severity of neurological impairments. Knockdown of KCNQ1OT1 could attenuate neural apoptosis induced by autophagy (Yu et al., 2019). In cerebral ischemia–reperfusion injury, silencing KCNQ1OT1 would attenuate endoplasmic reticulum stress via regulating the downstream miR-30b/GRP78 signaling cascade (Li et al., 2020). Moreover, KCNQ1OT1 aggravated fibrosis and pyroptosis in diabetic cardiomyopathy by targeting the miR-214-3p/caspase-1/TGF-β1/smad pathway (Yang et al., 2018). KCNQ1OT1 could competitively bind with miR-466 to mediate downstream Tead1 expression, promoting apoptosis of cardiomyocytes during acute myocardial infarction (Liao et al., 2020). Evidence also showed that the rising level of KCNQ1OT1 repressed cholesterol excretion and exacerbated lipid deposition in macrophages, which could facilitate the formation of atherosclerosis (Yu et al., 2020). However, there were few research studies about the roles of KCNQ1OT1 in TIA. In this study, we detected the upregulated level of KCNQ1OT1 and proposed KCNQ1OT1 as an independent risk factor in patients with further ischemic events after TIA. In addition, an optimal diagnostic value of KCNQ1OT1 expression as 1.29 was determined using the ROC curve analysis. Furthermore, we explored the underlying pathophysiological process associated with KCNQ1OT1 in TIA.

Inflammatory response was proven to be activated in acute cerebral cardiovascular diseases. In cerebral ischemia–reperfusion (I/R) injury, NLRP3 inflammasomes were accumulated in neurons and induced immune cell infiltration to destroy the integrity of the blood–brain barrier (Franke et al., 2021). In addition, microglial HDAC3 stimulated neuroinflammation and aggravated neurological impairments in I/R injury via the cGAS-STING pathway (Liao et al., 2020). Studies have reported that activated inflammation, which was reflected by the CRP level over 2 mg/L, would predict a high probability of recurrent cardiovascular diseases (McMurray et al., 2009; Blanco-Colio et al., 2021). In addition, inflammation could increase vulnerability of atherosclerotic plaques, which is the most common cause of recurrent ischemia (Badimon and Vilahur, 2014; Brinjikji et al., 2016). Inflammatory cytokines including IL-1β, IL-8, and hs-CRP were considered to predict recurrent ischemic stroke independently (Coveney et al., 2021). However, other researchers found that IL-6 and S-100B were decreased in the further events of TIA (Colas-Campas et al., 2020). Anti-inflammatory therapy with salvianolic acid D could impede the activation of the NF-κB pathway mediated by HMGB1 translocation in cerebral I/R injury (Zhang et al., 2020). Arginine acted as a neuroprotector to alleviate neurological impairments via inhibiting HIF-1α/LDHA-induced inflammation in microglia (Chen et al., 2020). Moreover, exosomes with conjugated curcumin could target the suppression of cerebral inflammatory response, so as to reduce neural apoptosis (Tian et al., 2018). As previously reported, KCNQ1OT1 could aggravate inflammatory response in myocardial infarction via the Notch pathway (Wang et al., 2019). Oxidative stress following myocardial infarction could be accelerated via the KCNQ1OT1/miR-130a-3p/ZNF791 axis (Xin et al., 2022). In addition, knockdown of KCNQ1OT1 would reduce the activation of NLRP3 inflammasome in acute kidney injury (Wang et al., 2021). Recent studies put forward that a high level of hs-CRP reflecting the early inflammation was an independent predictor for ischemic stroke after TIA or minor stroke (Mengozzi et al., 2020). Thus, we wondered whether the expression of KCNQ1OT1 was related to hs-CRP in further ischemic events after TIA. In our study, hs-CRP expression was found to be elevated up to 2.25 folds in patients with subsequent stroke, which was in agreement with the previous findings. Furthermore, we explored the latent association between upregulated KCNQ1OT1 expression and activated early inflammation reflected by hs-CRP in patients who had suffered further ischemic events of TIA. It was confirmed that the level of KCNQ1OT1 increased with the elevated expression of hs-CRP. This result implied that KCNQ1OT1 might be related to the activated early inflammatory response in the recurrence of TIA.

Nevertheless, there were still limitations to the research. Multiple-center research studies should be conducted to obtain more subjective data. Neither carotid stenosis nor low-density lipoprotein cholesterol (LDL-C) was identified with significant difference in patients who suffered subsequent stroke. It may be due to the relatively small sample size. More participants are needed in further studies.

In conclusion, patients with upregulated KCNQ1OT1 expression were at a high risk of further ischemic stroke after TIA. Our results indicated that KCNQ1OT1 had great predictive value for further ischemic events, especially when taken together with the ABCD2 score. Patients with the expression level of KCNQ1OT1 over 1.29 had a robust increased risk for further ischemic events. It would be due to the early inflammatory response after TIA, which was reflected by the hs-CRP level. These findings revealed the crucial roles of KCNQ1OT1 in ischemic events in patients with TIA. The underlying relationship between KCNQ1OT1 and early inflammation was discussed for the first time. However, there were still some gaps left in our study. The number of participants was relatively limited. More patients could be recruited to support our conclusion. Molecular biology experiments are needed to explore more specific regulatory mechanisms in our further study.