Antimicrobial protein REG3A and signaling networks are predictive of stroke outcomes

Abstract

Regenerating Family Member 3 Alpha (REG3A) is a multifunctional protein with antimicrobial activity, and primarily secreted by the intestine and pancreas. Studies have shown an increased expression of REG3A in systemic inflammatory responses to acute injury and infection, but studies investigating REG3A during the pathogenesis of ischemic stroke are limited. The aims of this study were to examine the associations between arterial expression of REG3A and other arterial inflammatory proteins implicated in stroke pathogenesis, as well as associations between REG3A and markers of poor outcome for ischemic stroke. The University of Kentucky Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (clinicaltrials.gov NCT03153683) utilizes thrombectomy to isolate intracranial arterial blood (i.e. distal to thrombus) and systemic arterial blood (i.e. carotid). Samples were analyzed by Olink Proteomics for N = 42 subjects. Statistical analyses of plasma proteins included 2-sample t-tests, spearman and biserial correlations, and robust regression models to elucidate network signaling and association to clinical outcomes. Results indicated that levels of systemic REG3A were positively correlated with inflammatory proteins interleukin IL6 (R = 0.344, p = 0.030) and IL17C (R = 0.468, p = 0.002). 2-sided t- tests examining differences of systemic REG3A within quartiles of NIHSS admission score depicted significant differences between quartiles. Those with NIHSS scores corresponding to moderate and moderate-severe neurofunctional deficits had significantly higher levels of systemic REG3A compared to those with NIHSS scores corresponding to mild and mild-moderate neurofunctional deficits (p = 0.016). STRING analyses of proteins in each robust regression model demonstrated substantial networking between REG3A and other systemic proteins highly relevant to ischemic stroke. The present study provides novel data on systemic REG3A in the context of ischemic stroke. These results demonstrate the influential role of REG3A regarding surrogate functional and radiographic outcomes of stroke severity. Additionally, they provide novel insight into the role of REG3A and related proteins during the complex neuroinflammatory process of ischemic stroke. These data provide a foundation for future studies to investigate REG3A and related networking proteins as potential biomarkers with prognostic potential, as well as potential therapeutic targets.

Keywords: Proteomics; Thrombectomy; antimicrobial protein; biomarker; stroke.

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© 2021 International Society for Neurochemistry.

Figures

Figure 1:

Spearman Correlations of arterial REG3A versus: (A) Infarct volume(R=0.226, p=0.160); (B) Edema volume (R=0.176, p=0.276); (C) IL6 (R =0.344, p=0.030); (D) IL17C (R=0.468, p=0.002).

Figure 2:

Systemic levels of REG3A versus Quartiled NIHSS Scores on admission. Error bars represent standard deviation. (A) Illustrates statistical quartiles of NIHSS Admission Scores. T-tests found significantly lower levels of systemic REG3A in those with ‘Minor’ strokes compared to ‘Minor and Moderate’ strokes (p=0.04); Those with scores corresponding to ‘Minor Stroke’ had near significantly lower levels of REG3A compared to those with scores corresponding to ‘Severe’ stroke (p=0.055). (B) NIHSS Scores on admission were also examined as two groups by combining ‘Minor and ‘Minor-Moderate’ quartiles, and combining ‘Moderate’ and ‘Severe’ quartiles. Subjects within the combined ‘Moderate and Severe’ quartiles had significantly higher levels of systemic REG3A compared to subjects who fell within the ‘Minor-Moderate’ NIHSS score quartile (p=0.016).

Figure 3:

STRING protein-protein network analyses for (A) Systemic REG3A and Infarct volume, (B) Systemic REG3A and Edema volume.