Expression of stromal‐cell‐derived factor‐1 (SDF‐1): a predictor of ischaemic stroke?

The stromal cell-derived factor-1 α (SDF-1α)/cysteine-X-cysteine chemokine receptor 4 (CXCR4) axis: a possible prognostic indicator of acute ischemic stroke

Objective

The stromal cell-derived factor-1α/cysteine-X-cysteine chemokine receptor 4 (SDF-1α/CXCR4) axis promotes neuroprotection and angiogenesis in animal studies. Few studies have investigated the potential clinical implications of the SDF-1α/CXCR4 axis in patients with acute ischemic stroke (AIS). We evaluated the prognostic values of the SDF-1α/CXCR4 axis in patients with proximal middle cerebral artery occlusion.

Methods

Fifty-five patients and 18 age- and sex-matched volunteers were enrolled. Baseline clinical characteristics and risk factors of stroke were recorded. Peripheral whole blood cells were double stained with anti-CD34 and anti-CXCR4 (CD184). CD34+CXCR4+ cells were analyzed by flow cytometry. Plasma SDF-1α levels were measured by enzyme-linked immunosorbent assay.

Results

In the AIS group, plasma SDF-1α levels and the number of circulating CD34+CXCR4+ cells were significantly higher than those in controls. Day 1 SDF-1α levels were negatively correlated with infarct volume (r = −0.521) and the initial National Institutes of Health Stroke Scale score (r = −0.489). SDF-1α levels (day 1: r = −0.514; day 3: r = −0.275; day 7: r = −0.375) and circulating CD34+CXCR4+ cells (day 7: r = −0.282) were inversely associated with the 90-day modified Rankin Scale score.

Conclusion

The SDF-1α/CXCR4 axis has potential applications for predicting the clinical outcome of AIS.

Neuroinflammatory mechanisms of blood-brain barrier damage in ischemic stroke

As part of the neurovascular unit, the blood-brain barrier (BBB) is a unique, dynamic regulatory boundary that limits and regulates the exchange of molecules, ions, and cells between the blood and the central nervous system. Disruption of the BBB plays an important role in the development of neurological dysfunction in ischemic stroke. Blood-borne substances and cells have restricted access to the brain due to the presence of tight junctions between the endothelial cells of the BBB. Following stroke, there is loss of BBB tight junction integrity, leading to increased paracellular permeability, which results in vasogenic edema, hemorrhagic transformation, and increased mortality. Thus, understanding principal mediators and molecular mechanisms involved in BBB disruption is critical for the development of novel therapeutics to treat ischemic stroke. This review discusses the current knowledge of how neuroinflammation contributes to BBB damage in ischemic stroke. Specifically, we provide an updated overview of the role of cytokines, chemokines, oxidative and nitrosative stress, adhesion molecules, matrix metalloproteinases, and vascular endothelial growth factor as well as the role of different cell types in the regulation of BBB permeability in ischemic stroke.

CCL23: a new CC chemokine involved in human brain damage

BACKGROUND

CCL23 role in the inflammatory response after acute brain injuries remains elusive. Here, we evaluated whether CCL23 blood levels associate with acquired cerebral lesions and determined CCL23 predictive capacity for assessing stroke prognosis. We used preclinical models to study the CCL23 homologous chemokines in rodents, CCL9 and CCL6.

METHODS

Baseline CCL23 blood levels were determined on 245 individuals, including ischaemic strokes (IS), stroke mimics and controls. Temporal profile of circulating CCL23 was explored from baseline to 24 h in 20 of the IS. In an independent cohort of 120 IS with a 3-month follow-up, CCL23 blood levels were included in logistic regression models to predict IS outcome. CCL9/CCL6 cerebral expression was evaluated in rodent models of brain damage. Both chemokines were also profiled in circulation and histologically located on brain following ischaemia.

RESULTS

Baseline CCL23 blood levels did not discriminate IS, but permitted an accurate discrimination of patients presenting acute brain lesions (P = 0.003). IS exhibited a continuous increase from baseline to 24 h in circulating CCL23 (P < 0.001). Baseline CCL23 blood levels resulted an independent predictor of IS outcome at hospital discharge (OR_adj : 19.702 [1.815-213.918], P = 0.014) and mortality after 3 months (OR_adj : 21.47 [3.434-134.221], P = 0.001). In preclinics, expression of rodent chemokines in neurons following cerebral lesions was elevated. CCL9 circulating levels decreased early after ischaemia (P < 0.001), whereas CCL6 did not alter within the first 24 h after ischaemia.

CONCLUSIONS

Although preclinical models do not seem suitable to characterize CCL23, it might be a novel promising biomarker for the early diagnosis of cerebral lesions and might facilitate the prediction of stroke patient outcome.

Serum CXCL12 levels are associated with stroke severity and lesion volumes in stroke patients

OBJECTIVE

Previous studies had shown that CXC chemokine ligand-12 (CXCL12) might play a significant role in stroke. The aim of this study was to test the serum baseline CXCL12 levels in Chinese patients with acute ischemic stroke (AIS).

METHODS

All consecutive patients with first-ever AIS from January 2013 to June 2014 were recruited to participate in the study. CXCL12 and National Institutes of Health Stroke Scale were measured at the time of admission. Logistic regression analysis was used to evaluate the risk of stroke according to serum CXCL12 levels. Receiver operating characteristic (ROC) curve was used to evaluate the accuracy of serum CXCL12 in diagnosing stroke.

RESULTS

From 306 screened patients, a total of 239 patients with first-ever AIS were included in this study. The results indicated that the serum CXCL12 levels were significantly higher in AIS patients as compared to normal controls (P < 0.0001). Serum CXCL12 were positively correlated with infarct volume(r = 0.307, P < 0.0001) and stroke severity(r = 0.288, P < 0.0001). After adjusting for all other possible covariates, CXCL12 was a stroke predictor with an adjusted OR of 2.047 [95% confidence interval (CI), 1.781-2.352; P < 0.0001]. Based on the ROC curve, the optimal cutoff value of serum CXCL12 levels as an indicator for auxiliary diagnosis of AIS was projected to be 3.4 ng/ml, which yielded a sensitivity of 87.9% and a specificity of 72.0%, with the area under the curve at 0.902 (95% CI, 0.875-0.929).

CONCLUSION

Our study demonstrated that serum CXCL12 levels increased significantly following AIS, and these changes in serum CXCL12 were positively correlated with infarct volume and stroke severity in Chinese sample.

Serum CXCL12 Levels as a Novel Predictor of Future Stroke Recurrence in Patients with Acute Ischemic Stroke

Previous studies had shown that CXC chemokine ligand-12 (CXCL12) plays a significant role in animal models of ischemic stroke, but its role in human stroke is unclear. The aim of this study was to test the relationship between elevated serum circulating CXCL12 levels and the 1-year stroke recurrence in Chinese patients with acute ischemic stroke (AIS). All consecutive patients with first-ever acute ischemic stroke from January 2011 to September 2013 were recruited to participate in the study. Serum levels of CXCL12 and National Institute of Health Stroke Scale (NIHSS) were measured at the time of admission. Logistic regression analysis was used to evaluate the stroke recurrence according to serum CXCL12 levels. Receiver operating characteristic (ROC) curve was used to evaluate the accuracy of serum CXCL12 in predicting stroke recurrence. Clinical follow-up was performed at 1 year. In our study, 248 patients finished the 1-year follow-up. At 1-year follow-up, 31 patients had a recurrence ischemic stroke. The median CXCL12 levels were significantly higher in those who sustained a recurrence ischemic stroke compared with those who did not [24.2 ng/mL (IQR 15.4-33.7) vs 6.5 ng/mL (IQR 3.4-10.2); Z = 8.258, P < 0.0001]. In multivariate analysis, there was an increased risk of stroke recurrence associated with serum CXCL12 levels ≥12.15 ng/mL (OR 9.122, 95 % CI 6.103-15.104) after adjusting for above possible confounders. The time to recurrence stroke distribution between patients with baseline CXCL12 levels ≥12.15 ng/mL and those with baseline CXCL12 levels <12.15 ng/mL were significantly different (P < 0.0001, log-rank test). Elevated circulating CXCL12 levels at admission are strongly associated with the future recurrence of ischemic stroke in Chinese patients with AIS. Further studies are warranted to confirm this association and define the role for CXCL12 as a novel predictor biomarker for stroke recurrence.

Increased VEGF and decreased SDF-1α in patients with silent brain infarction are associated with better prognosis after first-ever acute lacunar stroke

BACKGROUND

Pre-existing silent brain infarctions (SBIs) have been reported to be associated with better outcomes after first-ever symptomatic ischemic stroke, although the mechanism of this remains unclear. We investigated the association between SBIs, outcomes of acute lacunar infarction, and biomarkers including vascular endothelial growth factor (VEGF), stromal cell-derived factor-1α (SDF-1α), macrophage migration inhibitory factor (MIF), and high-mobility group box-1 (HMGB1).

METHODS

A total of 68 consecutive patients diagnosed with first-ever lacunar infarction (<20 mm) within 24 hours of symptom onset were included in this study. Clinical, laboratory, and imaging data were obtained. Plasma levels of VEGF, SDF-1α, MIF, and HMGB1 were assessed using Enzyme-Linked Immunosorbent Assay kits.

RESULTS

SBIs were noted in 31 of the 68 patients. Although the initial National Institutes of Health Stroke Scale scores were not related with the presence of SBIs (P = .313), patients with SBIs had better outcomes at 3 months (P = .029). Additionally, plasma VEGF levels were higher (P = .035) and SDF-1α levels were lower (P < .001) in patients with SBIs. Logistic regression analysis indicated that VEGF and SDF-1α were independently associated with the presence of SBIs.

CONCLUSIONS

SBIs are associated with favorable outcomes in patients with first-ever acute lacunar infarction and higher levels of VEGF, and lower levels of SDF-1α in these patients may contribute to their more favorable prognosis.

Platelet-derived CXCL12 (SDF-1α): basic mechanisms and clinical implications

Platelets are a major source of CXCL12 (stromal cell-derived factor -1α, SDF-1α) and store CXCL12 as part of their α-granule secretome. Platelet activation enhances surface expression and release of CXCL12. Platelets and megakaryocytes express CXCR4, the major receptor for CXCL12, and interaction of CXCL12 with CXCR4 regulates megakaryopoiesis and the function of circulating platelets. Platelet-derived CXCL12 also modulates paracrine mechanisms such as chemotaxis, adhesion, proliferation and differentiation of nucleated cells, including progenitor cells. Platelet-derived CXCL12 enhances peripheral recruitment of progenitor cells to the sites of vascular and tissue injury both in vitro and in vivo and thereby promotes repair mechanisms. CXCL12 expression on platelets is elevated in patients with acute myocardial infarction, correlates with the number of circulating progenitor cells, is associated with preservation of myocardial function and is an independent predictor of clinical outcome. Administration of recombinant CXCL12 reduces infarct size following transient ischemia in mice. The present review summarizes the role of platelet-derived CXCL12 in cardiovascular biology and its diagnostic and therapeutic implications.

Platelets are a previously unrecognised source of MIF

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like functions and a role in atherogenesis. MIF is secreted by various cells including endothelial cells and macrophages. Platelets are another prominent cell type with a role in atherogenesis and are a rich source of atherogenic chemokines. We asked whether platelets express and secrete MIF. In comparison, CXCL12 release was determined. We examined the subcellular localisation of MIF in platelets/megakaryocytes, studied its co-localisation with other platelet-derived mediators and asked whether platelets contain MIF mRNA. Moreover, we probed the functional role of platelet-derived MIF in inflammatory cell recruitment. Using Western blot and ELISA, we demonstrated and quantitated MIF protein in human and mouse platelets. Applying confocal-microscopy, MIF was found to localise in granular-like structures, but did not co-localise with known platelet cytokines. qPCR indicated that platelets contain low levels of MIF mRNA. ELISA measurements from human platelet supernatants showed that, whereas thrombin and collagen triggered the release of MIF and CXCL12, ADP and oxidised LDL promoted CXCL12 but not MIF secretion. Using Transwell assays, we demonstrated that platelet supernatants promoted monocyte chemotaxis and that this was blocked by neutralising MIF antibodies.This is the first report demonstrating MIF secretion from activated platelets, suggesting that platelets are a previously unrecognised source of MIF in inflammatory processes. There are distinct activating stimuli for MIF and CXCL12 secretion. A substantial portion of the chemotactic capacity of stimulated platelet supernatants is contributed by MIF, suggesting a role for platelet-derived MIF in atherogenic cell recruitment.

Plasma CXCL12 levels as a predictor of future stroke

BACKGROUND AND PURPOSE

The chemokine ligand CXCL12 is constitutively expressed in the bone marrow and other tissues including the brain endothelium and is responsible for regulating the trafficking of bone marrow progenitor cells. CXCL12 has been shown to play a significant role in animal models of ischemic stroke but its role in human stroke is unclear. The aim of this study was to test the hypothesis that elevated circulating baseline CXCL12 levels are associated with subsequent stroke.

METHODS

We prospectively collected demographic and angiographic data from consecutive patients referred for elective coronary angiography. Before coronary angiography a peripheral blood sample was collected for subsequent measurement of CXCL12. One-year stroke risk was calculated using the Framingham Risk Profile. Clinical follow-up was performed at 6 months and 1 year.

RESULTS

Of 206 subjects enrolled, 10 (4.9%) sustained an ischemic stroke over the 1 year follow-up. There were no significant differences in baseline clinical characteristics or angiographic findings. However, median CXCL12 levels were significantly higher in those who sustained an ischemic stroke compared with those who did not (10 856 pg/mL versus 2241 pg/mL, P=0.007). The time to stroke distribution between subjects with baseline CXCL12 levels≥10 421 pg/mL and those with baseline CXCL12 levels<10 421 pg/mL was significantly different (log rank P<0.001). The weighted Cox proportional hazard model demonstrated that baseline CXCL12 levels≥10 421 pg/mL were significantly associated with ischemic stroke at follow-up (hazard ratio, 15.29; 95% CI, 3.05-76.71).

CONCLUSIONS

Plasma CXCL12 levels may represent a novel biomarker of future ischemic stroke.