The effect of aspirin on circulating netrin-1 levels in humans is dependent on the inflammatory status of the vascular endothelium

Abstract

In atherosclerotic animal models, the cyclo-oxygenase (COX)-inhibitor aspirin counteracts downregulation of endothelial-derived netrin-1, thus reducing arterial inflammation. We here explored the effect of aspirin on netrin-1 in healthy subjects undergoing influenza immunisation, which is an established experimental model of inflammation-related endothelial dysfunction.Our data showed that netrin-1 undergoes reduction (-29.25% from baseline; p=0.0017) in the presence of endothelial activation (VCAM-1 rose by 9.98% 2-days post-vaccination; p=0.0022). Aspirin counteracted vaccine-induced endothelial activation and reduction of netrin-1 in a dose-dependent manner (-3.06% and -17.03% from baseline at a dose of 300mg and 75mg respectively; p=0.0465 and p>0.05 vs untreated). Clopidogrel, which was used as a comparator due to its similar anti-platelet activity, also reduced endothelial activation but, unlike aspirin, enhanced netrin-1 levels (+20.96% from baseline; p=0.0033 vs untreated). A correlation analysis incorporating cytokines, hs-CRP, VCAM-1, TXB2 and PGE2, showed that changes in netrin-1 were directly related to PGE2 variations only (r=0.6103; p=0.0002). In a separate population of 40 healthy unimmunised volunteers, 28-day treatment with aspirin 300mg reduced netrin-1 (-18.76% from baseline; p=0.0012) without affecting endothelial markers or hs-CRP; as expected, aspirin suppressed TXB2 and PGE2. Netrin-1 and PGE2 levels were directly related (r=0.358; p=0.0015), but other parameters including TXB2, hs-CRP and endothelial markers, were not.In conclusion, aspirin counteracts downregulation of netrin-1 following endothelial dysfunction due to its anti-inflammatory effect on the activated endothelium. However, inhibition of COX-dependent prostanoids negatively modulates netrin-1 synthesis in healthy subjects, and this could give rise to aspirin-dependent reduction in netrin-1 under steady state conditions.

Netrin-1 and the Grade of Atherosclerosis Are Inversely Correlated in Humans

“…In addition, it has been shown in both mice and human studies that acetylsalicylic acid increases Netrin-1 production by endothelial cells. 15 The cohorts used in the current study contained many patients with established CVD which invariably leads to inclusion of patients on these cohorts. However, if we would have been able to correct for the use of acetylsalicylic acid, we would probably have found an even greater difference in Netrin-1 levels between patients with and without CVD.…”

“…8,9 Supporting evidence for this anti-inflammatory endothelial Netrin-1 is found in mouse models with acute lung inflammation due to Staphylococcus aureus infection, where Netrin-1 was found to be expressed in the luminal surface of lung endothelial cells, where is acted to block migration of monocytes. [14][15][16] Also in the atherosclerotic mouse model with low-density lipoprotein receptor knockout (Ldlr -/-) mice receiving overexpression of human Netrin-1 by adenovirus delivery show a reduction in plaque formation compared with sham-treated mice. 17 The effect of Netrin-1 in humans is still unknown, and there is not much research done about Netrin-1 in the systemic circulation related to CVD.…”

Netrin-1 in coronary artery disease (CAD): mechanism of action and potential as a therapeutic target

“…The discovery of Netrin-1 and its receptors expressed by cells outside of the central nervous system indicates that Netrin-1 has additional functions beyond the central nervous system. Preclinical data supports the role for Netrin-1 in the atherosclerosis progression, and more effects of Netrin-1 in mouse studies have been shown to be equally potent in vitro on cells of human origin, or are being validated in human cohorts [1,2,3].…”

“…For example, aspirin treatment protected against disease burden via a reduction of monocyte plaque infiltration and lesion growth in mice [6]. Additionally, healthy human subjects receiving influenza immunization showed vascular activation-induced Netrin-1 depletion, which was counteracted following 300 mg aspirin for 28 days [3].…”

Neuronal guidance proteins in cardiovascular inflammation

“…Acetylsalicylic acid (ASS), which is usually administered to patients at increased cardiovascular risk, counteracts the inflammation-induced suppression of Ntn1 secretion by the endothelium and significantly reduces plaque sizes in a murine ApoE −/− model of atherosclerosis [ 61 ]. In humans, ASS counteracts the reduction in plasma Ntn1 levels after vaccination-induced endothelial dysfunction, and the effect is directly related to the extent of cyclooxygenase inhibition [ 40 ]. This finding reveals a protective effect of ASS and cyclooxygenase inhibition that extends beyond our current understanding and is driven by an NGP-mediated mechanism, preserving the endothelial barrier during vascular inflammation.…”