12- and 15-lipoxygenases in human carotid atherosclerotic lesions: Associations with cerebrovascular symptoms

Authors: GERTOW, KARL - Karolinska Institute; NOBILI, ELENA - University Of Milan; FOLKERSEN, LASSE - Karolinska Institute; Newman, John; Pedersen, Theresa; SWEDENBORG, JESPER - Karolinska Institute; PAULSSON-BERNE, GABRIELLE - Karolinska Institute; KUHN, HARTMUT - Charite' University Hospital Berlin; HEDIN, ULF - Karolinska Institute; WHEELOCK, CRAIG - Karolinska Institute; HANSSON, GORAN - Karolinska Institute; HAEGGSTROM, JESPER - Karolinska Institute; GABRIELSEN, ANDERS - Karolinska Institute

Submitted to: Atherosclerosis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2011
Publication Date: 1/21/2011
Citation: Gertow, K., Nobili, E., Folkersen, L., Newman, J.W., Pedersen, T.L., Swedenborg, J., Paulsson-Berne, G., Kuhn, H., Hedin, U., Wheelock, C.E., Hansson, G.K., Haeggstrom, J.Z., Gabrielsen, A. 2011. 12- and 15-lipoxygenases in human carotid atherosclerotic lesions: Associations with cerebrovascular symptoms. Atherosclerosis. 215:411-416.

Interpretive Summary: Lipoxygenase (ALOX) enzymes are implicated in both pro- and anti-atherogenic processes. The aim of this study was to investigate five ALOX genes (ALOX12, ALOX12B, ALOX15, ALOX15B and ALOXE3) in human carotid artery atherosclerotic lesions (plaques), in relation to cerebrovascular symptoms and risk factors. Specifically, levels of ALOX messenger RNAs (mRNA; the material facilitating the translation of genetic instructions into functional proteins) were investigated in plaque samples from the Biobank of Karolinska Endarterectomies (BiKE). BiKE consists of carotid plaque tissue specimens from patients undergoing surgical treatment of severe stenosis (narrowing) of the carotid artery and associated clinical data. Lesion mRNA levels were analyzed in a total of 132 BiKE samples. These analyses indicated that ALOX15B (also known as 15-LOX-2 or epidermis-type 15-LOX) is the only abundantly expressed mRNA in plaque tissue out of the five ALOX genes in question. Correlations between ALOX15B mRNA levels and clinical parameters were investigated. Comparing plaques with or without attributable cerebrovascular symptoms (such as stroke or less severe, more transient symptoms), ALOX15B mRNA levels were found to be higher in plaques from symptomatic than asymptomatic subjects (1.31 [1.11-1.56], n=102; and 0.79 [0.55-1.15], n=30, respectively; p=0.008; mean [95%CI], arbitrary units). Protein and metabolite measurements in a limited number of lesions confirmed the presence of ALOX15B protein and products in plaque tissue. In summary, we observed associations between high ALOX15B expression in carotid lesions and cerebrovascular symptoms. Although not allowing conclusions on causal relationships, these findings suggest a link between ALOX15B and atherothrombotic events that merits further investigation.

Technical Abstract: Lipoxygenase (ALOX) enzymes are implicated in both pro- and anti-atherogenic processes. The aim of this study was to investigate mRNA expression of 12- and 15-lipoxygenases (ALOX12, ALOX12B, ALOX15, ALOX15B) and the atypical ALOXE3 in human carotid atherosclerotic lesions, in relation to cerebrovascular symptoms and risk factors. The Biobank of Karolinska Endarterectomies (BiKE) collection of human carotid plaque tissue and associated clinical data was utilized (n=132). Lesion mRNA levels were analyzed by TaqMan qPCR (n=132) and microarray hybridization (n=77). Of the investigated mRNAs, only ALOX15B (also known as 15-LOX-2 or epidermis-type 15-LOX) was robustly detected in all plaque samples by qPCR, and thus suitable for quantitative statistical evaluation. Other ALOX mRNAs were detected with lower frequency and at lower levels, or virtually undetected. Microarray analysis confirmed ALOX15B as the most abundant 12- or 15-lipoxygenase mRNA in carotid lesions. Comparing plaques with or without attributable cerebrovascular symptoms (amaurosis fugax, TIA, or stroke), ALOX15B mRNA levels were higher in symptomatic than asymptomatic plaques (1.31 [1.11-1.56], n=102; and 0.79 [0.55-1.15], n=30, respectively; p=0.008; mean [95% CI], arbitrary units). Multivariate analysis confirmed symptomatic/asymptomatic status as a significant determinant of ALOX15B mRNA levels, independently of potentially confounding factors. Immunohistochemical and lipidomic analyses of a limited number of lesions confirmed the presence of ALOX15B protein and products in plaque tissue. In summary, we observed associations between high ALOX15B expression in carotid lesions and cerebrovascular symptoms. Although not allowing conclusions on causal relationships, these findings suggest a link between ALOX15B and atherothrombotic events that merits further investigation.