Interleukin-4 does not influence development of hypercholesterolemia or angiotensin II-induced atherosclerotic lesions in mice

Abstract

Interleukin-4 (IL-4) has been detected in both human and mouse atherosclerotic lesions, although its effects on the development of the disease are undefined. We determined the role of IL-4 in the most commonly used murine models of atherosclerosis by defining the effects of exogenous delivery and genetic deficiency of this cytokine on both hypercholesterolemia and AngII-induced atherosclerosis in apolipoprotein E (apoE)(-/-) mice and different dietary stimuli in low-density lipoprotein (LDL) receptor(-/-) mice. Exogenous administration of IL-4 (1.1 ng g(-1) day(-1) i.p. for 30 days) into female apoE(-/-) mice had no effect on lesion size or composition in mice fed normal or saturated fat diets. Also, IL-4 deficiency had no significant effect on the size or composition of atherosclerotic lesions in two vascular areas of male and female apoE(-/-) mice fed either a normal or saturated fat diet. IL-4 deficiency was also studied in age-matched male mice infused with AngII (1000 ng kg(-1) min(-1)) for 28 days. Whereas AngII infusion augmented atherosclerotic lesion formation, IL-4 deficiency did not influence atherosclerotic lesion size or composition. Finally, different dietary stimuli also had no effect on atherosclerotic lesion size in female LDL receptor(-/-) mice. These data demonstrate that IL-4 does not significantly influence the development of atherosclerotic lesions in apoE(-/-) mice of either gender or in female LDL receptor(-/-) mice, irrespective of the mode of induction of atherosclerosis.

Figure 1

Atherosclerotic lesion area on the intimal surface of the aortic arch is not altered by IL-4 deficiency in LDL receptor-deficient mice fed a diet enriched in saturated fat that was either cholate-free (A) or supplemented (B). Eight- to 10-week-old female LDL receptor-deficient mice that were either IL-4^+/+ or IL-4^−/− were fed saturated fat-enriched diet (A) or cholate-containing atherogenic diet (B) for 28 days. After feeding of the diets, atherosclerotic lesions on the intimal surface of the aortic arch were measured in IL-4^+/+ (□; n = 6 mice/group) and IL-4^−/− (▪; n = 9 mice/group) mice at 9 to 11 weeks of age.

Figure 2

Atherosclerotic lesion area in the aortic root is not altered by recombinant IL-4 administration in apoE^−/− mice fed a normal (A) or saturated fat-enriched (B) diet. Eight-week-old female apoE^−/− mice were fed either a normal or saturated fat-enriched diet for 30 days. Recombinant mouse IL-4 (1.1 ng g⁻¹ day⁻¹) or vehicle was administered daily by i.p. injection for a 30-day time course. Atherosclerotic lesions on the aortic root (A and B) were measured in vehicle (□) and recombinant IL-4-injected (▪) mice (n = 10 mice/group) at 9 weeks of age.

Figure 3

Atherosclerotic lesion area in the aortic root is not altered by IL-4 deficiency in apoE^−/− mice fed either a normal or saturated fat-enriched diet. Atherosclerotic lesion in the aortic root were measured in male (A and C) and female (B and D) apoE^−/− × IL-4^+/+ (□) and apoE^−/− × IL-4^−/− (▪) mice fed a normal diet (A and B) until 36 weeks of age or a saturated fat-enriched diet (C and D) (n = 10 mice/group) for 12 weeks, beginning at 8 to 10 weeks of age (n = 10 mice/group).

Figure 4

IL-4 deficiency does not alter atherosclerotic lesion area on the intimal surface of the aorta. Atherosclerotic lesions on the intimal surface of the aorta were measured in male (A and C) and female (B and D) apoE^−/− × IL-4^−/− (□) and apoE^−/− × IL-4^−/− (▪) mice fed either a normal diet (A and B) until 36 weeks of age or saturated fat-enriched diet (C and D) for 12 weeks, beginning at 8 to 10 weeks of age (n = 10 mice/group).

Figure 5

IL-4 deficiency has no effect on cellular lesion composition. Immunostaining was performed using a rabbit antisera against mouse macrophages (A) (magnification, ×100) and an anti-rat monoclonal antibody against T lymphocytes (B) (Thy1.2; magnification, ×200) in representative sections of aortic root. Lesion area immunostained for macrophages was quantified in male and female mice fed a normal diet until 36 weeks of age (C and D) or saturated fat-enriched diet for 12 weeks (E and F), beginning at 8 to 10 weeks of age, and normalized to total lesion area.

Figure 6

AngII-induced atherosclerotic lesion size in the aortic arch is not altered by IL-4 deficiency in apoE^−/− mice. Atherosclerotic lesions on the intimal surface of the aortic arch were measured by en face analysis in 9-week-old male apoE^−/− mice fed a normal diet and infused with saline (A) or AngII (B) (1000 ng kg⁻¹ min⁻¹) for 28 days that were IL-4^+/+ (□) or IL-4^−/− (▪; n = 8 mice/group).