Interleukin-18 in acute ischaemic stroke patients

Neutralization of Interleukin-18 Inhibits Neointimal Formation in a Rat Model of Vascular Injury

Background— Studies in humans and animal models suggest that interleukin-18 (IL-18) plays a crucial role in vascular pathologies. IL-18 is a predictor of cardiovascular death in angina and is involved in atherotic plaque destabilization. Higher IL-18 plasma levels also are associated with restenosis after coronary artery angioplasty performed in patients with acute myocardial infarction. We investigated the effective role of IL-18 in neointimal formation in a balloon-induced rat model of vascular injury.

Methods and Results— Endothelial denudation of the left carotid artery was performed by use of a balloon embolectomy catheter. Increased expression of IL-18 and IL-18Rα/β mRNA was detectable in carotid arteries from days 2 to 14 after angioplasty. The active form of IL-18 was highly expressed in injured arteries. Strong immunoreactivity for IL-18 was detected in the medial smooth muscle cells at days 2 and 7 after balloon injury and in proliferating/migrating smooth muscle cells in neointima at day 14. Moreover, serum concentrations of IL-18 were significantly higher among rats subjected to vascular injury. Treatment with neutralizing rabbit anti-rat IL-18 immunoglobulin G significantly reduced neointimal formation (by 27%; P <0.01), reduced the number of proliferating cells, and inhibited interferon-γ, IL-6, and IL-8 mRNA expression and nuclear factor-κB activation in injured arteries. In addition, in vitro data show that IL-18 affects smooth muscle cell proliferation.

Conclusions— These results identify a critical role for IL-18 in neointimal formation in a rat model of vascular injury and suggest a potential role for IL-18 neutralization in the reduction of neointimal development.

Interleukin-18 and transforming growth factor-beta 1 plasma levels in Alzheimer's disease and vascular dementia

Inflammation has been involved in the development of dementia in cerebrovascular diseases. To investigate the cellular activation of the peripheral immune system in patients with Alzheimer's disease (AD) and vascular dementia (VaD), we determined the presence of IL-18 and TGF-beta1 in the plasma by using ELISA. The levels of IL-18 and TGF-beta1 were significantly elevated in patients with AD and VaD compared to non-demented, age-matched subjects. We found an inverse correlation between the levels of IL-18 and TGF-beta1 in AD patients. In VaD patients, the correlation between IL-18 and TGF-beta1 reached a borderline positive value. Whereas, in the non-demented, age-matched subjects, a positive correlation between IL-18 and TGF-beta1 levels was observed. These findings indicate that IL-18 and TGF-beta1 elevation is associated with AD and VaD patients, confirming that the immune system might exert a remarkable role in the development and progression of neurodegenerative disorders. Moreover, as different modifications were detected in the patients affected by AD and VaD, we propose that IL-18 and TGF-beta1 plasma levels might represent possible differential biomarkers.

Inflammation following stroke

Stroke is one of the leading causes of mortality and morbidity. The stroke process triggers an inflammatory reaction that may last up to several months. Suppression of inflammation using a variety of drugs reduces infarct volume and improves clinical outcomes in animal models of stroke. This benefit occurs even with the initiation of therapy after 3 hours of onset of stroke, beyond the therapeutic window for thrombolysis with tPA. The use of neuroprotectants to suppress inflammation may widen the therapeutic time window for tPA while lessening its side-effects. Suppression of inflammation may also improve outcomes in animal models of haemorrhagic stroke. To date, clinical trials with anti-inflammatory agents in acute ischaemic stroke have failed to improve clinical outcomes. However, because of the potential for broader applicability across all aspects of stroke, a better understanding of anti-inflammatory mechanisms is important.

Serum interleukin-18 levels are associated with nephropathy and atherosclerosis in Japanese patients with type 2 diabetes

OBJECTIVE

Interleukin (IL)-18 is a proinflammatory cytokine secreted from mononuclear cells. Serum concentration of IL-18 is a strong predictor of death in patients with cardiovascular diseases. Recent studies have shown that microinflammation is involved in the pathogenesis of diabetic nephropathy as well as of cardiovascular diseases. This study aimed to test the hypothesis that the serum level of IL-18 is a common predictor of nephropathy and atherosclerosis in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eighty-two Japanese patients with type 2 diabetes and 55 age- and sex-matched healthy control subjects were enrolled. Patients with renal dysfunction (creatinine clearance <1 ml/s) were excluded. We assessed clinical parameters and measured serum and urinary IL-18 levels, serum IL-6 levels, carotid intima-media thickness (IMT), and brachial-ankle pulse wave velocity (baPWV) in all patients. Further, we evaluated changes of urinary albumin excretion rate (AER) after 6 months in 76 diabetic patients.

RESULTS

Serum and urinary IL-18 levels were significantly elevated in patients with type 2 diabetes as compared with control subjects (serum IL-18 179 +/- 62 vs. 121 +/- 55 pg/ml, P < 0.001; urinary IL-18 97 +/- 159 vs. 47 +/- 54 pg/ml, P = 0.035). Univariate linear regression analysis showed significant positive correlations between serum IL-18 and AER (r [correlation coefficient] = 0.525, P < 0.001), HbA(1c) (r = 0.242, P = 0.029), high-sensitivity C-reactive protein (hs-CRP) (r = 0.240, P = 0.031), and urinary beta-2 microglobulin (r = 0.235, P = 0.036). Serum IL-18 levels also correlated positively with carotid IMT (r = 0.225, P = 0.042) and baPWV (r = 0.232, P = 0.040). We also found a significant correlation between urinary IL-18 and AER (r = 0.309, P = 0.005). Multivariate linear regression analysis showed that AER (standard correlation coefficients [B] = 0.405, P < 0.001) and hs-CRP (B = 0.207, P = 0.033) were independently associated with serum IL-18 levels. AER was also independently associated with urinary IL-18 levels (B = 0.295, P = 0.005). Moreover, serum and urinary IL-18 levels correlated positively with AER after 6 months (r = 0.489, P < 0.001 and r = 0.320, P = 0.005) and changes in AER during the follow-up period (r = 0.268, P = 0.018 and r = 0.234, P = 0.042).

CONCLUSIONS

Serum levels of IL-18 might be a predictor of progression of diabetic nephropathy as well as cardiovascular diseases.

IL-18: a key player in neuroinflammation and neurodegeneration?

Interleukin (IL)-18 is a potent inflammatory cytokine of the IL-1 family. It is synthesized as an inactive precursor (pro-IL-18), which is cleaved into its functionally active form by caspase-1. Resident cells of the CNS express IL-18 and caspase-1 constitutively, thus providing a local IL-18-dependent immune response. Recent studies have highlighted a crucial role for IL-18 in mediating neuroinflammation and neurodegeneration in the CNS under pathological conditions, such as bacterial and viral infection, autoimmune demyelinating disease, and hypoxic-ischemic, hyperoxic and traumatic brain injuries. This review provides a synopsis of the current knowledge of IL-18-dependent mechanisms of action during acute neurodegeneration in immature and adult brains.

Role of interleukin 18 in acute lung inflammation induced by gut ischemia reperfusion

AIM: To study the changes of endogenous interleukin 18 (IL-18) levels and evaluate the role of IL-18 on lung injury following gut ischemia/reperfusion.

METHODS: A superior mesenteric artery occlusion model was selected for this research. The mice were randomly divided into four groups: Sham operation (sham), ischemia (0.5 h) followed by different times of reperfusion (I/R), and I/R pretreated with exogenous IL-18 (I/R+IL-18) or IL-18 neutralizing antibody (I/R+IL-18Ab) 15 min before ischemia. Serum IL-18 levels were detected by Western blot and ELISA, and the levels of IL-18 in lung tissue were evaluated by immunohistochemical staining. For the study of pulmonary inflammation, the lung myeloperoxidase (MPO) contents and morphological changes were evaluated.

RESULTS: Gut ischemia/reperfusion induced rapid increase of serum IL-18 levels, peaked at 1 h after reperfusion and then declined. The levels of IL-18 in lung tissue were gradually enhanced as the progress of reperfusion. Compared with I/R group, exogenous administration of IL-18 (I/R+IL-18) further remarkably enhanced the pulmonary MPO activity and inflammatory cell infiltration, and in I/R+IL-18Ab group, the content of MPO were significantly reduced and lung inflammation was also decreased.

CONCLUSION: Gut ischemia/reperfusion induces the increase of IL-18 expression, which may make IL-18 act as an important proinflammatory cytokine and contribute to gut ischemia/reperfusion-induced lung inflammation.

Associations of serum IL-18 levels with carotid intima-media thickness

OBJECTIVE

Elevated circulating levels of IL-18 can predict future coronary heart disease. Although IL-18 is thought to play a crucial role in atherosclerosis, whether circulating IL-18 levels are associated with the severity of atherosclerosis remains to be determined. With the use of B-mode ultrasound, this study examines the relationships of serum IL-18 levels with carotid intima-media thickness (IMT) as a reflector for systemic atherosclerosis.

METHODS AND RESULTS

The study comprised 366 patients without histories of cardiovascular accidents. Severity of carotid atherosclerosis was evaluated by the mean max IMT, ie, mean of the maximal wall thickness at 12 carotid segments. Serum IL-18, IL-6, and high-sensitive C-reactive protein (hs-CRP) levels were determined in all patients. Log-transformed IL-18 concentrations were positively correlated with IMT (r=0.36, P<0.001), and the association remained significant (beta=0.20, P<0.001) when controlling for traditional atherosclerotic risk factors, IL-6 and hs-CRP levels. Also, IMT was greater in the highest and the middle tertile of IL-18 levels than in the lowest tertile.

CONCLUSIONS

Higher serum IL-18 levels appear to be associated with greater carotid IMT, suggesting the link between IL-18 and atherosclerosis.