Association of apolipoprotein A1 -75 G/A polymorphism with susceptibility to the development of acute lung injury after cardiopulmonary bypass surgery

Emerging Roles of Apolipoprotein E and Apolipoprotein A-I in the Pathogenesis and Treatment of Lung Disease

Emerging roles are being recognized increasingly for apolipoproteins in the pathogenesis and treatment of lung diseases on the basis of their ability to suppress inflammation, oxidative stress, and tissue remodeling, and to promote adaptive immunity and host defense. Apolipoproteins, such as apolipoprotein E (apoE) and apolipoprotein A-I (apoA-I), are important components of lipoprotein particles that facilitate the transport of cholesterol, triglycerides, and phospholipids between plasma and cells. ApoE-containing lipoprotein particles are internalized into cells by low-density lipoprotein receptors (LDLRs), whereas apoA-I can interact with the ATP-binding cassette subfamily A member 1 (ABCA1) transporter to efflux cholesterol and phospholipids out of cells. ApoE and apoA-I also mediate receptor-independent effects, such as binding to and neutralizing LPS. Both apoE and apoA-I are expressed by lung cells, which allows apoE/LDLR- and apoA-I/ABCA1-dependent pathways to modulate normal lung health and the pathogenesis of respiratory diseases, including asthma, acute lung injury, cancer, emphysema, pulmonary fibrosis, and pulmonary hypertension. Data from human studies and research using experimental murine model systems have shown that both apoE and apoA-I pathways play primarily protective roles in lung biology and respiratory disease. Furthermore, apolipoprotein mimetic peptides, corresponding to the LDLR-binding domain of apoE or the class A amphipathic α-helical structure of apoA-I, have antiinflammatory and antioxidant effects that attenuate the severity of lung disease in murine models. Thus, the development of inhaled apolipoprotein mimetic peptides as a novel treatment paradigm could represent a significant advance for patients with respiratory disease who do not respond to current therapies.

Increased expression of ApoA1 after neuronal injury may be beneficial for healing

ApoA1 is a player in reverse cholesterol transport that initiates multiple cellular pathways on binding to its receptor ABCA1. Its relation to neuronal injury is however unclear. We found ApoA1 to be increasingly abundant at a later time point in the secondary phase of traumatic spinal cord injury. In a cellular injury model of neuroblastoma, ApoA1 showed an initial diminished expression after infliction of injury, which sharply increased thereafter. Subsequently, ApoA1 was shown to alter wound healing dynamics in neuroblastoma injury model. It was observed that an initial lag in scratch wound closure was followed by rapid healing in the ApoA1 treatment group. Activation of ERK pathway and Actin polymerisation by ApoA1 corroborated its role in healing after neuronal injury. We propose that ApoA1 is increasingly expressed and secreted as a delayed response to neuronal injury, and this is a self-protecting mechanism of the injured system.

High-density Lipoproteins and Apolipoprotein A-I: Potential New Players in the Prevention and Treatment of Lung Disease

Apolipoprotein A-I (apoA-I) and high-density lipoproteins (HDL) mediate reverse cholesterol transport out of cells. Furthermore, HDL has additional protective functions, which include anti-oxidative, anti-inflammatory, anti-apoptotic, and vasoprotective effects. In contrast, HDL can become dysfunctional with a reduction in both cholesterol efflux and anti-inflammatory properties in the setting of disease or the acute phase response. These paradigms are increasingly being recognized to be active in the pulmonary system, where apoA-I and HDL have protective effects in normal lung health, as well as in a variety of disease states, including acute lung injury (ALI), asthma, chronic obstructive pulmonary disease, lung cancer, pulmonary arterial hypertension, pulmonary fibrosis, and viral pneumonia. Similar to observations in cardiovascular disease, however, HDL may become dysfunctional and contribute to disease pathogenesis in respiratory disorders. Furthermore, synthetic apoA-I mimetic peptides have been shown to have protective effects in animal models of ALI, asthma, pulmonary hypertension, and influenza pneumonia. These findings provide evidence to support the concept that apoA-I mimetic peptides might be developed into a new treatment that can either prevent or attenuate the manifestations of lung diseases, such as asthma. Thus, the lung is positioned to take a page from the cardiovascular disease playbook and utilize the protective properties of HDL and apoA-I as a novel therapeutic approach.

Single nucleotide polymorphisms of APOA1 gene and their relationship with serum apolipoprotein A-I concentrations in the native population of Assam

Background

There is a growing interest in the role of allelic variants of the APOA1 gene in relation to a number of disorders. We described two common polymorphisms of the APOA1 gene, G-75A and C+83T and investigated their potential influence on the serum apolipoprotein A-I (apo A-I) levels in the native population of Assam — a region that is ethnically distinct and from where no information is hitherto available.

Methods

Blood samples were collected from 150 healthy volunteers. Apo A-I levels were estimated by immunoturbidometry. Genotyping was done by a PCR-RFLP method that involved DNA extraction from whole blood, followed by polymerase chain reaction and digestion of the PCR product by MspI restriction enzyme, and analysis of fragment sizes in 12% polyacrylamide gel.

Results

The GG variant at G-75A locus and CC variant at C+83T locus were the most prevalent. GG/CC was the most common combination. Homozygous TT genotype was not detected in any of the subjects. The rare allele frequencies for the G-75A and C+83T sites were found to be 0.22 and 0.06 respectively, which significantly differed from those reported in some other populations in neighbouring regions. Serum apo A-I concentrations did not vary significantly across the detected genotypes. These findings were consistent in both sexes.

Conclusion

We described the distribution of the G-75A and C+83T polymorphisms of the APOA1 gene in the population of Assam for the first time. These polymorphisms were not found to directly influence apo A-I concentrations in this population either individually or synergistically.

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The G-75A and C + 83T polymorphisms of the APOA1 gene are described for the first time in the native population of Assam, north-east India.

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The minor allelic frequencies of G-75A and C + 83T differ significantly from some populations in the adjoining regions.

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The G-75A and C + 83T polymorphisms do not influence the serum apolipoprotein A-I levels in the current population.

Apolipoprotein A1 -75 G/A and +83 C/T polymorphisms and renal cancer risk

Background

Apolipoprotein A1 (ApoA1) is the major apoprotein constituent of high-density lipoprotein that can play important roles in tumor invasion and metastasis. The objective of the present study was to evaluate the association of two genetic variants (−75 G/A and +83 C/T) of APOA1 with predisposition to renal cancer.

Methods

A total of 432 subjects, including 216 pathologically-proven renal cancer cases and 216 age- and gender-matched healthy controls, were recruited into this hospital-based case–control study. Genotyping of the APOA1 was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

Patients with renal cancer had a significantly higher frequency of APOA1 -75 AA genotype [odds ratio (OR) = 2.10, 95 % confidence interval (CI) = 1.18, 3.75; P = 0.01] and APOA1 -75 A allele (OR =1.40, 95 % CI = 1.05, 1.87; P = 0.02) than controls. When stratifying by the distant metastasis status, patients with distant metastasis had a significantly higher frequency of APOA1 -75 AA genotype genotype (OR =2.20, 95 % CI = 1.04, 4.68; P = 0.04).

Conclusion

This study is, to our knowledge, the first to examine prospectively an increased risk role of APOA1 -75 AA genotype and APOA1 -75 A allele in renal cancer susceptibility.

Effect of apolipoprotein A1 genetic polymorphisms on lipid profiles and the risk of coronary artery disease

Background

The disorder of lipid metabolism and genetic predisposition are major risk factors for coronary artery disease (CAD). Variants in the apolipoprotein A1 (APOA1) gene play an important role in the regulation of lipids. The objective of the present study was to investigate the effect of two polymorphisms (-75 G/A and +83 C/T) of APOA1 on lipid profiles and the risk of CAD.

Methods

A total number of 300 subjects with CAD and 300 age and sex matched healthy controls were enrolled for the study. Genotyping of the APOA1 was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

The frequencies of APOA1 -75 AA genotype [odds ratio (OR) =0.50, 95 % confidence interval (CI) = 0.28, 0.88; P = 0.02] and APOA1 -75 A allele (OR =0.76, 95 % CI = 0.59, 0.98; P = 0.04) were significantly lower in CAD than in controls. The APOA1 -75 A allele was significantly associated with increasing serum concentrations of ApoA1 and high-density lipoprotein cholesterol (HDL-C) (P < 0.001).

Conclusions

The individuals with the APOA1 -75 A allele were likely to have a lower risk of CAD as a result of its effect on higher serum concentrations of ApoA1 and HDL-C.

Haplotype analysis of ApoAI gene and sepsis-associated acute lung injury

BACKGROUND

Apolipoprotein A1 (ApoA1) is the major apoprotein constituent of high density lipoprotein (HDL) which exerts innate protective effects in systemic inflammation. However, its role in the acute lung injury (ALI) has not been well studied. In the present study we investigated the association between polymorphisms of ApoA1 gene and ALI in a Chinese population.

METHODS

Three polymorphisms of the ApoA1 gene (rs11216153, rs2070665, and rs632153) were genotyped by TaqMan method in 290 patients with sepsis-associated ALI, 285 patients sepsis alone and 330 age- and sex-matched healthy controls.

RESULTS

We found rs11216153 polymorphism of ApoA1 was associated with ALI, the GG genotype and G allele was common in the ALI patients (76.9%, 88.1%, respectively) than both in the control subjects (55.8%, 75.8%, respectively) and in the sepsis alone patients (58.2%, 78.4%, respectively). Haplotype consisting of these three SNPs strengthened the association with ALI susceptibility. The frequency of haplotype GTG in the ALI samples was significantly higher than that in the healthy control group (OR = 2.261, 95% CI: 1.735 ~ 2.946, P <0.001) and the sepsis alone group (OR = 1.789, 95% CI: 1.373 ~ 2.331.P < 0.001). Carriers of the haplotype TTG had a lower risk for ALI compared with healthy control group (OR = 0.422, 95% CI: 0.310 ~ 0.574, P < 0.001) and sepsis alone group (OR = 0.491, 95% CI: 0.356 ~ 0.676, P <0.001).

CONCLUSIONS

These results indicated that genetic variants in the ApoA1 gene might be associated with susceptibility to sepsis-associated ALI in Han Chinese population.