Liver-X-receptor-mediated expression of key genes in macrophages implicated in the control of cholesterol homeostasis and atherosclerosis

Atherosclerosis is a leading cause of morbidity and mortality in the western world. The deposition of lipoprotein cholesterol in the arterial wall is a critical early step in the pathogenesis of atherosclerosis. These atherogenic lipoproteins are then taken up by macrophages to transform into lipid-loaded foam cells. ATP-binding cassette transporter-Ai (ABCAi) is a membrane-bound protein that mediates efflux of cholesterol from cells, such as macrophages. Tangier disease, which arises due to mutations in the ABCAi gene, is associated with foam cells in a number of tissues and premature atherosclerosis. Proteins in HDL, such as apolipoprotein E (apoE), act as acceptors of cholesterol released from macrophages via the action of ABCAi, and take it to the liver where it can be excreted through the bile system. Increasing the expression of both ABCAi and apoE is therefore considered as a potential therapeutic approach for the prevention or treatment of atherosclerosis. Liver-X-receptors (LXRs) are members of a subfamily of nuclear receptors that are potent activators of ABCAi and apoE expression. Agonists of LXRs inhibit macrophage foam cell formation in vitro and atherosclerosis in mouse models of the disease. The signalling pathways through which LXR agonists induce the expression of ABCAi and apoE expression in macrophages are not known. The major aim of the studies presented in this thesis was to investigate such signalling pathways using the human macrophage THP-1 cell line as a model system with key findings confirmed in primary cultures. Both natural LXR agonists, such as combinations of 22-(R)-hydroxycholesterol (22-(R)-HC) and 9-cis-retinoic acid (9CRA), and synthetic ligands induced the expression of ABCAi and apoE. Such an induction of ABCAi and apoE expression was attenuated by treatment of the cells with pharmacological inhibitors of c-Jun-N-terminal kinase/stress- activated kinase (JNK/SAPK) and phosphoinositide-3-kinase (PI3K) pathways. The action of 22-(R)-HC and 9CRA was associated with activation of JNK/SAPK, its upstream component SEK1/MKK4 and its down-stream target c-Jun along with the key target for PI3K, protein kinase B (PKB). The role of these pathways was confirmed further by analysing the action of expression of dominant negative forms of key proteins on the activation of ABCAi promoter. In addition, small interfering RNA-mediated knockdown of JNK/SAPK was found to attenuate the induction of apoE expression. The action of these pathways culminated at the level of activator protein-1, a transcription factor that contains c-Jun, and whose binding sites are present in the regulatory regions of both the apoE and ABCAi genes. Finally, a potential cross-talk between the JNK/SAPK and PI3K pathways was identified in which protein kinase C played an important role. In conclusion, the studies presented in this thesis demonstrated, for the first time, an important role for a pathway involving PKB, PKC and JNK/SAPK cascade in the activation of ABCAi and apoE expression by LXR agonists, which has implications to macrophage foam cell formation and atherosclerosis

Liver-X-receptor-mediated expression of key genes in macrophages implicated in the control of cholesterol homeostasis and atherosclerosis

Atherosclerosis is a leading cause of morbidity and mortality in the western world. The deposition of lipoprotein cholesterol in the arterial wall is a critical early step in the pathogenesis of atherosclerosis. These atherogenic lipoproteins are then taken up by macrophages to transform into lipid-loaded foam cells. ATP-binding cassette transporter-Ai (ABCAi) is a membrane-bound protein that mediates efflux of cholesterol from cells, such as macrophages. Tangier disease, which arises due to mutations in the ABCAi gene, is associated with foam cells in a number of tissues and premature atherosclerosis. Proteins in HDL, such as apolipoprotein E (apoE), act as acceptors of cholesterol released from macrophages via the action of ABCAi, and take it to the liver where it can be excreted through the bile system. Increasing the expression of both ABCAi and apoE is therefore considered as a potential therapeutic approach for the prevention or treatment of atherosclerosis. Liver-X-receptors (LXRs) are members of a subfamily of nuclear receptors that are potent activators of ABCAi and apoE expression. Agonists of LXRs inhibit macrophage foam cell formation in vitro and atherosclerosis in mouse models of the disease. The signalling pathways through which LXR agonists induce the expression of ABCAi and apoE expression in macrophages are not known. The major aim of the studies presented in this thesis was to investigate such signalling pathways using the human macrophage THP-1 cell line as a model system with key findings confirmed in primary cultures. Both natural LXR agonists, such as combinations of 22-(R)-hydroxycholesterol (22-(R)-HC) and 9-cis-retinoic acid (9CRA), and synthetic ligands induced the expression of ABCAi and apoE. Such an induction of ABCAi and apoE expression was attenuated by treatment of the cells with pharmacological inhibitors of c-Jun-N-terminal kinase/stress- activated kinase (JNK/SAPK) and phosphoinositide-3-kinase (PI3K) pathways. The action of 22-(R)-HC and 9CRA was associated with activation of JNK/SAPK, its upstream component SEK1/MKK4 and its down-stream target c-Jun along with the key target for PI3K, protein kinase B (PKB). The role of these pathways was confirmed further by analysing the action of expression of dominant negative forms of key proteins on the activation of ABCAi promoter. In addition, small interfering RNA-mediated knockdown of JNK/SAPK was found to attenuate the induction of apoE expression. The action of these pathways culminated at the level of activator protein-1, a transcription factor that contains c-Jun, and whose binding sites are present in the regulatory regions of both the apoE and ABCAi genes. Finally, a potential cross-talk between the JNK/SAPK and PI3K pathways was identified in which protein kinase C played an important role. In conclusion, the studies presented in this thesis demonstrated, for the first time, an important role for a pathway involving PKB, PKC and JNK/SAPK cascade in the activation of ABCAi and apoE expression by LXR agonists, which has implications to macrophage foam cell formation and atherosclerosis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

PROTECTIVE ROLE OF CARNITINE SYNERGIZED WITH VITAMIN E AGAINST ISOPROTERENOL INDUCED CARDIAC INFARCTION IN RATS.

Background: The current study aimed to evaluate the role of carnitine in combination with vitamin E in protection against myocardial infarction induced by isoproterenol (ISO) in rats. Materials and Methods: Rats were grouped into 5 (each 10 rats): Group I. Control fed a standard diet. Group III: Rats were injected with vitamin E (100 IU/kg bw, i.p) daily. Group IV: Rats were given carnitine (20 mg/kg bw, i.p) daily .Group V: Rats were injected with both vitamin E (100 IU/kg bw, i.p) and carnitine (20 mg/kg bw, i.p) daily. On 7th, 8th, and 9th day, rats in groups (II-V) were injection i.p with ISO (55mg/kg b.w for successive three days). The treatment with carnitine and vitamin E were continuous for 21 days. Results: Canirine combined with vitamin E significantly increased coronary flow (CF) (

Efficiency of borage seeds oil against gamma irradiation-induced hepatotoxicity in male rats: possible antioxidant activity

Background: Borage (Borago officinal L.) is an annual herbaceous plant of great interest because its oil contains a high percentage of γ-linolenic acid (GLA). The present work was carried out to detect fatty acids composition of the oil extracted from borage seeds (BO) and its potential effectiveness against γ-irradiation- induced hepatotoxicity in male rats.Materials and Methods: GC-MS analysis of fatty acids methyl esters of BO was performed to identify fatty acids composition. Sixty rats were divided into five groups (12 rats each): Control, irradiated; rats were exposed to (6.5 Gy) of whole body γ-radiation, BO (50 mg/kg b.wt), irradiated BO post-treated and irradiated BO prepost-treated. Six rats from each group were sacrificed at two time intervals 7 and 15 days post-irradiation. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT) levels, lipids profile, as well as serum and hepatic reduced glutathione (GSH) and lipid peroxide (malondialdehyde) (MDA) levels were assessed. Histopathological examination of liver sections were also carried out.Results: The results showed that the high contents of BO extracted by cold pressing, were linoleic acid (34.23%) and GLA (24.79%). Also, oral administration of BO significantly improved serum levels of liver enzymes, lipids profile, as well as serum and hepatic GSH and MDA levels (p<0.001) as compared with irradiated rats after 15 days post irradiation. Moreover, it exerted marked amelioration against irradiation-induced histopathological changes in liver tissues. The improvement was more pronounced in irradiated BO prepost-treated group than irradiated BO post-treated.Conclusion: BO has a beneficial role in reducing hepatotoxicity and oxidative stress induced by radiation exposure. Therefore, BO may be used as a beneficial supplement for patients during radiotherapy treatment.Keywords: Borage seeds oil; γ-irradiation; Hepatotoxicity; Antioxidan

Thymoquinone ameliorates acrylamide-induced reproductive toxicity in female rats: An experimental study

Background: Acrylamide (AA) is a carcinogenic compound that causes severe reproductive impairments and represents a high environmental risk factor. Thymoquinone (TQ) has a unique antioxidant activity and has been widely used as a protective agent against various types of toxicity. Objective: To evaluate the protective effects of TQ against AA-induced reproductive toxicity in female rats. Materials and Methods: In this experimental study, 40 female albino rats (120-150 gr, 8-10 wk) were sorted into 4 groups, (n = 10/each), vehicle group (received a daily oral administration of 0.5 ml saline [9%]); AA group (received a daily oral administration with freshly prepared AA, 20 mg/kg body weight) for 21 days which is less than the lethal dose LD50 of AA in rats (20 mg/kg body weight); AA+TQ group (received a daily oral administration of TQ, 10 mg/kg body weight) after AA intoxication for 21 days, and TQ group (received a daily oral administration of TQ only, 10 mg/kg body weight) for 21 consecutive days. Reproductive hormones, carcinogenic biomarkers, and oxidative stress markers were measured. The histological assessment showed the protective effect of TQ against AA-induced ovarian injury. Network pharmacology analysis and molecular docking approach were carried out to determine the binding affinity of TQ with cyclooxygenase 2. Results: TQ administration significantly enhanced the functional capacity of the ovary at hormones, oxidative biomarkers, and tumor markers at a significant level of p < 0.001. Besides, TQ protects the ovary of AA-treated rats from the severe degeneration effect. Conclusion: TQ showed a promising protective effect against AA-induced reproductive toxicity in female rats. Key words: Acrylamide, Thymoquinone, Rats, Oxidative stress, Cyclooxygenase 2, Inflammation

Serum proteins C and S levels as early biomarkers for kidney dysfunction in hemophilic patients

Background: Hemophilia is an inherited genetic disease characterized by the inability to coagulate blood after injury. The rationale of the current study was to evaluate serum proteins S and C and correlate to kidney function test in hemophilic patients for early diagnosis of abnormality in renal function.Subjects and Methods: This study was conducted on 80 males subjects divided into four groups. Group I: Control: Healthy subjects. Group II: Renal dysfunction (serum Creatinine >2mg/dl): Group III: Hemophilic patients. Group IV: Hemophilic patients with renal disorder. Serum urea, creatinine, sodium, potassium, protein C and protein S level were determined. Resuts: Protein C and S levels showed a significant decrease in hemophilic/and with renal dysfunction (P < 0.001,p<0.001). The level of plasma protein C and S levels were positively correlated with increased urinary albumin (P < 0.01). Urinary albumin was increased about 15 folds in hemophilic patients with renal dysfunction and nephrotic patients as compared with the control group. The cut-off value in 90% patients at the hemophilic patients with renal dysfunction 70%. Positive correlations were observed between urinary albumin (r=0.66), and creatinine (r=0.73). Conclusion: These biomarkers showed good predictive values with regard to ROC-AUC (0.41 and 0.75 for Proteins C and S, respectively).Keywords: Hemophilia, renal dysfunction, protein C, protein S

EFFICIENCY OF BORAGE SEEDS OIL AGAINST GAMMA IRRADIATION-INDUCED HEPATOTOXICITY IN MALE RATS: POSSIBLE ANTIOXIDANT ACTIVITY

Background: Borage (Borago officinal L.) is an annual herbaceous plant of great interest because its oil contains a high percentage of -linolenic acid (GLA). The present work was carried out to detect fatty acids composition of the oil extracted from borage seeds (BO) and its potential effectiveness against γ-irradiation- induced hepatotoxicity in male rats. Materials and Methods: GC-MS analysis of fatty acids methyl esters of BO was performed to identify fatty acids composition. Sixty rats were divided into five groups (12 rats each): Control, irradiated; rats were exposed to (6.5 Gy) of whole body γ-radiation, BO (50 mg/kg b.wt), irradiated BO post-treated and irradiated BO prepost-treated. Six rats from each group were sacrificed at two time intervals 7 and 15 days post-irradiation. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT) levels, lipids profile, as well as serum and hepatic reduced glutathione (GSH) and lipid peroxide (malondialdehyde) (MDA) levels were assessed. Histopathological examination of liver sections were also carried out. Results: The results showed that the high contents of BO extracted by cold pressing, were linoleic acid (34.23%) and GLA (24.79%). Also, oral administration of BO significantly improved serum levels of liver enzymes, lipids profile, as well as serum and hepatic GSH and MDA levels (

Relationship between soil cobalt and vitamin B12 levels in the liver of livestock in Saudi Arabia: role of competing elements in soils.

Objective: This study aimed to analyze the agricultural soils from different regions in Saudi Arabia for cobalt and related metals as Cu2+, Ni2+, Cr3+, Zn2+ and Pb2+. Materlais and Methods: Liver and muscle tissues of livestock grazing on the selected areas were analyzed for the content of Co and vitamin B12. Results: Our results indicated that the levels of Co in surface soil (0-15 cm) were higher than in sub-surface soil (>15 cm- 45 cm). In contrast, Pb and Zn were higher in sub-surface soil than in surface soil. A significant positive correlation existed between the levels of Co and vitamin B12 in the liver of livestock. However, Co was not detected in muscle tissues while vitamin B12 was present at very low levels in comparison with the levels found in the liver. The results indicated that Zn2+, Pb2+ compete with Co in soil, which eventually affected the levels of vitamin B12 in liver. Conclusion: It was recommended that survey of heavy metals in grazing fields of cattle should consider inclusion of multiple elements that compete with the bioavailability of essential elements in plants and animals for the prevention of deficiency of essential elements such as Co

Serum proteins C and S levels as early biomarkers for kidney dysfunction in hemophilic patients

Background: Hemophilia is an inherited genetic disease characterized by the inability to coagulate blood after injury. The rationale of the current study was to evaluate serum proteins S and C and correlate to kidney function test in hemophilic patients for early diagnosis of abnormality in renal function. Subjects and Methods: This study was conducted on 80 males subjects divided into four groups. Group I: Control: Healthy subjects. Group II: Renal dysfunction (serum Creatinine >2mg/dl): Group III: Hemophilic patients. Group IV: Hemophilic patients with renal disorder. Serum urea, creatinine, sodium, potassium, protein C and protein S level were determined. Resuts: Protein C and S levels showed a significant decrease in hemophilic/and with renal dysfunction (P < 0.001,p<0.001). The level of plasma protein C and S levels were positively correlated with increased urinary albumin (P < 0.01). Urinary albumin was increased about 15 folds in hemophilic patients with renal dysfunction and nephrotic patients as compared with the control group. The cut-off value in 90% patients at the hemophilic patients with renal dysfunction 70%. Positive correlations were observed between urinary albumin (r=0.66), and creatinine (r=0.73). Conclusion: These biomarkers showed good predictive values with regard to ROC-AUC (0.41 and 0.75 for Proteins C and S, respectively)