Lead nitrate-induced development of hypercholesterolemia in rats: sterol-independent gene regulation of hepatic enzymes responsible for cholesterol homeostasis

Association between cumulative childhood blood lead exposure and hepatic steatosis in young Mexican adults

BACKGROUND

Exposure to environmental toxicants may play a role in the pathogenesis of Non Alcoholic Fatty Liver Disease (NAFLD). Cumulative exposure to lead (Pb) has chronic and permanent effects on liver function. Pediatric populations are vulnerable to the toxic effects of Pb, even at low exposure levels. The purpose of the study was to estimate the association between cumulative Pb exposure during childhood and hepatic steatosis biomarkers in young Mexican adults.

METHODS

A subsample of 93 participants from the ELEMENT cohort were included in this study. Childhood blood samples were collected annually from ages 1-4 years and were used to calculate the Cumulative Childhood Blood Lead Levels (CCBLL). Hepatic steatosis during adulthood was defined as an excessive accumulation of hepatic triglycerides (>5%) determined using Magnetic Resonance Imaging (MRI). Liver enzymes were also measured at this time, and elevated liver enzyme levels were defined as ALT (≥30 IU/L), AST (≥30 IU/L), and GGT (≥40 IU/L). Adjusted linear regression models were fit to examine the association between CCBLL (quartiles) and the hepatic steatosis in young adulthood.

RESULTS

In adulthood, the mean age was 21.4 years, 55% were male. The overall prevalence of hepatic steatosis by MRI was 19%. Elevate levels of the enzymes ALT, AST, and GGT were present in 25%, 15%, and 17% of the sample, respectively. We found a positive association between the highest quartile of CCBLL with the steatosis biomarkers of hepatic triglycerides (Q4 vs. Q1: β = 6.07, 95% CI: 1.91-10.21), elevated ALT (Q4 vs. Q1: β = 14.5, 95% CI: 1.39-27.61) and elevated AST (Q4 vs. Q1: β = 7.23, 95% CI: 0.64-13.82). No significant associations were found with GGT.

CONCLUSIONS

Chronic Pb exposure during early childhood is associated with a higher levels of hepatic steatosis biomarkers and hepatocellular injury in young adulthood. More actions should be taken to eliminate sources of Pb during the first years of life.

The protective role of Coenzyme Q10 in metallothionein-3 expression in liver and kidney upon rats' exposure to lead acetate

Metallothionein-3 (MT3) is an antioxidant protein that alters after exposure to heavy metals. In this study, we investigated the hepatic and renal expression of MT3 gene following exposure to lead acetate (PbAc) alone and PbAc plus CoQ10 as an adjuvant antioxidant. Twenty-four rats were allocated into three groups, including control, PbAc (free access to drinking water contaminated with PbAc at 1 g/100 ml), and PbAc plus CoQ10 (10 mg/kg/day Oral). After 28 consecutive days of treatment, the mRNA expression of MT3 and Cyt-c genes and MT3 protein levels were assessed using real-time PCR and immunosorbent assay. The serum lipid profile was also monitored in the three groups. PbAc exposure significantly reduced the hepatic and renal MT3 mRNA and protein expression compared to the control group. This reduction was significantly increased with addition of CoQ10 to levels near those of the control group. The hepatic and renal expression of Cyt-c mRNA increased after treatment with PbAc, while such effect was reversed after addition of CoQ10. Alteration in lipid profile including increased cholesterol and low-density lipoprotein levels were observed after PbAc exposure which were counteracted by CoQ10. Our results confirm the cytotoxic effects of acute lead exposure manifested as changes in the serum lipid profile and cellular levels of Cyt-c mRNA. These cytotoxic effects may have been caused by decreased MT3 gene expression and be reduced by the protective role of CoQ10.

Protective role of rutin against combined exposure to lipopolysaccharide and D-galactosamine-induced dysfunctions in liver, kidney, and brain: Hematological, biochemical, and histological evidences

Protective efficacy of rutin over liver, kidney, and brain dysfunctions was evaluated in this investigation. Rutin (5, 10, and 20 mg/kg) was administered continuously for 6 days followed by single dose of D-galactosamine (300 mg/kg I.P.) and lipopolysaccharide (50 µg/kg I.P.) on the 6th day. Hematological, serological, biochemical, and histological aspects were considered for this study. One-way ANOVA (p ≤ .05) followed by Tukey's HSD post hoc test determined the statistical significance. Serum AST, ALT, ALP, urea, uric acid, and creatinine were increased significantly, whereas albumin and glucose were significantly decreased after combined exposure to LPS and D-GalN. Glutathione level and activity of SOD and catalase were decreased, whereas lipid peroxidation, triglycerides, and cholesterol were increased in tissue samples due to LPS- and D-GalN-induced toxicity. Prophylactic treatment of rutin maintained studied variables toward control claiming the protective role of rutin. PRACTICAL APPLICATION: Rutin is plenteous in a variety of commonly ingested foods such as onion, wine, grape, citrus fruits, tea, and buckwheat. Rutin supplement is recommended for the treatment of various diseases such as varicose veins, internal bleeding, or hemorrhoids. Rutin is better than well-known antithrombic agent, Juniferdin, or Bacitracin. In the present study, rutin showed protective effects against LPS- and D-GalN-induced multiorgan dysfunctions due to its anti-inflammatory and antioxidant properties. Therefore, rutin may be developed and practiced as a food supplement to cope with acute organ dysfunctions caused by inflammatory and oxidative damage.

Time-Dependent Naphthalene Toxicity in Anabas testudineus (Bloch): A Multiple Endpoint Biomarker Approach

Polyaromatic compounds are the major, widespread contaminants in the aquatic environment. However, the adverse impacts of these compounds on blood pathophysiology (hematological profiling and serum biochemical responses) are poorly understood. As a consequence, this study was intended to evaluate the toxic effects of naphthalene, one of the polycyclic aromatic hydrocarbons, on the blood pathophysiology of Anabas testudineus using multiple end-point biomarker approach. A. testudineus was exposed to short-term (1 and 5 d) and long-term (10, 15, and 21 d) naphthalene concentrations, that is, T1 (0.71 mg/L indicates 25% of LC₅₀) and T2 (1.42 mg/L indicates 50% of LC₅₀ value). The results disclosed significant decrease in red blood cells, hemoglobin (Hb), packed cell volume, and platelet levels, while other blood parameters, namely, white blood cells, percent lymphocyte, mean cell volume, mean corpuscular Hb, and mean corpuscular Hb concentration showed enhanced levels under naphthalene intoxication. Results were more detrimental under T2 concentration. Cholesterol, glucose, calcium, high-density lipoprotein, and low-density lipoprotein levels gradually increased throughout the different exposure periods under T1 and T2 concentrations, while the triglyceride level gradually decreased during exposure periods. Finally, integrated biomarker responses (IBR) analysis indicated that serum biochemical parameters are more powerful than hematological parameters for determining the naphthalene-induced fish health status. Additionally, the IBR study clearly identified that long-term (>5 d) exposure was more harmful than short-term (<5 d) naphthalene exposure. So, these responses may be derived as biomarkers for monitoring naphthalene pollution in an aquatic ecosystem.

Gallic Acid Protects from Acute Multiorgan Injury Induced by Lipopolysaccharide and D-galactosamine

BACKGROUND

Secondary metabolites of plants, the polyphenols, play a vital role in protection from many health problems in human beings. Structurally favored phytochemicals may be studied to protect multiorgan injury. At pharmacological doses, gallic acid is nontoxic to mammals and is generally absorbed in the intestine.

AIMS

In this present study, gallic acid was evaluated for its protective efficacy against Lipo Polysaccharide (LPS) and d-Galactosamine (D-GalN) induced multiorgan injury, i.e., liver, kidney and brain.

METHODS

Three different doses of gallic acid (5, 10 and 20 mg/kg p.o.) were administered to the experimental animals for 6 consecutive days, followed by exposure to LPS (50 μg/kg I.P.) and D-GalN (300 mg/kg I.P.) on the 6th day.

RESULTS

Exposure to LPS and D-GalN resulted in increased oxidative stress and proinflammatory cytokines. Altered hematology and serology due to LPS and D-GalN were restored towards control by gallic acid. Declined antioxidants such as reduced glutathione, superoxide dismutase and catalase due to injurious effects of LPS and D-GalN were rejuvenated by gallic acid.

DISCUSSION

Exposure to LPS and D-GalN severely increased lipid peroxidation, CYP2E1 activity and tissue lipids while lowered protein content. Gallic acid restored all these parameters towards control in dose dependent manner and 20 mg/kg dose provided the best protection. Histological study showed improved histoarchitecture of liver, kidney and brain that supported biochemical endpoints.

CONCLUSION

Gallic acid minimized oxidative stress and provided best protection at 20 mg/kg dose against LPS and D-GalN induced multi organ acute injury.

Late-life Cardiac Injury in Rats following Early Life Exposure to Lead: Reversal Effect of Nutrient Metal Mixture

Early-life exposure to lead (Pb) can lead to health effects in later life. The neurotoxic effects of Pb have been well documented but its effects on the heart are poorly elucidated. We examined the late life cardiac impairments resulting from developmental exposure to Pb. Further, we investigated the protective effect of the nutrient metal mixture containing calcium (Ca), zinc (Zn) and iron (Fe) against Pb-induced long-term effects on cardiac functions.Male albino rats were lactationally exposed to 0.2% Pb-acetate or 0.2% Pb-acetate together nutrient metal mixture as 0.02% in drinking water of the mother from PND 1 to PND 21. The results showed increased levels of serum total cholesterol (TC), triglycerides (TG), low-density lipoproteins (LDLs) and lactate dehydrogenase (LDH) activity at postnatal day (PND) 28 [young], 4 months [adult] and 18 months [old] age group rats. Most notably, exposure to Pb decreased the activities of mitochondrial superoxide dismutase (SOD), thioredoxin reductase (TrxR), aconitase (Acon), isocitrate dehydrogenase (ICDH), xanthine oxidase (XO) and total antioxidant status while the MDA levels increased in all selected age groups of rats. The histological findings showed an age-dependent response to Pb exposure evidenced by extensive degeneration and necrosis in cardiac muscle, disruption in muscle connectivity, hemorrhage, and mononuclear cell infiltration. Co-administration of nutrient metal mixture reversed the Pb-induced cardiac impairments as reflected in the recovery of the chosen sensitive markers of oxidative stress, reduced Pb levels and cardiac tissue changes. In conclusion, the data demonstrate that early-life exposure to Pb continuously influence the cardiac mitochondrial functions from early life to older age and further suggesting that adequate intake of nutrient metals may be potential therapeutic treatment for Pb intoxication.

Metabolic adaptability in liver and gastrocnemius muscle of mice following subacute lead toxicity

Lead (Pb) is one of several environmental pollutants that adversely affect human health by producing toxicity at the tissue level. The aim of the study was to understand the effects of Pb on the metabolic profiles of liver and gastrocnemius muscle of mice in relation to carbohydrate and fat metabolisms. Swiss albino mice were chosen and divided into two groups, control and Pb-treated. The Pb-treated animals were exposed to Pb at a dose of 5 mg/kg body weight for 30 days orally, which resulted in hypoglycemia, glycosuria, and increased glycogenolysis in the liver and gastrocnemius muscle of treated mice. Pyruvic acid, the end product of glycolysis decreased in muscular tissue and increased in the liver. Additionally, the activity of G-6Pase was depressed in the liver, whereas lactate dehydrogenase activity was increased in skeletal muscle only. An adaptive mechanism was initiated by stimulating glycogenolytic and retarding glycolytic activity in the liver and also by alteration of liver and muscle pyruvate dehydrogenase activity along with increased activity of malate dehydrogenase in skeletal muscle. There was enhancement of succinate dehydrogenase and nicotinamide adenine dinucleotide phosphate oxidase activities in the studied tissues. Interestingly, cholesterol, high-density lipoprotein, and low-density lipoprotein levels were elevated, whereas those of triglycerides were decreased in Pb-treated mice serum. The activities of fatty acid synthase and glyceraldehyde 3 phosphate dehydrogenase were depressed in Pb-treated mice livers. Pb also significantly altered the morphological features of the liver, skeletal muscle, and pancreas. These data suggested that subacute Pb exposure was responsible for metabolic modulation in an adaptive fashion in the liver and skeletal muscle of mice.

Effect of Prepubertal Exposure to CdCl2 on the Liver, Hematological, and Biochemical Parameters in Female Rats; an Experimental Study

The examination chemical factors including industrial toxins and heavy metals seem to be crucial during the prepubertal period. In order to investigate the effects of prepubertal exposure to toxic doses of Cd on liver, hematological, and biochemical parameters in the serum, 16 female rats weaned on postnatal day (PND) 21 were randomly divided into four groups with four rats in each (n = 4). The treatments were as follows: control (0.5 mL distilled water), 25, 50, and 75 mg/kg/day received cadmium chloride (CdCl2). The CdCl2 were administered orally from PND 21 days until observed first vaginal opening (VO). The result showed that the treatment of 75 mg/kg CdCl2 dramatically increased the serum level of LDL (P < 0.0001) and LDL/HDL ratio (P = 0.0004). Conversely, treatment of 75 mg/kg CdCl2 considerably decreased the serum level of HDL in comparison with control group (P = 0.0002). Nevertheless, the rats that received different doses of CdCl2 showed no significant differences in Glu, TG, and TC compared to control group. Number of RBC and Hb of rats treated with 75 mg/kg CdCl2 were significantly less than the other groups (P < 0.0001), whereas a number of WBCs in rats treated with 75 mg/kg CdCl2 (5.27 ± 0.13 10³/μL) showed significant difference (P < 0.0001) compared to control group (4.23 ± 0.09 10³/μL). Histopathological exams showed nodular accumulation of lymphocytes in the liver (lymphocytic hepatitis) of rats, treated with 75 mg/kg CdCl2. These results showed that CdCl2 could cause change in serum lipidome and hematological parameters. What is more, exposure to Cd triggers liver injury and cardiovascular disease during the prepubertal period.

Effects of Nickel Supplementation on Antioxidant Status, Immune Characteristics, and Energy and Lipid Metabolism in Growing Cattle

Nickel (Ni) has not been elucidated as an essential mineral in dairy animals, though in plants and lower organisms, its role in activation of urease enzyme is well known. This study was conducted to evaluate the effect of Ni supplementation on intake, growth performance, urease activity, antioxidant and immune status, and energy and lipid metabolism in growing cattle. Eighteen growing Hariana heifers were randomly allocated into three groups on body weight (125 ± 3.0 kg) and age basis (10 ± 2.0 months). Feeding regimen was similar in all the groups except that treatment groups were supplemented with 0.0 (Ni_0.0), 1.5 (Ni_1.5), and 3.0 (Ni_3.0) mg of Ni/kg dry matter (DM) in three respective groups. DM intake (DMI), average daily gain (ADG), feed efficiency, plasma urease activity, biomarkers of antioxidant and immune status, energy and lipid metabolism, and plasma Ni levels were observed during the 90-day experimental period. There was linear increase (p < 0.05) in mean DMI and ADG without affecting feed efficiency was observed in 3.0 mg of Ni/kg DM supplemented heifers. Dietary Ni supplementation showed linear increase (p < 0.05) in mean plasma urease activity. No effects of (p > 0.05) of Ni supplementation were observed on superoxide dismutase (SOD) and catalase (CAT) activity and plasma lipid peroxide (LPO) concentration; whereas, mean plasma total antioxidant status (TAS) showed linear decrease (p < 0.001) in Ni-supplemented groups. Adding Ni up to 3.0 mg of Ni/kg DM did not exert (p > 0.05) any effect on plasma total immunoglobulin and immunoglobulin G (IgG) concentrations. Mean plasma cortisol level showed negative association with supplemental Ni levels and concentration was found lowest (p < 0.05) in 3.0 mg of Ni/kg DM-added group. Dietary Ni supplementation did not affect mean plasma concentrations of glucose, cholesterol, triglyceride, and non-esterified fatty acids (NEFA). There was a linear increase (p < 0.001) in plasma Ni concentrations as the Ni concentrations increased in the diet. The results of present study indicated that dietary supplementation of 3.0 mg of Ni/kg DM improved performance of growing cattle by increasing urease activity.

Hepato-Renal protective Effects of Egyptian Purslane Extract against Experimental Cadmium Toxicity in Rats with Special Emphasis on the Functional and Histopathological Changes

The study was designed to clarify the hapato-nephroprotective effects of purslane ethanolic extract (PEE) against cadmium toxicity. Cadmium (Cd) is a toxic heavy metal. Cd occurs as environmental and food/ feed contamination causing public and animals health hazards. Liver and kidney are the main target organs for acute and chronic cadmium toxicity. Portulaca oleracea is rich in several vitamins, minerals, antioxidant components, and omega-3 fatty acids mainly α-linolenic acid and eicosapentaenoic acid. Results showed significant elevation of the liver and kidney functions, lipid profile and lipid peroxidation. In contrast to the antioxidants enzymatic were greatly decreased. The hepatic and renal tissues showed severe degeneration and necrosis accompanied by severe congestion and multifocal hemorrhages in Cd intoxicated rats. All parameters and tissues showed no changes in rates-treated with both Cd and purslane extract as compared with the control rats. The administration of PEE provided a significantly protection against Cd-induced hepato-nephrotoxicity.

Multiple biomarker responses (serum biochemistry, oxidative stress, genotoxicity and histopathology) in Channa punctatus exposed to heavy metal loaded waste water

Experiments were conducted to investigate the health of fish Channa punctatus inhabiting heavy metal-loaded waste water. Heavy metals in the order of Fe > Mn > Zn > Co > Ni > Cu = Cr were present in the waste water. Gills had high metal load followed by liver and then kidney. Albumin, albumin to globulin (A:G) ratio, triglyceride, high density lipoprotein (HDL) and very low density lipoprotein (VLDL) were found to be lower but phospholipid, low density lipoprotein (LDL), total protein, lipid and cholesterol were higher as compared to the reference. Oxidative stress markers such as superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) and lipid peroxidation (LPO) were significantly higher in all tissues, whereas reduced glutathione (GSH) levels were comparatively low. Damage to DNA was observed with significantly higher mean tail length of comets in the exposed fish gill cells (30.9 µm) followed by liver (24.3 µm) and kidney (20.6 µm) as compared to reference fish (5.2, 4.8 and 5.9 µm respectively). Histopathology in gill, liver and kidney also showed marked damage. Integrated biochemical, oxidative stress, genotoxicity and histopathological findings are valuable biomarkers for native fish adaptive patterns, and monitoring of water quality/pollution of freshwater ecosystems.

Medium-term effect of sublingual l-glutathione supplementation on flow-mediated dilation in subjects with cardiovascular risk factors

OBJECTIVE

Supplementation of glutathione (GSH) may be a positive strategy to improve the endogenous antioxidant defense required to counteract many acute and chronic diseases. However, the efficacy of GSH treatment seems to be closely related to type of administration, degree of absorption, and increase of its concentrations. The aim of this study was to test a new sublingual formulation of L-GSH, which enters directly the systemic circulation, to assess its efficacy on circulating biochemical markers of hepatic metabolism, lipid profile, and oxidative stress and on peripheral vascular function compared with placebo in patients with cardiovascular risk factors (CVRF).

METHODS

We enrolled 16 healthy men with CVRF in a double-blinded, randomized placebo-controlled crossover study. At each visit, blood samples were collected for biochemistry analyses and peripheral endothelial function (reactive hyperemia index [RHI]) and stiffness were measured by Endo-PAT2000.

RESULTS

In the overall population, a decrease in total and low-density lipoprotein cholesterol was highlighted after L-GSH supplementation compared with placebo (P = 0.023 and P = 0.04, respectively). On the contrary, no difference was observed in RHI and oxidative stress markers between L-GSH and placebo in the study population. However, seven participants with baseline abnormal RHI (≤1.67) compared with those with normal RHI showed a significant reduction of arterial stiffness after L-GSH administration, (P = 0.007 and P = 0.037, respectively).

CONCLUSIONS

Supplementation of L-GSH compared with placebo influences the lipid profile of patients with CVRF. Sublingual L-GSH may represent a valid prevention of vascular damage in patients with CVRF and endothelial dysfunction.

Hepatic fibrogenesis and transforming growth factor/Smad signaling activation in rats chronically exposed to low doses of lead

Lead is an important heavy metal pollutant in the environment. The nervous system, kidney and liver are the most susceptible organs to lead deposition, showing that this pollutant has no single target system. To examine the cellular and molecular mechanisms involved in their pathobiology of chronic lead at low-dose exposure in the liver, male Wistar rats were exposed to 0.06% lead acetate in drinking water every day for 4 months. At the end of the study, hepatic metal accumulation, morphology and function were examined. Immunochemical staining and Western blot analysis were performed to detect extracellular matrix proteins, α-smooth muscle actin and transforming growth factor (TGF)β1/Smad pathway expression. Results showed increased laminin, collagen IV and fibronectin, located at the perisinusoidal space. Phenotypic transformation of hepatic stellate cells into myofibroblast-like cells was evidenced at the ultrastructural level and a significant expression of α-smooth muscle actin in Disse’s space was observed. These findings were associated with a marked increase in TGFβ1/Smad2/3 signaling. Our data suggest that, chronically, exposure to low levels of lead could trigger the onset of a hepatic fibrogenic process through upregulated TGFβ1/Smad signaling.

Unsaturated fatty acids supplementation reduces blood lead level in rats

Some dietary factors could inhibit lead toxicity. The aim of this study was to evaluate the effect of dietary compounds rich in unsaturated fatty acids (FA) on blood lead level, lipid metabolism, and vascular reactivity in rats. Serum metallothionein and organs' lead level were evaluated with the aim of assessing the possible mechanism of unsaturated FA impact on blood lead level. For three months, male Wistar rats that were receiving drinking water with (100 ppm Pb) or without lead acetate were supplemented per os daily with virgin olive oil or linseed oil (0.2 mL/kg b.w.) or egg derived lecithin fraction: “super lecithin” (50 g/kg b.w.). Mesenteric artery was stimulated ex vivo by norepinephrine (NE) administered at six different doses. Lecithin supplementation slightly reduced pressor responses of artery to NE. Lead administered to rats attenuated the beneficial effect of unsaturated FA on lipid metabolism and vascular reactivity to adrenergic stimulation. On the other hand, the super lecithin and linseed oil that were characterized by low omega-6 to omega-3 ratio (about 1) reduced the blood lead concentration. This effect was observed in lead poisoned rats (p < 0.0001) and also in rats nonpoisoned with lead (p < 0.05).

Arsenic-induced dyslipidemia in male albino rats: comparison between trivalent and pentavalent inorganic arsenic in drinking water

Background

Recent epidemiological evidences indicate close association between inorganic arsenic exposure via drinking water and cardiovascular diseases. However, the exact mechanism of this arsenic-mediated increase in cardiovascular risk factors remains enigmatic.

Methods

In order to investigate the effects of inorganic arsenic exposure on lipid metabolism, male albino rats were exposed to 50, 100 and 150 ppm arsenic as sodium arsenite and 100, 150 and 200 ppm arsenic as sodium arsenate respectively in their drinking water for 12 weeks.

Results

Dyslipidemia induced by the two arsenicals exhibited different patterns. Hypocholesterolemia characterised the effect of arsenite at all the doses, but arsenate induced hypercholesterolemia at the 150 ppm As dose. Hypertriglyceridemia was the hallmark of arsenate effect whereas plasma free fatty acids (FFAs) was increased by the two arsenicals. Reverse cholesterol transport was inhibited by the two arsenicals as evidenced by decreased HDL cholesterol concentrations whereas hepatic cholesterol was increased by arsenite (100 ppm As), but decreased by arsenite (150 ppm As) and arsenate (100 ppm As) respectively. Brain cholesterol and triglyceride were decreased by the two arsenicals; arsenate decreased the renal content of cholesterol, but increased renal content of triglyceride. Arsenite, on the other hand, increased the renal contents of the two lipids. The two arsenicals induced phospholipidosis in the spleen. Arsenite (150 ppm As) and arsenate (100 ppm As) inhibited hepatic HMG CoA reductase. At other doses of the two arsenicals, hepatic activity of the enzyme was up-regulated. The two arsenicals however up-regulated the activity of the brain enzyme. We observed positive associations between tissue arsenic levels and plasma FFA and negative associations between tissue arsenic levels and HDL cholesterol.

Conclusion

Our findings indicate that even though sub-chronic exposure to arsenite and arsenate through drinking water produced different patterns of dyslipidemia, our study identified two common denominators of dyslipidemia namely: inhibition of reverse cholesterol transport and increase in plasma FFA. These two denominators (in addition to other individual perturbations of lipid metabolism induced by each arsenical), suggest that in contrast to strengthening a dose-dependent effect phenomenon, the two forms of inorganic arsenic induced lipotoxic and non-lipotoxic dyslipidemia at “low” or “medium” doses and these might be responsible for the cardiovascular and other disease endpoints of inorganic arsenic exposure through drinking water.

Mitogen-activated protein kinase signaling and its association with oxidative stress and apoptosis in lead-exposed hepatocytes

Lead toxicity has become a serious public health concern all over the world. Previous studies have shown that lead induces biochemical and structural changes in liver. However, although lead is known to alter liver functions, the underlying molecular mechanisms of hepatotoxicity are not yet clear. We hypothesized that a correlation exists between oxidative stress, apoptosis and mitogen-activated protein kinases (MAPKs) in lead-exposed liver. Wistar rats were treated with 0, 0.5%, and 1% lead acetate for 3d, 14d, and 35d and sacrificed the next day. On 4d, oxidative stress and apoptosis were correlated with downregulated expressions of ERK1/2 and p38-MAPKα/β, and upregulated expressions of JNK1/3 in males. In females, the correlation was with downregulated expressions of ERK1/2 and upregulated expressions of p38-MAPKα/β and JNK1/3. On 15d, the correlation was observed with upregulated expressions of p38-MAPKα/β in males and downregulated expressions of p38-MAPKα/β in females. In both sexes, a correlation was observed with upregulated expressions of ERK1/2 and JNK1/3 in 1% groups. On 36d, the correlation was observed with downregulated expressions of p38-MAPKα/β in males and their upregulated expressions in females. Time-dependent increase in lipid peroxidation on 15d and 36d correlated with upregulated expressions of p38-MAPKα/β in females and ERK1/2 in 1% groups in both sexes. The lower dose induced more apoptosis up to 15d in females and the higher dose induced in males on 36d. Generally, the female livers had more p38-MAPKα/β than the male livers. On 36d, the female livers showed more p38-MAPKα/β and JNK1/3 than the male livers. In conclusion, although not clearly defined, a correlation exists among oxidative stress, apoptosis, and the MAPKs in lead-exposed hepatocytes. The sex-dependent effects may be due to differences in hormonal or other physiological mechanisms. In lead-exposed hepatocytes, the apoptosis may be induced via oxidative stress-mediated alterations in the MAPKs.

Cinnamon extract improves the body composition and attenuates lipogenic processes in the liver and adipose tissue of rats

Cinnamon attenuates lipogenic processes, regulating the expression of key enzymes, transcriptional factors and their target genes in the liver and adipose tissue.

Protective effect of curcumin against heavy metals-induced liver damage

Occupational or environmental exposures to heavy metals produce several adverse health effects. The common mechanism determining their toxicity and carcinogenicity is the generation of oxidative stress that leads to hepatic damage. In addition, oxidative stress induced by metal exposure leads to the activation of the nuclear factor (erythroid-derived 2)-like 2/Kelch-like ECH-associated protein 1/antioxidant response elements (Nrf2/Keap1/ARE) pathway. Since antioxidant and chelating agents are generally used for the treatment of heavy metals poisoning, this review is focused on the protective role of curcumin against liver injury induced by heavy metals. Curcumin has shown, in clinical and preclinical studies, numerous biological activities including therapeutic efficacy against various human diseases and anti-hepatotoxic effects against environmental or occupational toxins. Curcumin reduces the hepatotoxicity induced by arsenic, cadmium, chromium, copper, lead and mercury, prevents histological injury, lipid peroxidation and glutathione (GSH) depletion, maintains the liver antioxidant enzyme status and protects against mitochondrial dysfunction. The preventive effect of curcumin on the noxious effects induced by heavy metals has been attributed to its scavenging and chelating properties, and/or to the ability to induce the Nrf2/Keap1/ARE pathway. However, additional research is needed in order to propose curcumin as a potential protective agent against liver damage induced by heavy metals.

Interleukin-1 controls the constitutive expression of the Cyp7a1 gene by regulating the expression of Cyp7a1 transcriptional regulators in the mouse liver

Our previous study using interleukin-1α/β-knockout (IL-1-KO) and wild-type (WT) mice demonstrated that IL-1 acts as a positive factor for constitutive gene expression of hepatic cytochrome P4507a1 (Cyp7a1). In this study, to clarify the role of IL-1 in the expression of the hepatic Cyp7a1 gene, we focused on Cyp7a1 transcriptional regulators such as α-fetoprotein transcription factor (FTF), liver X receptor α (LXRα), hepatocyte nuclear factor 4α (HNF4α) and small heterodimer partner (SHP) and examined the effects of IL-1 on their gene expression by real-time reverse-transcription polymerase chain reaction using IL-1-KO and WT mice. We observed no significant differences between sex-matched IL-1-KO and WT mice with regard to gene expression levels of FTF, LXRα, and HNF4α, all of which are positive transcriptional regulators for the Cyp7a1 gene. However, interindividual differences in hepatic FTF and LXRα expression were closely dependent on the gene expression level(s) of hepatic IL-1 and tumor necrosis factor-α (TNF-α), while interindividual differences in hepatic HNF4α were clearly correlated with the expression of IL-1, but not TNF-α. In contrast, the gene expression level of SHP, which is a negative transcriptional regulator of the Cyp7a1 gene through inhibition of FTF function, was higher in IL-1-KO mice than in sex-matched WT mice. These findings demonstrate that, like TNF-α, IL-1 positively controls the gene expression of Cyp7a1 transcriptional upregulators but, in contrast to the previously reported action of TNF-α, IL-1 also acts to downregulate SHP gene expression.

Hepatic expression of spermatogenic genes and their transiently remarkable downregulations in Wistar-Kyoto rats in response to lead-nitrate administration: strain-difference in the gene expression patterns

Administration of lead ion (Pb) to rats and mice affects hepatic functions such as the induction of hepatic cell proliferation and upregulation of cholesterol biosynthesis. To identify the genes for which expression changes in response to Pb-administration, we analyzed hepatic gene expression patterns in stroke-prone spontaneously hypertensive rat (SHRSP), its normotensive control, Wistar-Kyoto rat (WKY), and Spraque-Dawley (SD) rat strains, 3, 6, and 12 hr later after single i.v. injection of lead nitrate (LN) at a dose of 100 µmol using a DNA microarray technique. The data analysis demonstrated that the expression of a great number of genes was transiently and remarkably downregulated 3 hr after LN-injection, and then recovered to control levels only in LN-injected WKY. These normal hepatic expression levels in WKY and SHRSP were much higher than those in SD rats. Furthermore, most of these genes were ones thought to be expressed specifically in the spermatids and/or testes; i.e. genes encoding protamin 1, transition protein 1, and transition protein 2. These findings suggest that the regulation system common to expression of all of these genes could be a target site of Pb-toxic action, at least, in the liver of WKY, and that this system might be similar to the system essential for spermatogenesis, especially spermiogenesis, in the testis. In addition, it appears that clarifying the cause of the difference between the systems of WKY and SHRSP might aid in identifying the pathologic genes in SHRSP. Finally, it will be an important to clarify how the products of the genes related to spermatogenesis, including spermiogenesis, are functional in the livers of WKY and SHRSP.

Protective role of puerarin on lead-induced alterations of the hepatic glutathione antioxidant system and hyperlipidemia in rats

Puerarin (PU), a natural flavonoid, has been reported to have many benefits and medicinal properties. The aim of the present study was to investigate the effects of puerarin on hepatic oxidative stress and hyperlipidemia in rats exposed to lead. Our data showed that puerarin significantly prevented lead-induced hepatotoxicity, indicated by both diagnostic indicators of liver damage (serum aminotransferase levels) and histopathological analysis. Moreover, lead-induced profound elevation of ROS production and oxidative stress, as evidenced by increasing of lipid peroxidation level, reducing of GPx, GST, GR and GCL activities and depleting of intracellular reduced GSH level in liver, were suppressed by treatment with puerarin. Furthermore, the increase of serum cholesterol, triglycerides and LDL induced by lead was effectively suppressed by puerarin. The HDL level in the lead treatment rats was also increased by puerarin. Western blot analysis showed that puerarin remarkably inhibited hyperlipidemia by regulating the expression of cholesterol 7a-hydroxylase (CYP7A1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and low-density lipoprotein receptor (LDL-R) in liver of lead treated rats. Altogether, these results suggest that puerarin could protect the lead-induced liver injury and hyperlipidemia by reducing ROS production, renewing the activities of antioxidant enzymes and influencing expression of hepatic lipid biosynthesis and metabolism genes.

Polychlorinated biphenyls, lead, and mercury are associated with liver disease in American adults: NHANES 2003-2004

BACKGROUND

High-level occupational exposures to some industrial chemicals have been associated with liver diseases, including nonalcoholic fatty liver disease (NAFLD). However, the potential role of low-level environmental pollution on liver disease in the general population has not been evaluated.

OBJECTIVE

We determined whether environmental pollutants are associated with an elevation in serum alanine aminotransferase (ALT) activity and suspected NAFLD in U.S. adults.

METHODS

This cross-sectional cohort study evaluated adult participants without viral hepatitis, hemochromatosis, or alcoholic liver disease from the National Health and Nutrition Examination Survey (NHANES) for 2003-2004. ALT elevation was defined in men as ≥ 37 IU/L (age 18-20 years) and ≥ 48 IU/L (age ≥ 21 years) and in women as ≥ 30 IU/L (age 18-20 years) and ≥ 31 IU/L (age ≥ 21 years). Adjusted odds ratios (ORs) for ALT elevation were determined across exposure quartiles for 17 pollutant subclasses comprising 111 individual pollutants present with at least a 60% detection rate. Adjustments were made for age, race/ethnicity, sex, body mass index, poverty income ratio, and insulin resistance. Individual pollutants from subclasses associated with ALT elevation were subsequently analyzed.

RESULTS

The overall prevalence of ALT elevation was 10.6%. Heavy metals and polychlorinated biphenyls (PCBs) were associated with dose-dependent increased adjusted ORs for ALT elevation. Within these subclasses, increasing whole-blood levels of lead and mercury and increasing lipid-adjusted serum levels of 20 PCBs were individually associated with ALT elevation.

CONCLUSIONS

PCB, lead, and mercury exposures were associated with unexplained ALT elevation, a proxy marker of NAFLD, in NHANES 2003-2004 adult participants.

Changes in brain cholesterol metabolome after excitotoxicity

Excitotoxicity due to excess stimulation of glutamate receptors in neurons is accompanied by increased Ca(2+) influx, stimulation of Ca(2+)-dependent enzymes, ATP depletion, increase in lipid peroxidation products, and loss of glutathione. These changes resemble neurochemical alterations in acute neuronal injury (stroke, spinal cord injury, and traumatic brain injury) and chronic neurodegenerative diseases such as Alzheimer's disease. Intracerebroventricular injection of the potent glutamate analog kainate in rats results in increased cholesterol concentration in the hippocampus at short to medium time intervals, i.e., 3 days-1 week post-injection, as detected by gas chromatography-mass spectrometry in the lesioned hippocampus. This is accompanied by an early increase in levels of cholesterol biosynthetic precursors and increases in both enzymatically derived oxysterols such as 24-hydroxycholesterol and cholesterol oxidation products (COPs) generated by reactive oxygen species, including cholesterol epoxides and 7-ketocholesterol. In contrast to COPs, no change in concentration of the neurosteroid pregnenolone was found after KA injury. Cholesterol and COPs significantly increase exocytosis in cultured PC12 cells and neurons, and both oxysterols and COPs are able to induce cytotoxic and apoptotic injuries in different cell types, including neurons. Together, the findings suggest that increased cholesterol and COPs after KA excitotoxicity could themselves lead to disturbed neuronal ion homeostasis, increased neurotransmitter release, and propagation of excitotoxicity.

Changes in cholesterol biosynthetic and transport pathways after excitotoxicity

The present study was carried out to elucidate changes in the gene expression and activity of cholesterol biosynthetic enzymes and transporters in the rat hippocampus after kainate excitotoxicity. Significantly increased cholesterol level was detected in the degenerating hippocampus, reaching double normal levels at 1 week after kainate injury. RT-PCR analyses of hippocampal homogenates showed significantly decreased mRNA expression of the transcription factor controlling cholesterol biosynthesis SREBP-2, and the rate-controlling enzyme HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase at all time points after kainate injection; and decreased lanosterol synthase and CYP51 at 1 and 2 weeks post-kainate injection respectively. GC-MS analyses showed a significant increase in cholesterol biosynthetic precursors lanosterol, desmosterol and 7-dehydrocholesterol at 1 day after kainate injection presumably reflecting biosysnthesis in injured neurons, and significant decreases in precursors at 1 and 2 weeks post-kainate injection, at time of gliosis in the degenerating hippocampus. Levels of cholesterol autooxidation including 7 ketocholesterol and cholesterol epoxides were elevated in the kainate lesioned hippocampus. Furthermore, loss of expression of the cholesterol transporter, ABCA1 was detected in neurons, but increased expression in astrocytes was detected after kainate lesions. The results suggest that increased cholesterol biosynthesis and loss of ABCA1 expression in injured neurons might result in increase in cholesterol in the degenerating hippocampus. The increased cholesterol might predispose to increased formation of cholesterol oxidation products which have been shown to be toxic to neurons.

Effect of garlic (Allium sativum) on heavy metal (nickel II and chromium VI) induced alteration of serum lipid profile in male albino rats

We have studied the effect of simultaneous oral treatment of aqueous garlic extract (Allium sativum) on heavy metal (nickel II and chromium VI) induced changes in serum lipid profile. Nickel sulfate and potassium dichromate treated rats showed a significant increase in serum low density lipoprotein-cholesterol (LDL-C), very low density lipoprotein-cholesterol (VLDL-C) and triglyceride (TG) level as well as decrease in serum high density lipoprotein-cholesterol (HDL-C) level. Simultaneous garlic administration with nickel sulfate showed improvement in serum LDL-C, HDL-C, VLDL-C and TG level. But in case of potassium dichromate, garlic administration did not show satisfactory improvement in lipid profile except VLDL-C and TG level. The results indicate that garlic (Allium sativum) has some beneficial effect in preventing heavy metal (nickel and chromium VI) induced alteration of lipid profile.

IL-1 regulates the Cyp7a1 gene and serum total cholesterol level at steady state in mice

We examined the role of hepatic interleukin (IL)-1alpha/beta in serum total cholesterol homeostasis using male and female IL-1-knockout (KO) mice and wild-type (WT) mice. Serum total cholesterol level was higher in males than in females in WT and KO mice. The difference between sexes was closely correlated with the difference in gene expression level of cholesterol 7alpha-hydroxylase (Cyp7a1), a rate-limiting enzyme for bile acid synthesis. No significant sex difference in gene expression level of 3-hydroxy-3-methylglutaryl-CoA reductase, a rate-limiting enzyme for cholesterol synthesis, was observed in WT mice. Interestingly, the gene expression level of hepatic Cyp7a1 was lower in KO mice than in sex-matched WT mice, while the serum total cholesterol level was the opposite. The present findings demonstrate that IL-1alpha and IL-1beta are positive regulators for the Cyp7a1 gene in steady-state mice and that Cyp7a1 is one of the factors that mediate the difference in serum total cholesterol level between sexes.

TNF-alpha interferes with lipid homeostasis and activates acute and proatherogenic processes

The interaction between disrupted lipid homeostasis and immune response is implicated in the pathogenesis of several diseases, but the molecular bridges between the major players are still a matter of controversy. Our systemic study of the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in the livers of mice exposed to 20-h cytokine/fasting for the first time shows that TNF-alpha interferes with adaptation to fasting and activates harmful proatherogenic pathways, partially through interaction with the insulin-Insig-sterol regulatory element binding protein (Srebp) signaling pathway. In addition to the increased expression of acute-phase inflammatory genes, the most prominent alterations represent modified lipid homeostasis observed on the gene expression and metabolite levels. These include reduction of HDL-cholesterol, increase of LDL-cholesterol, and elevated expression of cholesterogenic genes, accompanied by increase of potentially harmful precholesterol metabolites and suppression of cholesterol elimination through bile acids, likely by farnesoid X receptor-independent mechanisms. On the transcriptional level, a shift from fatty oxidation toward fatty acid synthesis is observed. The concept of the influence of TNF-alpha on the Srebp regulatory network, followed by downstream effects on sterol metabolism, is novel. Observed acute alterations in lipid metabolism are in agreement with chronic disturbances found in patients.

The H295R system for evaluation of endocrine-disrupting effects

The present studies were undertaken to evaluate the utility of the H295R system as an in vitro assay to assess the potential of chemicals to modulate steroidogenesis. The effects of four model chemicals on the expression of ten steroidogenic genes and on the production of three steroid hormones were examined. Exposures with individual model chemicals as well as binary mixtures were conducted. Although the responses reflect the known mode of action of the various compounds, the results show that designating a chemical as "specific inducer or inhibitor" is unwise. Not all changes in the mixture exposures could be predicted based on results from individual chemical exposures. Hormone production was not always directly related to gene expression. The H295R system integrates the effects of direct-acting hormone agonists and antagonists as well as chemicals affecting signal transduction pathways for steroid production and provides data on both gene expression and hormone secretion which makes this cell line a valuable tool to examine effects of chemicals on steroidogenesis.

Effect of L-ascorbic acid on nickel-induced alterations in serum lipid profiles and liver histopathology in rats

Nickel exposure greatly depletes intracellular ascorbate and alters ascorbate-cholesterol metabolism. We studied the effect of the simultaneous oral treatment with L-ascorbic acid (50 mg/100 g body weight (BW) and nickel sulfate (2.0 mg/100 g BW, i.p) on nickelinduced changes in serum lipid profiles and liver histopathology. Nickel-treated rats showed a significant increase in serum low-density lipoprotein-cholesterol, total cholesterol, triglycerides, and a significant decrease in serum high-density lipoprotein-cholesterol. In the liver, nickel sulfate caused a loss of normal architecture, fatty changes, extensive vacuolization in hepatocytes, eccentric nuclei, and Kupffer cell hypertrophy. Simultaneous administration of L-ascorbic acid with nickel sulfate improved both the lipid profile and liver impairments when compared with rats receiving nickel sulfate only. The results indicate that L-ascorbic acid is beneficial in preventing nickel-induced lipid alterations and hepatocellular damage.

Puerarin decreases serum total cholesterol and enhances thoracic aorta endothelial nitric oxide synthase expression in diet-induced hypercholesterolemic rats

Hypercholesterolemia is a dominant risk factor for the development and progression of atherosclerosis and cardiovascular diseases. Natural compounds have been proved to be useful in lowering serum cholesterol to slow down the progression of cardiovascular diseases. Pueraria lobata is employed clinically to treat cardiovascular diseases in China. In the present study, the atheroscleroprotective potential of the herb's major active compound, puerarin, was investigated by monitoring serum lipid profile and major enzyme expressions on cholesterol homeostasis in Sprague-Dawley rats fed with control diet, hypercholesterolmic diet or hypercholesterolmic diet plus administration of puerarin (300 mg/kg/day, p.o.) for 4 weeks. Puerarin markedly attenuated the increased total cholesterol induced by hypercholesterolmic diet in both serum and liver. It caused a significant reduction in the atherogenic index. Expression of mRNA for hepatic 7alpha-hydroxylase (CYP7A1) was significantly enhanced but not for those of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and lanosterol 14alpha-demethylase (CYP51). To further explore the atheroscleroprotective potential of puerarin, acetylcholine induced endothelium-dependent vasorelaxation and endothelial nitric oxide synthase (eNOS) expression on isolated thoracic aortas were analyzed. Animals administered with puerarin suppressed the hypercholesterolemic diet induced impairment of eNOS expression, whereas there was no significant difference in the endothelium-dependent vasorelaxation among various groups of animals. These data indicated that puerarin reduced the atherogenic properties of dietary cholesterol in rats. Its hypocholesterolemic function may be due to the promotion of cholesterol and bile acids excretion in liver. Whether puerarin targets directly on cholesterol homeostasis or both cholesterol homeostasis and endothelial function remains to be determined.

Gender-related difference in altered gene expression of a sterol regulatory element binding protein, SREBP-2, by lead nitrate in rats: Correlation with development of hypercholesterolemia

Changes in gene expression levels of hepatic sterol regulatory element binding protein-2 (SREBP-2) and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) after a single i.v. injection of lead nitrate (LN, 100 micromol kg(-1) body weight) were examined comparatively by real time reverse transcriptase-polymerase chain reaction (RT-PCR) in male and female rats. Significant increases in the gene expression level of SREBP-2, a transcription factor for the HMGR gene, occurred at 6-12 h in male and at 24-36 h in female rats after LN-treatment. The gene expression level of HMGR, a rate-limiting enzyme for cholesterol biosynthesis, significantly increased at 3-48 h in male rats and 12-48 h in female rats. Subsequently, significant increases in the amount of hepatic total cholesterol in male and female rats were also observed at 3-48 h and 24-48 h, respectively. The present findings demonstrate that increases in gene expressions of hepatic SREBP-2 and HMGR and the amount of hepatic total cholesterol by LN occur earlier in male rats than in the females, and that increases in the gene expression level of HMGR and the amount of hepatic total cholesterol occur prior to the increase in the gene expression level of SREBP-2 in either sex of rats.

Tumor Necrosis Factor-α-Independent Downregulation of Hepatic Cholesterol 7α-Hydroxylase Gene in Mice Treated with Lead Nitrate

We previously reported that lead nitrate (LN), an inducer of hepatic tumor necrosis factor-alpha (TNF-alpha), downregulated gene expression of cholesterol 7alpha-hydroxylase. Herein, to clarify the role of TNF-alpha in LN-induced downregulation of cholesterol 7alpha-hydroxylase, effects of LN on gene expression of hepatic cholesterol 7alpha-hydroxylase (Cyp7a1) in TNF-alpha-knockout (KO) and TNF-alpha-wild-type (WT) mice were comparatively examined. Gene expression of hepatic Cyp7a1 in both WT and KO mice decreased to less than 5% of the corresponding controls at 6-12 h after treatment with LN (100 mumol/kg body weight, iv). Levels of hepatic TNF-alpha protein in either WT or KO mice were below the detection limit, although expression levels of the TNF-alpha gene markedly increased at 6 h in WT mice by LN treatment, but not in KO mice. In contrast, in both WT and KO mice, levels of hepatic IL-1beta protein, which is known to be a suppressor of the cholesterol 7alpha-hydroxylase gene in hamsters, were significantly increased 3-6 h after LN treatment. Furthermore, LN-induced downregulation of the Cyp7a1 gene did not necessarily result from altered gene expression of hepatic transcription factors, including positive regulators (liver X receptor alpha, retinoid X receptor alpha, fetoprotein transcription factor, and hepatocyte nuclear factor 4alpha) and a negative regulator small heterodimer partner responsible for expression of the Cyp7a1 gene. The present findings indicated that LN-induced downregulation of the Cyp7a1 gene in mice did not necessarily occur through a TNF-alpha-dependent pathway and might occur mainly through an IL-1beta-dependent pathway.