Hepatic toxicity and recovery of Fischer 344 rats following exposure to 2-aminoanthracene by intraperitoneal injection

The hepatic effects in dams that ingested 2-aminoanthracene during gestation and lactation

Diabetes mellitus has been on a continual rise as one of the top chronic diseases to affect individuals worldwide. The goal of this study was to determine how exposure from a well-known toxicant, a polycyclic aromatic hydrocarbon called 2-aminoanthracene (2AA), could potentially lead to diabetes, damage the liver, and have negative effects to the offspring. Humans are exposed to 2AA from foods cooked in high heat and tobacco smoke, among others. To analyze the effects of 2AA, three groups of Sprague Dawley dams consumed an adulterated 2AA diet from gestation to their postnatal period. Timed-pregnant dams ingested 0 mg/kg (control group (C)), 50 mg/kg (low dose group (LD)), and 100 mg/kg (high dose group (HD)) 2AA. Hepatic gene expressions of Adam8, Bax, Ccng1, CD68, CD93, Cdkn1c, and Ddit4 indicated a significant overexpression of Bax, Ccng1, CD68, CD93, and Cdkn1c in treated groups. Although there was no significant difference in the damage to the liver architecture by 2AA, the positively stained CD68+ cells were slightly increased in treated rats. Significant decreases in the albumin and aspartate aminotransferase levels might indicate an inflammatory response from 2AA exposure in dams. Immunoglobulin A (IgA) concentration was also decreased, in contrast to studies of liver cirrhosis that reported increased serum IgA concentration. Overexpression of genes Ddit4, Cdkn1c, Ccng1, Bax, CD93, and CD68 point to hepatic inflammation and apoptosis. Overall results suggest a link between environmental 2AA exposure and adverse liver effects, which has potential to increase susceptibility to type 2 diabetes and other diseases.

Assessment of the link between in utero exposure to 2-aminoanthracene (2AA) and type-1 diabetes (T1D)

BACKGROUND

A recent diabetes report revealed an increased incidence in diabetes including type 1-diabetes (T1D). The increase in the numbers of T1D incidences are thought to be related to environmental reasons such as the exposure to environmental chemicals including arylamine 2-aminoanthracene (2AA). T1D is an autoimmune disease of the pancreatic islet in which insulin-producing beta cells are destroyed by auto-reactive T-cells and monocytic cells.

METHODS

The purpose of this study is to examine the extent to which 2AA exposure contributes to T1D. Three groups of pregnant Sprague Dawley dams ingested various concentrations of dietary 2AA from gestation through the postnatal period. A select number of cytokines and adipokines previously noted to play a significant role in inflammatory response were analyzed in the pancreas of the pups for alteration. The anatomy of the pancreas was also evaluated to determine any histological changes.

RESULTS

Results showed over-expression of pro-inflammatory protein IL-6. Up-regulation of humoral genes IL-7 and IL-21 were also noted. Pathologic characterization showed no significant changes. Moreover, serum total protein was significantly reduced in exposed groups. Elevated serum glucose concentration seems to correspond to slightly lower insulin levels in serum. Cumulative neonatal weight gain analysis showed no major alterations between the control and gestationally-exposed rats.

CONCLUSION

It appears that systemic effects of 2AA ingestion were mild in the neonates. Further assessments of pups who lived longer than two weeks could be a useful way to measure the progression and possibly further support our hypothesis that 2AA can lead to systemic effects that are indicative of inducing T1D.

Inflammatory effect of 2-aminoanthracene (2AA) on adipose tissue gene expression in pregnant Sprague Dawley rats

Adipocyte dysfunction may be a critical link between obesity and insulin resistance as a result of abnormal fat storage and mobilization. Adipocytes uniquely secrete adipokines and cytokines, such as leptin and TNFα, wich promote insulin sensitivity. Previously we reported insulin-signaling related altered gene expression in animals exposed to 2-Aminoanthracene (2AA). 2AA is an amino-substituted polycyclic aromatic hydrocarbon used in manufacturing dyes, chemicals, inks, resins, and polyurethanes. The objective of this study was to examine the inflammation related effects of 2AA exposure from gestation to postnatal period on dams that ingested 2AA. To examine 2AA effects, pregnant dams were assigned into dose regimens of 2AA. Dams were fed 2AA contaminated diet during the period of gestation and postpartum. The expression of key gene transcripts reported to be important in mediating inflammatory processes was examined via quantitative RT-PCR. Histologic examination of adipose tissue (AT) was also carried out to understand the anatomy of AT due to 2AA exposure during gestation and two weeks postpartum. Examination of the adipose tissue for microscopic changes revealed no alterations between control and low-dose animals. However, AT of the high-dose animals was infiltrated by increased numbers of CD68+mononuclear cells (macrophages) and small numbers of eosinophils and mast cells, consistent with inflammation. In addition, analysis of the mRNA expression of cytokines and adipokines demonstrated the importance of inflammation in AT dysfunction. For instance, TNFα, LEPTIN and IL-6 transcripts were relatively more expressed in the low dose animals than in the high dose and control rats. At the protein level, however, high amounts of cytokines were noted. The effects of 2AA on pregnant dams appear to be more pronounced in the high dose group than in the low dose group, possibly indicating increased susceptibility of rat offspring within this group to elicit a diabetic-type response.

The Inhibitory Effects of Aqueous Extract from Guava Twigs,Psidium guajavaL., on Mutation and Oxidative Damage

This study examines the inhibitory effects of the aqueous extract from guava twigs (GTE),Psidium guajavaL., on mutation and oxidative damage. The results show that GTE inhibits the mutagenicity of 4-nitroquinoline-N-oxide (4-NQO), a direct mutagen, and 2-aminoanthracene (2-AA), an indirect mutagen, towardSalmonella typhimuriumTA 98 and TA 100. In addition, GTE shows radical scavenging, reducing activities, tyrosinase inhibition, and liposome protection effects. Meanwhile, GTE in the range of 0.1–0.4 mg/mL protects liver cells fromtert-butyl-hydroperoxide-(t-BHP-) induced cytotoxicity. Furthermore, the cytotoxicity inhibition of GTE in thet-BHP-treated cells was demonstrated in a dose-dependent manner. High-performance liquid chromatography analysis suggests that the major phenolic constituents in GTE are gallic acid, ferulic acid, and myricetin. These active phenolic components may contribute to the biological protective effects of GTE in different models. The data suggest that GTE exhibiting biological activities can be applied to antimutation, antityrosinase, and antioxidative damage.

Inhibitory effects of water extract from longan twigs on mutation and nitric oxide production

This study examines the inhibitory effects of water extract from longan twigs (WLTs) on mutation and nitric oxide (NO) production. The results show that WLT inhibited the mutagenicity of 2-aminoanthracene (2-AA), an indirect mutagen, and 4-nitroquinoline-N-oxide (4-NQO), a direct mutagen toward Salmonella typhimurium TA 98 and TA 100. In addition, WLT in the range 0-0.6 mg/ml showed radical scavenging, reducing activities and chelating activity, as well as decreased lipid oxidative damage. Meanwhile, WLT also inhibited tyrosinase activity and NO generation in lipopolysaccharide (LPS) stimulated macrophages. High performance liquid chromatography analysis suggests that the major phenolic constituents in WLT are epicatechin, ellagic acid and gallic acid. These bioactive components may contribute to the protective effects of WLT. Our data suggests that WLT can be applied to antimutation, anti-inflammation and antityrosinase.

Decreases in binding capacity of the mitochondrial 18 kda translocator protein accompany oxidative stress and pathological signs in rat liver after DMBA exposure

7,12-Dimethylbenz[a]anthracene (DMBA) presents a pollutant implicated in various toxicological effects. The aim of this experiment was to study the effects of DMBA administration on oxidative stress, histopathological signs, and 18 kDa translocator protein (TSPO) binding characteristics in rat liver. We also studied the effects of dose stoichiometry, dose frequency, and duration of protocol of DMBA administration. In this study, rats surviving eighteen weeks after DMBA exposure showed mild to moderate histopathological changes in the liver, mainly characterized by glossy appearance of hepatocytes, heterochromatic nuclei, and glycogen overload in the midzonal region of the hepatic lobe. These changes were accompanied by significant rises in oxidant levels, along with declines in nonenzymic antioxidants, indicating that DMBA induced oxidative stress in the liver. This finding correlated well with decreases in TSPO binding capacity in the liver of the rats in our study. Other studies have shown that TSPO can be affected by oxidative stress, as well as contribute to oxidative stress at mitochondrial levels. Further studies are needed to assay whether the decreases in TSPO density in the liver are part of the damaging effects caused by DMBA or a compensatory response to the oxidative stress induced by DMBA.

The role of p28GANK in rat oval cells activation and proliferation

BACKGROUND

Human gankyrin gene product (p28GANK) is a novel oncogenic protein ubiquitously overexpressed in hepatocellular carcinoma and also plays a role in cell cycle progression in normal hepatocytes and liver regeneration. However, little is known about the physiological role of p28GANK in the liver oval cell activation and proliferation. We investigated the possible involvement of p28GANK in oval cell-mediated liver regeneration and cell cycle progression.

METHODS

We examined the different p28GANK expression in 2-acetylaminofuorene/partial heptectomy (2-AAF/PH) rats, as a model of oval cell activation, and PH rats by Western blot and immunohistochemistry. Oval cells isolated from 2-AAF/PH rat model were cultured in our study. p28GANK expression was examined in the oval cells after mitogenic stimulation.

RESULTS

In 2-AAF/PH rats, p28GANK was expressed in the activated oval cells and located in the nucleus. p28GANK protein expression was increased in 2-AFF/PH rats after hepatectomy lasting for 96 h when retinoblastoma maintained hyperphosphorylation status at Ser-795. The isolated oval cells express AFP, OV6, CK19, CD34, CD45, c-kit and albumin. After epidermal growth factor stimulation, p28GANK protein was up-regulated in oval cells from 24 to 72 h, which coincided with increased expression of CyclinD1, CDK4 and decreased of Rb protein.

CONCLUSIONS

p28GANK expression was increased in oval cell-mediated liver regeneration and oval cells after mitogenic stimulation. Thus, p28GANK may play a role in oval cell-mediated liver regeneration and liver oval cell cycle progression.