Differential expression of HO-1 and CYP1A2 during up-regulation of ERK in stressed fish hepatocytes

Melatonin ameliorates H2O2-induced oxidative stress through modulation of Erk/Akt/NFkB pathway

Background

Improper control on reactive oxygen species (ROS) elimination process and formation of free radicals causes tissue dysfunction. Pineal hormone melatonin is considered a potent regulator of such oxidative damage in different vertebrates. Aim of the current communication is to evaluate the levels of oxidative stress and ROS induced damage, and amelioration of oxidative status through melatonin induced activation of signaling pathways. Hepatocytes were isolated from adult Labeo rohita and exposed to H₂O₂ at three different doses (12.5, 25 and 50 µM) to observe peroxide induced damage in fish hepatocytes. Melatonin (25, 50 and 100 μg/ml) was administered against the highest dose of H₂O₂. Enzymatic and non-enzymatic antioxidants such as malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) was measured spectrophotometrically. Expression level of heat shock proteins (HSP70 and HSP90), HSPs-associated signaling molecules (Akt, ERK, cytosolic and nuclear NFkB), and melatonin receptor was also measured by western blotting analysis.

Results

H₂O₂ induced oxidative stress significantly altered (P < 0.05) MDA and GSH level, SOD and CAT activity, and up regulated HSP70 and HSP90 expression in carp hepatocytes. Signaling proteins exhibited differential modulation as revealed from their expression patterns in H₂O₂-exposed fish hepatocytes, in comparison with control hepatocytes. Melatonin treatment of H₂O₂-stressed fish hepatocytes restored basal cellular oxidative status in a dose dependent manner. Melatonin was observed to be inducer of signaling process by modulation of signaling molecules and melatonin receptor.

Conclusions

The results suggest that exogenous melatonin at the concentration of 100 µg/ml is required to improve oxidative status of the H₂O₂-stressed fish hepatocytes. In H₂O₂ exposed hepatocytes, melatonin modulates expression of HSP70 and HSP90 that enable the hepatocytes to become stress tolerant and survive by altering the actions of ERK, Akt, cytosolic and nuclear NFkB in the signal transduction pathways. Study also confirms that melatonin could act through melatonin receptor coupled to ERK/Akt signaling pathways. This understanding of the mechanism by which melatonin regulates oxidative status in the stressed hepatocytes may initiate the development of novel strategies for hepatic disease therapy in future.

Characterization and expression patterns of ERK1 and ERK2 from Epinephelus coioides against Cryptocaryon irritans infection

Mitogen-activated protein kinases (MAPKs), a group of serine-threonine protein kinases, play a crucial role in immunoreaction response to extra environmental stresses. In this study, two novel MAPKs, Ec-ERK1 and Ec-ERK2, were identified from Epinephelus coioides. Both Ec-ERK1 and Ec-ERK2 sequences contain a highly conserved Thr-Glu-Tyr (TEY) motif, an HRD domain, and an ATP binding loop containing GXGXXG. An analysis of phylogenetic relationships demonstrated that ERK amino acid sequences were conserved between different species indicating that the functions may be similar. Ec-ERK1 and Ec-ERK2 mRNA can be detected in all thirteen tissues examined, but the expression level is different in these tissues. The expression patterns of these two genes in E. coioides were also detected against Cryptocaryon irritans infection, which is capable of killing large numbers of fish in a short time and has a serious impact on aquaculture. The expression was up-regulated in most of the tissues examined, with the highest expressions of Ec-ERK1 (3.9 times) occurring in the head kidney and Ec-ERK2 (3.5 times) occurring in the spleen. There was no significant correlation between the expression of Ec-ERK1/Ec-ERK2 and the expression of nuclear factor kappaB (NF-kB). The results indicated the sequences and the characters of Ec-ERK1/ERK2 were conserved, Ec-ERK1/ERK2 showed tissue-specific expression patterns in healthy grouper, and their expressions were significantly varied post C. irritans infection, suggesting Ec-ERK1/ERK2 may play important roles in these tissues during pathogen-caused inflammation.

Decreased expression of hepatic cytochrome P450 1A2 (CYP1A2) in a chronic intermittent hypoxia mouse model

Background

Hepatic cytochrome P450 (CYP) isoforms, CYP1A2, is one of important enzymes for many drugs metabolism. Studies have confirmed that sustained hypoxia can influence the expression of hepatic CYP, including CYP1A2. The impact of chronic intermittent hypoxia (CIH), a marked characteristic of sleep apnea, on CYP1A2 remains unclear. The aim of the present study was to evaluate the effect of CIH on the expression of hepatic CYP1A2 in a mouse model with sleep apnea.

Methods

Twenty four old male (6-8 weeks) C57BL/6J mice (n=12 in each group) were randomly assigned to either normoxia group or CIH group. Mice in CIH group underwent 12 weeks intermittent hypoxia exposure. The different gene expression of hepatic CYP1A2 between two groups was analyzed by quantity real-time polymerase chain reaction. The protein levels of hepatic CYP1A2 in each group were observed by using western blotting and immunohistochemistry.

Results

After 12 weeks of exposure to intermittent hypoxia, the expression of hepatic CYP1A2, at the mRNA and protein levels was decreased more significantly in the CIH group than the normoxia group (P<0.01).

Conclusions

CIH contributes to inhibiting the expression of hepatic CYP1A2. This implies that the dosage of drugs metabolized by CYP1A2, should be adjusted in patients with sleep apnea.

Characterization of duplicated heme oxygenase-1 genes and their responses to hypoxic stress in blunt snout bream (Megalobrama amblycephala)

The heme oxygenase (HO)-1 is a cytoprotective enzyme that can be involved in cytoprotection against hypoxia stress. In this study, we cloned duplicated HO-1a and HO-1b cDNAs in hypoxia-sensitive blunt snout bream (Megalobrama amblycephala). HO-1a and HO-1b encode peptides with 272 amino acids and 246 amino acids, respectively, and they share a low sequence identity of 55%. HO-1a and HO-1b mRNAs were maternally deposited in the zygote, and the mRNAs decreased to the lowest levels at 8 hpf. Both mRNAs were significantly (p < 0.01) expressed from 12 hpf and fluctuated but maintained a high level after 16 hpf. Using in situ hybridization, HO-1a and HO-1b mRNAs were ubiquitously expressed in embryos at 12 hpf. At 24 and 36 hpf, HO-1b transcripts were detected in the mid- and hindbrain, respectively, whereas HO-1a was mainly transcribed in the eyes and endoderm at 24 hpf and in the brain at 36 hpf. In adult fish, HO-1a was abundantly expressed in the heart, liver, gill, kidney, spleen, and brain, while HO-1b mRNA was detected mainly in the kidney. After exposure to hypoxic stress, both HO-1a and HO-1b mRNAs were upregulated significantly in the gill and liver but downregulated significantly in the brain (p < 0.01). These findings suggest that duplicated HO genes have evolved divergently and yet play overlapping biological roles in regulating the response to hypoxia in M. amblycephala.

The anti-inflammatory effects of E-α-(p-methoxyphenyl)-2',3,4,4'-tetramethoxychalcone are mediated via HO-1 induction

Inflammation plays a central role in the pathophysiology of many diseases. The inducible enzyme heme oxygenase-1 (HO-1) protects cells against inflammation and can be induced by electrophilic compounds like the chalcones (1,3-diphenylprop-2-enones) from the class of α,β-unsaturated carbonyl compounds. We hypothesized that the synthetic chalcone E-α-(p-methoxyphenyl)-2',3,4,4'-tetramethoxychalcone (E-α-p-OMe-C6H4-TMC) exerts anti-inflammatory effects in RAW264.7, Jurkat lymphocytes and HK-2 cells via HO-1 induction. RAW264.7 cells were treated with lipopolysaccharide prior to E-α-p-OMe-C6H4-TMC treatment. Subsequently, HO-1 protein induction and activity were analyzed, as well as expression of pro- and anti-inflammatory mediators, transcription factors and mitogen-activated protein kinases to evaluate the possible molecular mechanism. These results were confirmed in human cell lines (Jurkat T-lymphocytes and HK-2 epithelial cells). We found that the E-α-p-OMe-C6H4-TMC exerts significant anti-inflammatory effects in a dose dependent manner, showing no toxic effects in LPS-treated RAW264.7 macrophages. E-α-p-OMe-C6H4-TMC induced HO-1 and SOD-1 protein expression and HO-1 enzyme activity, reduced the upregulation of COX-2 and iNOS, while inducing the translocation of Nrf2. NF-κB activity was attenuated following E-α-p-OMe-C6H4-TMC treatment accompanied by the downregulation of proinflammatory cytokines IL-1β, IL-6 and MCP-1. Pretreatment with E-α-p-OMe-C6H4-TMC revealed significant changes in phosphorylation of ERK and p38, but not JNK. These anti-inflammatory effects of E-α-p-OMe-C6H4-TMC were approved in Jurkat and HK-2 cells, furthermore revealing a downregulation of IL-8 and IL-10. In conclusion, it is tempting to speculate about E-α-p-OMe-C6H4-TMC as a new and non-toxic agent, inducing HO-1 in cells. This opens up new opportunities regarding the development of therapeutic agents using beneficial effects of HO-1 and its products.