Tomoko Nishino

Detection of a smaller, 32-kDa 8-oxoguanine DNA glycosylase 1 in 3'-methyl-4-dimethylamino- azobenzene-treated mouse liver

We previously reported that 3′‐methyl‐4‐dimethylaminoazobenzene (3′‐MeDAB) increased the 8‐hydroxyguanine (8‐OH‐Gua) content in nuclear DNA and the base excision repair activity in mouse liver. However, to understand the mechanism of 3′‐MeDAB carcinogenesis, a further investigation of the 8‐OH‐Gua repair systems was necessary. In this report, we examined the expression of the repair enzyme, 8‐oxoguanine DNA glycosylase 1 (OGG1), in 3′‐MeDAB‐treated mouse liver. We prepared four kinds of anti‐peptide polyclonal antibodies raised against mouse OGG1 (mOGG1). The sequences used as epitopes were designed from positions located close to the N‐terminus, the nuclear localization signal (NLS), and the regions containing Lys249 and Asp267, which are involved in the catalytic mechanisms of mOGG1 (glycosylase and lyase, respectively). Immunoblotting, using all four antibodies, revealed a 32‐kDa protein (mOGG1‐32) in addition to the 38‐kDa mOGG1 in the 3′‐MeDAB‐treated mouse liver. Moreover, immunostaining with mOGG1 antibody yielded strong, positive signals in the 3′‐MeDAB‐treated mouse liver nuclei. However, we could not detect any difference in the Ogg1 mRNA expression pattern. Although the function of mOGG1‐32 remains unclear, these findings suggest that 3′‐MeDAB may alter the function of the DNA repair protein, and this action may be related to 3′‐MeDAB carcinogenesis.

Increased immunoreactivities against endothelin-converting enzyme-1 and monocyte chemotactic protein-1 in hepatic stellate cells of rat fibrous liver induced by thioacetamide.

The progression of rat liver fibrosis induced by intraperitoneal administration of thioacetamide (TAA) was evaluated by immunocytochemistry using anti-α-smooth muscle actin (α-SMA), antiendothelin-converting enzyme (ECE)-1, and anti-monocyte chemotactic protein (MCP)-1 antibodies. The fibrous septal spaces gradually increased after administration of TAA, and pseudolobules were established in the 7-week TAA-treated groups. Immunoreactivities against α-SMA were not detected in hepatic stellate cells (HSCs) of the control group without TAA treatment, although they were observed in the HSCs around the fibrous septal spaces in all TAA-treated groups, indicating that activation of HSCs occurs during the establishment of pseudolobules. Immunoreactivities against ECE-1 and MCP-1 were seen in such HSCs of the TAA-treated groups, but few or no immunoreactivities were detected in the HSCs of the control group. The most significant increase in the ECE-1 immunoreactivities was detected in the 1-week TAA-treated group, whereas that in MCP-1 was observed in the 7-week TAA-treated group. The present immunocytochemistry indicated a difference in the accelerated expression period between immunoreactivities against ECE-1 and MCP-1 in the HSCs during the progression of TAA-induced liver fibrosis, suggesting that ECE-1 is involved in the early phase of liver fibrosis and that MCP-1 plays a role during the later phase.

Apical tubules in marginal cells of the differentiating stria vascularis.

Apical tubules (ATs) in marginal cells (MCs) of the stria vascularis appear in limited stages of differentiation of the MCs, but their origin and roles remain uncertain. The present study was designed to solve the problem of whether the ATs are intracellular compartments derived from the Golgi apparatus (GA).