Satoru Mitazaki

Interleukin-6 modulates oxidative stress produced during the development of cisplatin nephrotoxicity.

AIMS We reported that interleukin-6 (IL-6) plays a protective role in the development of cisplatin-induced acute renal failure (ARF) through upregulation of anti-oxidative stress factors. In this study, we examined the effects of dimethylthiourea (DMTU), a hydroxyl radical scavenger, on the development of cisplatin-induced ARF in wild-type (WT) and IL-6(-/-) mice to determine how IL-6 contributes to modulation of oxidative stress caused by cisplatin. MAIN METHODS WT and IL-6(-/-) male mice were given either cisplatin (30 mg/kg) or saline intraperitoneally. DMTU (100mg/kg) or saline was given 30 min before cisplatin or saline administration. Blood and kidney samples were collected on days 1 and 3 after cisplatin administration. KEY FINDINGS In WT mice, DMTU markedly improved cisplatin-induced renal dysfunction and survival rate. DMTU reduced the expression levels of TNF-α, Bax and c-fos and increased the expression levels of IL-6, Bcl-xL and Nrf2 in WT mice. Reduced reactive oxygen species (ROS) by DMTU resulted in increases of IL-6, anti-apoptosis and anti-oxidant gene expression levels. In IL-6(-/-) mice, DMTU also improved cisplatin-induced renal dysfunction and reduced expression levels of TNF-α, Bax and c-fos, but not Bcl-xL and Nrf2. Since Nrf2 induces IL-6 expression, IL-6 and Nrf2 may influence each other during anti-oxidant responses. The basal level of HO-1 in IL-6(-/-) mice was higher than that in WT mice. SIGNIFICANCE In IL-6(-/-) mice, overproduction of ROS by cisplatin results in upregulation of HO-1 expression in order to eliminate oxidative stress. IL-6 mediates the generation and elimination of ROS during cisplatin-induced ARF.

Interleukin-6 deficiency accelerates cisplatin-induced acute renal failure but not systemic injury

Cisplatin (CDDP), a major chemotherapeutic agent used to treat solid tumors, is known to induce acute renal failure (ARF). The progression of tissue injury involves the coordination of inflammatory and repair responses. Interleukin-6 (IL-6) has been suggested to modulate inflammatory and repair processes in various tissue injuries. In this study, we analyzed IL-6 regulation during CDDP-induced ARF in wild-type (WT) mice and determined the pathological role of IL-6 using IL-6 knockout ((-/-)) mice. A correlation between increase in serum IL-6 level and blood urea nitrogen level was found in WT mice. Renal IL-6 expression in most proximal tubular cells and suppressor of cytokine signaling 3 (SOCS3) gene expression significantly increased in WT mice after administration of CDDP, suggesting active IL-6 signaling during CDDP-induced ARF development. Interestingly, renal dysfunction occurred soon after administration of CDDP and became more severe in IL-6(-/-) mice than that in WT mice. In contrast, the survival rate of IL-6(-/-) mice (50% at 8 days) was better than that of WT mice (10%). Induction levels of proapoptotic Bcl-2 associated X protein (Bax) in renal proximal tubular cells was significantly higher in IL-6(-/-) mice than in WT mice at 24h after CDDP injection. Levels of antiapoptotic proteins, Bcl-2 and Bcl-extra large (Bcl-x(L)), in IL-6(-/-) groups were significantly higher than those in CDDP-treated WT groups throughout the experimental period. Bax might contribute to the development of CDDP-induced ARF at 24h; however, high expression levels of Bcl-x(L) and Bcl-2 might overcome the proapoptosis signaling at 72 h in IL-6(-/-) mice. These results indicated that local and systemic elevation of IL-6 contributes to the development of CDDP-induced ARF and that IL-6 produced in renal tubular cells prevents progression of ARF at the early stage. IL-6 deficiency accelerates CDDP-induced ARF but not development of systemic injury.

Amelioration of cisplatin-induced mouse renal lesions by a cyclooxygenase (COX)-2 selective inhibitor.

In this study, we investigated the effects of the cyclooxygenase (COX)-2 selective inhibitor, meloxicam, on cisplatin-induced inflammation, oxidative stress and renal lesions in BALB/c mice. A single cisplatin injection (13 mg/kg, i.p.) significantly increased plasma creatinine, blood urea nitrogen and urinary glucose accompanied by a concomitant increase in COX-2 mRNA and COX-2 protein levels. These changes in renal lesion parameters were diminished by simultaneous treatment of meloxicam (0.7 mg/kg/day in drinking water). The expression of oxidative stress markers, p47(phox), p67(phox), hemoxygenase-1 (HO-1), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and 4-hydroxy-2-nonenal (4-HNE)-modified protein were increased with cisplatin injection. Simultaneous treatment of meloxicam with cisplatin significantly inhibited the increase in p47(phox), HO-1 and 4-HNE-modified protein. The phosphorylation of extracellular regulated kinase (ERK) and c-jun-N-terminal kinase (JNK) were increased with cisplatin injection, but these changes were inhibited by meloxicam. Moreover, concomitant meloxicam treatment also prevented the cisplatin-induced infiltration of macrophages to the tubulointerstitial area. These results suggest that meloxicam can ameliorate cisplatin-induced mouse renal lesions, potentially through the inhibition of inflammatory and oxidative stress responses.

Interleukin-6 plays a protective role in development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors

AIMS Cisplatin, a major chemotherapeutic agent, accumulates in proximal tubules of the kidneys and causes acute renal failure dose-dependently. We previously reported that cisplatin induced more severe renal dysfunction in interleukin-6 (IL-6) knockout (IL-6(-/-)) mice than in wild-type (WT) mice. Expression of a pro-apoptotic protein was significantly increased with cisplatin in IL-6(-/-) mice compared to that in WT mice. IL-6, locally expressed in renal tubular cells after cisplatin administration, prevents the development of renal dysfunction at an early stage. In the present study, we focused on downstream signals of IL-6 and oxidative stress induced by cisplatin in order to evaluate the protective role of IL-6 in the development of acute renal failure. MAIN METHODS WT and IL-6(-/-) mice were given either cisplatin (30 mg/kg) or saline intraperitoneally. Blood and kidney samples were collected at 24h and 72 h after cisplatin administration. The changes in expression of 4-hydroxy-2-nonenal protein (4-HNE, oxidative stress marker) and cyclooxygenase-2 (cox-2), activities of superoxide dismutases and caspase-3, and phosphorylation of extracellular signal-regulated kinase (ERK) were examined. KEY FINDINGS Cisplatin increased the expression of 4-HNE and cox-2, and phosphorylation of ERK in IL-6(-/-) mice than in WT mice. On the other hand, activity of superoxide dismutase, an anti-oxidative enzyme, was significantly decreased in the kidney obtained from IL-6(-/-) mice after cisplatin administration. SIGNIFICANCE Our findings suggest that IL-6 plays a protective role in the development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors.

Behavioral and neurochemical characterization of mice deficient in the N-type Ca2+ channel α1B subunit

N-type voltage-dependent calcium channels (VDCCs) play an important role in neurotransmission, synaptic plasticity, and brain development. They are composed of several subunits named alpha(1), alpha(2), delta, beta and gamma. The alpha(1) subunit is essential for channel functions and determines fundamental channel properties. Since N-type VDCC are critically involved in the release of neurotransmitters and clinical relevance, we predicted that alpha(1) subunit KO mice would show several alterations in behavior. In the present study, we investigated neuronal functions in mice lacking the alpha(1B) (Ca(V)2.2) subunit of the N-type calcium channels. Ca(V)2.2(-/-) mice exhibited a significant increase in locomotion on an activity wheel during the dark phase. Furthermore, when challenged with apomorphine, mutant mice showed enhanced locomotor activity. Cognitive functions were examined using a Y-maze task for short-term memory and a passive avoidance task for long-term memory. The Y-maze revealed no differences in spontaneous alternation behavior between mutant and wild-type mice. The passive avoidance test revealed that the latency time in mutant mice was significantly decreased. The mutant mice showed prepulse inhibition deficits reminiscent of the sensorimotor gating deficits observed in a large majority of schizophrenic patients. Decreases in baseline levels of dopamine and serotonin within the striata and frontal cortices of mutant mice were also observed. These results suggest that Ca(2+) in the central nervous system modulates various neurophysiological functions, such as locomotor activity, long-term memory, and sensorimotor gating through the alpha(1B) subunit of the N-type calcium channels.

Effect of cyclooxygenase (COX)-2 inhibition on mouse renal interstitial fibrosis.

Unilateral ureteral obstruction (UUO) is a well-established model for the study of interstitial fibrosis in the kidney. In this study, we investigated the effects of a COX-2 inhibitor, meloxicam, on UUO-induced renal interstitial fibrosis in mice. Serum creatinine, blood urea nitrogen and urinary glucose were significantly increased by UUO. However, all of these changes were attenuated by meloxicam (1 mg/kg/day). Masson׳s trichrome staining showed that interstitial fibrosis was significantly increased by UUO, but that meloxicam also significantly diminished the area of UUO-induced fibrosis. Heat shock protein (HSP) 47 protein, a collagen-specific molecular chaperone essential for the biosynthesis of collagen molecules, and type IV collagen mRNA were increased in kidneys of UUO mice. Meloxicam reduced the expression of both HSP47 protein and type IV collagen mRNA. The phosphorylation of extracellular regulated kinase (ERK) and c-jun-N-terminal kinase (JNK) was increased by UUO, but these changes were inhibited by meloxicam. Collectively, these results suggest that COX-2 may be involved in the expression of HSP47 and type IV collagen through the phosphorylation of ERK and JNK, accelerating renal interstitial fibrosis.

Subchronic stress-induced depressive behavior in ovariectomized mice

AIMS Mood disorders including depression are more common in women than men, particularly in times of lower estradiol levels. In this study, we investigated the effect of estrogen on emotional behavior in mice in a stress environment. MAIN METHODS Female mice were divided into four groups: two groups were ovariectomized (OVX) and two were sham-operated. One group each of OVX and sham mice was kept in a normal environment and the other groups were assigned to a daily stress (1 h/day) for 7 days from 5 days after operation. On the 14th day after operation, subjects were measured to assess behavioral specificity, locomotor activity, elevated plus-maze (EPM) behavior, passive avoidance (PA) behavior and forced swimming behavior. KEY FINDINGS The OVX plus stress (OVX+S) group showed a significant prolongation of immobility compared with the other groups. In all the groups there were no changes in locomotor activity, EPM behavior or PA behavior. We further examined the effect of estrogen against depressive behavior in the OVX+S group. The vehicle or 17beta-estradiol (E2) was administered s.c. to OVX+S mice for 4 days beginning on post-operative day 11. Subchronic E2 treatment decreased the stress response and improved depressive behavior relative to the vehicle group. SIGNIFICANCE These data have important implications regarding the prevention of depression in postmenopausal women undergoing estrogen therapy.

p-Hydroxyamphetamine causes prepulse inhibition disruptions in mice: Contribution of dopamine neurotransmission

It is well known that amphetamine induces disrupted prepulse inhibition (PPI) in humans and rodents. We have previously reported that intracerebroventricular (i.c.v.) administration of p-hydroxyamphetamine (p-OHA) induces multiple behavioral responses, such as increased locomotor activity and head-twitch response in rodents. To reveal the characteristics of p-OHA on sensorimotor function in rodents, herein we tested the effects of p-OHA on PPI in mice. i.c.v. administration of p-OHA dose-dependently induced PPI disruptions for all prepulse intervals tested. This effect of p-OHA on PPI was attenuated by pretreatment with haloperidol or clozapine. p-OHA-induced PPI disruptions were also attenuated by pretreatment with L-741,626 (a selective D(2) receptor antagonist), L-745,870 (a selective D(4) receptor antagonist) or 6-hydroxydopamine (a neurotoxin which targets DA-containing neurons), but not by SCH 23390 (a selective D(1) receptor antagonist), eticlopride (a D(2)/D(3) receptor antagonist) or GBR 12909 (a DA-reuptake inhibitor). These results indicate that selective blockade of either the D(2) or D(4) receptor subtype may prevent disruption of PPI induced by p-OHA via presynaptic DA release.

Apocynin reduced doxycycline-induced acute liver injury in ovariectomized mice

Highlights • Ovariectomy accelerates doxycycline-induced acute liver injury.• The expression levels of IL-6, IL-10, c-fos, cox-2 and HO-1 genes were strongly upregulated in ovx mice.• Apocynin, totally improved DOXY-induced liver injury in both sham and ovx mice.• NADPH oxidase is responsible for the development of drug-induced acute liver injury

Effect of amlodipine on mouse renal interstitial fibrosis.

Unilateral ureteral obstruction (UUO) is a well-established method to study interstitial fibrosis of the kidney. In this study, we investigated the effects of a calcium channel blocker, amlodipine, on UUO-induced renal interstitial fibrosis in mice. UUO significantly increased the fibrotic area in the obstructed kidney, but this change was inhibited by amlodipine (6.7mg/kg/day in drinking water). mRNA expression of heat shock protein (HSP) 47 and type IV collagen was increased in the kidneys of UUO mice. Amlodipine reduced the expression of both HSP47 and type IV collagen mRNAs. Phosphorylation of c-jun-N-terminal kinase (JNK) was significantly increased by UUO, but the change was inhibited by amlodipine. Collectively, these results suggest that amlodipine may inhibit the expression of HSP47 and type IV collagen by reducing phosphorylation of JNK and ameliorating the renal interstitial fibrosis induced by UUO.