Yoshihiko Masaki

Immunosuppressive effect of bredinin on cell-mediated and humoral immune reactions in experimental animals.

Bredinin (BR), an imidazole nucleoside isolated from Eupenicillium brefeldianum was previously reported to prolong kidney allograft survival in dogs. The immunosuppressive effect of BR was studied in experimental animals. In beagles, in vitro responses of lymphocytes stimulated by mitogens or allogeneic cells were suppressed by in vitro BR treatment. BR, given in vivo, also showed an inhibitory action against development of delayed hypersensitivity reaction to tubercle bacilli in guinea pigs or against hemagglutinin production following booster SRBC injection in rabbits. Of note may be the fact that BR was found to have an immunosuppressive potency comparable to that of azathioprine and, in addition, to show a decreased hepatotoxicity compared with the latter.

Effect of altering cerebrospinal fluid pressure on spinal cord blood flow

Removal of cerebrospinal fluid (CSF) has been proposed as a means of protecting the spinal cord against ischemic injury during thoracoabdominal aneurysm operations. We investigated the effect of altering CSF pressure (CSFP) on lumbar spinal cord blood flow (SCBF) in an experiment using dogs. The SCBF was measured before and after withdrawal of CSF in settings with and without thoracic aortic clamping. Furthermore, SCBF was measured at the basal state and after elevation of CSFP to 20 mm Hg and to 40 mm Hg. The SCBF did not change significantly before and after removal of CSF in settings both with and without thoracic aortic clamping. Elevation of CSFP significantly reduced SCBF. Elevation of CSFP reduces SCBF, but lowering CSFP per se does not increase SCBF whether the thoracic aorta is occluded or not. This supports the notion that removal of CSF offers spinal cord protection only when CSFP is abnormally elevated.

Angiotensin II-mediated up-regulation of connective tissue growth factor promotes atrial tissue fibrosis in the canine atrial fibrillation model

Aims Remodelling of the extracellular matrix (ECM) plays an important role in the production of arrhythmogenic substrate for atrial fibrillation (AF), and is considered to be promoted by the connective tissue growth factor (CTGF). Our objective was to assess the relationship between CTGF and ECM synthesis, and the effect of olmesartan on these processes. Methods and results Fifteen canine AF models were produced by rapid atrial stimulation. They were divided into three groups: pacing control (n = 5): 6-week pacing, pacing + olmesartan (n = 5): pacing with olmesartan (2 mg/kg/day), and non-pacing group (n = 5). In the pacing control group, messenger ribonucleic acid expressions of CTGF and collagen types 1 and 3 were up-regulated in comparison with the non-pacing group (P < 0.05) while transforming growth factor-β (TGF-β) did not exhibit a significant difference. In the pacing + olmesartan group, these up-regulations were suppressed (P < 0.05). In fluorescent immunostaining, the expression of CTGF was localized in the cytoplasm. The protein level of collagen type 3 was increased in the pacing control and it was suppressed in the pacing + olmesartan group. Conclusions CTGF and associated genes were up-regulated in the atria with the appearance of fibrosis. Because this up-regulation was independent of TGF-β and suppressed by olmesartan, CTGF up-regulation was considered to be mediated by angiotensin II.

Suppressive effect of mizoribine on humoral antibody production in DBA/2 mice

The mode of action of mizoribine (MZR) as a B cell inhibitor was studied using DBA/2 mice. Its in vitro administration significantly delayed the primary response in hemagglutinin production against sheep erythrocytes by suppressing the IgM antibody formation. In vitro plaque-forming cell (PFC) response against both T-dependent and T-independent antigens, such as TNP-SRBC and TNP-Brucella abortus, was dose-dependently suppressed by MZR. Since PFC formation by the T-depleted fraction of splenocytes was likewise suppressed, MZR may inhibit humoral antibody response by directly affecting the B cells (and/or macrophages) as well as by modulating the regulatory T cells. MZR may only act on a certain stage of the cell cycle of B lymphocytes following antigenic stimulation. It may not interfere with the initial antigen recognition or with mature B cells.

Effect of mizoribine on lupus nephropathy of New Zealand black/white F1 hybrid mice

Therapeutic trials with mizoribine (MZR), an imidazole nucleoside immunosuppressant, on experimental lupus nephropathy of NZB/W F1 mice resulted in the following. The MZR treatment, 20 mg per kilogram of body weight every other day, starting at 14 weeks of age, caused a significantly prolonged survival time of mice with a mean life span of 54.3 +/- 4.2 weeks, compared with the untreated controls, who had a mean survival time of 38.1 +/- 2.9 weeks (P less than 0.01). In addition, MZR suppressed the elevation of serum anti-DNA antibody titers, the spontaneous development of splenomegaly, and the histological development and progression of glomerulonephritis observed in untreated animals. Although no definite explanation is available at present to explain how MZR caused decreased anti-DNA antibody production and delay in the development of glomerulonephritis in these animals, it is suggested that it acts by directly suppressing the hyperfunctioning B cells of lupus mice. MZR may prove to be a promising immunosuppressant for the treatment of human lupus, in view of its lesser side effects such as bone marrow suppression or hepatotoxicity.

Modification of crescentic masugi nephritis in the rabbit by bredinin, a new immunosuppressant

SummaryExperiments were undertaken to ascertain whether progression of crescentic Masugi nephritis in rabbits could be prevented by the administration of Bredinin (BR). Crescentic glomerulonephritis can be induced with high reproducibility by intramuscular preimmunization on day 1, followed by intravenous injections on days 3 and 5 of nephrotoxic duck γ-globulin (NTD γ-gl). 30 rabbits were divided into 3 groups including controls (group 1). Two groups of 10 nephritic rabbits were each treated with 10 mg/kg of BR either after or before the development of proteinuria (groups 2 and 3). In group 3, the onset of proteinuria showed a significant delay and duration of survival was significantly prolonged, compared with controls. Serum antibody titers after day 8 and creatinine levels after day 10, as well as the initial amounts of proteinuria, were also significantly lower during treatment in group 3 than in controls. Histologically, the prominent diffuse intra- and extra-capillary proliferation with monocyte accumulations observed in the control group were markedly diminished in group 3. These results suggest that early treatment in crescentic glomerulonephritis with BR will suppress the production of humoral antibody and prevent progression of the glomerular lesions.

Toxicological and immunological evaluation of the immunosuppressant 15-deoxyspergualin in BALB/c mice: an in vivo and in vitro study.

The toxicological aspects as well as the immunosuppressive mechanism of 15-deoxyspergualin (DSP) were studied using BALB/c mice. Five-week-old animals were subcutaneously given phosphate-buffered saline (PBS; Group 1) or DSP at 0.5 (Group 2) to 5.0 mg (Group 4) per kg body weight daily for 1 to 3 months. They were sacrificed to obtain blood for hematology and liver function studies. The spleen, taken simultaneously, was histologically examined, the T cell surface markers of splenocytes were flow cytometrically measured, and their interleukin 2 (IL-2) production induced in vitro by Enterotoxin A (Ent A) was assayed using CTLL cells. Additionally, the in vitro effect of DSP on IL-2 generation and plaque forming cell (PFC) production was studied using splenocytes of non-treated mice. During the 3 months of treatment, the body weight slowly increased in Groups 1 and 2, while the body weight of the 2.5-mg DSP mouse group (Group 3) was significantly lower on days 28 and 56 of treatment compared with Group 1 of the same age (P less than 0.05). The administration of DSP at 5.0 mg/kg (Group 4) caused marked reduction in body weight of the animals. They were sacrificed on day 28 because of their worsening general condition. WBC and RBC counts decreased in Group 3 on days 57 and 93, and the platelet number increased on day 57. A liver function test was not affected by DSP treatment except for an elevated SGOT in Group 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of methylprednisolone on progressive Masugi nephritis in the rabbit. I. Suppression of antibody production and crescent formation.

SummaryExperiments were undertaken to clarify whether a large dose of methylprednisolone (MPSL) could have any suppressive effect on progressive Masugi nephritis in the rabbit. Progressive crescentic Masugi nephritis could be induced with high reproducibility by preimmunization with a small amount of nephrotoxic duck γ-globulin incorporated with complete Freund’s adjuvant, followed by an intravenous injection 4 days later. Two groups of rabbits treated with 80 mg/kg of MPSL either before or after the development of proteinuria, showed a significant decrease in both antibody titers and serum creatinine levels during treatment. Histologically, the prominent diffuse intracapillary proliferation and crescent formation observed in controls, were markedly diminished. Accumulations of monocytes in the intra and extracapillary space were also decreased. These results suggest that suppression of antibody production by a large dose of MPSL is one of its most fundamental actions, and can prevent the processes leading to crescentic glomerular lesions.

Combined effects of up- and downstream therapies on atrial fibrillation in a canine rapid stimulation model

BACKGROUND Recent reports suggest angiotensin receptor blockers (ARBs) and some antiarrhythmic agents affect atrial remodeling in atrial fibrillation (AF). We evaluated the effect of combination therapy with olmesartan (Olm) and bepridil (Bep) in a canine model of AF. METHODS AND RESULTS An atrial stimulation device was implanted in 10 dogs undergoing 6-week pacing at 400 bpm. They were divided into Olm (2 mg/kg/day) (n=5) and Olm+Bep (Olm, 2 mg/kg/day; Bep, 10 mg/kg/day) groups (n=5). Atrial effective refractory period (AERP), conduction velocity (CV), and AF inducibility were evaluated weekly, and hemodynamics, atrial histology, and mRNA expression and protein expression of ion-channel and gap junction-related molecules at 6 weeks. Data were compared between groups and with non-pacing control and pacing-control groups from our previous report. The pacing-control group exhibited shortened AERP, decreased CV, increased AF inducibility and tissue fibrosis, and down-regulated L-type Ca(2+) channel (LCC), SCN5A, Kv4.3 and connexin43 (Cx43). By comparison, the Olm group exhibited suppression of the decrease in CV and of the increase in AF inducibility, but no change in AERP shortening. The Olm+Bep group exhibited suppression of AERP shortening as well as the greatest decrease in AF inducibility. Histologically, tissue fibrosis was suppressed in Olm and Olm+Bep groups. Down-regulation of Cx43 was partly suppressed in the Olm group while that of LCC, SCN5A, and Cx43 was suppressed in the Olm+Bep group. CONCLUSION Olm and Bep in combination suppressed AF inducibility more strongly than Olm alone, and may be more useful in the suppression of AF.

Prolongation of the kidney preservation period by simple cold storage up to 72 hours by human atrial natriuretic peptide

To prolong the preservation period of donor kidneys, we tried to evaluate the effect of human atrial natriuretic peptide (hANP), which has vasodilator, natriuretic, and GFR-increasing effects. Autotransplantations were successful in 6 of 8 hANP-treated cases, but only one of 7 untreated cases (P<0.05) was successful. When removed kidneys were perfused prior to preservation, the gravity perfusion time was shorter in hANP-treated kidneys, resulting in rapid cooling. Renal biopsy 1 hr after transplantation revealed normal histology in the hANP-treated kidneys while a remarkable capillary collapse occurred in controls. A hANP-like immunoreactivity contents of biopsied tissue in the hANP-treated kidneys showed a higher value than in the controls, and cyclic GMP contents were also higher in the hANP-treated kidneys. Microangiography showed complete clarity, down to the peripheral vessels, in the hANP-treated kidneys, but not in the controls. Thus, the present study suggests that hANP is useful for prolonging the preservation time of donor kidneys.