Protopic
Effects of tacrolimus on infection of Friend murine leukemia virus to Fv-4 gene heterozygous mice.

Zhang FM, Yang BF, Gu HX, Chen XB, Zhong ZH, Cheng Z.

Department of Microbiology, Harbin Medical University, Harbin 150086, China. zhangfm ems.hrbmu.edu.cn

AIM: To investigate the effect of tacrolimus (FK506) on the infection of Friend murine leukemia virus (Friend MuLV) in vivo. METHODS: Three kinds of mice were used including Friend MuLV-sensitive BALB/c mice, Friend MuLV-resistant Fv-4 gene-homozygous mice (Fv-4 mice), and Friend MuLV-resistant Fv-4 gene-heterozygous mice (F1 mice). Tacrolimus was administrated i.p. to those mice in every 2 d. Those treated mice were inoculated i.p. with Friend MuLV once on d 3. The symptoms and viral proliferations in those mice were observed to recognize the Friend MuLV infection. The expression and genotype of Fv-4 gene that resistant against the infection of Friend MuLV were analyzed to confirm the genomic background and related mechanism of the resistance. RESULTS: BALB/c mice and F1 mice, but not Fv-4 mice, appeared obvious early death, spleenomegaly, and viral proliferation after both treatments of viral inoculation and tacrolimus administration, whereas the expression and genotype of Fv-4 gene was not changed in F1 mice and Fv-4 mice with treatment of tacrolimus. Compared to the virus-inoculated control, the Friend MuLV-sensitivity of tacrolimus-treated BALB/c mice and the Friend MuLV-resistance of tacrolimus-treated Fv-4 mice were the same as the controls, but only F1 mice became the symptoms and viral proliferation after both treatments. It suggested the Friend MuLV-resistant F1 mice could be converted to be Friend MuLV-sensitive by treatment of tacrolimus, and this conversion was not depended on the expression and genotype of Fv-4 gene. CONCLUSION: Tacrolimus could not inhibit the infection of Friend MuLV in all mice, furthermore, it could enhance the infection of Friend MuLV in F1 mice. The enhancement may be related to the immunosuppressive effect of tacrolimus.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14769211&dopt=Abstract tacrolimus Protopic



Protopic
Tacrolimus dosage requirements after initiation of azole antifungal therapy in pediatric thoracic organ transplantation.

Mahnke CB, Sutton RM, Venkataramanan R, Michaels M, Kurland G, Boyle GJ, Law YM, Miller SA, Pigula FA, Gandhi S, Webber SA.

Division of Cardiology, Children's Hospital of Pittsburgh, PA 15213, USA.

Azole antifungals inhibit the metabolism of tacrolimus mediated by CYP3A4. Upon initiation of azole therapy, the required dose reduction of tacrolimus is unknown. We reviewed our experience with azole antifungals in our pediatric thoracic transplant population receiving tacrolimus. Tacrolimus levels and dosage requirements were compared before and during azole therapy. Thirty-one patients received both tacrolimus and an azole antifungal (fluconazole = 9, itraconazole = 22). The tacrolimus dose was empirically reduced by approximately one-third when azole therapy was initiated. Mean tacrolimus dose requirements decreased by 68% within the first month of therapy (pre-azole: 0.27 +/- 0.14 mg/kg/day; 30 day post-azole: 0.087 +/- 0.069 mg/kg/day; p < 0.001). Despite a mean decrease in tacrolimus dose from baseline of 33, 42, and 55% on day 1, 2, and 4 of azole therapy, respectively, there was still an unintended 38% increase in tacrolimus levels during the first month of azole therapy. A calculated dose-reduction protocol of 50% on day of azole initiation, 70% on day 3, and 75% on day 14 should result in minimal mean changes in the tacrolimus levels. There was no difference in tacrolimus dose reduction between fluconazole and itraconazole groups. Azole antifungals markedly decrease tacrolimus requirements within the first few days of therapy. An initial reduction in tacrolimus dose by one-third is insufficient, and dose reduction of at least 50% upon azole initiation seems warranted. Once azole antifungal therapy is initiated, frequent therapeutic drug monitoring is required.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14870897&dopt=Abstract tacrolimus Protopic



Protopic
Tacrolimus impairment of insulin secretion in isolated rat islets occurs at multiple distal sites in stimulus-secretion coupling.

Uchizono Y, Iwase M, Nakamura U, Sasaki N, Goto D, Iida M.

Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka City 812-8582, Japan.

Tacrolimus causes posttransplant diabetes mellitus, although the pathogenetic mechanisms remain controversial. We studied the mechanism of tacrolimus-induced impairment of insulin secretion using isolated rat pancreatic islets. Tacrolimus caused reductions in DNA and insulin contents per islet during 7-d culture. Tacrolimus time-dependently suppressed glucose-stimulated insulin secretion, and at a therapeutic concentration of 0.01 micromol/liter, it suppressed glucose-stimulated insulin secretion to 32 +/- 5% of the control value after 7-d incubation. Tacrolimus did not change islet glucose utilization and oxidation, ATP production, insulin mRNA expression, or the capacity for high glucose to increase intracellular Ca(2+), but altered the rapid frequency oscillations of Ca(2+) concentration. Tacrolimus suppressed insulin secretion stimulated by mitochondrial fuel (combination of l-leucine and l-glutamine, and alpha-ketoisocaproate) and glibenclamide, but not by l-arginine. Tacrolimus suppressed insulin secretion induced by carbachol and by a protein kinase C agonist in the presence or absence of extracellular Ca(2+). Under stringent Ca(2+)-free conditions, tacrolimus did not affect mastoparan-induced insulin secretion, but suppressed its glucose augmentation. Our results suggest that tacrolimus impairs glucose-stimulated insulin secretion downstream of the rise in intracellular Ca(2+) at insulin exocytosis, and that protein kinase C-mediated (Ca(2+)-dependent and independent) and Ca(2+)-independent GTP signaling pathways may be involved. However, tacrolimus-induced impaired insulin secretion was reversed 3 d after removal of the drug. Our study demonstrated that tacrolimus impairs insulin secretion at multiple steps in stimulus-secretion coupling.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14962991&dopt=Abstract tacrolimus Protopic



Protopic
Acute rejection after renal transplantation is reduced by approximately 50% by prior therapeutic blood transfusions, even in tacrolimus-treated patients.

Higgins RM, Raymond NT, Krishnan NS, Veerasamy M, Rahmati M, Lam FT, Kashi H, West N.

Renal Transplant Unit, University Hospitals Coventry and Warwickshire, Coventry, UK. robert.higgins uhcw.nhs.uk

BACKGROUND: The authors investigated the relationship between therapeutic blood transfusion before renal transplantation and rejection rates in cyclosporine- and tacrolimus-treated patients. METHODS: In one center, 265 consecutive recipients were studied. Protocol induction was with azathioprine, prednisolone, and cyclosporine or tacrolimus; 37% had biopsy-proven acute rejection in the first 6 months and 46% had received zero to two units of blood before transplantation. RESULTS: Lower risk of rejection was associated with tacrolimus induction (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.29-0.95; P=0.049), prior transfusion of three or more units of blood (OR, 0.54; 95% CI, 0.33-0.90; P=0.024), and older age at transplantation (mean, 44.23 +/- 12.56 [+/- SD] years vs. 38.96 +/- 12.37 years; P=0.001). Multiple logistic regression modeling showed the effect of three or more prior transfusions on acute rejection was as follows: OR, 0.49; 95% CI, 0.29 to 0.83; P=0.008. CONCLUSIONS: Induction immunosuppression should take account of the higher risk of rejection in patients coming to transplantation who have previously received zero to two units of blood.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14966430&dopt=Abstract tacrolimus Protopic



Protopic
Neuroprotective action of tacrolimus (FK506) in focal and global cerebral ischemia in rodents: dose dependency, therapeutic time window and long-term efficacy.

Furuichi Y, Katsuta K, Maeda M, Ueyama N, Moriguchi A, Matsuoka N, Goto T, Yanagihara T.

Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., 2-1-6, Kashima, Yodogawa-Ku, Osaka 532-8514, Japan. yasuhisa_furuichi po.fujisawa.co.jp

Tacrolimus (FK506), a potent immunosuppressive drug, is effective in attenuating brain infarction after cerebral ischemia. However, there has been no report characterizing the neuroprotective action and therapeutic time window of tacrolimus systematically using different types of stroke models and extended observation periods. Therefore, we evaluated the neuroprotective effect of tacrolimus in three different animal models of cerebral ischemia: transient and permanent focal ischemia in rats and transient global ischemia in gerbils. Tacrolimus at doses higher than 0.1 mg/kg (i.v.) produced a statistically significant reduction in ischemic brain damage following permanent and transient focal ischemia in rats when administered immediately after the onset of ischemia. Tacrolimus (1 mg/kg, i.v.) demonstrated similar neuroprotective activity even after delayed administration (2 h after permanent or 1 h after transient focal ischemia). The neuroprotective effect of tacrolimus was still present 2 weeks after transient focal ischemia and 1 week after permanent focal ischemia. After transient global ischemia in gerbils, tacrolimus (1 mg/kg, i.v.) given immediately after reperfusion also produced long-lasting neuroprotective effects with a protective time-window of 1-2 h. Taken together, the results clearly indicate that tacrolimus exerts potent, long-term neuroprotective effects with a favorable therapeutic time-window, regardless of the model of cerebral ischemia. These results strengthen the notion that tacrolimus might be of clinical value for the treatment of acute stroke.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12591130&dopt=Abstract tacrolimus Protopic



Protopic
Tacrolimus suppresses glucose-induced insulin release from pancreatic islets by reducing glucokinase activity.

Radu RG, Fujimoto S, Mukai E, Takehiro M, Shimono D, Nabe K, Shimodahira M, Kominato R, Aramaki Y, Nishi Y, Funakoshi S, Yamada Y, Seino Y.

Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.

Tacrolimus is widely used for immunosuppressant therapy, including various organ transplantations. One of its main side effects is hyperglycemia due to reduced insulin secretion, but the mechanism remains unknown. We have investigated the metabolic effects of tacrolimus on insulin secretion at a concentration that does not influence insulin content. Twenty-four-hour exposure to 3 nM tacrolimus reduced high glucose (16.7 mM)-induced insulin secretion (control 2.14 +/- 0.08 vs. tacrolimus 1.75 +/- 0.02 ng.islet(-1).30 min(-1), P < 0.01) without affecting insulin content. In dynamic experiments, insulin secretion and NAD(P)H fluorescence during a 20-min period after 10 min of high-glucose exposure were reduced in tacrolimus-treated islets. ATP content and glucose utilization of tacrolimus-treated islets in the presence of 16.7 mM glucose were less than in control (ATP content: control 9.69 +/- 0.99 vs. tacrolimus 6.52 +/- 0.40 pmol/islet, P < 0.01; glucose utilization: control 103.8 +/- 6.9 vs. tacrolimus 74.4 +/- 5.1 pmol.islet(-1).90 min(-1), P < 0.01). However, insulin release from tacrolimus-treated islets was similar to that from control islets in the presence of 16.7 mM alpha-ketoisocaproate, a mitochondrial fuel. Glucokinase activity, which determines glycolytic velocity, was reduced by tacrolimus treatment (control 65.3 +/- 3.4 vs. tacrolimus 49.9 +/- 2.8 pmol.islet(-1).60 min(-1), P < 0.01), whereas hexokinase activity was not affected. These results indicate that glucose-stimulated insulin release is decreased by chronic exposure to tacrolimus due to reduced ATP production and glycolysis derived from reduced glucokinase activity.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15479952&dopt=Abstract tacrolimus Protopic



Protopic
Graft expression of p38 and tumor necrosis factor-alpha in heart transplantation in rats.

Zhang X, Cao Y, Meng A, Bai Y.

Cardiothoracic Surgery, Department, Hebei Provincial People's Hospital, Shijiazhuang, China.

OBJECTIVES: To investigate the expression of p38 mitogen-activated protein kinase and its relationship with myocardial apoptosis and tumor necrosis factor-alpha during acute cardiac allograft rejection and to study the effects of tacrolimus on the expression of the kinase. METHODS: Rats were divided into 3 groups: isograft (Lewis heart to Lewis rat; control group), allograft (Brown Norway heart to Lewis rat), and tacrolimus-treated allograft (Brown Norway heart to tacrolimus-treated Lewis rat). Grafts were collected 1, 3, 5, and 7 days after transplantation for determination of histopathological features, apoptosis of cardiac cells (by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick labeling), number of cells positive for both p38 and CD8 (by laser scanning confocal imaging), and expression of the kinase (by Western immunoblotting) and tumor necrosis factor-alpha (by reverse-transcriptase polymerase chain reaction). RESULTS: Compared with isografts from the control group, grafts from the untreated allograft group had significantly more apoptotic cells, greater expression of tumor necrosis factor-alpha and p38 mitogen-activated protein kinase, and more CD8-p38 double-positive cells at 5 and 7 days (P < .05). The increases were prevented by treatment with tacrolimus. CONCLUSIONS: The findings that the number of apoptotic cells, the number of CD8-p38 double-positive cells, the expression of tumor necrosis factor-alpha and p38 mitogen-activated protein kinase all increased during the same period in the allografts in nonimmunosuppressed recipients suggests that intragraft expression of p38 would be associated with the rejection in acute cardiac allograft rejection. Tacrolimus may alleviate rejection partly by inhibiting p38 mitogen-activated protein kinase.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12593072&dopt=Abstract tacrolimus Protopic