Abstract P4-09-10: Epigenetically altered microRNA mediated pathway dysregulation in ER negative breast cancer

Background: Micro RNAs (miRNA) are endogenous, small non-coding RNAs that control gene expression by directing their target mRNAs for degradation and/or posttranscriptional repression. Compared to mRNA signatures, miRNAs have better and stronger biomarker properties with 20 times more power in biomarker studies as compared to mRNAs (when comparing 20,000 mRNAs to ∼1,000 miRNAs). Emerging evidence now supports the idea that DNA methylation is crucially involved in the dysregulation of miRNAs in cancer, representing a novel class of potential biomarkers for diagnosis, prediction of treatment, or prognosis. ER-negative breast cancer (BC) is an aggressive histological subtype with limited treatment options and very poor prognosis. Our long term objective is to derive a diagnostic, prognostic, and predictive ER-negative specific miRNA panel for detection of early cancer, recurrence/metastasis, and as potential therapeutic targets for better management of ER-negative BC.

Methods: The initial discovery step profiled 39 primary ER negative and 40 ER positive BC cases using the Illumina Infinium HumanMethylation450 BeadChip followed by a subanalysis focusing on 2249 miRNA CpGs assigned to 615 unique miRNAs. T-tests were used to compare the means of the M-values for the ER-positive and ER-negative groups. The t-test p-values were used to generate adaptive FDR (aFDR) levels and aFDRs of 0.05 or lower were considered to be statistically significant (Tier 1). Tier 1 CpGs were subsequently filtered to select only those with a mean beta ratio between ER positive and ER negative of under 0.5 or over 2.0 (Tier 2). The Tier 2 CpGs were further filtered to select only those with a mean beta difference of 0.2 or more (Tier 3). Because miRNAs perform their important functions via their targets, the targets of miRNAs were assessed for functional enrichment analysis in IPA for biologic involvement.

Results: Over half of the miRNA CpGs (1224/2249, 54%) were differentially methylated between ER negative and ER positive BC with significant aFDR levels. The 1224 CpGs at Tier 1 were associated with 379 miRNAs; the 24 and 2 CpGs for Tiers 2 and 3 with 22 and 2 miRNAs, respectively. The 22 miRNA genes were assigned to 4621 targets using online databases that predict miRNA targets. The degree of confidence that a target gene is associated with a miRNA is characterized in these databases as either "experimentally observed", or just as "high" (predicted). Of these 4621 targets, 87 were designated as experimentally observed and were examined in IPA. Top pathways and networks designated by miRNA targets included the cell cycle G1/S checkpoint regulation canonical pathway, and the cell-to-cell interaction/cancer networks among others. MiRNA targets in top pathways and networks were circled back to their respective miRNAs revealing cooperatively mediated pathway dysregulation of ER negative BC.

Conclusion: Aberrantly methylated miRNAs showed perturbation of biologically significant pathways and networks, suggesting that miRNAs mediate pathway dysregulation in a coordinated manner, strengthening the case for utility of miRNAs as viable biomarkers in ER negative BC. Support: Komen Foundation: KG110218.

Citation Format: Worsham MJ, Chen KM, Datta I, Stephen JK, Chitale D, Divine G. Epigenetically altered microRNA mediated pathway dysregulation in ER negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-10.

POS0235 INTEGRATED SAFETY ANALYSIS UPDATE FOR FILGOTINIB (FIL) IN PATIENTS (PTS) WITH MODERATELY TO SEVERELY ACTIVE RHEUMATOID ARTHRITIS (RA) RECEIVING TREATMENT OVER A MEDIAN OF 2.2 YEARS (Y)

Background

The preferential Janus kinase-1 inhibitor FIL significantly improved signs and symptoms of RA in Phase 2 and 3 trials.1–5 FIL is approved for treatment of moderate to severe active RA in Europe and Japan. Integrated safety analysis of FIL with patient data through 2019 was presented at the 2020 ACR virtual meeting.6

Objectives

To report updated, as-treated data from the FIL integrated safety analysis with increased study drug exposure.

Methods

Data were integrated from 2 Phase 2 (NCT01668641, NCT01894516), 3 Phase 3 (NCT02889796, NCT02873936, NCT02886728), and 2 long-term extension (LTE) (NCT02065700, NCT03025308) trials. Phase 2 and 3 LTE data were through Nov 2020 and Jan 2021, respectively. The as-treated analysis set included all available data for pts receiving ≥1 dose FIL 200 (FIL200) or 100 mg (FIL100), including those rerandomized to FIL for LTE. Exposure-adjusted incidence rates (EAIR)/100 patient-y exposure (PYE) of treatment-emergent adverse events (TEAEs; onset after first dose and no later than 30 days after last dose or new drug first dose date −1 day) and TEAEs of special interest (AESIs) are presented.

Results

3691 pts received FIL200 or FIL100 for 8085.1 PYE (median 2.2, maximum 6.8 y). In the as-treated set, 61% of FIL200 and 45% of FIL100 pts received FIL for ≥2 y, 19% and 5% for ≥3 y, and 11% and 0.5% for ≥4.5 y, respectively. EAIR for TEAEs was higher with FIL100 than FIL200; EAIRs for deaths were 0.5 and 0.3 for FIL200 and FIL100 (Figure 1). Incidences of infections and serious infections were numerically greater for FIL100 vs FIL200, while EAIRs for other AESIs were comparable between doses (Table 1). EAIRs for AESIs tended to decrease since the previous update, except for venous thromboembolism (total FIL 0.1 to 0.2) and malignancies excluding NMSC (total FIL 0.5 to 0.6).

Table 1.

TEAEs of special interest, as-treated set

TEAE, n (%) and EAIR per 100 PYE (95% CI)FIL 200 mgn=2267PYE=5302.5FIL 100 mgn=1647PYE=2782.6Total FILN=3691PYE=8085.1Infectious AEs1206 (53.2)747 (45.4)1927 (52.2)EAIR21.1 (19.7, 22.5)30.2 (26.8, 34.0)21.0 (19.9, 22.3)Serious infectious AEs80 (3.5)57 (3.5)137 (3.7)EAIR1.5 (1.1, 1.9)2.7 (1.9, 3.9)1.6 (1.3, 2.0)Opportunistic infections5 (0.2)4 (0.2)9 (0.2)EAIR0.1 (0, 0.2)*0.1 (0.1, 0.4)*0.1 (0.1, 0.2)*Active tuberculosis03 (0.2)3 (<0.1)EAIR00.1 (0, 0.3)*0 (0, 0.1)*Herpes zoster84 (3.7)30 (1.8)114 (3.1)EAIR1.6 (1.2, 2.0)1.1 (0.8, 1.5)*1.4 (1.1, 1.7)Major adverse cardiovascular eventsa19 (0.8)14 (0.9)33 (0.9)EAIR0.3 (0.2, 0.5)0.5 (0.3, 0.8)*0.4 (0.2, 0.6)Venous thromboembolismb11 (0.5)4 (0.2)15 (0.4)EAIR0.2 (0.1, 0.4)*0.1 (0.1, 0.4)*0.2 (0.1, 0.3)*Atrial systemic thrombotic eventsa1 (<0.1)1 (<0.1)2 (<0.1)EAIR0 (0, 0.1)0 (0, 0.3)0 (0, 0.1)Malignancy excluding NMSC32 (1.4)17 (1.0)49 (1.3)EAIR0.6 (0.4, 0.9)0.6 (0.4, 1.0)*0.6 (0.4, 0.8)NMSC15 (0.7)5 (0.3)20 (0.5)EAIR0.3 (0.2, 0.5)*0.2 (0.1, 0.4)*0.2 (0.2, 0.4)*Gastrointestinal perforations3 (0.1)1 (<0.1)4 (0.1)EAIR0.1 (0, 0.2)*0 (0, 0.3)*0 (0, 0.1)*

*Except when any study had 0 event within the treatment, the Poisson model was not adjusted by study. PYE was defined as (last dose date − first dose date + 1)/365.25.

a

Positively adjudicated.

b

Adjudicated as deep vein thrombosis or pulmonary embolism.

NMSC, nonmelanoma skin cancer

Conclusion

With 1 additional year of exposure since the 2020 report, FIL continues to be well tolerated with no new safety concerns emerging. EAIRs of TEAEs, including deaths, and AESIs remained stable or decreased since the 2020 report, except for slight increases in rates of NMSC and malignancies excluding NMSC. In the context of demonstrated efficacy, both FIL doses had an acceptable risk/benefit profile.

References

[1]Westhovens R et al. Ann Rheum Dis 2017;76:998–1008.

[2]Kavanaugh A et al. Ann Rheum Dis 2017;76:1009–19.

[3]Combe B et al. Ann Rheum Dis 2021;80:848–58.

[4]Genovese MC et al. JAMA 2019;322:315–25.

[5]Westhovens R et al. Ann Rheum Dis 2021;80:727–38.

[6]Winthrop K et al. Arthritis Rheumatol 2020;72(suppl 10); abstract 0229.

Acknowledgements

Funding for DARWIN 1 and 2 was provided by Galapagos NV, and funding for DARWIN 3, FINCH 1, 2, 3, and 4 was provided by Gilead Sciences, Inc., Foster City, CA. Funding for this analysis was provided by Gilead Sciences, Inc. The sponsors participated in the planning, execution, and interpretation of the research. Medical writing support was provided by Gregory Bezkorovainy, MA, of AlphaScientia, LLC, San Francisco, CA; and funded by Gilead Sciences, Inc., Foster City, CA.

Disclosure of Interests

Kevin Winthrop Consultant of: AbbVie, Bristol-Myers Squibb, Eli Lilly and Co., Galapagos NV, Gilead Sciences, Inc., GlaxoSmithKline, Pfizer, Roche, Regeneron, Sanofi, and UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, and Pfizer, Yoshiya Tanaka Speakers bureau: Daiichi-Sankyo, Eli Lilly, Novartis, YL Biologics, Bristol Myers Squibb, Eisai, Chugai, AbbVie, Astellas, Pfizer, Sanofi, Asahi-Kasei, GSK, Mitsubishi-Tanabe, Gilead Sciences, Inc., and Janssen, Consultant of: AbbVie, Ayumi, Daiichi-Sankyo, Eli Lilly, GSK, Taisho, and Sanofi, Grant/research support from: AbbVie, Asahi-Kasei, Chugai, Daiichi-Sankyo, Eisai, Mitsubishi-Tanabe, and Takeda, Tsutomu Takeuchi Speakers bureau: AbbVie, AYUMI, Bristol Myers Squibb, Chugai, Daiichi Sankyo, Dainippon Sumitomo, Eisai, Eli Lilly Japan, Gilead Sciences, Inc., Mitsubishi-Tanabe, Novartis, Pfizer Japan, and Sanofi, Consultant of: Astellas, Chugai, and Eli Lilly Japan, Grant/research support from: AbbVie, Asahi Kasei, Astellas, Chugai, Daiichi Sankyo, Eisai, Mitsubishi-Tanabe, Shionogi, Takeda, and UCB Japan, Alan Kivitz Shareholder of: Amgen, Gilead Sciences, Inc., GlaxoSmithKline, Pfizer, and Sanofi, Speakers bureau: AbbVie, Celgene, Flexion, Genzyme, Horizon, Merck, Novartis, Pfizer, Regeneron, and Sanofi, Paid instructor for: Celgene, Genzyme, Horizon, Merck, Novartis, Pfizer, Regeneron, and Sanofi, Consultant of: AbbVie, Boehringer Ingelheim, Flexion, Genzyme, Gilead Sciences, Inc., Janssen, Novartis, Pfizer, Regeneron, Sanofi, and SUN Pharma Advanced Research, Mark C. Genovese Shareholder of: Gilead Sciences, Inc., Consultant of: AbbVie, Amgen, Beigene, Eli Lilly and Co., Genentech, Inc., Gilead Sciences, Inc., Sanofi Genzyme, RPharm, and SetPoint, Employee of: Gilead Sciences, Inc., Alena Pechonkina Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Franziska Matzkies Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Beatrix Bartok Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Kun Chen Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Deyuan Jiang Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Iyabode Tiamiyu Shareholder of: Gilead Sciences, Inc., Employee of: Gilead Sciences, Inc., Robin Besuyen Shareholder of: Galapagos BV, Employee of: Galapagos BV, Sander Strengholt Shareholder of: Galapagos BV, Employee of: Galapagos BV, Gerd Rüdiger Burmester Speakers bureau: AbbVie, Eli Lilly and Co., Galapagos, Gilead Sciences, Inc., and Pfizer, Consultant of: AbbVie, Eli Lilly and Co., Galapagos, Gilead Sciences, Inc., and Pfizer, Jacques-Eric Gottenberg Speakers bureau: AbbVie, Eli Lilly and Co., Galapagos BV, Gilead Sciences, Inc., Roche, Sanofi Genzyme, and UCB, Consultant of: Bristol Myers Squibb, Sanofi Genzyme, and UCB, Grant/research support from: Bristol Myers Squibb and Pfizer

Nitric oxide induces heme oxygenase-1 via mitogen-activated protein kinases ERK and p38

Heme oxygenase-1 (HO), the heat shock/stress cognate of the heat shock protein 32 (HSP32) family of proteins, is postulated to be a component of cellular defense mechanisms against oxidative stress-mediated injury. Nitric oxide (NO) is among the extensive array of stimuli that induce HO-1. The cellular signaling mechanisms that regulate the induction of HO-1 by NO are not understood. In the present study, we have demonstrated that exposure of HeLa cells to the NO donor, sodium nitroprusside (SNP), results in concentration and time-dependent increase in HO-1 mRNA and activation of MAPKs: ERK (ERK1 and ERK2) and p38 pathways, but not SAPK/JNK pathway. Pre-treatment of the cells with PD98059, a selective ERK pathway inhibitor, and SB203580, a p38 MAPK inhibitor, blocked the induction of HO-1 by the NO donor in a dose-dependent manner. In addition, an increase in HO-1 mRNA level that was detected as early as 2 hrs.following SNP treatment preceded c-jun and c-fos induction. These transcription factors are downstream of SAPK/JNK pathway, and their increased expression was detected at 3hr. and 6hr. after SNP treatment. Similarly, AP-1 DNA binding activity was not increased when measured 6 hrs. after SNP treatment. ERK and p38 inhibitors also suppressed induction of HO-1 by SNAP and GSNO. The increase in HO-1 mRNA was inhibited by actinomycin D and cycloheximide, but not by NAC, and was not mimicked by the lipophilic cGMP analogue, 8-bromo-cGMP, suggesting that NO-mediated induction required de novo RNA and protein synthesis and was unrelated to cGMP and redox signaling. Collectively, the findings suggest that MAP kinase ERK and p38 pathways are involved in the NO-mediated induction of HO-1 and that SAPK/JNK pathway and increased DNA binding of AP-1 transcription factor are not involved in HO-1 gene activation by NO. A plausible mechanism by which the NO donors cause HO-1 induction may involve HO-1 gene regulation by its substrate, heme.

Glutathione antagonized cyclophosphamide- and acrolein-induced cytotoxicity of PC3 cells and immunosuppressive actions in mice

AIM

To study the antagonistic effect of glutathione (GSH) on toxicity of PC3 cell induced by cyclophosphamide (Cyc) and acrolein (Acr) and on immunosuppressive actions caused by Cyc.

METHODS

Splenocyte, PC3 cell proliferation and cell protein content were measured by tetrazolium (MTT) assay and Coomassie brilliant blue assay. Serum anti-SRBC hemolysin, agglutinin, and splenocyte proliferation were measured in normal and S-180-bearing mice. Tumors were weighed.

RESULTS

Pretreatment with GSH 2 mmol.L-1 reduced splenocyte proliferation inhibition from 18.64%, 49.72% to 6.78%, 18.36% (induced by Cyc 1, and 5 mmol.L-1), and PC3 cell proliferation inhibition from 27.7%, 45.3%, and 74.6% to 14.6%, 18.8%, and 49.1% (induced by Cyc 1, 3, and 5 mmol.L-1), and from 62.6%, 85.4%, and 90.6% to 41.9%, 57.7%, and 86.4% (induced by Acr 10, 25, and 50 mumol.L-1), respectively. In normal mice, s.c. GSH 75 or 150 mg.kg-1 b.i.d. x 5 d after i.p. Cyc 40 mg.kg-1, the hemolysin and the splenocyte proliferation were higher than those in normal mice i.p. Cyc 40 mg.kg-1 alone. Hemolysin, serum agglutinin, and splenocyte proliferation in S-180-bearing mice given s.c. GSH 150 mg.kg-1 b.i.d. x 10 d after i.p. Cyc 40 mg.kg-1 were also markedly higher than those in S-180-bearing mice given i.p. Cyc alone. But, according to tumor weight, GSH did not interfere the antitumor activity of Cyc in S-180-bearing mice.

CONCLUSION

GSH exhibited protective effects against Cyc and Acr, but had no effect on the antitumor action of Cyc.

Expression of NOS II and its role in experimental small bowel ulceration in rats

BACKGROUND

Overproduction of nitric oxide (NO) has been implicated in the pathogenesis of experimental and clinical inflammatory bowel disease (IBD).

METHODS

We observed the expression and localization of inducible NO synthase (NOS-II) in small intestinal ulceration induced by indomethacin in rats. The role of NO was investigated by using NO synthase inhibitors.

RESULTS

The small intestine was affected by longitudinal ulcers after indomethacin administration and ulceration was associated with distinctive expression of NOS-II protein and mRNA. The amount of its expression was found to correlate with the extent of inflammation. Histologically, both immunohistochemistry and in situ hybridization revealed a similar localization of NOS-II to inflammatory and epithelial cells. The possible amelioration of the inflammation was modulated by aminoguanidine (AG) and NG-nitro-L-arginine methyl ester (L-NAME) treatment for 10 days. Both AG and L-NAME attenuated intestinal myeloperoxidase activity and gross inflammation, only AG was found to decrease intestinal permeability with a significant amelioration of body weight loss.

CONCLUSION

These findings indicate that NO derived mainly from inflammatory cells may play an important role in the pathophysiology of intestinal ulceration and offer the potential for future treatment directed at blocking neutrophils recruitment and NO overproduction in IBD.

[A molecular and epidemiology study in patients with ventilator-associated pneumonia]

OBJECTIVE

To evaluate causative agents in patients with ventilator-associated (VA) pneumonia epidemiologically, then to provide useful suggestion for diagnosis and treatment of VA pneumonia.

METHOD

Prospectively, a protected specimens brush was used to obtain the secretion of lower respiratory tract of 65 patients, who had been receiving mechanical ventilation or tracheostomy for more than 72 hours. At the same time, other samples were collected from the relevant places, including pharyngeal and gastric juice of patients as well as other persons, ward's air. The secretion obtained were cultured with a quantitative method. Then all bacteria isolated were studied with the analysis of pattern of plasmids and chromosomal restriction endonuclease.

RESULT

It was showed that the route of infection of the Gram-negative bacilli in VA pneumonia (19 cases) was intrinsic, a retrograde colonization from patient's stomach, that was the pattern of clonization from stomach to pharynx, then into lower respiratory tract, and the Gram-positive staphylococcus spread mainly through the ward's air, then directly into lower respiratory tract, or extrinsic (20 cases).

CONCLUSION

The Gram-positive staphylococcus is also major disease-producing germs in VA pneumonia, and the infection routes of G+ and G- bacteria might be different.

[Clinical study of physiological age in accordance with the integration of traditional Chinese and Western medicine]

OBJECTIVE

TCM and western geriatric medical principles were used to study the assessment of aging in mankind.

METHODS

The authors studied and examined 387 healthy subjects ranging from 45 to 69 years of age. Its indices included 24 TCM senility syndromes, 5 western medical neurophysiological indices. Thereafter, regression analysis was used to deduce a TCM-WM aging formula.

RESULTS

Data from all clinical subjects were processed using integrated TCM-WM, physiological age formula to determine the physiological ages (Y) and their corresponding calendar ages (y). The mean values of the age differential of zero, and a standard deviation of 2.29 years were calculated. From statistical view point, a 95 percentage is an acceptable normal value range. Also, as the objective of the aging assessment only used the higher end of the range. I.E., it is considered there is excessive aging when physiological age is higher than calendar age by 3.37 years. In the process of conducting regression analysis, the authors also discovered that LPO can increase TCM senility syndrome score, whereas CuZnSOD decrease it.

CONCLUSIONS

The above clinical study showed that the regression analysis and age-related TCM indices can comprehensively reflect the natural process of aging in mankind. It also demonstrated the highly predictive nature of TCM senility syndrome score.

[Erythroid differentiation denucleation factor: a family of erythroid regulators for mammalian erythroid terminal differentiation/tumor suppression and the cloning of their related genes]

The role of regulation of erythroid differentiation denucleation factor(EDDF) on mammalian erythroid differentiation and myeloma cell malignancy as well as cloning of their stage related genes were serially studied. Through a series of cybrid and hybridization experiments between mammalian erythroid cells and erythroleukemia or non-erythroid myeloma cells, we have demonstrated a novel family of erythroid regulators(EDDFs) in the mammalian differentiating erythroblasts which with an active peak occurred concomitantly with marked decreases in DNA, RNA and the nuclear anchoring vimentin-IF, but increased in hemoglobin synthesis in cytoplasm prior to the denucleation process during terminal differentiation. The results of cell fusion experiments verified that the supplement of regulators(EDDFs) was critical to the recovery of the originally lost features of terminal differentiation and the reversion of malignant phenotype of tumor cells. Here we showed that the erythroid regulator family EDDFs were essential regulators for the sequential expression of stage related genes of erythroid terminal differentiation, and for the redifferentiation of tumor cells to express the originally inactive globe genes, repressed the oncogenes, and vimentin-IF system, thus initiated nuclear condensation and denucleation. The EDDF gene family consisted of MEDDF, HEDDF-1, HEDRF-1, HEDRF-2 and HCNBP-1 were cloned. All were novel cDNA sequences that have been searched and registered in GenBank. They expressed varying in a stage specific manner, and acted on corresponding genes of terminal differentiation.

[The thumb reconstruction by transferring the injured index finger with pedicles]

OBJECTIVE

In order to inquire the methods of thumb reconstruction by transferring the index finger with incomplete conditions of nerve or blood vessels.

METHODS

From April 1987 to October 1997, 6 cases were treated by 3 kinds of operative methods according to the damage type of thumb and complications injures of the rest of hand: 1. transferring the index finger with pedicle without proximal phalanx, 2. transferring the index finger with palmar nerve and blood vessels, and dorsal skin pedicle, 3. transferring the index finger with compound pedicle.

RESULTS

All 6 cases of thumb reconstruction were successful. Followed up 6 months to 2 years, the pinching and gribing functions in 6 cases were completely recovered, and the sensation were partly recovered.

CONCLUSION

The operative method of thumb reconstruction had following advantages: Simple operation, high survival rate and certain function recovery. It can enlarge the indications of thumb reconstruction.

[Study on chemical constituents of essential oil of Michelia leaves by gas chromatography-mass spectrometry]

The essential oil in Michelia leaves was extracted by steam distillation. The oil obtained was dried with anhydrous magnesium sulfate. The chemical constituents were analyzed by GC-MS. Thirty three peaks were separated by GC, and 27 of them were identified by MS with NBS mass spectral data and Wiley/NBS registry of mass spectral data. The structure of linalool was further verified by GC/FTIR. The identified constituents represent 97% of the peak area of the essential oil on FID. The major chemical constituent of them are linalool, trans-caryophyllene and diethyl-o-phthalate.

[Synergic effects on primary hepatocellular cancer between history of hepatitis B, family histories of cancers and psychosocial factors]

To study the risk factors of primary hepatocellular cancer (PHC) and their interactions, a case-control study with calculated odds ratios(OR) and synergy effects index(SI) was conducted. The history of hepatitis B, family histories of cancers and psychosocial factors were main risk factors of PHC, and their effects were positive and synergic. The SI between hepatitis B and family histories of cancers, psychosocial factors are 1.65 and 1.16 respectively.

[Metallothionein involvement in the delayed protection after ischemic or anoxic preconditioning in myocardium or cultured cardiomyocytes]

OBJECTIVE

To study whether metallothionein (MT) is an OH scavenger and plays a protective role in cardiac ischemic/reperfusion injury. MT involves in the delayed protection 24 hr after preconditioning (PC).

METHODS

MT contents in myocardium or cultured cardiomyocytes are assayed at the 0 hr, 12 hr, and 24 hr after PC on the model of rabbit heart in situ or that of the cultured cardiomyocytes. The myocardial infarct size, LDH release, cell viability, and the content of cellular MDA were measured with or without the intervention of PD098059, the inhibitor of mitogen-activated protein kinase in the models before PC and different time intervals after PC.

RESULTS

The MT contents were increased significantly at 2 hr (1406.2 +/- 112.2 vs 129.9 +/- 10.4 pmol/mg Pr., P < 0.01, in cardiomyocytes) and 24 hr (1032.7 +/- 199.1 vs 129.9 +/- 10.4 pmol/mg Pr., P < 0.01, in cardiomyocytes; 62.1 +/- 12.6 vs 27.2 +/- 3.7 pmol/mg Pr., P < 0.01, in myocardium) after PC compared with those in normal group. The infarct sizes (13.2 +/- 3.6% vs 32.3 +/- 5.7%, P < 0.05) and the rise of LDH release in plasma (1944 +/- 256 vs 2826 +/- 239 IU/L, P < 0.05) were greatly decreased in preconditioned myocardium after a long time ischemia-reperfusion than those in the unpreconditioned. Compared with the cardiomyocytes unconditioned, the number of viable cell (71.0 +/- 1.6 vs 48.2 +/- 2.2%, P < 0.01) was greatly increased, the cellular MDA contents (33.5 +/- 12.8 vs 103.5 +/- 15.0 nmol/mg Pr., P < 0.01) and the LDH release (850.0 +/- 139.1 vs 1552.0 +/- 102.6 IU/L, P < 0.01) were dramatically decreased in preconditioned ones. All the delayed protection at 24 hr after PC were completely disappeared with the inhibition of MT's production with PD098059 (P > 0.05).

CONCLUSION

The myocardium or cardiomyocytes at 24 hr after PC are offered more capacity to tolerate the I/R damage, and MT involves in the delayed protection.