Pharmacological inhibition of the acetyltransferase Tip60 mitigates myocardial infarction injury

Abstract

Pharmacologic strategies that target factors with both pro-apoptotic and anti-proliferative functions in cardiomyocytes (CMs) may be useful for the treatment of ischemic heart disease. One such multifunctional candidate for drug targeting is the acetyltransferase Tip60, which is known to acetylate both histone and non-histone protein targets that have been shown in cancer cells to promote apoptosis and to initiate the DNA damage response, thereby limiting cellular expansion. Using a murine model, we recently published findings demonstrating that CM-specific disruption of the Kat5 gene encoding Tip60 markedly protects against the damaging effects of myocardial infarction (MI). In the experiments described here, in lieu of genetic targeting, we administered TH1834, an experimental drug designed to specifically inhibit the acetyltransferase domain of Tip60. We report that, similar to the effect of disrupting the Kat5 gene, daily systemic administration of TH1834 beginning 3 days after induction of MI and continuing for 2 weeks of a 4-week timeline resulted in improved systolic function, reduced apoptosis and scarring, and increased activation of the CM cell cycle, effects accompanied by reduced expression of genes that promote apoptosis and inhibit the cell cycle and reduced levels of CMs exhibiting phosphorylated Atm. These results support the possibility that drugs that inhibit the acetyltransferase activity of Tip60 may be useful agents for the treatment of ischemic heart disease.

Evidence of Histone H2A.Z Deacetylation and Cardiomyocyte Dedifferentiation in Infarcted/Tip60-depleted Hearts

“…Here, as shown in Figure 1a, depletion of Tip60 ( Kat5 Δ/Δ ) in CMs of infarcted adult hearts resulted in the absence of acetylated histone H2A.Z, i.e, H2A.Zac K4/K7 , in nearly all CM nuclei. This was the most pronounced biochemical effect of Tip60 depletion that we have observed, in this as well as in our previous studies 10–12 . To verify that depletion of H2A.Zac K4/K7 was confined to CM nuclei, CM identity was con-firmed by immunostaining the nuclear marker Nkx2-5 (Supp.…”

“…The findings reported here indicating that genetic depletion of Tip60 nearly completely extinguishes acetylation of H2A.Zac K4/K7 in CM nuclei while inducing CM dedifferentiation, considered with our previous findings that Tip60 depletion in CMs beginning three days post-MI promotes CM cell-cycle activation, reduces apoptosis and scarring, and preserves cardiac function 10,11 --effects that are mimicked using drugs that inhibit Tip60's acetyltransferase (AT) domain (TH1834 in ref 12 ; pentamidine in an 'in preparation' manuscript) --warrant pharmaceutical targeting of this pleiotropic factor to ameliorate cardiac injury. Toward this end we are developing drugs that target Tip60's chromodomain because this moiety, which reportedly binds H3K4 me3 75, 76 , unlike the AT domain is unique with the ~20-member acetyltransferase family.…”

“…Resume: Recent findings in this laboratory have supported the hypothesis that genetic depletion 10,11 or pharmaceutical inhibition 12 of the pleiotropic acetyltransferase Tip60 (Kat5) confers cardioprotection and regeneration after myocardial infarction (MI) by preventing the site-specific acetylation and activation of targets that are pro-apoptotic (i.e., p53) and anti-proliferative (i.e., Atm). Here we report findings showing that depletion of Tip60 post-MI extinguishes acetylation of the histone variant H2A.Z in CMs, a chromatin target associated with induction and maintenance of the differentiated state in other cell types; we accordingly also show that reduced acetylation of H2A.Z is associated with CM dedifferentiation, a status considered pre-requisite for the ability of CMs to undergo cell-cycle reactivation and bona fide proliferation to effect myocardial regeneration 13-17, 22, 59-61 .…”

TIP60 is required for tumorigenesis in non‐small cell lung cancer

“…Last, to investigate the effects of TH1834 in vivo , we used xenograft mouse models injected with A549 cells. After tumors reached optimal volume (100–200 mm 3 ), we administered TH1834 at 10 mg/kg or vehicle intraperitoneally five times per week for 3 weeks 23 . Body weight remained unchanged by TH1834 treatment (Figure S8B).…”

“…After tumors reached optimal volume (100-200 mm 3 ), we administered TH1834 at 10 mg/kg or vehicle intraperitoneally five times per week for 3 weeks. 23 Body weight remained unchanged by TH1834 treatment (Figure S8B). TH1834 treatment significantly inhibited tumor growth in mice bearing A549 tumors relative to vehicle-treated mice (Figure 7G,H).…”