Pretreatment of therapeutic cells with poly(ADP-ribose) polymerase inhibitor enhances their efficacy in an in vitro model of cell-based therapy in myocardial infarct

Inhibition of GSDMD Activates Poly(ADP-ribosyl)ation and Promotes Myocardial Ischemia-Reperfusion Injury

The precise control of cardiomyocyte viability is imperative to combat myocardial ischemia-reperfusion injury (I/R), in which apoptosis and pyroptosis putatively contribute to the process. Recent researches indicated that GSDMD is involved in I/R as an executive protein of pyroptosis. However, its effect on other forms of cell death is unclear. We identified that GSDMD and GSDMD-N levels were significantly upregulated in the I/R myocardium of mice. Knockout of GSDMD conferred the resistance of the hearts to reperfusion injury in the acute phase of I/R but aggravated reperfusion injury in the chronic phase of I/R. Mechanistically, GSDMD deficiency induced the activation of PARylation and the consumption of NAD+ and ATP, leading to cardiomyocyte apoptosis. Moreover, PJ34, a putative PARP-1 inhibitor, reduced the myocardial injury caused by GSDMD deficiency. Our results reveal a novel action modality of GSDMD in the regulation of cardiomyocyte death; inhibition of GSDMD activates PARylation, suggesting the multidirectional role of GSDMD in I/R and providing a new theory for clinical treatment.

Specific protein 1 inhibitor mithramycin A protects cardiomyocytes from myocardial infarction via interacting with PARP

Specific protein 1 (SP1) might act as a critical transcription regulator in myocardial infarction (MI), but little evidence about its function in regulating cardiac apoptosis, a major cause of MI development, has been revealed. This study tried to investigate the role of SP1 in MI and its interaction with poly-ADP-ribose polymerase (PARP)-1 by using SP1 inhibitor, mithramycin A (mithA). Primary mouse cardiomyocytes and commercial mouse cardiomyocytes were subjected to mithA treatment under hypoxia conditions, while cell viability, Nix promoter activity, and its expression were detected correspondingly. PARP overexpression and knockdown were conducted, respectively, in mithA-treated and SP1-overexpressing cells. Co-immunoprecipitation was used to verify the interaction between PARP and SP1. For in vivo experiments, mithA administration was performed after the injections of adenovirus for PARP overexpression, and then, MI introduction was carried out. Infarct size and lactate dehydrogenase level were measured to assess MI injury. SP1 inhibitor mithA attenuated hypoxia-induced decrease of cell viability and Nix transcriptional activation, which could be inhibited by PARP overexpression. Knockdown of PARP prevented SP1-induced transcription of Nix and cell viability change, and PARP showed direct interaction with SP1. Furthermore, mithA administration reduced MI injuries, while PARP overexpression could suppress the improvement. The cardioprotective role of SP1 inhibitor mithA was demonstrated here expanding the role of SP1 in MI development involving hypoxia-induced cardiac apoptosis. Moreover, PARP acted as a transcriptional coactivator in Nix transcription involving its interaction with SP1.

Another "string to the bow" of PJ34, a potent poly(ADP-Ribose)polymerase inhibitor: an antiplatelet effect through P2Y12 antagonism?

Background

Neuro- and vasoprotective effects of poly(ADP-ribose)polymerase (PARP) inhibition have been largely documented in models of cerebral ischemia, particularly with the potent PARP inhibitor PJ34. Furthermore, after ischemic stroke, physicians are faced with incomplete tissue reperfusion and reocclusion, in which platelet activation/aggregation plays a key role. Data suggest that certain PARP inhibitors could act as antiplatelet agents. In that context, the present in vitro study investigated on human blood the potential antiplatelet effect of PJ34 and two structurally different PARP inhibitors, DPQ and INO-1001.

Methods and results

ADP concentrations were chosen to induce a biphasic aggregation curve resulting from the successive activation of both its receptors P2Y₁ and P2Y₁₂. In these experimental conditions, PJ34 inhibited the second phase of aggregation; this effect was reduced by incremental ADP concentrations. In addition, in line with a P2Y₁₂ pathway inhibitory effect, PJ34 inhibited the dephosphorylation of the vasodilator stimulated phosphoprotein (VASP) in a concentration-dependent manner. Besides, PJ34 had no effect on platelet aggregation induced by collagen or PAR1 activating peptide, used at concentrations inducing a strong activation independent on secreted ADP. By contrast, DPQ and INO-1001 were devoid of any effect whatever the platelet agonist used.

Conclusions

We showed that, in addition to its already demonstrated beneficial effects in in vivo models of cerebral ischemia, the potent PARP inhibitor PJ34 exerts in vitro an antiplatelet effect. Moreover, this is the first study to report that PJ34 could act via a competitive P2Y₁₂ antagonism. Thus, this antiplatelet effect could improve post-stroke reperfusion and/or prevent reocclusion, which reinforces the interest of this drug for stroke treatment.

Comparison of the direct effects of human adipose- and bone-marrow-derived stem cells on postischemic cardiomyoblasts in an in vitro simulated ischemia-reperfusion model

Regenerative therapies hold a promising and exciting future for the cure of yet untreatable diseases, and mesenchymal stem cells are in the forefront of this approach. However, the relative efficacy and the mechanism of action of different types of mesenchymal stem cells are still incompletely understood. We aimed to evaluate the effects of human adipose- (hASC) and bone-marrow-derived stem cells (hBMSCs) and adipose-derived stem cell conditioned media (ACM) on the viability of cardiomyoblasts in an in vitro ischemia-reperfusion (I-R) model. Flow cytometric viability analysis revealed that both cell treatments led to similarly increased percentages of living cells, while treatment with ACM did not (I-R model: 12.13 ± 0.75%; hASC: 24.66 ± 2.49%; hBMSC: 25.41 ± 1.99%; ACM: 13.94 ± 1.44%). Metabolic activity measurement (I-R model: 0.065 ± 0.033; hASC: 0.652 ± 0.089; hBMSC: 0.607 ± 0.059; ACM: 0.225 ± 0.013; arbitrary units) and lactate dehydrogenase assay (I-R model: 0.225 ± 0.006; hASC: 0.148 ± 0.005; hBMSC: 0.146 ± 0.004; ACM: 0.208 ± 0.009; arbitrary units) confirmed the flow cytometric results while also indicated a slight beneficial effect of ACM. Our results highlight that mesenchymal stem cells have the same efficacy when used directly on postischemic cells, and differences found between them in preclinical and clinical investigations are rather related to other possible causes such as their immunomodulatory or angiogenic properties.