Molecular mechanisms of liver ischemia reperfusion injury: Insights from transgenic knockout models

Table 1 Suzuki classification of liver ischaemia reperfusion injury

Numerical assessment	Sinusoidal congestion	Vacuolisation/ballooning	Necrosis
0	None	None	None
1	Minimal	Minimal	Single cell
2	Mild	Mile	< 30%
3	Moderate	Moderate	30%-60%
4	Severe	Severe	> 60%

Table 2 Summary of knockout models of liver ischemia reperfusion injury pertaining to reactive oxygen species, cellular metabolism/adenosine and cells involved in the injurious mechanisms

Ref.	Knockout model	IR protocol	Outcome measure	Agent	Adaptive responses	Injurious responses
Kuboki et al[29]	OTII; TCRd deficient	70% I 90 min/R 4, 8 h	Histology; serum ALT; MPO	AntiCD1d Ab; anti NK1.1 Ab; anti CD25+ Ab		Antigen dependent CD4+ T cell activation via TCR and NKT cell activation increase IRI; GD T cell recruit PMN but not affect IRI
Evans et al[2]	ob/ob or double knockout of leptin and UCP2	Total hepatic ischaemia 15 min/R 1, 24 h	Histology (Neil and Hubscher scoring); serum ALT; WB; liver ATP assay; lipid peroxidation; 24 h survival			In steatotic livers of ob/ob mice only, UCP-2 depletes liver ATP which increases IRI 1 h onwards
Hanschen et al[12]	IL6 (-/-); CD4 (-/-); TNFR1 (-/-)	Left lobe I 90 min/R 30 min, 2, 3, 4 h	Kupffer cell activity (fluorescent latex beads and intravital microscopy, IVM); IH; serum AST and ALT	GdCl3 or glutathione to wild types (WT) only		Kupffer cells activation, ROS, IL6 and TNF-α increase SEC VAP-1 expression and CD4+ Tcell sinusoidal recruitment which increase IRI; CD4+ T cells inhibit Kupffer cell phagocytic activity
Kim et al	Adenosine A1 receptor (A1AR) (-/-)	70% I 1 h/R 24 h	Histology; serum ALT; IH; semiquantitative PCR; WB; TUNEL	CCPA (AIAR agonist); DPCPX (A1AR antagonist)	Endogenous adenosine via A1AR reduces IRI	Exogenous adenosine increase IRI most likely via a different adenosine receptor subtype to A1AR
Ben-Ari et al[18]	Bax (-/-); Bax (+/-)	Isolated liver perfused in environmental chamber: Global I 90 min/R 1 or 15 min	Histology (apoptosis features); serum ALT, AST, LDH; TUNEL and caspase-3 assay; WB			Bax activation after 15 min reperfusion activates caspase-3 which increases liver apoptosis
Lappas et al[30]	Rag1 (-/-), i.e., lack mature lymphocytes A2AR (-/-); IFNγ (-/-)	70% I 72 min/R 2, 24 h	Histology; serum ALT; intracellular IFNγ	ip ATL146 (A2AR agonist); PK136 (NK1.1 depletion); CD1d Ab (inhibit NKT cell); NKT cell adoptive transfer from WT, A2AR and IFNγ KO to Rag1 KO	Exogenous and endogenous adenosine acts through A2AR to reduce NKT cell recruitment	NKT cell recruitment increases IRI through release of IFNγ from at least 2 h reperfusion onwards and increased neutrophil recruitment from at least 24 h after reperfusion
Shimamura et al[25]	Cd1d (-/-); nu/nu (no NKT cell, normal NK cells); perforin (-/-); gld/gld (Fas ligand deficient)	Total hepatic ischaemia 30 min/R 2 ,6, 12, 24, 48 h	Serum ALT; peroxide assay; cytotoxic assay; IH; ELISA	Anti-NK and anti-NKT Ab		NKT cell activation 1 to 24 h after reperfusion releases IFNγ and PMN activation 6 to 12 h after reperfusion with increased oxidative burst lead to increased apoptosis and necrosis in IRI
Caldwell et al[28]	CD4 (-/-); B cell (-/-)	70% I 90 min/R 1, 2, 4, 8 h	Histology; serum ALT; MPO	Adoptive transfer CD4+T cell to CD4(-/-); anti-IL17 Ab	CD4+ T cell only 1-4 h after reperfusion secrete IL17 releasing MIP-2 increasing neutrophil infiltration, but inhibiting their oxidative burst, and reducing necrosis 8 h reperfusion onwards
Baskin-Bey et al	Cathepsin B (-/-)	Two weeks fed methionine choline deficient (MCD) diet to induce steatosis; liver stored 24 h 4  °C UWS then perfused in isolated apparatus at 37  °C for 1 h	Histology; electron microscopy (EM); TUNEL; IH; liver tissue ALT and LDH	R-3032 ip 2 h preop (cathepsin B inhibitor)		Reduced lysosomal integrity more pronounced in steatotic livers with increased cathepsin B release into cytosol associated with increased apoptosis and necrosis
Khandoga et al[22]	ICAM (-/-)	Left lobe I 90 min/R 20 min	Serum AST and ALT; IH; caspase-3 assay; lipid peroxidation assay; IVM	Anti-fibronectin Ab		Platelets bind fibronectin deposited on ICAM-1 expressed on SECs, associated with reduced sinusoidal perfusion, increased lipid peroxidation and apoptosis
Shen et al[33]	nu/nu; CD154 (-/-)	70% I 90 min/R 4 h	Serum ALT; histology; MPO; WB	Anti-CD154 Ab to WT; adoptive transfer spleen lymphocytes into KO or Ab treated group	IRI induces HO-1 protein	CD4-CD154 T cell costimulation is associated with increased IRI
Wyllie et al[69]	Natural resistance associated macrophage protein 1 (Nramp) (-/-)	70%I 45 min/R 30, 60 min	Plasma GOT and TNF-α; histology; WB; Northern Blot; IH; EMSA (NFκβ)		HO-1 expressed in this model is protective in IRI	Macrophage activation after reperfusion increases TNF-α release and NFκβ activity which increases IRI
Young et al[21]	P-selectin/ ICAM-1 double KO	70% I 90 min/R 1.5, 3, 6 h	Serum ALT; histology			P-selectin and ICAM-1 do affect the severity of IRI up to 6 h reperfusion in this model, although PMN infiltration is slightly increased in midzonal area
Ozaki et al[13]	gp91 phox component of phagocyte NADPH oxidase (-/-)	70% I 60 min/R 5, 8, 24 h +/- iv injection 3 d preop of adenovirus	Serum GOT; histology (HE; ELISA for DNA histone fragments); TUNEL; IH; WB; assays for lipid peroxidation, hydrogen peroxide and superoxide; EMSA (NFκβ)	Replication deficient adenovirus encoding Rac1 (control: Adβgal)	Rac1 is activated in IRI and is protective	Liver tissue releases ROS within 5 min of reperfusion and PMN from 8 h onwards, associated with increased lipid peroxidation, apoptosis and necrosis. NFκβ DNA binding is associated with increased IRI; NADPH oxidase regulated by Rac1 small GTP binding protein is a source of ROS in IRI
Sawaya et al[19]	P-selectin (-/-)	Left lobe I 30 min/R 15, 30, 60, 120 min	Serum AST, ALT, LDH; histology; IVM in terminal hepatic venule (THV)	Radiolabelled anti P-selectin Ab		P selectin expression on SECs increases rolling, saltating and adherent leucocytes in THV peaking at 30 min reperfusion
Singh et al[20]	P-selectin (-/-)	Left lobe I 30 min/R 20 min, 2, 5, 12, 24 h	Serum AST, ALT, LDH; histology; WB	Radiolabelled anti P-selectin Ab		P-selectin expression peaks at 20 min and 5 h after reperfusion and is associated with worse IRI

KO: Transgenic knockout; I: Ischemia; R: Reperfusion; IR: Ischemia reperfusion; IRI: Ischemia reperfusion injury; ROS: Reactive oxygen species; ATP: Adenosine triphosphate; IH: Immunohistochemistry; HE: Hematoxylin and eosin; WB: Western blotting; MPO: Myeloperoxidase assay; PCR: Polymerase chain reaction; ELISA: Enzyme labelled immunosorbent assay; EMSA: Electrophoretic mobility shift assay; AST: Aspartate transaminase; ALT: Alanine transaminase; LDH; Lactate dehydrogenase; GOT: Glutamic oxaloacetic transaminase; NADPH; Nicotinamide adenine dinucleotide phosphate; IR: Ischemia reperfusion; IVM: Intravital microscopy; A2AR: Adenosine (subtype 2A) receptor; PMN: Polymorphonuclear cell; NKT: Natural killer T cell; NK: Natural killer cell; IFN: Interferon; Ab: Antibody; TNF: Tumour necrosis factor; TNFR1: Tumour necrosis factor receptor (subtype 1); TCR: T cell receptor; TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling (assay for cell death); IL: Interleukin; ICAM: Intercellular adhesion molecule; VAP: Vascular adhesion protein.

Table 3 Cytokine, chemokine, tolllike receptor, complement knockout models of liver ischemia reperfusion injury

Ref.	Knockout model	IR protocol	Outcome measure	Agent	Adaptive responses	Injurious responses
Kuboki et al[26]	CXCR2	70% I 90 min/R 12, 24, 48, 96 h	Histology; MPO; serum ALT, TNF-α, IL6; WB and NFκβ activity		CXCR2 activates STAT3 hepatocyte proproliferative pathway	MIP2 activates CXCR2 which increases neutrophil recruitment and IRI. Nuclear factor (NF) κβ activity reduced in IRI
Zhai et al[44]	IFNAR type1 (-/-); IFNAR type 2 (-/-)	70% I 90 min/R 6 h	Histology; quantitative PCR			IFNβ (not IFNγ) mediates IRI by binding to IFNAR type 1
Zhao et al	CXCL10 (-/-)	70% I 90 min/R 1, 2, 4, 8 h	Histology; serum ALT; IH; quantitative PCR; WB			CXCL10 activation increases TNF-α, IL6, IL1b, iNOS, MIP-2 mRNA and PMN and Kupffer cell activation contributes to IRI
Fondevilla et al	C6 deficient rats	Donor/recipient: WT/WT, KO/WT, WT/KO, KO/KO;	Serum GOT; histology; MPO; IH; TUNEL; WB; PCR; ELISA			Membrane attack complex (C5b-C9) activation in this OLT model of cold/warm IRI increases apoptosis, necrosis, PMN and macrophage infiltration and TNF-α, IFNγ and IFNβ expression
		OLT and organ storage 24 h 4  °C UWS
Shen et al[32]	Toll like receptor 4 (TLR4) (-/-)	Donor/recipient: WT/WT, KO/WTWT/KO, KO/KO; OLT with dearterialisation, organ stored 24 h 4  °C UWS	Histology; IH; MPO; quantitative PCR; capsase-3 activity; WB		TLR4 activation increases IL4 and IL10, but inhibits HO-1	TLR4 activation increases TNF-α, IL1b, IL2, IFNγ, ICAM1, CXCL10, PMN and CD4+ T cell recruitment leading to increased liver necrosis and apoptosis
Conzelmann et al	TNFR (-/-)	Donor/recipient: WT/WT, KO/WTWT/KO, KO/KO; organ storage 12 h 4  °C UWS; 8 h graft harvest	Histology; serum ALT; MPO; TUNEL and caspase-3 assay; IH		TNFR within liver mediates reduced IRI	TNFR outside liver increases IRI in terms of necrosis, apoptosis and neutrophil infiltration
Tsung et al[37]	Interferon regulatory factor-1 (IRF-1) (-/-)	70% I 60 min/R 1, 3, 6, 12 h	Histology; serum ALT; WB; PCR	Adenovirus IRF-1 vector		IFNγ, IFNβ, TNF-α, IL1β all activate IRF-1 which increase JNK (not p38 MAPK) and TNF-α and iNOS expression in IRI
Tian et al[40]	TNFR1 (-/-); IL6 (-/-)	Donor/recipient: WT/WT, KO/WT, WT/KO, KO/KO; OLT: 50% or small for size 30% arterialised graft	Histology; serum AST; portal flow measurement; IVM; IH; PCR; 30 d mortality	GdCl3 (ip to donor); pentoxifylline (to donor and recipient sc); recombinant IL6 to KO only	Increased IL6	Increased activation of Kupffer cells and TNF-α mediated activation of IFNR1 from 3 h reperfusion onwards increases liver necrosis, nonperfused sinusoids, adherent leucocytes and reduces hepatocyte regeneration
Shen et al[38]	TLR4 (-/-); TLR2 (-/-)	70% I 90 min/R 6 h	Histology; serum ALT; MPO; WB; PCR	Snpp (inhibit HO-1); CoPP	HO-1 is expressed which inhibits TLR4	TLR4 activation increases TNF-α expression associated with increased IRI
Lagoa et al[81]	PAI-1 (-/-)	MAP 25-30 mmHg for 2.5 h (2.25 mL/100 g blood withdrawn)/Resuscitation MAP > 80 mmHg for 4 h (30 min with shed blood and crystalloid)	Serum ALT, IL6, IL10; histology; Electron microscopy; IH; zymography for plasminogen activators; DNA microarray; PCR; WB	PAI-1 to PAI-1 (-/-) mice		PAI-1 expression in SEC contributes to IRI with periportal/pericentral injury, loss of sinusoidal fenestra and prominent SEC injury; PAI-1 inhibits u-PA which reduces formation of active HGF and increases active TGF-β1, but no effect on IL6 or IL10; this is associated with reduced activation of ERK-1/-2 pathway.
Teoh et al[36]	TNF-α (-/-)	70%I 90 min/R 2, 4, 24 h	Serum ALT; IH; serum TNF-α; EMSA (NFκβ); WB	Low dose or high dose TNF-αip		TNF-α from at least 2 h reperfusion onwards is injurious to ischaemic but not normal liver, increasing NFκβ DNA binding
Inderbitzin et al[57]	CI inhibitor overexpressed	Total hepatic ischaemia 30 min/R 2 h	Endothelial permeability index (measured using radiolabelled albumin iv into inferior vena cava) of liver, lung and gut		C1 inhibitor overexpression is protective in IRI	Classical complement pathway is activated in IRI; liver ischaemia and reperfusion causes liver and gut, but not lung, IRI in this model
Zhai et al	TLR4 (-/-); TLR2 (-/-)	70%I 90 min/R 6 h	Serum ALT; histology; PCR			TLR4 activation increases expression of IRF3 which upregulates IFNβ associated with increased IRI
Rudiger et al[39]	TNFR (-/-); Fas (-/-); FasL (-/-)	70% I 75 min/R 3 h	Serum AST; TUNEL; caspase-3 assay; ELISA; WB	Pentoxifylline		TNF-α binds to TNFR1 which increases apoptosis in IRI; fas and FasL not involved in this model
Kato et al[82]	IL1R (-/-)	70%I 90 min/R 1, 2, 4, 8, 16, 24 h	Serum ALT, IL1β, TNF-α and MIP-2; histology (PMN score); MPO; EMSA (NFκβ); PCR			IL1R not involved in IRI
Calmargo et al	IL6 (-/-)	Median lobe (45%) I 90 min/R 30, 60, 90, 120 min	Serum AST and ALT; histology; PCR	Recombinant IL6	IL6 released in IRI is protective	TNF-α expression during reperfusion is associated with worse IRI

KO: Transgenic knockout; WT: Wild type (normal animals); IH: Immunohistochemistry; WB: Western blotting; MPO: Myeloperoxidase assay; PCR: Polymerase chain reaction; ELISA: Enzyme labelled immunosorbent assay; EMSA: Electrophoretic mobility shift assay; AST: Aspartate transaminase; ALT: Alanine transaminase; GOT: Glutamic oxaloacetic transaminase; I: Ischemia; R: Reperfusion; IR: Ischemia reperfusion; IRI: Ischemia reperfusion injury; IVM: Intravital microscopy; IFN: Interferon; Ab: Antibody; TNF: Tumour necrosis factor; TNFR1: Tumour necrosis factor receptor (subtype 1); TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling (assay for cell death); IL: Interleukin; CXCR: Chemokine receptor; PAI: Plasminogen activator inhibitor; NF: Nuclear factor; C1-9: Complement protein 1 to 9; MAP: Mean arterial pressure; MIP: Major intrinsic protein.

Table 4 Nitric oxide synthase, HSP/heme oxygenase-1, matrix metalloproteinase knockout models of liver ischemia reperfusion injury

Ref.	Knockout model	IR protocol	Outcome measure	Agent	Adaptive responses	Injurious responses
Hamada et al[26]	iNOS (-/-); MMP-9 (-/-)	70% I 90 min/R 3, 6, 24 h	Histology; serum ALT, NO2-/NO3-; myeloperoxidase activity (MPO); immunohistochemistry; PCR, Western blotting; MMP-9 activity assay; MMP-9 protein levels; neutrophil (PMN) migration assay; TUNEL and caspase-3 activity	ONO-1714 (iNOS inhibitor); NO donor (DETA NONOate)		Increased macrophage iNOS producing NO increases PMN MMP-9 and PMN transmigration over fibronectin
Hamada et al[42]	MMP-9 (-/-)	70% I 90 min/R 6, 24 h	Histology; serum GPT and GOT; MPO; IH; PCR	Anti MMP-9 iv; MMP-2/9 inhibitor; anti MMP-2 (all to WT only)		MMP-9 (not MMP-2) increase TNF-α, IFNg, IL2, IL6 and increase PMN and CD4+ T cell recruitment leading to increased liver necrosis
Kuboki et al[73]	HSP70 (-/-)	70% I 90 min/R 1, 8 h	Histology; serum AST; TNF-α; IL6; MIP-2; MPO; WB; EMSA (NFκβ)	Sodium arsenite iv to induce HSP70; recombinant HSP70		No involvement of HSP70 in IRI; NFκβ activity associated with IRI
Theruvath et al[59]	eNOS (-/-)	Donor (WT/KO) to WT recipient; organ stored 18 h, 4  °C, UWS	Histology; serum ALT; IVM; TUNEL; IH (macrophage infiltration)		eNOS activation reduces necrosis and apoptosis, with associated inhibition of macrophage infiltration, increased sinusoidal diameter and blood flow
Tsuchiashi et al	HO-1 (+/-); HO-1 (-/-)	70% I 90 min/R 6 h	Histology; serum GOT; MPO; quantitative real time RT-PCR; WB; TUNEL	CoPP (induces HO-1) 24 h preop	HO-1 upregulated which inhibits expression of cytokines TNF-α and IFNγ	TNF-α and IFNγ expression increased overall in IRI associated with increased apoptosis and necrosis
Hines et al[23]	eNOS (-/-); iNOS (-/-)	70% I 45 min/R 1, 3 h	Serum ALT; histology; PCR		Increased eNOS expression in IRI inhibits TNF-α and IL12 expression; iNOS activates eNOS in this model	No PMN infiltration at 3 h reperfusion
Lee et al[58]	eNOS (-/-); iNOS (-/-)	70% I 1 h/R 1, 3, 6 h	Serum ALT and AST; perfusion studies; PCR		eNOS activated during IRI is protective	Increased iNOS mRNA expression from 3 h reperfusion onwards regulates reperfusion and is associated with worse IRI
Hines et al[60]	iNOS (-/-)	70% I 45 min/R 1, 3, 6 h	Serum ALT; histology; MPO	L-NIL (iNOS inhibitor)		Reduced IRI in iNOS (-/-), but no iNOS mRNA or L-NIL effect in WT; may be genetic compensation effect in KO
Kawachi et al[24]	eNOS (-/-); iNOS (-/-)	70% I 45 min/R 5 h	Serum ALT; histology; MPO		eNOS is activated in IRI and is protective	There is no PMN infiltration up to 5 h reperfusion and iNOS is not activated in IRI in this model

IH: Immunohistochemistry; WB: Western blotting; MPO: Myeloperoxidase assay; RT-PCR: Reverse transcriptase polymerase chain reaction; ELISA: Enzyme labelled immunosorbent assay; EMSA: Electrophoretic mobility shift assay; AST: Aspartate transaminase; ALT: Alanine transaminase; GOT: Glutamic oxaloacetic transaminase; I: Ischemia; R: Reperfusion; IR: Ischemia reperfusion; IRI: Ischemia reperfusion injury; IVM: Intravital microscopy; IFN: Interferon; Ab: Antibody; TNF: Tumour necrosis factor; TNFR1: Tumour necrosis factor receptor (subtype 1); TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling (assay for cell death); IL: Interleukin; NF: Nuclear factor; MMP: Matrix metalloproteinase; HSP: Heat shock protein; eNOS: Endothelial nitric oxide synthase; iNOS: Inducible nitric oxide synthase; HO-1: Heme oxygenase (subtype 1).

Table 5 Knockouts of downstream mediators and models of liver ischemia reperfusion injury

Ref.	Knockout model	IR protocol	Outcome measure	Agent	Adaptive responses	Injurious responses
Theruvath et al[14,15]	JNK (-/-)	70% I 1 h/R 4, 8 h	Histology; serum ALT; IVM (dyes to probe mitochondrial function and cell death); survival 14 d			JNK2 activation leads to mitochondrial depolarization and increased necrosis only
Theruvath et al[14,15]	JNK (-/-)	WT or KO donor; 30 h, 4  °C, UWS preservation; WT recipient	Histology 8 h posttransplant; serum ALT, TUNEl and caspase-3 assay; IVM; IH; lipid peroxidation			JNK2 activation leads to caspase-3 activation, mitochondrial depolarisation and release of cytochrome c, lipid peroxidation which all translate into reduced survival posttransplant
Beraza et al[72]	Conditional hepatocyte specific NEMO knockout	70% I 1 h (caudate lobe resected)/R 3, 6 h	TUNEL and caspase-3 assay; WB; IH; Southern blotting; EMSA (NFκβ)		NFκβ activity reduces necrosis and apoptosis, inhibits TNF-α, JNK and iNOS
Okaya et al[35]	PPARα (-/-)	70%I 90 min/R 4, 8 h	Serum ALT; TNF-α; MIP-2; MPO; liver NO2/NO3; WB; EMSA (AP-1, NFκβ)	WY14643 iv (PPARα agonist)	PPARα protective in IRI	PPARα independent release of TNF-α and MIP-2 and increased NO2/NO3 associated with IRI
Shen et al[78]	STAT4 (-/-); STAT6 (-/-); nu/nu	70%I 90 min/R 6 h	Serum ALT; histology; MPO; WB; PCR	Adoptive transfer of CD4+ T cells from WT or other KO to nu/nu; SnPP ip	HO-1 expressed at very low levels after 6 h in this model, but protective in IRI	CD4+T cell activation involving T cell STAT4 activation, but not STAT6 associated with increased IRI
Khandoga et al[61]	PARP (-/-)	Left lobe I 90 min/R 30 min	Serum ALT; IVM; IH; PCR			PARP activation in IRI upregulates E-selectin, ICAM1 and VCAM1, associated with increased platelet and leucocyte endothelial interaction and reduced sinusoidal perfusion
Kato et al[82]	P50 NFκβ (-/-)	70% I 90 min/R 1, 8 h	Serum ALT; histology; MPO WB; EMSA (p50 and p65 subunits of NFκβ)			No effect of p50 subunit deletion, but increased p50/p65 heterodimer in WT and some p65 in KO, so there may be some functional redundancy of NFκβ subunits
Kato et al[83]	STAT4 (-/-)	70% I 90 min/R 30 min, 1, 2, 4, 8 h	Serum ALT; histology; MPO; WB	Anti IL12 Ab		IL12 expression associated with IRI. STAT4 not activated in IRI in this model
Kato et al[70]	STAT6 (-/-)	70% I 90 min/R 1, 4, 8 h	Serum ALT, TNF-α; MPO; PCR; EMSA (NFκβ)	IL4 or IL13 iv		STAT6 is not activated in IRI in this model, although STAT6 activation by iv IL4 or IL13 is protective. IRI is associated with increased NFκβ DNA binding

KO: Transgenic knockout; WT: Wild type (normal animals); IH: Immunohistochemistry; WB: Western blotting; MPO: Myeloperoxidase assay; PCR: Polymerase chain reaction; EMSA: Electrophoretic mobility shift assay; ALT: Alanine transaminase; I: Ischemia; R: Reperfusion; IR: Ischemia reperfusion; IRI: Ischemia reperfusion injury; IVM: Intravital microscopy; IFN: Interferon; Ab: Antibody; TNF: Tumour necrosis factor; TNFR1: Tumour necrosis factor receptor (subtype 1); TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling (assay for cell death); IL: Interleukin; NF: Nuclear factor; STAT: Signal Transducer and Activator of Transcription; JNK: A survival kinase; PARP: Poly (ADP-ribose) polymerase.