Table A1.

Animal studies evaluating the potential reno-protective effects of sildenafil.

Reference /Country/Year	Studied Animal	Model	PDE5I Route	Timing	Sample	Renal Injury Effects	PDE5I Renal Effects	Outcome
[81]/ Venezuela/2005	Male Sprague Dawley rats	5/6 nephrectomy	Sildenafil Orally 2.5 mg/kg/day Either immediately after nephrectomy for 8 weeks Or 4 weeks after nephrectomy for 4 weeks	POST	8 weeks	↑sCr, ↑SBP, ↑proteinuria ↓urinary NOX, ↓cGMP Glomerulosclerosis Tubulo-interstitial damage Macrophage accumulation Increased number of apoptotic cells	↓sCr, ↓SBP, ↓proteinuria ↑ urinary NOX, ↑cGMP All changes improved especially if PDE5i was given early	POS
[82]/ Spain/2007	Laboratory large-white pigs	Right single nephrectomy after 45 min of vascular clamping + Auto-transplantation + Left nephrectomy	Sildenafil Orally 100 mg, 2 h pre-op	PRE	0/15/30/45/60 min after unclamping	↓RVF, ↑RVR, ↓NO Minimal differences in tubular and endothelial structure	↑↓RVF, ↓RVR, ↑NO Minimal differences in tubular and endothelial structure	POS
[83]/ Egypt/2008	Adult male Wistar albino rats	L-NAME Orally 50 mg/kg/day for 4 weeks	Sildenafil Orally 5 mg/kg/day 2 weeks after L-NAME for 2 weeks	POST	At 4 weeks	↓NO, ↓cGMP Glomerular collapse/mesangial matrix expansion with minimal cellular proliferation	↑NO, ↑cGMP Improvement in histological alterations	POS
[84]/ Spain/2009	Laboratory minipigs	Right single nephrectomy after 45 min of vascular clamping +Auto-transplantation +Left nephrectomy	Sildenafil Orally 100 mg, 1.5 h pre-op	PRE	0/15/30/45/60 min after unclamping	↓RVF, ↓RVR	↑RVF, ↓ RVR, ↑NO Reduced tubular edema, Improved endothelial cell integrity and mitochondrial ultrastructure	POS
[85]/ Korea/2009	Male Sprague Dawley	Streptozotocin Single intravenous dose 60 mg/kg	Sildenafil Orally 3 mg/kg/day For 8 weeks	POST	At 8 weeks	↑glucose, ↑urine output ↑urine 8-OH dG ↑urine albumin ↑Kidney/BW ratio, ↑iNOS ↑Nitrotyrosine, ↑MCP-1 ↑ED-1	↑glucose, ↓urine output ↓urine 8-OH dG ↓urine albumin ↓Kidney/BW ratio, ↓iNOS ↓Nitrotyrosine, ↓MCP-1, ↓ED-1	POS
[86]/ Korea/2012	Male Sprague Dawley rats	Unilateral Nephrectomy and 1 week later DOCA strip 200 mg/kg implantation	Sildenafil Orally 50 mg/kg/day 2 weeks after DOCA for 2 weeks	POST	At 4 weeks	↑mortality, ↑SBP, ↑ Kidney weight ↓CrCl, ↑sCr, ↑FeNa, ↑ACR ↑ED-1, ↑BAX, ↓Bcl2, ↑aSMA, ↑TGF-b1 ↑TUNEL +ve, ↑fibronectin ↑mRNA TGF-β1/MCP-1 ↑ICAM 1t Tubular casts/Tubular obstruction/Vessel dilatation/Glomerulosclerosis/interstitial expansion	↓mortality, ⇔ SBP, ↓Kindey weight ↑CrCl, ↓sCr, ↓FeNa, ↓ACR ↓aSMA ↓ED-1, ↓BAX, ↑Bcl2, ↓TGF-b1 ↓TUNEL +ve, ↓fibronectin ↓mRNA TGF-β1/MCP-1/↓ mRNA ICAM1 Reversed all renal injuries	POS
[87]/ Venezuela/2012	Male Wistar rats	5/6 nephrectomy	Sildenafil Orally 5 mg/kg/day for 60 days 24 h after nephrectomy	POST	Every 2 weeks	↑Kidney hypertrophy ↑Proteinuria, ↓NO2/NO3 ↓GMP (urine) ↑Nitrotyrosine	↓Kidney hypertrophy ↓Proteinuria, ↑NO2/NO3 ↑cGMP (urine) ↓Nitrotyrosine	POS
[19]/ Egypt/2013	Male Wistar rats	Cyclosporine A Subcutaneously 20 mg/kg/day 21 days	Sildenafil Orally 5 mg/kg/day 21 days	POST	At 21st day–urine sample/blood sample/renal tissue excision	↑BUN, ↑sCr, ↑MDA levels ↑Urine Albumin/Cr ↓GSH/NO/catalase activity ↑iNOS, TNF-a, Caspase 3 activity Tubular degeneration and dilation and necrosis/Glomerulat damage/Congestion Dilated Bowman’s space/Hemorrhage	↓BUN, ↓sCr, ↓MDA levels ↓Urine Albumin/Cr, ↑eNOS ↑GSH/NO/catalase activity ↓iNOS, TNF-a, Caspase 3 activity Improved all histological changes	POS
[88]/ United Kingdom/2014	Porcine kidneys	20 min warm ischemia followed by 2 or 18 h of cold storage	Sildenafil Intravenously 1.4 mg/kg 10 min prior to injury and 20min after reperfusion	PRE and POST	Samples during reperfusion	↓RBF, ↑intrarenal resistance ↓Urine cGMP ↑ sCr Steady increase of K+ ↑Tubular injury No difference in groups Tubular dilatation and debris and interstitial edema/Ischemic changes	↑RBF, ↓intrarenal resistance ↑Urine cGMP, ↓sCr No significant difference in K+ No effect on tubular injury regarding GAL/Endothelin1 Slight improvement of histological	POS
[89]/ Brazil/2014 [90]/ Brazil/2014	C57BL/6 mice	Left renal artery clamping for 2 weeks	Sildenafil Orally 40 mg/kg/day 2 weeks post op for 2 weeks	POST	4 weeks	Left kidney atrophy (clipped) Right kidney hypertrophy ↓BW, ↑SBP, ↑HR ↑Intrarenal angiotensin I/II ⇔Plasma angiotensin I/II/1-7 ↓NO, ↑ONOO-, ↑O2- Impaired vasodilation response to Ach	↓Left kidney atrophy ↓Right kidney hypertrophy Normal BW, ↓SBP, ↓HR ↓Intrarenal angiotensin I/II ↑Plasma angiotensin 1-7 ↑NO, ↓ONOO-, ↓O2- Normal vasodilation response to Ach	POS
[91]/ Egypt/2016	White albino male rats	Streptozocin Single intraperitoneal dose 55 mg/kg	Sildenafil Orally 3 mg/kg/day For 8 weeks after Diabetic nephropathy	POST	8 weeks	↓SOD, ↑TGF-β1, ↓NO, ↑sCr ↑BUN, ↑proteinuria ↑Kidney IL-1β ↑Advanced glycation end products (AGEPs)	↑SOD, ↓TGF-β1, ↑NO, ↓sCr ↓BUN, ↓proteinuria ↓Kidney IL-1β ↓Advanced glycation end products (AGEPs)	POS
[92]/ India/2016	Sprague-Dawley rats	Streptozocin Single intraperitoneal dose 60 mg/kg	Sildenafil Orally 2.5 mg/kg/day for 6 weeks after 28 days	POST	At 28th and 70th day	↑sCr, ↑BUN, ↓CrCl ↑Total protein excretion ↑albumin (urine) Bowman’s capsule thickening, glomerular sclerosis	↓sCr, ↓BUN, ↑CrCl ↓Total protein excretion ↓albumin (urine) Histopathology improvement	POS
[93]/ Italy/2017	Male CD-1 mice	Streptozotocin Single intraperitoneal dose 150 mg/kg	Sildenafil Intraperitoneally 1.6 mg/kg 3 days after STZ, for 4 weeks	POST		↑Glucose (urine), ↑MAP, ↓GFR ↑urinary ACR, ↑NGAL, ↑RRI ↓Renal volume, ↓BMP7 ↑suPAR, ↑Vascular leakage ↑FITC-dextran extravasation Reduced glomerular diameter/focal and segmental hyperplasia with diffuse mesangial proliferation/increased mesangial matrix deposition/acute tubular degeneration/eosinophilia/proximal tubule basal membrane thickening	↓Urine glucose, ↓MAP, ↑GFR ↓urinary ACR, ↓NGAL, ↓RRI ↑Renal volume, ↑BMP7, ↓miR-22 ↓suPAR, ↓Vascular leakage ↓FITC-dextran extravasation Reduced mesangial matrix deposition	POS
[94]/ Egypt/2017	Adult male Sprague-Dawley rats	Doxorubicin Intraperitoneally 3.5 mg/kg Twice weekly for 3 weeks	Sildenafil Orally 5 mg/kg/day for 21 days	POST		↑Urea, ↑sCr, ↑uric acid ↑MDA, ↓GSH, ↑TNF-a ↑caspase-3 Eosinophilic casts, tubule degeneration, vacuolization, endothelial cell edema	↓Urea, ↓sCr, ↓uric acid ↓MDA, ↑GSH, ↓TNF-a ↓caspase-3 Histological improvement	POS
[95]/ South Africa/2017	Nulliparous pregnant female Sprague-Dawley rats	L-NAME Orally 0.3 g/L (drinking water) 4-8 days for EOPE + 8-14 days for LOPE	Sildenafil Orally 10 mg/kg 4-8 days for EOPE 8-14 days for LOPE	POST	Gestational Day 19	↑BP, ↑Urine excretion ↑Urinary nephrin mRNA ↑Podocin (urine), ↑sFlt-1(mRNA) ↓VEGF (mRNA), ↓PIGF Glomerular and tubular damage and mononuclear cell infiltration	↓BP ↓Urinary nephrin mRNA ↓Podocin (urine) ↓sFlt-1 (mRNA) ↑VEGF (mRNA), ↑PIGF levels Attenuated histopathological changes	POS
[96]/ Netherlands/2017	Rats	Adriamycin Or Streptozocin	Sildenafil Orally 5 mg/kg/day for 6 weeks	POST	Immortalized mouse podocytes + Mouse kidney cortex	↑TRPC6 expression ↓Nephrin, ↑Glomerular desmin ↑Urinary albumin ↑Glomerular lesions	↓TRPC6 expression, ↓Ca2+ influx ↑Nephrin ↓Glomerular desmin ↓Urinary albumin	POS
[97]/ Oman/2018	Male Sprague-Dawley rats	Adenine (0.25% w/w) orally Daily for 5 weeks	Sildenafil Orally (0.1, 0.5 or 2.5 mg/kg) Daily for 5 weeks (alone or concomitantly with adenine)	SIM	At Day 5	↑BUN, sCr, uric acid, P, NGAL, ↑total NO, IS, Caspase 3 +ve cells ↑Albumin, NAG activity ↓Osmolality, CrCl in urine ↓CAT, glutathione reductase, SOD ↓TAC, ↑MAPK ↑Fibrosis ↑Adiponectin, cystatin-C, TNF-a ↓Sclerostin, ↑MDA Tubular necrosis, tubular dilatation, tubular cast formation, necrotic nuclei, tubular cells apoptosis, cellular shedding, mononuclear infiltration	↓BUN, sCr, uric acid, ↓P, NGAL, ↓total NO, IS, ↓Caspase 3 +ve cells ↓Albumin, ↓ NAG activity ↑Osmolality, ↓CrCl in urine ↑CAT, SOD ↓glutathione reductase, ↑TAC, ↓MAPK, ↓Fibrosis ↓Adiponectin, cystatin-C, TNF-a ↑Sclerostin (not 0.1 mg/kg) ↓MDA Improved tubular necrosis, tubular dilatation, tubular cast formation, mononuclear infiltration	POS
[98]/ Egypt/2018	Male albino rats Sprague-Dawley	Streptozotocin Single intraperitoneal dose 45 mg/kg	Sildenafil Orally: 3 mg/kg/Day 3 weeks after STZ for 15 days	POST	Day 16 after initiation of Sildenafil	↑sCr, ↑BUN ↑fasting and post prandial glucose ↓insulin levels ↑insulin resistance ↑MDA, ↓GSH, ↓CAT, ↓GPx, ↓SOD, ↓TAC	↓sCr, ↓BUN ↓fasting and post prandial glucose ↑insulin levels ↓insulin resistance (insignificant) ↓MDA, ↑GSH, ↑CAT, ↑GPx, ↑SOD, ↑TAC	POS

Abbreviations: AKI, acute kidney injury; ACR, albumin-creatinine ratio; aSMA, α-smooth muscle actin; Bax, proapoptotic protein; Bcl-2, antiapoptotic gene; BP, blood pressure; BUN, blood urea nitrogen; BW, body weight; Ca²⁺, calcium; CAT, catalase; cGMP, cyclic guanosine monophosphate; CrCl, creatinine clearance, ED-1, monoclonal antibody, eNOS, endothelial NOS, FeNa, fractional excretion of sodium, FITC, fluorescein isothiocyanate, GFR, glomerular filtration rate; GPx, glutathione peroxidase; GSH, glutathione; HR, heart rate; ICAM-1, intercellular adhesion molecule 1; IL, interleukin; IS, indoxyl sulfate; iNOS, inducible NOS; K, potassium; MAP, mean arterial pressure; MAPK, mitogen-activated protein kinase; MCP-1, monocyte chemoattractant protein 1; MDA, malondialdehyde; Na, sodium; NAG, N-acetyl-beta-D-glucosaminidase; NGAL, neutrophil gelatinase-associated lipocalin; NO, nitric oxide; NOX, NADPH oxidase; P, phosphorus; PDE5I, phosphodiesterase 5 inhibitor; PIGF, placenta growth factor; RRI, renal resistive index; RVF, renal vascular flow; RVR, renal vascular resistance; sCr, serum creatinine; sFlt1, soluble fms-like tyrosine kinase-1; SOD, superoxide dismutase; SBP, systolic blood pressure; suPAR, soluble urokinase-type plasminogen activator receptor; TAC, total antioxidant capacity; TGF-β1, transforming growth factor beta 1; TRPC6, transient receptor potential cation channel 6; TNF-a, tumor necrosis factor a; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; VEGF, vascular endothelia growth factor; 8-OH dG, 8-hydroxydeoxyguanosine; ↓, reduced; ↑, increased.