Table 2.
Summary of studies utilising AT2R agonism in experimental stroke. Abbreviations: Akt: protein kinase B; Aβ: β-amyloid; BBB: blood brain barrier, BDNF: brain derived neurotrophic factor; BP: blood pressure, C21: compound 21, CBF: cerebral blood flow, CGP42112: peptide agonist of AT2R; eNOS: endothelial nitric oxide synthase; ET-1: endothelin-1 injection, GAP43: growth associated protein B; ICV: intracerebroventricular, IL-1β/10: interleukin 1β/10; iNOS: inducible nitric oxide synthase; IP: intraperitoneal, IV: intravenous; KO: knockout; MCP-1: monocyte chemoattractant protein-1; mTOR: mammalian target of rapamycin; PI3K: phosphoinositide-3-kinase; PPAR-γ: peroxisome proliferator-activated receptor-γ; SD: Sprague Dawley, SHR: spontaneously hypertensive rat, t/pMCAO: transient/permanent middle cerebral artery occlusion, TNF-α: tumor necrosis factor-α; tPA: tissue plasminogen activator; TrkB: tropomyosin receptor kinase B; ZO-1: zona occludens protein 1.
| Animal. | Drug delivery dose, route & timing | Stroke model | Outcome | Mechanistic insight (if any) | Reference |
|---|---|---|---|---|---|
| Male SHR (15–16 week) | CGP42112, 0.1, 1 or 10 ng/kg/min, ICV minipump infusion 5 days prior +3 days post | ET-1, conscious | No effect BP. ↓ infarct volume at 3 days (1 & 10 ng doses). ↑ motor function at 1 & 3 days. |
Increased neuronal survival Increased AT2R expression Reduced superoxide production All effects abolished by AT2R blockade |
260 |
| Male SHR | CGP42112 3 μg/kg/dose, ICV bolus at 6, 24, 48 & 72 h post stroke | ET-1, conscious | No effect BP. ↓ infarct volume at 3 days. ↑ motor function at 1 & 3 days. |
Increased neuronal survival Reduced apoptosis Increased microglia activation All effects abolished by AT2R blockade |
261 |
| Male C57BL/6 mice (8–12 week) | CGP42112, 1 mg/kg, IP at reperfusion | Filament tMCAO, 30 min | ↑ CBF at reperfusion. ↑ neurological score and motor function at 24 h. ↓ infarct volume at 24 h. |
Reduced neuronal apoptosis in vitro prevented by AT2R blockade | 192 |
| Male SD (8 week) | C21, ICV 7.5 ng/μl/h minipump infusion for 7 days prior +3 days post OR IP 0.03 or 0.1 mg/kg prior to (2 h) and post(4, 24 & 48 h) OR IP 0.03 mg/kg 4, 24 & 48 h post |
ET-1 | ↓ infarct volume with all delivery schemes at 3 days. ↑ neurological score with all delivery schemes at 3 days. IP delivery no effect on non-stroked BP or CBF. |
Positive stroke outcome effects abolished by AT2R blockade Reduced expression of some pro-inflammatory genes: iNOS, CCL2 and CCR2 (chemokines) |
264 |
| Male SHR | C21, 50 ng/kg/min ICV minipump infusion 5 days prior & 3 days post OR 144 μg/kg ICV bolus at 6, 24, 48 & 72 h post |
ET-1, conscious | No effect on BP ↓ infarct at 3 days with pre- and post delivery. ↑ motor deficit at 1 day (pre-treatment only). |
Positive stroke outcome effects abolished by AT2R blockade Increased neuronal survival* Reduced apoptosis Increased microglia activation Suggestion of link between AT2R positive microglia and BDNF production Ex vivo vasorelaxation of cerebral arteries* *these effects also abolished by AT2R blockade |
263 |
| Male C57BL/6 mice (10–12 week) | C21, 10 μg/kg/day, IP after pMCAO, 24 h and daily thereafter | Electrocoagulation (pMCAO) | ↓ infarct volume at days 1–5. ↑ neurological score at days 3–7. ↑ CBF at days 1 & 3 ↓ BBB disruption at 3 days. |
AT2R KO mice had larger infarcts and infarcts not reduced by C21 Reduced superoxide production Reduced expression of proinflammatory cytokines TNF-α and MCP-1 |
262 |
| Male Wistar rats | C21, 0.03 mg/kg IP at reperfusion | Filament tMCAO 90 min or 3 h | No effect BP ↓ infarct volume at 24 h ↑ neurological score & motor function at 1–7 days |
Positive stroke outcome effects abolished by AT2R blockade Upregulation of AT2R and downregulation of AT1R expression Increased Akt and eNOS phosphorylation (pro-survival) Increased BDNF and IL-10 expression (neuroprotective) Decreased cleaved caspase-3 (apoptosis) Decreased nNOS, iNOS and nitrotyrosine (nitrative stress) Increased vascular density in vivo plus In vitro evidence of BDNF and AT2R dependent endothelial cell migration (pro-angiogenic) |
267 |
| Male C57BL/6 mice, WT or AT2R KO | C21 0.03 mg/kg IP 45 min post and daily thereafter | Filament tMCAO 30 min | No effect BP. No effect CBF. No effect infarct volume at 4 days. ↑ survival ↑ neurological score at day 1, 2 & 4 |
Increased levels of BDNF, its receptor TrkB and GAP43 (marker of neuronal outgrowth) Decreased neuronal apoptosis These effects plus improved neurological score were not seen with C21 treatment in AT2R KO mice |
193 |
| Male Wistar rats (8–12 week) | C21, 0.3 mg/kg/day, IP 6 h, 1, 2, 3, 4 & 5 days post | Filament pMCAO | ↑ neurological score at days 3 & 4 ↓ infarct volume at days 5 & 21 |
Increased VEGF expression mediated by mTOR dependent mechanism Confirmed in vitro neuronal cultures to be mediated by PI3K/Akt/mTOR pathway |
266 |
| Male SD rats (12 weeks) | CGP42112 IP 1 mg/kg per day post (specific timing not stated) | Filament tMCAO 2 h | ↓ infarct volume at 7 days | Increased AT2R expression Reduced expression of pro-inflammatory cytokines IL-1β & TNF-α. All effects abolished by AT2R blockade |
79 |
| Male SD (18–20 month) | C21 0.03 mg/kg IP 90 min, 1 & 2 days post | Filament tMCAO 45 min | ↑ neurological score and motor function from 1 to 21 days. ↓ infarct volume at 3 weeks. |
Not investigated | 268 |
| Male Wistar rats | C21 0.03 mg/kg IP at reperfusion | Filament tMCAO 3 h | ↓ infarct volume at 21 h. ↑ neurological score and motor function at 21 h. |
Positive outcomes partially mediated by IL-10 Reduced expression of pro-inflammatory TNF-α In vitro evidence of increased neuronal survival and reduced neuronal apoptosis |
195 |
| Male SHR (4 month) | C21 0.03 mg/kg/day IP at 2 h post | Filament tMCAO 60 min | No effect on BP. No effect neurological score and motor function at day 1 or 28. ↑ cognition at 21 days. |
Reduced Aβ accumulation In vitro evidence of Aβ toxicity to neurons and endothelial cells Reduced sustained (30 days post stroke) microglial activation |
265 |
| Male SD (10–13 week) | C21 1.5 μg/kg intranasal delivery 1.5, 4, 24 & 48 h post | ET-1 | No effect on BP. ↓ infarct volume at 3 days. ↑ neurological score at 1% 3 days. |
Not investigated | 271 |
| Male C57BL6/J mice | C21 10 μg/kg/day IP for 2 weeks prior | Filament pMCAO | No effect on BP. ↓ infarct volume at 24 h. ↑ neurological score at 24 h. ↑ CBF at 24 h. |
Positive outcomes partially mediated by PPAR-γ activation Reduced superoxide production and increased superoxide dismutase activity Increased expression of BBB stabilisation genes, occludin, claudin-5 and ZO-1 |
194 |
| Male Wistar rats (8–10 week) | C21 0.01, 0.03 or 0.06 mg/kg IV at 3 h OR 0.01 mg/kg at 3 h & 0.04 mg/kg/day orally days 2–5 alone or in combination with tPA |
Embolic | No effect on BP. ↑ neurological and motor function at days 3 or 5 (0.01 mg.kg dose). No effect infarct size. Trend towards ↑ cognition at 7 days. No effect when used in combination with tPA. |
Not investigated | 273 |
| Male Wistar rats, healthy or diabetic (12–15 weeks) | C21 0.12 mg/kg orally at day 3 post | Filament tMCAO 60 min | ↑ sensorimotor deficit at 1–8 weeks. ↑ cognition of diabetic rats at 1–8 weeks. Preserved brain volume at 8 weeks. |
No effect on number of activated microglia but shift towards the M2 anti-inflammatory phenotype In vitro evidence suggests microglial may be independent of AT2R |
270 |
| Male Wistar (14 month) | C21 0.12 mg/kg orally at 24 h post and daily thereafter | Distal pMCAO, electrocoagulation | ↓ weight loss No effect on neurological score or sensorimotor function at 28 days. ↑ cognition at 21 & 28 days. |
Reduced Aβ accumulation No effect on BDNF concentration |
272 |
| Female Wistar rats (3–6 month) | C21 0.03 mg/kg/day IP at reperfusion followed by daily IP or 0.12 mg/kg/day orally | Filament tMCAO 1, 2 or 3 h | Trend towards ↓ infarct volume at 24 h and 14 days ↑ neurological score and trends with sensorimotor function at 24 h. |
Trend towards increased PPAR-γ expression | 269 |