Effects of candesartan and enalaprilat on the organ-specific microvascular permeability during haemorrhagic shock in rats

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Enhancement of Small Molecule Delivery by Pulsed High-Intensity Focused Ultrasound: A Parameter Exploration

Chemotherapeutic drug delivery is often ineffective within solid tumors, but increasing the drug dose would result in systemic toxicity. The use of high-intensity focused ultrasound (HIFU) has the potential to enhance penetration of small molecules. However, operation parameters need to be optimized before the use of chemotherapeutic drugs in vivo and translation to clinical trials. In this study, the effects of pulsed HIFU (pHIFU) parameters (spatial-average pulse-average intensity, duty factor and pulse repetition frequency) on the penetration as well as content of small molecules were evaluated in ex vivo porcine kidneys. Specific HIFU parameters resulted in more than 40 times greater Evans blue content and 3.5 times the penetration depth compared with untreated samples. When selected parameters were applied to porcine kidneys in vivo, a 2.3-fold increase in concentration was obtained after a 2-min exposure to pHIFU. Pulsed HIFU has been found to be an effective modality to enhance both the concentration and penetration depth of small molecules in tissue using the optimized HIFU parameters. Although, performed in normal tissue, this study has the promise of translation into tumor tissue.

A Comparative Study of Neuroprotective Effect of Single and Combined Blockade of AT1 Receptor and PARP-1 in Focal Cerebral Ischaemia in Rat

Background

Cerebral ischaemia results in enhanced expression of type 1 angiotensin receptor and oxidative stress. Free radicals due to oxidative stress lead to excessive DNA damage causing overactivation of poly (ADP-ribose) polymerase-1 resulting in neuronal death. Activation of both type 1 angiotensin receptors and poly (ADP-ribose) polymerase-1 following cerebral ischaemia takes place simultaneously, but until now, no study has explored the effect of combined blockade of both angiotensin type 1 angiotensin receptor and poly (ADP-ribose) polymerase-1 in cerebral ischaemia.

Aim

Our purpose was to compare the effect of single and combined treatment with angiotensin type 1 angiotensin receptor blocker, candesartan, and the poly (ADP-ribose) polymerase-1 inhibitor, 1, 5 isoquinolinediol, on brain damage and oxidative stress in transient focal cerebral ischaemia in rats.

Method

Transient focal cerebral ischaemia was induced in Sprague-Dawley rats by an intraluminal technique for two-hours following 48 h of reperfusion. Candesartan (0·05 mg/kg) was administered just after initiation of ischaemia followed by a repeat administration at 24 h while 1, 5 isoquinolinediol (0·1 mg/kg) was given one-hour after of ischaemia. After 24 h of reperfusion, neurological deficit was evaluated in the different treatment groups. After 48 h of reperfusion, the rats were sacrificed and the brain was isolated. Ischaemic brain damage by 2,3,5 triphenyl tetrazolium chloride staining, oxidative stress markers, and levels of reactive oxygen species were determined biochemically.

Result

Single treatment with candesartan and 1, 5 isoquinolinediol significantly reduced neurological deficit, infarct, and oedema volume as compared to ischaemic control and different vehicle groups for each of the drugs. However, treatment with candesartan + 1, 5 isoquinolinediol offered greater reduction in neurological deficit, cerebral infarct volume, and oedema as compared to single-drug treatments. Furthermore, treatment with candesartan + 1, 5 isoquinolinediol significantly decreased oxidative stress as compared to single treatments with each drug.

Conclusion

The study suggests that blockade of either type 1 angiotensin receptor or poly (ADP-ribose) polymerase-1 alone provides neuroprotection, but the better result was achieved when both type 1 angiotensin receptor and poly (ADP-ribose) polymerase-1 were blocked together by the combined use of their pharmacological inhibitor in transient cerebral ischaemia in rat.

Role of angiotensin-converting enzyme (ACE and ACE2) imbalance on tourniquet-induced remote kidney injury in a mouse hindlimb ischemia-reperfusion model

In this study, the relationship between the local imbalance of angiotensin converting enzymes ACE and ACE2 as well as Ang II and Ang (1-7) and renal injury was observed in the different genotypes mice subjected to tourniquet-induced ischemia-reperfusion on hind limbs. In wild-type mice, renal ACE expression increased while renal ACE2 expression decreased significantly after reperfusion, accompanied by elevated serum angiotensin II (Ang II) level and lowered serum angiotensin (1-7) (Ang (1-7)) level. However, renal Ang (1-7) also increased markedly while renal Ang II was elevated. Renal injury became evident after limb reperfusion, with increased malondialdehyde (MDA), decreased super-oxide dismutase (SOD) activity and increased serum blood urea nitrogen (BUN) and creatinine (Cr), compared to control mice. These mice also developed severe renal pathology including infiltration of inflammatory cells in the renal interstitium and degeneration of tubule epithelial cells. In ACE2 knock-out mice with ACE up-regulation, tourniquet-induced renal injury was significantly aggravated as shown by increased levels of MDA, BUN and Cr, decreased SOD activity, more severe renal pathology, and decreased survival rate, compared with tourniquet-treated wild-type mice. Conversely, ACE2 transgenic mice with normal ACE expression were more resistant to tourniquet challenge as evidenced by decreased levels of MDA, BUN and Cr, increased SOD activity, attenuated renal pathological changes and increased survival rate. Our results suggest that the deregulation of ACE and ACE2 plays an important role in tourniquet-induced renal injury and that ACE2 up-regulation to restore the proper ACE/ACE2 balance is a potential therapeutic strategy for kidney injury.

Vascular endothelial cadherin modulates renal interstitial fibrosis

BACKGROUND/AIMS

Renal interstitial fibrosis is a final common pathway of all chronic, progressive kidney diseases. Peritubular capillary rarefaction is strongly correlated with fibrosis. The adherens junction protein vascular endothelial cadherin (VE-cadherin) is thought to play a critical role in vascular integrity. We hypothesized that VE-cadherin modulates the renal microcirculation during fibrogenesis and ultimately affects renal fibrosis.

METHODS

Unilateral ureteral obstruction (UUO) was used as a renal fibrosis model in VE-cadherin heterozygote (VE+/-) and wild-type (WT) mice, and the kidneys were harvested at days 3, 7, and 14. Peritubular capillary changes and fibrogenesis were investigated.

RESULTS

VE+/- mice had lower levels of VE-cadherin protein than WT mice at 3 and 7, but not 14 days after UUO. Vascular permeability was significantly greater in VE+/- mice 7 days after UUO, while peritubular capillary density was not significantly different in VE+/- and WT mice. Interstitial myofibroblast numbers and collagen I and III mRNA levels were significantly higher in VE+/- mice, consistent with a stronger early fibrogenic response. Expression of the pericyte marker neuron-glial antigen 2 was upregulated after UUO, but was not greater in VE+/- mice compared to the WT mice.

CONCLUSION

Our data suggest that VE-cadherin controls vascular permeability and limits fibrogenesis after UUO.

Candesartan improves memory decline in mice: involvement of AT1 receptors in memory deficit induced by intracerebral streptozotocin

The Renin-angiotensin system, besides blood pressure regulation, affects learning and memory as evidenced by improvement of cognition in hypertensive patients being treated with AT1 receptor blockers like candesartan. The present study examined the influence of candesartan on memory impairment induced by intracerebral streptozotocin (IC STZ 0.5 mg/kg) in mice. Candesartan (0.05 mg/kg and 0.1 mg/kg, i.p.) was given for 14 days following IC STZ administration. The dose of 0.1 mg/kg significantly improved latency period in passive avoidance test. Further, treatment with 0.1 mg/kg candesartan for 14 days significantly improved spatial memory in mice in water maze test also. In another group, after memory impairment in mice following IC STZ administration, memory improving effect of a 7 days treatment with 0.1 mg/kg candesartan lasted only for 3 subsequent days in water maze task. IC STZ increased oxidative stress but pretreatment with 0.1 mg/kg candesartan decreased oxidative stress as indicated by a decrease in MDA and increase in GSH. Further, candesartan decreased free radicals as evidenced by flow cytometry. IC STZ affected cholinergic system also by increasing acetylcholine esterase activity that was restored by pretreatment with 0.1 mg/kg candesartan. Locomotor activity and serum glucose level remained unaffected by candesartan treatment. These results suggest that AT1 receptors play a facilitatory role in STZ induced memory deficit and corroborate number of human studies that AT1 receptor blockers can be used therapeutically against cognitive decline in hypertensive patients.

Ultrasound targeted microbubble destruction increases capillary permeability in hepatomas

Ultrasound-targeted microbubble destruction (UTMD) has evolved as a promising tool for organ-specific gene and drug delivery. Taking advantage of high local concentrations of therapeutic substances and transiently increased capillary permeability, UTMD could be used for the treatment of ultrasound accessible tumors. The aim of this study was to evaluate if UTMD can locally increase capillary permeability in a hepatoma model of the rat. Furthermore, we evaluated whether UTMD can transfect DNA into such tumors. Subcutaneous Morris hepatomas were induced in both hind limbs of ACI rats by cell injection. A total of 18 rats were divided into three groups. Only one tumor per rat was treated by ultrasound. The first group received injection of Evans blue, followed by UTMD. The second group received a phosphate-buffered saline solution infusion and ultrasound to the target tumor after Evans blue injection. The third group received UTMD first, followed by Evans blue injection. Tumors and control organs were harvested, and Evans blue extravasation was quantified. Another 12 rats received DNA-loaded microbubbles by UTMD to one tumor, encoding for luciferase. Evans blue injection followed by UTMD showed about fivefold higher Evans blue amount in the target tumors compared with the control tumors. In contrast, no significant difference in Evans blue content was detected between target and control tumors when ultrasound was applied without microbubbles or when UTMD was performed before Evans blue injection. Plasmid transfection was not successful. In conclusion, ultrasound targeted microbubble destruction is able to transiently increase capillary permeability in hepatomas. Using naked DNA, this technique does not seem to be feasible for noninvasive transfection of hepatomas.