Therapeutic effects of lipo-prostaglandin E1 on angiogenesis and neurogenesis after ischemic stroke in rats

Angiogenesis after ischemic stroke

Owing to its high disability and mortality rates, stroke has been the second leading cause of death worldwide. Since the pathological mechanisms of stroke are not fully understood, there are few clinical treatment strategies available with an exception of tissue plasminogen activator (tPA), the only FDA-approved drug for the treatment of ischemic stroke. Angiogenesis is an important protective mechanism that promotes neural regeneration and functional recovery during the pathophysiological process of stroke. Thus, inducing angiogenesis in the peri-infarct area could effectively improve hemodynamics, and promote vascular remodeling and recovery of neurovascular function after ischemic stroke. In this review, we summarize the cellular and molecular mechanisms affecting angiogenesis after cerebral ischemia registered in PubMed, and provide pro-angiogenic strategies for exploring the treatment of ischemic stroke, including endothelial progenitor cells, mesenchymal stem cells, growth factors, cytokines, non-coding RNAs, etc.

Role of cyclooxygenases and prostaglandins in adult brain neurogenesis

The telencephalon of adult mammals shows constitutive neurogenesis, and disease or traumatic injuries alter the rate of neurogenesis in the adult brain. Understanding the molecular signals that control adult brain neurogenesis is of crucial importance for the development of therapies to promote regeneration in the injured or diseased brain. Here, I reviewed our current knowledge on the role of cyclooxygenases and prostaglandins in controlling adult brain neurogenesis. Current data indicate that cyclooxygenase-2 derived prostaglandin E2 acting through EP receptors promotes neurogenesis in adult neurogenic niches of the telencephalon and that manipulations of this signalling pathway could be used to promote neurogenesis under pathological conditions. In this review article, I also propose new research directions to increase our knowledge on the role of this signalling pathway in neurogenesis.

Pro-angiogenic activity of Tongnao decoction on HUVECs in vitro and zebrafish in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Tongnao Decoction (TND) is a Chinese decoction approved and used in Jiangsu Province Hospital for the treatment of ischemic stroke. It shows conclusive efficiency in the improvement of neurologic impairment and activities of daily living of the patients.

AIM OF THE STUDY

Recently, angiogenesis has been recognized as a potential therapeutic strategy for treating cerebral ischemia. This study was aimed to provide comprehensive evidence for the pro-angiogenic effect of TND and characterize the underlying mechanism.

MATERIALS AND METHODS

We firstly established the chemical fingerprinting of TND. Then, the in vitro pro-angiogenic activities of TND were tested on human umbilical vein endothelial cells (HUVECs) through cell viability, wound healing and tube formation assays. The in vivo pro-angiogenic effects were evaluated on transgenic zebrafish embryos [Tg (fli-1: EGFP)] through the formation of intersegmental vessels (ISVs), subintestinal vessels (SIVs) and central arteries (CtAs). Lastly, the potential mechanisms of TND were analyzed by a blocking assay with eight pathways-specific kinase inhibitors.

RESULTS

TND promoted the proliferation, migration and tube formation of HUVECs. TND also rescued the impairment of ISVs, SIVs and CtAs caused by VRI in a dose-dependent manner in zebrafish embryos. TND could activate vascular endothelial growth factor receptor-2 (VEGFR-2), phosphoinositide 3-kinase (PI3K) - protein kinase B (Akt) and Raf - mitogen-activated protein kinase1/2 (MEK1/2) - extracellular regulated kinase 1/2 (ERK1/2) signaling pathways.

CONCLUSION

Our study firstly demonstrated the pro-angiogenic activities of TND. Our work provided evidences for the clinical usage of TND in restoring neurovascular function through promoting angiogenesis in the ischemic cerebral microvascular.

Prostaglandin E1 attenuates high glucose-induced apoptosis in proximal renal tubular cells by inhibiting the JNK/Bim pathway

Proximal renal tubular damage is a critical process underlying diabetic kidney disease (DKD). Our previous study shows that prostaglandin E1 (PGE1) reduces the apoptosis of renal tubular cells in DKD rats. But its underlying mechanisms remain unclear. In this study we investigated the protective effects of PGE1 in DKD rats and high glucose (HG, 30 mM)-treated HK-2 proximal tubular cells. Four weeks after uninephrectomized streptozotocin-induced diabetic rats were established, the DKD rats were administered PGE1 (10 µg· kg⁻¹· d⁻¹, iv.) for 10 consecutive days. We showed that PGE1 administration did not change blood glucose levels, but alleviated diabetic kidney injury in the DKD rats, evidenced by markedly reduced proteinuria and renal tubular apoptosis. In the in vitro experiments, PGE1 (0.1–100 µM) significantly enhanced HG-reduced HK-2 cell viability. In HG-treated HK-2 cells, PGE1 (10 µM) significantly suppressed the c-Jun N-terminal kinase (JNK) and the mitochondrial apoptosis-related protein expressions such as Bim, Bax, caspase-3 and cleaved caspase-3; similar changes were also observed in the kidney of PGE1-treated DKD rats. By using two pharmacological tools-JNK activator anisomycin (AM) and JNK inhibitor SP600125, we revealed that PGE1 blocked HG-triggered activation of JNK/Bim pathway in HK-2 cells; JNK was an upstream regulator of Bim. In conclusion, our results demonstrate that the nephroprotective effects of PGE1 against apoptosis of proximal renal tubule in DKD rats via suppressing JNK-related Bim signaling pathway.

Immunomodulatory Therapeutic Strategies in Stroke

The role of immunity in all stages of stroke is increasingly being recognized, from the pathogenesis of risk factors to tissue repair, leading to the investigation of a range of immunomodulatory therapies. In the acute phase of stroke, proposed therapies include drugs targeting pro-inflammatory cytokines, matrix metalloproteinases, and leukocyte infiltration, with a key objective to reduce initial brain cell toxicity. Systemically, the early stages of stroke are also characterized by stroke-induced immunosuppression, where downregulation of host defences predisposes patients to infection. Therefore, strategies to modulate innate immunity post-stroke have garnered greater attention. A complementary objective is to reduce longer-term sequelae by focusing on adaptive immunity. Following stroke onset, the integrity of the blood–brain barrier is compromised, exposing central nervous system (CNS) antigens to systemic adaptive immune recognition, potentially inducing autoimmunity. Some pre-clinical efforts have been made to tolerize the immune system to CNS antigens pre-stroke. Separately, immune cell populations that exhibit a regulatory phenotype (T- and B- regulatory cells) have been shown to ameliorate post-stroke inflammation and contribute to tissue repair. Cell-based therapies, established in oncology and transplantation, could become a strategy to treat the acute and chronic stages of stroke. Furthermore, a role for the gut microbiota in ischaemic injury has received attention. Finally, the immune system may play a role in remote ischaemic preconditioning-mediated neuroprotection against stroke. The development of stroke therapies involving organs distant to the infarct site, therefore, should not be overlooked. This review will discuss the immune mechanisms of various therapeutic strategies, surveying published data and discussing more theoretical mechanisms of action that have yet to be exploited.

Prostaglandin E1 Alleviates Cognitive Dysfunction in Chronic Cerebral Hypoperfusion Rats by Improving Hemodynamics

Compensatory vascular mechanisms can restore cerebral blood flow (CBF) but fail to protect against chronic cerebral hypoperfusion (CCH)-mediated neuronal damage and cognitive impairment. Prostaglandin E1 (PGE1) is known as a vasodilator to protect against ischemic injury in animal models, but its protective role in CCH remains unclear. To determine the effect of PGE1 on cerebral hemodynamics and cognitive functions in CCH, bilateral common carotid artery occlusion (BCCAO) was used to mimic CCH in rats, which were subsequently intravenously injected with PGE1 daily for 2 weeks. Magnetic resonance imaging, immunofluorescence staining and Morris water maze (MWM) were used to evaluate CBF, angiogenesis, and cognitive functions, respectively. We found that PGE1 treatment significantly restored CBF by enhancing vertebral artery dilation. In addition, PGE1 treatment increased the number of microvascular endothelial cells and neuronal cells in the hippocampus, and decreased the numbers of astrocyte and apoptotic cells. In the MWM test, we further showed that the escape latency of CCH rats was significantly reduced after PGE1 treatment. Our results suggest that PGE1 ameliorates cognitive dysfunction in CCH rats by enhancing CBF recovery, sustaining angiogenesis, and reducing astrocyte activation and neuronal loss.

Protective Effect and Mechanism of Alprostadil in Acute Respiratory Distress Syndrome Induced by Oleic Acid in Rats

BACKGROUND This study investigated the role and mechanism of alprostadil in acute respiratory distress syndrome (ARDS) induced by oleic acid (OA) in rats. MATERIAL AND METHODS Sprague-Dawley rats were randomly divided into control, OA model, and OA + Alprostadil (2.5, 5, and 10 μg/kg, respectively) groups. The ARDS model was induced by femoral vein injection of OA, and alprostadil was administrated immediately. Lung injury was evaluated by lung wet-dry weight ratio (W/D) and histological analyses. Expressions of ACE, inflammatory mediators, apoptotic-related proteins, and proteins in the MAPKs and NF-κB signaling pathways were determined by Western blot or immunohistochemical staining. RESULTS Compared with the control group, the OA model group had significantly increased W/D, lung injury score, and collagen deposition at 3 h after OA injection. However, alprostadil (10 μg/kg) treatment significantly reduced OA-induced elevation of these indicators. Additionally, OA-induced expression of TNF-α and IL-1β were suppressed by alprostadil. The OA-induced activation of nuclear factor (NF) κB p65 was also reduced by alprostadil. Furthermore, we found that Alprostadil had an inhibitory effect on the phosphorylation of JNK, ERK1/2, and p38 MAPKs. Alprostadil inhibited Bax but increased Bcl-2, indicating a suppressive role in apoptosis. Remarkably increased expression of ACE in the OA model group was observed, which was decreased by alprostadil. CONCLUSIONS Alprostadil has a protective effect on ARDS induced by OA in rats, possibly through inhibiting apoptosis, suppressing the activation of MAPKs and NF-κB signaling pathways, and decreasing ACE protein expression. Therefore, the use of alprostadil in clinical ARDS treatment is promising.

Pharmacological approaches promoting stem cell-based therapy following ischemic stroke insults

Stroke can lead to long-term neurological deficits. Adult neurogenesis, the continuous generation of newborn neurons in distinct regions of the brain throughout life, has been considered as one of the appoaches to restore the neurological function following ischemic stroke. However, ischemia-induced spontaneous neurogenesis is not suffcient, thus cell-based therapy, including infusing exogenous stem cells or stimulating endogenous stem cells to help repair of injured brain, has been studied in numerous animal experiments and some pilot clinical trials. While the effects of cell-based therapy on neurological function during recovery remains unproven in randomized controlled trials, pharmacological agents have been administrated to assist the cell-based therapy. In this review, we summarized the limitations of ischemia-induced neurogenesis and stem-cell transplantation, as well as the potential proneuroregenerative effects of drugs that may enhance efficacy of cell-based therapies. Specifically, we discussed drugs that enhance proliferation, migration, differentiation, survival and function connectivity of newborn neurons, which may restore neurobehavioral function and improve outcomes in stroke patients.

Integrated Treatment of Prostaglandin E1 and Angiotensin-Converting Enzyme Inhibitor in Diabetic Kidney Disease Rats: Possible Role of Antiapoptosis in Renal Tubular Epithelial Cells

To investigate the therapeutic mechanisms underlying prostaglandin E1 (PGE1) and angiotensin-converting enzyme inhibitor (ACEI) on reducing urinary protein in diabetic kidney disease (DKD). DKD rats were established and randomly divided into four groups: PGE1 (10 μg/kg/day) (P group), ACEI (10 mg/kg/day) (A group), combination of PGE1 with ACEI treatment (P + A group), and saline treatment group (DKD group). Untreated rats were used as normal control (N group). Urinary albumin, endothelin-1 (ET-1), angiotensin II (AngII), TUNEL assay, Masson's trichrome staining, and immunohistochemistry staining for CD68 were evaluated in all groups. Ten days after treatment, urinary albumin was significantly decreased in the P and P + A groups (p < 0.01 vs. the DKD group). At the end of 8 weeks, the albumin was still significantly reduced in the P + A group (p < 0.05 vs. the A group). ET-1 and AngII were also significantly decreased in three treatment groups (p < 0.01 vs. the DKD group), especially in the P + A group. Few cells underwent apoptosis in glomerular regions in DKD rats, while amounts of apoptotic cells were seen in tubules regions. Further, apoptosis and the areas of fibrosis in tubulointerstitial were both decreased most in the P + A group compared with the DKD group. Apoptosis of renal tubular epithelial cells may participate in the development and progression of DKD in rats. Combination of PGE1 with AGEI remarkably protects renal function compared with PGE1 or ACEI monotherapy. The potential therapeutic mechanisms of PGE1 and AGEI might be via multiple targets and, at least in part, through inhibiting the apoptosis of renal tubular epithelial cells.

Potential Therapeutic Mechanisms and Tracking of Transplanted Stem Cells: Implications for Stroke Treatment

Stem cell therapy is a promising potential therapeutic strategy to treat cerebral ischemia in preclinical and clinical trials. Currently proposed treatments for stroke employing stem cells include the replacement of lost neurons and integration into the existing host circuitry, the release of growth factors to support and promote endogenous repair processes, and the secretion of extracellular vesicles containing proteins, noncoding RNA, or DNA to regulate gene expression in recipient cells and achieve immunomodulation. Progress has been made to elucidate the precise mechanisms underlying stem cell therapy and the homing, migration, distribution, and differentiation of transplanted stem cells in vivo using various imaging modalities. Noninvasive and safe tracer agents with high sensitivity and image resolution must be combined with long-term monitoring using imaging technology to determine the optimal therapy for stroke in terms of administration route, dosage, and timing. This review discusses potential therapeutic mechanisms of stem cell transplantation for the treatment of stroke and the limitations of current therapies. Methods to label transplanted cells and existing imaging systems for stem cell labeling and in vivo tracking will also be discussed.

Lipo‑prostaglandin E1 modifies cognitive impairment in rats with vascular cognitive impairment by promoting angiogenesis via the VEGF/VEGFR pathway

The pathological mechanism of vascular cognitive impairment (VCI) involves ischemic lesions in the hippocampus. Prostaglandin E1 (PGE1) serves roles in the promotion of vascular endothelial growth factor (VEGF) expression, angiogenesis and enhances blood flow to ischemic regions. However, the effect of PGE1 on cognitive function in VCI rats and the underlying mechanism are unknown. In the current study, learning and memory function in VCI rats treated by lipo-PGE1 injection was assessed through Morris Water Maze test. Furthermore, the histological alterations, blood vessel numbers in the hippocampal CA1 region and relative VEGF protein and mRNA expression were researched. The results confirmed that VCI rats treated with lipo-PGE1 presented improved cognitive function, less neuronal cell loss, a greater number of blood vessels in the hippocampal region and higher VEGF protein and mRNA expression. However, the role of lipo-PGE1 in VCI rats can be inhibited by SU5416 (a specific VEGFR2 antagonist). The results indicated that lipo-PGE1 may alleviate cognitive deficits in VCI rats. The underlying mechanism may be associated with angiogenesis promoted by lipo-PGE1, which may involve the VEGF/VEGFR pathway. These findings may have therapeutic implications for cognitive impairment induced by hypoperfusion or chronic ischemic lesions.

Changes in the content of fatty acids in CA1 and CA3 areas of the hippocampus of Krushinsky-Molodkina rats after single and fivefold audiogenic seizures

Audiogenic seizures (AS) are generalized seizures evoked by high frequency sounds. Since the hippocampus is involved in the generation and maintenance of seizures, the effect of AS on the composition and content of fatty acids in the CA1 and CA3 hippocampal areas of AS-susceptible Krushinsky-Molodkina (KM) rats on days 1, 3, and 14 after single and fivefold seizures were examined. The total content of all fatty acids in field СА1 was found to be lower compared with the control at all times of observation after both a single seizure or fivefold seizures. The total content of fatty acids in field СА3 decreased at all times of examination after a single seizure, whereas it remained unchanged on days 3 and 14 following five AS. The content of omega-3 fatty acids in both fields at all times of observation after a single seizure and fivefold AS did not significantly differ from that in intact animals. The absence of significant changes in the content of stearic and α-linolenic acids and a considerable decrease in the levels of palmitic, oleic, and eicosapentaenoic acids were common to both fields at all times after both a single seizure or fivefold AS. The changes in the content of fatty acids in the СА3 and СА1 fields of the brain of AS-susceptible rats indicate that fatty acids are involved in both the development of seizure activity and neuroprotective anticonvulsive processes.