Restorative effect of modified dioscorea pills on the structure of hippocampal neurovascular unit in an animal model of chronic cerebral hypoperfusion

The promoting effect of modified Dioscorea pills on vascular remodeling in chronic cerebral hypoperfusion via the Ang/Tie signaling pathway

Objective

The objective of this study was to investigate the effect of modified Dioscorea pills (MDP) on microcirculatory remodeling in the hippocampus of rats with chronic cerebral hypoperfusion (CCH) through the angiopoietin (Ang)/tyrosine kinase receptor tyrosine kinase with immunoglobulin-like and EGF-like domains (Ang receptor) 2 (Tie-2) signaling pathways, which may underlie the cognitive improvement observed in CCH rats.

Methods

Forty male Sprague-Dawley rats raised under specific pathogen-free conditions were randomly divided into three groups: control group (10 rats), model group (15 rats), and MDP group (15 rats). The rats in the model group and MDP group underwent bilateral common carotid artery occlusion using the 2-vessel occlusion (2-VO) method to induce CCH. Rats in the control group underwent the same surgical procedures as those in the model group, except for ligation and occlusion of the carotid arteries. After 1 week of 2-VO, rats in the MDP group were administered MDP condensed decoction intragastrically at a dose of 1 ml/100 g body weight (prepared by the Preparation Room of Hubei Provincial Hospital of Traditional Chinese Medicine) for 45 days, while rats in the other two groups received normal saline intragastrically with the same dose and duration as the MDP group. After the intervention, all rats were euthanized, and brain perfusion was performed to obtain the hippocampal tissue for analysis. Immunohistochemical staining for CD43 was performed to assess microvessel density (MVD); western blot and the reverse transcription-polymerase chain reaction (RT-PCR) were used to analyze the expression of proteins and genes in angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), Tie-2, and vascular endothelial growth factor (VEGF) proteins and genes in the hippocampal tissue and compute the Ang-1/Ang-2 ratio.

Results

MDP treatment reduced neuronal loss and promoted restoration of the damaged hippocampal structure in CCH rats. The model group showed significantly higher MVD (14.93 ± 1.92) compared to the control group (5.78 ± 1.65) (P < 0.01), whereas MDP treatment further increased MVD (21.19 ± 2.62). Western blot and RT-PCR analysis revealed that CCH significantly increased the expression of Ang-1, Ang-2, Tie-2, and VEGF proteins and genes, while MDP treatment further significantly upregulated the expression of these proteins and genes. In addition, MDP significantly elevated the gene and protein expression of the Ang-1/Ang-2 ratio compared to the control group (P = 0.041, P = 0.029).

Conclusion

CCH induces microvascular neogenesis in the hippocampus, and MDP promotes angiogenesis and microcirculation remodeling in CCH rats via the Ang/Tie signaling pathway, which may be an important mechanism for its restorative effects on hippocampal perfusion and improvement of cognitive function in CCH rats.

Exploring the Mechanism on the Medullary Visceral Zone Inhibiting the Cholinergic Anti-inflammatory Pathway Induced by Sepsis

Inflammatory storm is an important pathological mechanism of multiple organ dysfunction, and it is associated with most deaths in septic patients, deserving to be studied. Recent findings have confirmed that the Medullary Visceral Zone (MVZ) regulates inflammation and immunity through the cholinergic anti-inflammatory pathway (CAP), but how sepsis affects the MVZ and leads to uncontrolled inflammation remain unclear. The current study reported that sepsis induced MVZ to inhibit CAP which underlies the inflammation storm. Our studies have shown that the rat models of sepsis prepared by cecal ligation and puncture had a higher inflammatory level, higher mortality, and higher Murine Sepsis Score. In septic rats, some indicators of heart rate variability (HRV) such as SDNN, HF band, RMSSD, SD1, and SD2 significantly reduced. In MVZ of septic rats, many cholinergic and catecholaminergic neurons showed apoptotic, with low expressions of tyrosine hydroxylase and choline acetyltransferase. The α7nAChR agonist GTS-21 can improve these pathologies, while the α7nAChR antagonist MLA is the opposite. Our study demonstrates for the first time that cholinergic and catecholaminergic neurons in MVZ went through significant apoptosis and inactiveness in sepsis, which contributes to the inhibition of CAP and acceleration of the inflammation storm in early sepsis. Intervening with CAP has a significant effect on the activity and apoptosis of MVZ neurons while altering systemic inflammation and immunity; in addition, for the first time, we confirmed that some indicators of HRV such as SDNN, HF band, RMSSD, SD1, and SD2 can reflect the activity of CAP, but the CAP interference had little effect on these indicators.

[Cholinergic anti-inflammatory pathway plays negative regulatory role in early inflammatory and immune responses in septic rats]

OBJECTIVE

To investigate the role of cholinergic anti-inflammatory pathway (CAP) in neuro-regulation of inflammatory and immune response in the early stage of sepsis.

METHODS

Sixty-four SD rats were randomly divided into control Group (n=8) with normal feeding without any treatment; sham operation group (n=8) with laparotomy but without cecal ligation and puncture (CLP), followed by intraperitoneal injection 50 mg/kg piperacillin 3 times a day for 3 consecutive days; and sepsis group (n=48) with CLP-induced sepsis. The rat models of sepsis were randomized into model groups (n=16) with intraperitoneal injection of piperacillin (50 mg/kg) and normal saline (1 mL/100 g) for 3 times a day for 3 days; GTS-21 group (n=16) with additional intraperitoneal injection of 4 mg/kg GTS-21 (once a day for 3 days); and methyllycaconitine (MLA) group (n=16) with intraperitoneal injection of MLA (4.8 mg/kg) in addition to piperacillin (once a day for 3 days). Murine Sepsis Score (MSS) of the rats and short-range HRV analysis were recorded. Three days later, the rats were sacrificed and serum levels of TNF-α, IL-1α, IL-10, IL-6, HMGB1, and sCD14 were measured with ELISA. The percentages of CD4+CD25+ Treg and TH17 lymphocytes and their ratios were measured using flow cytometry.

RESULTS

Compared with the control rats, the septic rats had significantly increased MSS scores and lowered HRV indexes (SDNN, RMSSD, HF, SD1, and SD2; P < 0.05); treatment with GTS-21 significantly decreased while MLA increased MSS scores (P < 0.05), but neither of them obviously affected HRV of the rats. Serum levels TNF-α, IL-1α, IL-10, IL-6, HMGB1, and sCD14 and the percentages of CD4+CD25+ Treg and TH17-positive lymphocytes were significantly higher and Treg/TH17 ratio was significantly lower in the septic rats compared with those in the control group (P < 0.05); treatment with GTS-21 significantly decreased the levels of serum levels of TNF-α, IL-1α, IL-6, HMGB1, and sCD14 and TH17 lymphocyte percentage (P < 0.05), whereas MLA treatment significantly increased serum levels of TNF-α, IL-1α, IL-10, IL-6, HMGB1, and sCD14 and the percentages of CD4+ CD25+ Treg and TH17-positive lymphocytes and decreased Treg/TH17 ratio in the septic rats (P < 0.05).

CONCLUSIONS

CAP plays negative regulatory role in early inflammatory and immune response to sepsis, and some of the HRV indicators can well reflect the regulatory effect of CAP on inflammation and immunity in the septic rats.