MicroRNA-135a participates in the development of astrocytes derived from bacterial meningitis by downregulating HIF-1α.

Accumulating evidence has highlighted the potential of microRNAs (miRs) as biomarkers in various human diseases. However, the roles of miRs in bacterial meningitis (BM), a severe infectious condition, still remain unclear. Thus, the present study aimed to investigate the effects of miR-135a on proliferation and apoptosis of astrocytes in BM. Neonatal rats were injected with Streptococcus pneumoniae to establish the BM model. The expression of miR-135a and hypoxia-inducible factor 1α (HIF-1α) in the BM rat models were characterized, followed by determination of their interaction. Using gain- and loss-of-function approaches, the effects of miR-135a on proliferation, apoptosis, and expression of glial fibrillary acidic protein (GFAP), in addition to apoptosis-related factors in astrocytes were examined accordingly. The regulatory effect of HIF-1α was also determined along with the overexpression or knockdown of HIF-1α. The results obtained indicated that miR-135a was poorly expressed, whereas HIF-1α was highly expressed in the BM rat models. In addition, restored expression levels of miR-135a were determined to promote proliferation while inhibiting the apoptosis of astrocytes, along with downregulated Bax and Bad, as well as upregulated Bcl-2, Bcl-XL, and GFAP. As a target gene of miR-135a, HIF-1α expression was determined to be diminished by miR-135a. The upregulation of HIF-1α reversed the miR-135a-induced proliferation of astrocytes. Taken together, the key findings of the current study present evidence suggesting that miR-135a can downregulate HIF-1α and play a contributory role in the development of astrocytes derived from BM, providing a novel theoretical perspective for BM treatment approaches.

Effects of dexamethasone on aquaporin-4 expression in brain tissue of rat with bacterial meningitis.

Aquaporin-4 (AQP4) is the most popular water channel protein expressed in brain tissue and plays a very important role in regulating the water balance in and outside of brain parenchyma. To investigate the expression of aquaporin-4 in the rat brain tissue after dexamethasone therapy of meningitis induced by Streptococcus pneumonia, total 40 of 3-week old Sprague-Dawley rats were divided into infection group (n=30) and normal control group (n=10). The meningitis groups were infected with 1×10(7) cfu/ml of Streptococcus pneumoniae and then randomized into no treatment (untreated group, n=10), treatment with ceftriaxone (CTRX group, n=10) and treatment with dexamethasone combined ceftriaxone (CTRX+DEXA group, n=10). The normal control group was established by using saline. The rats were euthanized when they reached terminal illness or five days after infection, followed by detection of AQP4 through using immunohistochemistry and Western blot methods. Data has showed that expression of AQP4 in model group remained higher than the control and treatment group (P<0.05). AQP4 expression in CTRX+DEXA group was lower than that in CTRX group (P<0.05). There was no statistical difference between CTRX+DEXA group and the control group (P>0.05). These data suggested that Dexamethasone could down-regulate the expression of AQP4 in the brain tissue of rats with meningitis and provides evidence for the mechanism of protective effect of Dexamethasone on central neurosystem.

[Effects of levetiracetam on the expression of NCAM and GAP-43 mRNA in the hippocampus of rats with epilepsy].

OBJECTIVE: This study explored the effects of levetiracetam (LEV) on the expression of nerve cell adhesion molecule (NCAM) and growth-associated protein 43 (GAP-43) mRNA in the hippocampus of rats with epilepsy induced by lithium-pilocarpine (Li-PILO) in order to provide a basis for investigating the antiepileptic mechanism of LEV and its doseresponse. METHODS: Forty-eight Wistar rats were randomly divided into a normal control, a Li-PILO model and two LEV treatment groups (LEV: 150 and 300 mg/kg) (n=12 each). The LEV treatment groups received LEV by intragastric administration 6 hrs after status epilepticus (once daily for 2 two weeks). The expressions of NCAM and GAP-43 mRNA in the hippocampus was determined by real-time PCR. RESULTS: The expression of NCAM and GAP-43 mRNA in the Li-PILO model group was significantly higher than in the normal control group (P<0.05). LEV treatment of 150 and 300 mg/kg significantly decreased the expression of NCAM and GAP-43 mRNA compared with the Li-PILO model group (P<0.05). The LEV treatment group at the dose of 300 mg/kg showed significantly lower expression of NCAM and GAP-43 mRNA than the 150 mg/kg LEV treatment group (P<0.05). CONCLUSIONS: Li-PILO can up-regulate the expressions of NCAM and GAP-43 mRNA in the hippocampus of rats with epilepsy. LEV can inhibit the expression of NCAM and GAP-43 mRNA and the effect is associated with the dose of LEV.

[Effects of electric stimulation at the cerebellar fastigial nucleus on astrocytes in the hippocampus of neonatal rats with hypoxic-ischemic brain damage].

OBJECTIVE: To study the effects of electric stimulation at the cerebellar fastigial nucleus on astrocytes in the hippocampus of neonatal rats with hypoxic-ischemic brain damage (HIBD) and the possible mechanism. METHODS: One hundred and eighty 7-day-old neonatal Sprague-Dawley rats were randomly divided into three groups: sham-operation (control group) and HIBD with and without electric stimulation (n=60 each). The HIBD model of neonatal rats was prepared by the Rice-Vennucci method. Electric stimulation at the cerebellar fastigial nucleus was given 24 hrs after the operation in the electric stimulation group once daily and lasted for 30 minutes each time. The other two groups were not subjected to electric stimulation but captured to fix in corresponding periods. Rats were sacrificed 3, 7, 14 and 21 days after stimulations to observe the glial fibrillary acidic protein (GFAP) expression by immunohistochemisty and the ultrastructural changes of astrocytes in the hippocampus under an electron microscope. RESULTS: Immunohistochemical analysis showed the expression of GFAP in the HIBD groups with and without electric stimulation increased significantly compared with the control group on day 3, reached the peak on day 7, and the increased expression remained till to day 21. The GFAP expression in the electric stimulation group was significantly lower than that in the untreated HIBD group at all time points. Under the electron microscope, the astrocytes in the untreated HIBD group were swollen and the amount of organelles was reduced, while the swelling of astrocytes was alleviated and the organelles remained in integrity in the electric stimulation group. CONCLUSIONS: The electric stimulation at the cerebellar fastigial nucleus can inhibit the excessive proliferation of astrocytes and relieve the structural damage of astrocytes in neonatal rats following HIBD.

[Experimental study of DNA synthesis in the airway cells and airway remodeling in asthmatic rats].

OBJECTIVE: To study the DNA synthesis in the airway cells of asthmatic rats after allergen stimulation in association with airway remodeling. METHODS: Double staining immunohistochemical techniques was used to determine DNA synthesis of the airway cells of 12 asthmatic and 12 normal rats. BrdU incorporation into the airway smooth muscle (ASM) and epithelium was quantified by employment of computer-assisted image analysis. RESULTS: BrdU indices in both the ASM and the epithelium of asthmatic model group were higher than those of the control group (P<0.01, P<0.05), and positive linear correlation of the BrdU indices in the ASM and epithelium with the airway diameter was observed (r=0.7828, P<0.01; r=0.5852, P<0.05), which was not found in the control group (r=-0.3755, P>0.05; r=-0.5208, P>0.05). The epithelial thickness of the model group was significantly greater than that of the control group (P<0.01). There was no significant difference in terms of airway diameter, thickness of the ASM and the area positive of alpha-smooth muscle actin between the 2 groups (P>0.05). CONCLUSION: Increased DNA synthesis and accelerated proliferation of ASM and epithelial cells in sensitized SD rats following repeated allergen challenges may lead to airway remodeling.