Role Of Progranulin In Pneumococcal Meningitis

Objective:Bacterial meningitis is a life threatening infection disease of the central nervous system(CNS) in childhood, and is associated with high morbidity and mortality. The three main pathogens of bacterial meningitis are Haemophilus influenzae, Streptococcus pneumoniae and Diplococcus meningitis. In addition to the high morbidity and mortality, and about a third of the patients will appear serious neurological sequelae including cognition disorder, hearing loss, secondary cerebral edema, neurons and glia form a necrotic lesions, etc. The pathogenesis and exact etiology of bacterial meningitis is still unclear. It is difficult to effectively control the root cause of the disease, therefore, it is necessary to explore the molecular mechanism of the disease. Progranulin(PGRN) is not only an autocrine growth factor with multiple function but also immunoregulation factor. Recent studies show which is important in infection disease, wound healing, tumorigenesis, neuroproliferative and degenerative disease. Recently, PGRN has been found to be a novel ligand of TNF receptors(TNFR), which can exhibits anti-inflammatory function through competing with TNF-α binding to TNFR1/2 in inflammatory arthritis and inflammatory bowel disease. In contrast to its anti-inflammatory role, PGRN also has proinflammatory effects in obesity and insulin-resistant diabets mellitus by regulating IL-6. However, the expression and role of PGRN in bacterial meningitis has not been fully investigated. In this study, we will compare the difference expression of PGRN in patients with bacterial meningitis and observe the symptoms, inflammation, bacteria loads and survival rate of mice infected pneumococcal meningitis after PGRN defects, preliminary investigate the role and mechanism of PGRN in bacterial meningitis.Method:A total of 22 patients with culture-proven in cerebrospinal fluid, clinical confirmed bacterial meningitis, 12 clinical confirmed virus meningitis with IgM of various virus in cerebrospinal fluid and 10 controls matched for age, gender with no bacterial meningitis were enrolled in the study. The plasma and cerebrospinal fluid of them were collected, while gathering the relevant clinical information. ELISA analysis was used to detect the plasma levels and cerebrospinal fluid of PGRN.Wild-type(WT) mice 8-10 weeks,male and female half, were purchased and were injected 15μl suspension of standard Ⅲ streptococcus pneumoniae(including 4.5×106 CFU) to intracerebral ventricular, while injecting same volume physiological saline as control group. Using the common index to assess the model of experimental pneumococcal meningitis. We analyzed the different expression of PGRN in brain and plasma between the experimental pneumococcal meningitis group and control group in mice.The C57BL/6 background PGRN-/- mice were purchased and 8-10 weeks mice PGRN-/- mice along with their WT counterparts were used for these experiments. All of them were injected 15μl suspension of standard Ⅲ Streptococcus pneumoniae(including 4.5×106 CFU) to intracerebral ventricular. Compared the severity of clinical symptoms, survival rate, bacterial loads in brain and the inflammation level of brain to investigate the role of PGRN in bacterial meningitis.Results:In plasma, the protein levels of PGRN were dramatically elevated in bacterial meningitis patients compared with non-meningitis(P<0.05), while no different with virus meningitis. In cerebrospinal fluid, the PGRN protein level was significantly higher in virus meningitis than non-meningitis(P<0.001), while which in bacterial meningitis was more significantly higher than virus meningitis(P<0.01). The protein concentration of PGRN was the white blood cell count, significantly positive correlation with protein of cerebrospinal fluid. Above results shown the concentration of PGRN in plasma and cerebrospinal fluid may differential diagnosis the bacterial meningitis, virus meningitis, non-meningitis.Injected 15μl suspension of standard Ⅲ Streptococcus pneumoniae(including 4.5×106 CFU) to intracerebral ventricular of WT mice to model the experimental pneumococcal meningitis. After 24 hours, the experimental pneumococcal meningitis group of mice have the typical symptoms of bacterial meningitis, difficult to roll over, slow of movement, hair scattered, poor mobility, sleepiness, carpenter. The H&E stain of brain tissue shown the meningitis groups inflammatory was higher than the control group, manifesting by the more neutrophil infiltration at subarachnoid space, the broken of subarachnoid and so on. The proinflammatory factor levels of IL-6, TNF-α,IL-1β were higher in meningitis group(P<0.05). Above results has shown we have successfully established the experimental penumococcal meningitis model of mice.Injecting 15μl suspension of standard Ⅲ Streptococcus pneumoniae(including 4.5×106 CFU) at intracerebral ventricular in PGRN-/- mice and their WT counterparts, we found significantly more severity clinical symptoms(P<0.01), lower survival rate(P<0.01), higher of bacterial loads(P<0.05), stronger inflammatory response of brain(more neutrophil infiltration in subarachnoid).Conclusion:Our study demonstrates that PGRN have helped bacterial meningitis, playing a protective role in the pathogensis by increasing the clear of bacteria, inhibiting the inflammation levels to increasing the survival rate. Cerebrospinal fluid PGRN maybe a useful biomarker for diagnosis of bacterial meningitis and the therapeutic targets.