Study On Effects Of Nerve Growth Factor Expression Level Induced By Formaldehyde Exposure

Nerve growth factor(NGF),discovered by Rita Levi-Montalcini more than 50 years ago,is a high molecular weight peptide that is a complex composed ofα,βandγ, subunits.NGF belongs to the neurotrophin family together with brain-derived neurotrophic factor(BDNF)and neurotrophins(NT)-3,(NT)-4,and(NT)-5,it is essential for cholinergic neuron of central nervous system,sympathetic and sensory neuron of peripheral nerveous system in development and differentiation.Previous researches of NGF were mainly focused on nervous system.The recent studies indicated that NGF could affect immunity and hematopoietic system,connect closely to allergia and inflammatory diseases.NGF can induce production,proliferation,differentiation and maturation of inflammatory and airway structural cells,mediate these cells migration and recruitment in inflammatory area,and facilitate peripheral nerveous system to secrete neuropeptide.Especially,many reports confirmed that NGF might play a key role in inflammation and airway hyperresponsiveness in bronchial asthma.Formaldehyde(FA),a kind of popular indoor air pollutant,is also an endogenous chemical.FA has become one of the most important and serious indoor air pollutants in China because of its characteristics of extensive sources,serious toxicity,high level pollution and long-term duration.The effects of FA on human health include eyes and upper respiratory irritancy,allergy and immunological effects,genotoxicity and cancer, neurotoxicity et al.Many investigation and researches indicated that FA exposure could result in asthma,but it was still unclear for its molecular mechanism.The previous studies of our research team have confirmed that FA-exposure could up-regulate some genes,such as vanilloid receptor type 1(VR1),N-methyl-D-aspartate(NMDA),thymic stromal lymphopoietin(TSLP),S-nitrosoglutathione reductase(GSNOR).This study took NGF as object,assessed NGF mRNA expression levels in the mice mast cells in vitro and mice brain and lung tissues in vivo,and then assessed NGF mRNA expression levels in rat lung tissues and lung function in being built rat asthma model in order to establish relation among FA,NGF and asthma.The results show as follows:1 FA induce NGF mRNA expression levels alteration of mice mast cells in vitroTo study whether FA can up-regulate NGF mRNA of the cultured cells in vitro,this study made mice mast cells exposure to different concentration FA respectively(0μmol/L, 5μmol/L,25μmol/L,125μmol/L)for 3h.Then we applied RT-PCR to assess NGF mRNA expression levels.The results showed that FA could up-regulate NGF mRNA justly in low concentration(5μmol/L),and NGF expression levels increased with FA concentration increasing.But in higher concentration(125μmol/L),NGF expression level dropped hardly.Thus FA can result in DNA damage,especially DNA-Protein Crosslinks(DPC).The effect can influent DNA replication and transcription severely.So this study also took mice mast cells as materials,assessed DPC effect after FA exposure that was relative to RT-PCR assess.The results showed that FA could induce DPC effect significantly at 125μmol/L concentration in vitro(P＜0.05).2 FA-inhaled induce NGF mRNA expression levels alteration of mice brain and lung tissues in vivoTo confirm whether FA can alter NGF mRNA expression levels of mice brain and lung tissues in vivo,we divided 24 kunming mice into 4 groups(n=6)randomly,the mice were exposured to 0,3.0 mg/m~3 FA for 24h and 72h respectively.Then we applied RT-PCR to assess NGF mRNA expression levels in mice brain and lung tissues.The results showed that there were different expression effects of NGF mRNA in these two tissues.There was significant up-regulation effect of NGF mRNA expression levels in mice lung after 24h FA-inhaled(P＜0.01),but it dropped after 72h FA-inhaled,even lower than the control group,however,there was no significant difference between the two groups(P＞0.05).NGF mRNA expression levels in mice brain increased with FA-inhaled time increasing,it was higher than the control group after 24h FA-inhaled and there was no significant difference between the two groups(P＞0.05),but there was significant difference between the 3.0 mg/m~3 FA-inhaled group and control group(P＜0.01)for 72h FA-inhaled.Meanwhile,different concentration FA-inhaled could not induce DPC effects in mice brain and lung in vivo(P＞0.05).3 NGF mRNA expression levels of lung tissues and lung function alteration in FA-induced rat asthma modelIn order to explore the relation among FA,NGF and asthma,we established a FA-induced rat asthma model,divided 21 wistar rats into 3 groups(n=7)randomly:the control group,1.0 mg/m~3 FA-inhaled group and 3.0 mg/m~3 FA-inhaled group.Then using AniRes2005 animal lung function system assessed index of rat lung function.After that, we executed rats and applied RT-PCR to assess NGF mRNA expression levels in lung tissues.The results showed that expiratory resistance(Re)and inspiratory resistance(Ri) increased gradually with FA-inhaled concentration increasing,and dynamic lung compliance(Cldyn)decreased gradually with FA-inhaled concentration increasing,there was different degree variability compared with the control group.NGF mRNA expression level of 1.0mg/m~3 FA-induced group was up-regulated significantly(P＜0.01), but that level of 3.0mg/m~3 FA-induced group dropped hardly compared with 1.0mg/m~3 FA-induced groups(P＜0.01),just higher than the control groups(P＞0.05).