Mechanisms And Effects Of Synergy Between Different Doses Of1,25-（OH）₂D₃&Methylprednisolone In Asthmatic Mice Airway Inflammation

objective: The increasing studies are very suggestive that vitamin Dhas synergistic effects on the administration of corticosteroids by eitherenhancing corticosteroid effects or reversing steroid resistance in thetreatment of asthma. When it comes to vitamin D supplementation,the mostconcerned problem is dose.the effects of different circulating level anddoses of vitamin D reach no agreement.This study will be needed to clarifywhat dose of vitamin D affords the greatest potential for synergy with steroids.Methods:Forty BALB/C female mice of four to five weeks were randomlydivided into five groups. there are8BALB/C female mice in each group,controlgroup (A), asthma group (B), methylprednisolone group (C), low-dose1,25(OH)2D3combined with methylprednisolone group (D), high-dose1,25(OH)2D3combined with methylprednisolone group (E). On2and9days,the mice inB、C、D、E group were sensitized with ovalbumin via introperitoneal injectionand challenged with daily ovalbumin inhalation for5consecutive days sinceday16．Methylprednisolone at5mg／kg was administered intraperitoneallyinjection1hour before the challenge for C、D、E group respectively，the micein low-dose1,25(OH)2D3combined with methylprednisolone group (D), high-dose1,25(OH)2D3combined with methylprednisolone group (E) groupwere given different doses of1,25-(OH)2D3by intraperitoneal injection with5μg/kg(equivalent to our daily recommended intake of vitamin D (RNI)400IU),10μg/kg(equivalent to twice of our daily recommended intake ofvitamin D (RNI)) respectively1hour before the challenge.The control groupreceived the same dose of0.9%saline by intraperitoneal injection andinhalation.24hours after the last challenge,each mouse sacrificed after airwayresponsiveness was measured. cell counts in bronchoalveolar lavage fluid andhematoxylin and eosin (HE) staining was carried out to lung tissue to observeairway inflammation. The lung tissue homogenates were then detected byimmunoblotting for determination of the expression of MKP-1（Mitogen-activated protein kinase phosphatase-1）． Enzyme-linkedimmunosorbent assay was used to detect serum concentrations of IL-10,chemokine FKN (fractalkine) Results: After the intervention different dose of1,25(OH)2-D3,Group D、E compared with group B、C respectively：enhancement of forced expiratory airway (Penh) value and airway reactivitydecreased（P<0.05）;serum IL-10levels were significantly increased (P <0.05);serum chemokine FKN (fractalkine) levels were significantly decreased (P<0.05);the concentrations of protein MKP-1（Mitogen-activated protein kinasephosphatase-1） in lung tissue homogenates were significantly increased（P<0.05）；both total cells and the percentage of eosinophils(EOS) weretatistically decreased in BALF(bronchoalveolar lavage fluid) （P<0.05）;Pathological changes in lung tissue revealed lighter eosinophilicinfiltration、 mucosal edema,and inflammation, no significant structuralmorphology damage to the alveolar structure,no obvious alveolar thickeningand alveolar interstitialfibrosis.Asthma group shows the heaviest inflammationof lung tissue, a lot of eosinophils and neutrophils infiltration were found inBronchial mucos and Massive necrosis and exudates in alveolar.pathologicalchanges of Methylprednisolone group fall in between.Group D compared withgroup E：The difference of enhancement of forced expiratory airway (Penh)value and airway reactivity、serum IL-10and chemokine FKN (fractalkine)levels、the concentrations of protein MKP-1（Mitogen-activated protein kinasephosphatase-1） in lung tissue homogenates、 both total cells and thepercentage of eosinophils(EOS) in BALF(bronchoalveolar lavage fluid)between those two groups were not statistically significant（P>0.05）;Inflammation of the lung tissue were mild,and no significantdifference between the two groups.Conclusion:1:Both High doses of1,25(OH)2D3and low-dose1,25(OH)2D3have synergistic effects on the administrationof methylprednisolone by alleviating airway inflammation in the asthmaticmice;No significant difference between the synergistic effects on high-dose of1,25(OH)2D3and low-dose1,25(OH)2D3with methylprednisolone.