| Diabetes mellitus is one of the important diseases that threaten the health of the publics.It is well known that it is important to prevent the chronic complications in order to decreasethe incidence of mutilation and mortality besides to control the levels of blood glucose.Among diabetic patients, 90 to 100% of them will live with chronic diabetic complications.Neurological complications are the most common complications of diabetes. We have noticedthat most of the neurological complications are not diagnosed and treated promptly. Pharmacal treatment for diabetic complications hasn't been settled yet. We noticed thatthere were some clinical reports about some drugs in the therapy of the chronic complicationsof diabetes. Pancreatic Kallidinogenase (PK) is a kind of proteinase with many kinds offunctions which include dilating small vessels and blood capillary and increasing capillaryblood flow, activating fibrinolysin, degrading blood viscosity and inhibiting the plateletaggregation, making kidney medulla secrete PGE2 and increasing renal blood flow. It candegrade the resistance of peripheral vessels and promote egestion of aqua and natrium. It hasbecome practical to consider its application in the treatment of neurological disease. BDNF and NT-3 are two important neurotrophin family numbers which share significantstructural homology and have structurally similar receptors. They are neurotrophin factors thatact directly on neurons;their actions include supporting the growth, differentiation andsurvival of neurons in the developing nervous system and maintaining neurons in the maturenervous system. CGRP is a well known neuropeptide that is released from primary nociceptive afferentsand involved in nociception in both the peripheral and the nervous system. It not onlyparticipates in the development of pain, inflammation and diabetic peripheral neuropathy butalso contributes to neuroprotection in neuron. VIP is a 28-amino-acid peptide that was firstisolated from porcine intestine and is involved with many regulatory functions, includingvasodilation, gastrointestinal secretion and motility, and glycogenolysis. VIP is also widelydistributed throughout the central and peripheral nervous system where it may serve as aputative neuromodulator. VIP has been found to produce a variety of actions includingalterations in intrinsic properties of neurons or synaptic transmission in the CNS.To our knowledge we speculate that BDNF, NT-3, CGRP and VIP take part in thepathological process of diabetic neuropathy.In this study, diabetic rat model was produced by an intraperitoneal (i.p.) injection ofstreptozocin (STZ). We exam the ethology, hemorheological impact of PK on theSTZ-induced diabetic rats.With the application of histopathology, immunohistochemistry,RT-PCR we observed the expression of BDNF, NT-3, CGRP and VIP in spinal cord, dorsalroot ganglion and gastrocnemius .The study tried to investigate the neuroprotective impact ofPK on diabetic peripheral neurology and the possible mechanisms.Methods:The experiments were carried out in the following three steps:1. We established Wistar rat model of diabetic peripheral neuropathy by anintraperitoneal injection of STZ.The rats were divided into three groups: normal group,diabetes mellitus group (DM group) and PK treatment group (PK group).2. The investigations of ethology, hemorheological alterations and nerve morphology 8weeks after onset of the diabetes were observed. We also examed the expression of BDNF,NT-3, CGRP and VIP in spinal cord, dorsal root ganglion and gastrocnemius 8 weeks afteronset of dibabetes with histopathology, immunohistochemistry and RT-PCR in each grouprats.3. The investigations of ethology, hemorheological alterations and nerve morphology 12weeks after onset of the diabetes were observed. We also examed the expression of BDNF,NT-3, CGRP and VIP in spinal cord, dorsal root ganglion and gastrocnemius 12 weeks afteronset of dibabetes with histopathology, immunohistochemistry and RT-PCR in each group.The methods of the experiments included: Water caloric test was applied to observe thebehaviroral alterations of the rats, the blood viscosity and plasma viscosity were measured byR80A type blood rheometer. We observed the nerve morphological alterations with thestaining of LFB and silver staining, with histopathology, immunohistochemistry and RT-PCRwe observed the expression of BDNF, NT-3, CGRP and VIP in spinal cord, dorsal rootganglion and gastrocnemius.Results:1. The demyelination of the peripheral nerve developed 8 weeks after the onset ofdiabetes induced by i.p. injection of STZ.The animal model is suitable for the study of chroniccomplications of diabetes.2. The demyelination of the peripheral nerve aggravated gradually with the extension ofthe time. PK can delay the development of demyelination of the peripheral nerves.3. The plasma viscosity and blood viscosity increased sharply for the rats 8 weeks and 12weeks after onset of diabetes compared with control rats. PK treatment can degrade theplasma viscosity and blood viscosity and delay the pathological process of peripheral nerves.4. There was no statistical difference in the total number of cells immunostained forCGRP and VIP in spinal cord among DM, PK and normal groups 8 weeks after onset ofdiabetes. There was a decrease in the number of CGRP and VIP immunoreactive cells of DMgroup compared with PK and control groups in the dorsal root ganglion (P<0.05), the totalnumber of cells immunostained for CGRP and VIP in the dorsal root ganglion in PK groupincreased compared with DM group 8 weeks after onset of diabetes (P<0.05).There was a decrease in the number of CGRP and VIP immunoreactive cells of DM andPK groups compared with control group in the spinal and the dorsal root ganglion (P<0.05)after 12 weeks onset of diabetes. There was no statistical difference in the total number ofcells immunostained for CGRP and VIP in spinal cord or in the DRG between DM and PKgroup 12 weeks after onset of diabetes.5. There was a decrease in the number of BDNF immunoreactive cells and BDNFmRNA expression of DM groups compared with normal group in the spinal cord (P<0.05)and the utilization of PK improved the change after 8 weeks onset of diabetes. There was anincrease in the number of BDNF immunoreactive cells in the DRG and BDNF mRNAexpression in gastrocnemius of DM groups compared with normal group (P<0.05) and theutilization of PK improved the allteration after 8 weeks onset of diabetes.There was a decrease in the number of BDNF immunoreactive cells and BDNF mRNAexpression of DM groups compared with normal group in the spinal cord (P<0.05). Theutilization of PK improved the BDNF mRNA expression compared with DM group in thespinal cord after 12 weeks onset of diabetes. There was an increase in the number of BDNFimmunoreactive cells in the DRG and BDNF mRNA expression in gastrocnemius of DMgroups compared with normal group (P<0.05) and the utilization of PK can't improve thealteration after 12 weeks onset of diabetes.There was a decrease in the number of BDNF immunoreactive cells and NT-3 mRNAexpression of DM groups compared with normal group in the spinal cord (P<0.05) and PKimproved the alteration after 8 weeks onset of diabetes. There was an increase in the numberof NT-3 immunoreactive cells of DM group in the DRG compared with PK or normal group(P<0.05) and there was no difference among the three groups of the NT-3 mRNA expressionin gastrocnemius after 8 weeks onset of diabetes.There was a decrease in the number of NT-3 immunoreactive cells of DM groupscompared with normal group in the spinal cord (P<0.05) and no difference compared with PKgroup after 12 weeks onset of diabetes. There was a decrease NT-3 mRNA expression of DMgroups compared with normal and PK group in the spinal cord (P<0.05) after 12 weeks onsetof diabetes. There was an increase in the number of NT-3 immunoreactive cells of DM groupin the DRG compared with normal group (P<0.05) and there was no difference compared withPK group after 12 weeks onset of diabetes. There was no difference of the NT-3 mRNAexpression in gastrocnemius among the three groups after 12 weeks onset of diabetes.Conclusions:1. The demyelination of the peripheral nerve developed 8 weeks after the onset ofdiabetes induced by i.p. injection of STZ and the demyelination of the peripheral nerveaggravated gradually with the extension of the time. PK can delay the development ofdemyelination of the peripheral nerve.2. PK can decrease the plasma viscosity and blood viscosity in the STZ-induced diabeticrats.3. PK can increase the number of CGRP and VIP immunoreactive cells in the dorsal rootganglion of DM diabetic rats after early onset of diabetes.4.The expression of BDNF and NT-3 decreased in the spinal cord of the diabetic rats andthe utilization of PK can increase the level of the expression. PK treatment can decrease theaccumulation of BDNF in the DRG after early onset of diabetes.5. PK has no efffec on the expression of CGRP,VIP,BDNF and NT-3 in the spinal cordand dorsal root ganglion of 12 weeks diabetic rats.The study provided the evidence of degenerative alterations in nerve system in diabeticrats and the pathological mechanism of diabetic neuropathy and possible mechanism of thePK treatment for diabetic neuropathy. The study also encouraged us to investigate nerveregeneration in the development of diabetic neuropathy and the contribution of PK on it.
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