Hydrogen Sulfide Modulates Sympathetic Outflow By Suppressing Activation Of NLRP3 Inflammasome

Objective: Primary hypertension is often accompanied by overactivation of sympathetic nervous system,and leads to the disruption of many endogenous neuroendocrine and cytokines which in turn promote cardiovascular remodeling,thus forming a vicious circle.The expression of inflammation in central nervous system is closely related to the activation of sympathetic-outflow.Microglia play a key role in regulating inflammation response and maintaining brain homeostasis.Under certain pathological stimuli,microglia can be activated,then resulting in producing and releasing inflammatory factors.Hydrogen sulfide(H2S)is a new type of gas signal molecule involved in regulating of cardiovascular system.Spontaneously hypertensive rats(SHR)were adopted in this experiment.Microinjection of H2 S donor sustained-release drug GYY4137 into the lateral ventricle.To observe whether it could attenuate the blood pressure and its central inflammatory response in spontaneously hypertensive rat and explore its relevant mechanism.Methods:1.Experimental groups:8 weeks old male SHR and wistar-Kyoto rats(WKY).Weight 290 � 20 g.Divided into four groups: WKY+ a CSF(Artificial cerebrospinal fluid),WKY+ GYY4137,SHR + a CSF,and SHR + GYY4137.2.Lateral ventricle catheterizationAccording to the rat brain in stereotaxic coordinates map of Paxinos&Watson,determined surface position with a1.5 mm side away sagittal suture,located at 0.8 mm behind the bregma.Implanted a stainless steel catheter slowly,tightening the bolt and secured.3.Record blood pressure,heart rate,and RSNARight femoral artery was used to cathetered.Renal sympathetic nerve activity(RSNA)was recorded by bipolar platinum electrode.Connected with Powerlab the biological signal acquisition system to record blood pressure,heart rate and RSNA.4.Implantation of transmitters5-7 days after telemetry surgery,BP was continuously recorded at a sampling rate of 1 k Hz using a Power Lab data acquisition system(ML880;ADInstruments).Heart rate(HR)was derived from the arterial pressure pulse.5.ImmunofluorescenceBrain tissue was treated with polyformaldehyde for fixing,dehydration,transparency,and paraffin embedded.Sliced the brain tissue in PVN and RVLM sections.Observed its expression through immunofluorescence double staining of ED-1(A marker for the activity of microglia)and IL-1?..6.Western blotDetected expression of inflammation related protein NLRP3,Caspase-1and IL-1? within nucleus paraventricularis(PVN)region.Results:1.Arterial blood pressure in SHR group(SBP,DBP,MAP)was obviously higher than that in WKY group.For SHR group,the blood pressure and renal sympathetic nerve activity in SHR group distinctly lowered upon acute injection of GYY4137 in lateral ventricle(SBP 190.60�6.55 vs.167.40�7.39 mm Hg,P<0.05;DBP 124.60�7.43 vs.106.60�6.08 mm Hg,P<0.05;MAP 146.60�7.0 vs.126.86�6.28 mm Hg,P < 0.05;?RSNA187.50�9.02% vs.110.68�7.12%,P<0.05),according to which there was statistical differences.2.The systolic blood pressure(SBP)in the SHR group was significantly higher than that in the WKY group after chronic administration.The blood pressure and renal sympathetic nerve activity in the SHR group significantly decreased after 6 weeks' GYY4137 treatment(SBP 173.94�0.49 vs.156.64�2.62 mm Hg,P<0.05;?RSNA 160.40�3.76% vs.128.80�3.02%,P<0.05).There was no significant effect on the WKY group(SBP 115.94�1.29 vs.110.30�2.55 mm Hg,P>0.05;?RSNA 100% vs.92.50�4.81%,P>0.05).3.It was observed through immunofluorescence confocal microscopy that the expression of microglia activation markers ED1 and inflammatory factor IL-1? increased significantly in PVN and RVLM region of SHR group,and that the expression of these proteins mentioned above significantly decreased after supplementation of exogenous GYY4137.4.Compared with WKY group,the expression of inflammation related protein NLRP3,Caspase-1 and IL-1? was significantly increased in PVN of SHR group.Administration of exogenous GYY4137,the expression of NLRP3,Caspase-1 and IL-1? significantly decreased.There was no significant effect on the WKY group.Conclusion: Exogenous administration of H2 S can attenuate the blood pressure of spontaneously hypertensive rats and decrease the activity of sympathetic nerve activity.The improvement may be attributed to inhibiting the activation of microglia and NLRP3 inflammasome of the central nervous system.