THE ROLE OF ENDOTHELIAL DYSFUNCTION (ED) AND EXCESSIVE OXIDATIVE STRESS IN THE DEVELOPMENT OF CARDIOVASCULAR DISEASES HAS RECENTLY BEEN HIGHLIGHTED. THE PRESENT STUDY EXAMINED THE EFFECT OF A HYDRO-ETHANOLIC EXTRACT OF A CHILEAN BERRY ARISTOTELIA CHILENSIS (FOLK NAME ?MAQUI), AND ITS FLAVONOIDS ANTIOXIDANTS RUTIN (RT) AND QUERCETIN (QC), ON THE RESPONSIVITY OF BLOOD VESSELS EXPOSED TO OXIDATIVE STRESS. FOR FUNCTIONAL RELAXATION STUDIES, THE ISOLATED RAT AORTIC RINGS (RARS) OF MALE WISTAR RATS WERE USED. TO MODEL ACUTE OXIDATIVE STRESS IN VITRO, RARS WERE INCUBATED IN KREBS' SOLUTION CONTAINING EITHER HIGH GLUCOSE (46 MM) OR THE O2- GENERATOR PYROGALLOL (50 ?M). RARS EXPOSED TO EITHER GLUCOSE OR PYROGALLOL DISPLAYED ATTENUATED MAXIMUM VASORELAXATION RESPONSES TO THE ENDOTHELIUM-DEPENDENT VASODILATOR ACETYLCHOLINE (ACH), AND REDUCED NITRIC OXIDE (NO) BIOAVAILABILITY. THESE EFFECTS WERE FULLY SUPPRESSED BY PRE-INCUBATION OF THE VESSELS WITH THE MAQUI BERRY EXTRACT (MBE), RT AND QC. BOTH, REMOVAL OF THE ENDOTHELIUM AND THE ADDITION OF NITRIC OXIDE SYNTHASE (NOS) INHIBITOR, NG-NITRO-L-ARGININE METHYL ESTER (L-NAME) INCREASED THE PHENYLEPHRINE (PHE) RESPONSE. THESE OBSERVATION SUGGEST THAT MBE, QC AND RT MAY PROTECT AGAINST HIGH GLUCOSE AND PYROGALLOL-INDUCED ENDOTHELIAL DYSFUNCTION VIA ENHANCED THE GENERATION AND BIOAVAILABILITY OF NO.

BAHUINIA CANDICANS IS A PLANT USED IN CHILE FOR DIABETES MANAGEMENT. THE AIM OF THE PRESENT STUDY WAS TO INVESTIGATE THE RELAXING RESPONSIVENESS TO ACETYLCHOLINE (ACH) OF PHENYLEPHRINE-PRECONTRACTED AORTIC RINGS FROM ALLOXAN-DIABETIC RATS TREATED WITH AN AQUEOUS-ETHANOL EXTRACT OF B.CANDICANS LEAVES (EBC-RATS, 120 MG/KG/DAY). EBC SIGNIFICANTLY REDUCED FASTING BLOOD SUGAR FROM 292.4 ± 9.2 MG/DL TO 174.6 ± 12.8 MG/DL. ACH INDUCED A NEGLIGIBLE REDUCTION OF TENSION (28 ± 6%) OF AORTIC RINGS FROM ALX-RATS COMPARED WITH EBC-RATS (48 ± 5.5 %) AND NORMAL (57 ± 5 %). THE ENHANCED SENSITIVITY TO PHENYLEPHRINE IN AORTIC RINGS FROM DIABETIC RATS WAS REDUCED IN EBC-RATS. REMOVAL OF THE ENDOTHELIUM OR PRETREATMENT OF RINGS OF EBC-RATS WITH NITRIC OXIDE SYNTHASE (NOS) INHIBITOR, NG-NITRO-L-ARGININE METHYL ESTER (L-NAME) INCREASED THE PHE RESPONSE. THE NITRIC OXIDE (NO) DONOR SODIUM NITROPRUSSIDE (SNP) INDUCED A NORMAL RELAXATION IN THESE RINGS. THE RESULTS SUGGEST THAT THE EXTRACT OF LEAVES OF B. CANDICANS INCREASES ENDOTHELIUM-DEPENDENT RELAXATION OF AORTIC RINGS OF ALX-RATS AND ITS USE MAY BE HELPFUL IN THE PREVENTION OF DIABETIC COMPLICATIONS.

NON-TECHNICAL SUMMARY EACH HEARTBEAT IS ACCOMPANIED BY THE COORDINATED RELEASE OF CALCIUM IONS INTO CARDIAC CELLS THROUGH RYANODINE RECEPTORS, WHICH SPAN THE MEMBRANE OF THE SARCOPLASMIC RETICULUM. WE SHOW THAT AN INTRA-SARCOPLASMIC RETICULUM PROTEIN, JUNCTIN, INTERACTS WITH RYANODINE RECEPTOR CHANNELS AND APPEARS TO ACTIVATE THEM WHEN CALCIUM INSIDE THE SARCOPLASMIC RETICULUM IS LOW. CONVERSELY, JUNCTIN APPEARS TO ACT AS AN INHIBITOR OF RYANODINE RECEPTORS WHEN CALCIUM INSIDE THE SARCOPLASMIC RETICULUM IS HIGH. KNOWLEDGE OF HOW JUNCTIN INTERACTS WITH RYANODINE RECEPTORS HELPS US TO UNDERSTAND HOW CALCIUM WITHIN THE SARCOPLASMIC RETICULUM HELPS TO REGULATE RYANODINE RECEPTOR ACTIVITY IN NORMAL HEARTS AND ALSO HELPS US TO UNDERSTAND WHY JUNCTIN IS DECREASED IN PATIENTS DIAGNOSED WITH CERTAIN FORMS OF HEART FAILURE.

PHOSPHATIDYLINOSITOL 3,5-BISPHOSPHATE (PI(3,5)P2) IS THE MOST RECENTLY IDENTIFIED PHOSPHOINOSITIDE, AND ITS FUNCTIONS HAVE YET TO BE FULLY ELUCIDATED. RECENTLY, MEMBERS OF OUR MUSCLE GROUP HAVE SHOWN THAT PI(3,5)P2 PLAYS AN IMPORTANT ROLE IN SKELETAL MUSCLE FUNCTION BY ALTERING CA(2+) HOMEOSTASIS. THEREFORE, WE HYPOTHESIZED THAT PI(3,5)P2 MAY ALSO MODULATE CARDIAC MUSCLE CONTRACTILITY BY ALTERING INTRACELLULAR CA(2+) ([CA(2+)](I)) IN CARDIAC MYOCYTES. WE FIRST CONFIRMED THAT PI(3,5)P2 WAS PRESENT AND INCREASED BY INSULIN TREATMENT OF CARDIOMYOCYTES VIA IMMUNOHISTOCHEMISTRY. TO EXAMINE THE ACUTE EFFECTS OF PI(3,5)P2 TREATMENT, ELECTRICALLY PACED LEFT VENTRICULAR MUSCLE STRIPS WERE INCUBATED WITH PI(3,5)P2. TREATMENT WITH PI(3,5)P2 INCREASED THE MAGNITUDE OF ISOMETRIC FORCE, THE RATE OF FORCE DEVELOPMENT, AND THE AREA ASSOCIATED WITH THE CONTRACTILE WAVEFORMS. THESE ENHANCED CONTRACTILE RESPONSES WERE ALSO OBSERVED IN MIP/MTMR14(-/-) MOUSE HEARTS, WHICH WE FOUND TO HAVE ELEVATED LEVELS OF PI(3,5)P2. IN CARDIAC MYOCYTES LOADED WITH FURA-2, PI(3,5)P2 PRODUCED A ROBUST ELEVATION IN [CA(2+)](I). THE PI(3,5)P2-INDUCED ELEVATION OF [CA(2+)](I) WAS NOT PRESENT IN CONDITIONS FREE OF EXTRACELLULAR CA(2+) AND WAS COMPLETELY BLOCKED BY RYANODINE. WE INVESTIGATED WHETHER THE PHOSPHOINOSITIDE ACTED DIRECTLY WITH THE CA(2+) RELEASE CHANNELS OF THE SARCOPLASMIC RETICULUM (RYANODINE RECEPTORS; RYR2). PI(3,5)P2 INCREASED [(3)H]RYANODINE BINDING AND INCREASED THE OPEN PROBABILITY (P(O)) OF SINGLE RYR2 CHANNELS RECONSTITUTED IN LIPID BILAYERS. THIS STRONGLY SUGGESTS THAT THE PHOSPHOINOSITIDE BINDS DIRECTLY TO THE RYR2 CHANNEL. THUS, WE PROVIDE INAUGURAL EVIDENCE THAT PI(3,5)P2 IS A POWERFUL ACTIVATOR OF SARCOPLASMIC RETICULUM CA(2+) RELEASE AND THEREBY MODULATES CARDIAC CONTRACTILITY.