Free heme and amyloid-β: a fatal liaison in Alzheimer's disease

While the etiology of Alzheimer's disease (AD) is still unknown, an increased formation of amyloid-β (Aβ) peptide and oxidative processes are major pathological mechanism of the disease. The interaction of Aβ with free heme leads to the formation of peroxidase-active Aβ-heme complexes. However, enzyme-kinetic data and systematic mutational studies are still missing. These aspects were addressed in this study to evaluate the role of Aβ-heme complexes in AD. The enzyme-kinetic measurements showed peroxidase-specific pH- and H2O2-dependencies. In addition, the enzymatic activity of Aβ-heme complexes constantly increased at higher peptide excess. Moreover, the role of the Aβ sequence for the named enzymatic activity was tested, depicting human-specific R5, Y10, and H13 as essential amino acids. Also by studying Y10 as an endogenous peroxidase substrate for Aβ-heme complexes, ratio-specific effects were observed, showing an optimal dityrosine formation at an about 40-fold peptide excess. As dityrosine formation promotes Aβ fibrillation while free heme disturbs protein aggregation, we also investigated the effect of Aβ-heme complex-derived peroxidase activity on the formation of Aβ fibrils. The fluorescence measurements showed a different fibrillation behavior at strong peroxidase activity, leading also to altered fibril morphologies. The latter was detected by electron microscopy. As illustrated by selected in vivo measurements on a mouse model of AD, the disease is also characterized by Aβ-derived microvessel destructions and hemolytic processes. Thus, thrombo-hemorrhagic events are discussed as a source for free heme in brain tissue. In summary, we suggest the formation and enzymatic activity of Aβ-heme complexes as pathological key features of AD.Solid state NMR/Biophysical Organic Chemistr

Experimental periodontal disease treatment by subgingival irrigation with tetracycline hydrochloride in rats

OBJECTIVE: The aim of this study was to compare subgingival irrigation with tetracycline hydrochloride (TTC-HCL) as adjunctive treatment to scaling and root planning (SRP) on induced periodontitis in rats. MATERIAL AND METHODS: In 60 rats, periodontal disease was ligature-induced at the mandibular left first molar. After 7 days, the ligature was removed and all animals were submitted to SRP, and divided into 2 groups according to the following treatment: C (n=30) - subgingival irrigation with 1 mL of saline; T (n=30) - subgingival irrigation with 1 mL of TTC-HCL (50 mg/mL). Ten animals in each group were euthanized at 7, 15 and 30 days posttreatment. The histometric values were statistically analyzed (p<0.05). RESULTS: In the histometric analysis, at 7, 15 and 30 days, Group T (0.72±0.05 mm(2), 0.57±0.14 mm(2), 0.62±0.07 mm(2)), showed less bone loss (p<0.05) than Group C (1.35±0.25 mm(2); 1.40±0.31 mm(2); 1.29±0.27 mm(2)), respectively. CONCLUSIONS: Subgingival irrigation with TTC-HCL was an effective adjunctive treatment for periodontal disease induced in rats

Non-surgical instrumentation associated with povidone-iodine in the treatment of interproximal furcation involvements

OBJECTIVE: The aim of this controlled clinical trial was to evaluate the effect of topically applied povidone-iodine (PVP-I) used as an adjunct to non-surgical treatment of interproximal class II furcation involvements. MATERIAL AND METHODS: Thirty-two patients presenting at least one interproximal class II furcation involvement that bled on probing with probing pocket depth (PPD) ≥5 mm were recruited. Patients were randomly chosen to receive either subgingival instrumentation with an ultrasonic device using PVP-I (10%) as the cooling liquid (test group) or identical treatment using distilled water as the cooling liquid (control group). The following clinical outcomes were evaluated: visible plaque index, bleeding on probing (BOP), position of the gingival margin, relative attachment level (RAL), PPD and relative horizontal attachment level (RHAL). BAPNA (N-benzoyl-Larginine-p-nitroanilide) testing was used to analyze trypsin-like activity in dental biofilm. All parameters were evaluated at baseline and 1, 3 and 6 months after non-surgical subgingival instrumentation. RESULTS: Six months after treatment, both groups had similar means of PPD reduction, RAL and RHAL gain (p>0.05). These variables were, respectively, 2.20±1.10 mm, 1.27±1.02 mm and 1.33±0.85 mm in the control group and 2.67±1.21 mm, 1.50±1.09 mm and 1.56±0.93 mm in the test group. No difference was observed between groups at none of the posttreatment periods, regarding the number of sites showing clinical attachment gain ≥2 mm. However, at 6 months posttreatment, the test group presented fewer sites with PPD ≥5 mm than the control group. Also at 6 months the test group had lower BAPNA values than control group. CONCLUSION: The use of PVP-I as an adjunct in the non-surgical treatment of interproximal class II furcation involvements provided limited additional clinical benefits

Amyloid beta and free heme: bloody new insights into the pathogenesis of Alzheimer's disease

Solid state NMR/Biophysical Organic Chemistr