GSK3β is involved in promoting Alzheimer's disease pathologies following chronic systemic exposure to Porphyromonas gingivalis lipopolysaccharide in amyloid precursor proteinNL-F/NL-F knock-in mice

In line with the strong association between periodontitis and Alzheimer's disease (AD) clinically, preclinical studies have shown that systemic exposure to Porphyromonas gingivalis (Pg) initiates AD pathologies. However, the involvement of periodontitis in promoting AD pathologies is unclear. In the present study, we provided evidence that chronic systemic exposure to lipopolysaccharide derived from Pg (PgLPS, 1 mg/kg, daily, intraperitoneally) prompted neuroinflammation and tau hyperphosphorylation in 10-month-old of amyloid precursor protein (APP) knock-in mice, a model of AD, carrying the Swedish and Beyreuther/Iberian mutation (APP^NL-F/NL-F). The learning and memory function were assessed using the passive avoidance test. The production of APP, Amyloid (A)β_1-42, cytokines, synaptic proteins and the activation of glycogen synthase kinase (GSK)-3β as well as phosphorylation of tau were analyzed by immunohistochemistry, Western blotting or an enzyme-linked immunosorbent assay (ELISA) in the cortex of APP^NL-F/NL-F mice. We found that systemic exposure of PgLPS for three consecutive weeks induced learning and memory deficits with significantly reduced postsynaptic density protein (PSD95). Increased hyperphosphorylation of tau in multiple residues, including Ser202, Thr231 and Ser396, but not the accumulation of Aβ_1-42 was detected in the neurons of APP^NL-F/NL-F mice. Furthermore, PgLPS increased the GSK3β activity by reducing its phosphorylation of the serine residue at position 9 (Ser9) and promoted neuroinflammation by increasing the expression of interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) while decreasing that of interleukin-10 (IL-10) and transforming growth factor (TGFβ) in the cortex of APP^NL-F/NL-F mice. Moreover, the PgLPS-increased GSK3β activity was detected in both microglia and neurons, while the PgLPS-increased TNF-α expression was mainly detected in the microglia in the cortex of APP^NL-F/NL-F mice. In in vitro studies, PgLPS (1 µg/ml) stimulation increased the mRNA and protein level of TNF-α in MG6 microglia, which were significantly inhibited by the GSK3β-specific inhibitor TWS119. In contrast, the tau hyperphosphorylation and activation of GSK3β in N2a neurons were enhanced after treatment with conditioned medium from PgLPS-stimulated microglia, which was attenuated after pre-treatment with TNF-α inhibitor. Taken together, these findings indicate that GSK3β is involved in prompting microglia (TNF-α)-dependent tau hyperphosphorylation in neurons, resulting in learning and memory deficits in APP^NL-F/NL-F mice without changes in the Aβ expression during chronic systemic exposure to PgLPS. We propose that dampening GSK3β activation may help delay the periodontitis-promoted pathological progression of AD.

Modulation of startle and the startle-elicited P300 by the conditions of the cued continuous performance task in school-age boys

OBJECTIVES

This study compares the modulation of the startle response by conditions requiring response preparation, production, and inhibition during a cued continuous performance task (CPT) in children to the results of previous studies in adults and evaluates the modulation of the startle-elicited P300 under the same conditions. The latter variable, reflecting the cognitive processing of the startling stimulus (SS), has not been studied under these conditions.

METHODS

Normal boys completed a cued CPT in which the cue was the letter T, the go condition requiring a button press was an X following the T, and the no-go condition requiring response inhibition was a letter other than X following the T. SS were presented 450 ms following the letter of interest in each condition. The amplitudes of the startle-elicited P300 at Fz, Cz, and Pz and the startle blink were compared in the different CPT conditions.

RESULTS

The startle blink, measured by orbicularis oculi electromyography, was not inhibited by the no-go CPT condition as is the case in adults. The vertical electro-oculogram was actually largest in the no-go condition. The startle-elicited P300 showed a central predominance and was significantly larger in the no-go condition and in the cue condition than in the go condition.

CONCLUSIONS

The absence of inhibition of the startle response during the no-go condition probably reflects a relative inefficiency of prefrontal cortical mechanisms that mediate response inhibition in children compared to adults. The enhanced startle-elicited P300 in the no-go and cue conditions of the CPT reflects cognitive processing of the SS that has been influenced by response inhibition or its anticipation.

Predictors of posttraumatic stress symptoms in childhood cancer survivors

OBJECTIVE

The diagnosis and treatment of childhood cancer are extremely stressful experiences, with psychological sequelae which can persist many years after the end of treatment. This study investigated the relative contributions of general anxiety, treatment intensity, medical sequelae of treatment, and the subjective appraisal of life threat and treatment intensity to later posttraumatic stress symptoms, such as intrusive memories, avoidance, and hypervigilance.

METHOD

One hundred eighty-six childhood cancer survivors ages 8 through 20 years, off of treatment for more than 1 year, and their parents completed questionnaires. Medical sequelae of treatment and intensity of treatment were rated by a pediatric oncologist.

RESULTS

Significant, independent predictors of persistent posttraumatic stress symptoms included: 1) the survivor's retrospective subjective appraisal of life threat at the time of treatment, and the degree to which the survivor experienced the treatment as "hard" or "scary"; 2) the child's general level of anxiety; 3) history of other stressful experiences; 4) time since the termination of treatment (negative association); 5) female gender; and 6) family and social support. Mother's perception of treatment and life threat contributed to anxiety and subjective appraisal for the survivor, but did not independently contribute to posttraumatic stress symptoms.

CONCLUSIONS

Symptoms of posttraumatic stress seem to decrease with time, but are persistent in a subset of childhood cancer survivors. Other than time and gender, the predictors of posttraumatic stress symptoms are primarily subjective factors (ie, anxiety and subjective appraisal) rather than objective stressors of treatment and medical sequelae.

Children's PTSD reactions one year after a sniper attack at their school

Fourteen months after a sniper attack at an elementary school, level of exposure to that event remained the primary predictor of ongoing posttraumatic stress reactions in 100 schoolchildren who were followed up. Guilt feelings and knowing the child who was killed were associated with a greater number of symptoms. Grief reactions occurred independent of degree of exposure to the event. The authors discuss the public health implications of these longitudinal findings.

Attitudes toward mental illness prevention in routine pediatric practice

Attitudes toward preventive mental health activities with high-risk children in clinical practice were surveyed in 316 pediatricians. Although generally positive attitudes were expressed regarding appropriateness and efficacy of such activities, uncertainty was expressed regarding the ethical issues and knowledge on which such activities rest. Pediatricians perceived serious barriers to preventive activities related to financial, educational, and time factors. Pediatricians whose personal health beliefs favored an internal locus of control were more positively inclined toward preventive activities. Studies relating reported attitudes and beliefs to actual practice patterns are necessary. Pediatricians also require additional training in mental health-related preventive activities.

Sexual assault of a mother by her preadolescent son

The authors report a case of an 8-year-old boy who sexually assaulted his mother. Pertinent literature on incest and rape and the relevant clinical issues are briefly reviewed.