Central administration of aminoprocalcitonin inhibits food intake and stimulates the hypothalamic-pituitary-adrenal axis in rats via the corticotrophin-releasing factor system

Aminoprocalcitonin protects against hippocampal neuronal death via preserving oxidative phosphorylation in refractory status epilepticus

Refractory status epilepticus (RSE) is a neurological emergency where sustaining seizure causes severe neuronal death. Currently, there is no available neuroprotectant effective in RSE. Aminoprocalcitonin (NPCT) is a conserved peptide cleaved from procalcitonin, but its distribution and function in the brain remain enigmatic. Survival of neurons relies on sufficient energy supply. Recently, we found that NPCT was extensively distributed in the brain and had potent modulations on neuronal oxidative phosphorylation (OXPHOS), suggesting that NPCT might be involved in neuronal death by regulating energy status. In the present study, combining biochemical and histological methods, high-throughput RNA-sequence, Seahorse XFe analyser, an array of mitochondria function assays, and behavior-electroencephalogram (EEG) monitoring, we investigated the roles and translational values of NPCT in neuronal death after RSE. We found that NPCT was extensively distributed throughout gray matters in rat brain while RSE triggered NPCT overexpression in hippocampal CA3 pyramidal neurons. High-throughput RNA-sequence demonstrated that the influences of NPCT on primary hippocampal neurons were enriched in OXPHOS. Further function assays verified that NPCT facilitated ATP production, enhanced the activities of mitochondrial respiratory chain complexes I, IV, V, and increased neuronal maximal respiration capacity. NPCT exerted multiple neurotrophic effects including facilitating synaptogenesis, neuritogenesis, spinogenesis, and suppression of caspase-3. A polyclonal NPCT immunoneutralization antibody was developed to antagonize NPCT. In the in vitro 0-Mg²⁺ seizure model, immunoneutralization of NPCT caused more neuronal death, while exogenous NPCT supplementation, though did not reverse death outcomes, preserved mitochondrial membrane potential. In rat RSE model, both peripheral and intracerebroventricular immunoneutralization of NPCT exacerbated hippocampal neuronal death and peripheral immunoneutralization increased mortality. Intracerebroventricular immunoneutralization of NPCT further led to more serious hippocampal ATP depletion, and significant EEG power exhaustion. We conclude that NPCT is a neuropeptide regulating neuronal OXPHOS. During RSE, NPCT was overexpressed to protect hippocampal neuronal survival via facilitating energy supply.

Diagnostic Accuracy of Cerebrospinal Fluid Procalcitonin in Bacterial Meningitis Patients with Empiric Antibiotic Pretreatment

Accurate diagnosis of bacterial meningitis (BM) relies on cerebrospinal fluid (CSF) Gram staining and bacterial culture, which often present high false-negative rates because of antibiotic abuse. Thus, a novel and reliable diagnostic biomarker is required. Procalcitonin (PCT) has been well demonstrated to be specifically produced from peripheral tissues by bacterial infection, which makes it a potential diagnostic biomarker candidate. Here, we performed a prospective clinical study comprising a total of 143 patients to investigate the diagnostic value of CSF PCT, serum PCT, and other conventional biomarkers for BM. Patients were assigned to the BM (n = 49), tuberculous meningitis (TBM) (n = 25), viral meningitis/encephalitis (VM/E) (n = 34), autoimmune encephalitis (AIE) (n = 15), or noninflammatory nervous system diseases (NINSD) group (n = 20). Empirical antibiotic pretreatment was not an exclusion criterion. Our results show that the CSF PCT level was significantly (P < 0.01) higher in patients with BM (median, 0.22 ng/ml; range, 0.13 to 0.54 ng/ml) than in those with TBM (median, 0.12 ng/ml; range, 0.07 to 0.16 ng/ml), VM/E (median, 0.09 ng/ml; range, 0.07 to 0.11 ng/ml), AIE (median, 0.06 ng/ml; range, 0.05 to 0.10 ng/ml), or NINSD (median, 0.07 ng/ml; range, 0.06 to 0.08 ng/ml). Among the assessed biomarkers, CSF PCT exhibited the largest area under the receiver operating characteristic curve (0.881; 95% confidence interval, 0.810 to 0.932; cutoff value, 0.15 ng/ml; sensitivity, 69.39%; specificity, 91.49%). Our study sheds light upon the diagnostic dilemma of BM due to antibiotic abuse. (This study has been registered at ClinicalTrials.gov under registration no. NCT02278016.).

Potential Role of Aminoprocalcitonin in the Pathogenesis of Alzheimer Disease

Increasing evidence suggests that inflammatory responses cause brain atrophy and play a prominent and early role in the progression of Alzheimer disease. Recent findings show that the neuroendocrine peptide aminoprocalcitonin (NPCT) plays a critical role in the development of systemic inflammatory response; however, the presence, possible function, regulation, and mechanisms by which NPCT may be involved in Alzheimer disease neuropathology remain unknown. We explored the expression of NPCT and its interaction with amyloid-β (Aβ), and proinflammatory and neurogenic effects. By using brain samples of Alzheimer disease patients and APP/PS1 transgenic mice, we evaluated the potential role of NPCT on Aβ-related pathology. We found that NPCT is expressed in hippocampal and cortical neurons and Aβ-induced up-regulation of NPCT expression. Peripherally administered antibodies against NPCT decreased microglial activation, decreased circulating levels of proinflammatory cytokines, and prevented Aβ-induced neurotoxicity in experimental models of Alzheimer disease. Remarkably, anti-NPTC therapy resulted in a significant improvement in the behavioral status of APP/PS1 mice. Our results indicate a central role of NPCT in Alzheimer disease pathogenesis and suggest NPCT as a potential biomarker and therapeutic target.

Aminoprocalcitonin-mediated suppression of feeding involves the hypothalamic melanocortin system

Aminoprocalcitonin (N-PCT), a neuroendocrine peptide encoded by the calcitonin-I (CALC-I) gene, suppresses food intake when administered centrally in rats. However, the neural pathways underlying this effect remain unclear. N-PCT and calcitonin receptors (CT-R) have been identified in hypothalamic regions involved in energy homeostasis, including the arcuate nucleus (ARC). Here, we hypothesized an involvement of the hypothalamic ARC in mediating the anorexic effects of central N-PCT based on its content of peptidergic neurons involved in feeding and its expression of N-PCT and CT-R. Fasting strongly reduced expression of the N-PCT precursor gene CALC-I in the ARC, and central immunoneutralization of endogenous N-PCT increased food intake. Intracerebroventricular administration of N-PCT reduced food intake in fed and fasted rats, and its effect was attenuated by a neutralizing anti-N-PCT antibody. Immunohistochemistry for N-PCT showed that it is expressed in astrocytes and neurons in the ARC and is colocalized with anorexigenic proopiomelanocortin (POMC) neurons. Fasting reduced coexpression of N-PCT and POMC, and N-PCT administration activated hypothalamic neurons, including rostral POMC neurons. We also found that N-PCT stimulates POMC mRNA expression in fed and fasted rats, whereas it reduced the expression of orexigenic peptides neuropeptide Y (NPY) and agouti-related peptide (AgRP) only in fasted rats in which those mRNAs are normally elevated. Finally, we showed that the melanocortin-3/4 receptor antagonist SHU 9119 attenuates the intake-suppressive effect of N-PCT. These data demonstrate that hypothalamic N-PCT is involved in control of energy balance and that its anorexigenic effects are mediated through the melanocortin system.