The Role of Neurotransmitters in Protection against Amyloid- β Toxicity by KiSS-1 Overexpression in SH-SY5Y Neurons.

Recent studies have suggested that the kisspeptin (KP) and kissorphin (KSO) peptides have neuroprotective actions against the Alzheimer's amyloid- β (A β ) peptide. Overexpression of the human KiSS-1 gene that codes for KP and KSO peptides in SH-SY5Y neurons has also been shown to inhibit A β neurotoxicity. The in vivo actions of KP include activation of neuroendocrine and neurotransmitter systems. The present study used antagonists of KP, neuropeptide FF (NPFF), opioids, oxytocin, estrogen, adrenergic, cholinergic, dopaminergic, serotonergic, and γ -aminobutyric acid (GABA) receptors plus inhibitors of catalase, cyclooxygenase, nitric oxide synthase, and the mitogen activated protein kinase cascade to characterize the KiSS-1 gene overexpression neuroprotection against A β cell model. The results showed that KiSS-1 overexpression is neuroprotective against A β and the action appears to involve the KP or KSO peptide products of KiSS-1 processing. The mechanism of neuroprotection does not involve the activation of the KP or NPFF receptors. Opioids play a role in the toxicity of A β in the KiSS-1 overexpression system and opioid antagonists naloxone or naltrexone inhibited A β toxicity. The mechanism of KiSS-1 overexpression induced protection against A β appears to have an oxytocin plus a cyclooxygenase dependent component, with the oxytocin antagonist atosiban and the cyclooxygenase inhibitor SC-560 both enhancing the toxicity of A β

The effects of catalase and kisspeptin overexpression on amyloid peptide toxicity

Amyloid β (Aβ) is the major component of the senile plaques in Alzheimer’s disease (AD). The mechanism underlying cell death in AD includes oxidative stress, apoptosis, impaired mitochondrial function and receptor mediated effects. Compounds that specifically bind to Aβ are neuroprotective. Catalase is an antioxidant enzyme that specifically binds Aβ. Kisspeptin (KP) is a product of the KiSS-1 gene and contains an Aβ binding domain, which also interacts with Aβ. The localization of catalase, KP and Aβ in the AD brain plus the effects of catalase and KiSS-1 overexpression in neuronal cells were investigated in the present study. Tissue sections from the AD pons region were immunohistochemically stained to determine if catalase or KP colocalized with Aβ deposits. The immunohistochemistry results show that immunoreactive KP or immunoreactive catalase co-localizes with immunoreactive Aβ in AD pons sections. These results suggest that endogenous catalase and KP could play neuroprotective roles in AD. Catalase and KiSS-1 overexpressing gene models were created by stably transfecting human catalase and KiSS-1 constructs into SH-SY5Y cells and overexpression confirmed by RT-PCR, immunocytochemistry and Western blotting. The effects of Aβ and H2O2 on cell viability were determined by either MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) or trypan blue assay. Catalase overexpressing SH-SY5Y neurons showed a reduced susceptibility to Aβ and H2O2 toxicity compared to vector control cells. The catalase overexpression neuroprotection could by reduced by the catalase activity inhibitor 3-Amino-1,2,4-triazole and an inhibitor of catalase-Aβ interactions benzothiazole aniline-tetra (ethylene glycol). The KiSS-1 overexpressing SH-SY5Y neurons also showed a reduced susceptibility to Aβ and H2O2 toxicity compared to vector control cells. The KiSS-1 overexpression neuroprotection could by reduced by an anti-KP antibody, the oyxtocin antagonist atosiban and the cyclooxygenase inhibitor SC-560. In conclusion, both catalase and KP colocalize with Aβ in AD pons sections and overexpression of catalase or KiSS-1 is neuroprotective against Aβ toxicity

Immunolocalization of Kisspeptin Associated with Amyloid-β Deposits in the Pons of an Alzheimer's Disease Patient.

The pons region of the Alzheimer’s disease (AD) brain is one of the last to show amyloid-ß (Aß) deposits and has been suggested to contain neuroprotective compounds. Kisspeptin (KP) is a hormone that activates the Hypothalamic-pituitary- gonadal axis and has been suggested to be neuroprotective against Aß toxicity. The localization of KP, plus the established endogenous neuroprotective compounds corticotropin releasing hormone (CRH) and catalase, in tissue sections from the pons region of a male AD subject have been determined in relation to Aß deposits. Results showed Aß deposits also stained with KP, CRH and catalase antibodies. At high magnification the staining of deposits was either KP or catalase positive and there was only a limited area of the deposits with KP-catalase co-localization. The CRH does not bind Aß, whilst both KP and catalase can bind Aß, suggesting that co- localization in Aß deposits is not restricted to compounds that directly bind Aß. The neuroprotective actions of KP, CRH and catalase were confirmed in vitro and fibrillar Aß preparations were shown to stimulate the release of KP in vitro. In conclusion, neuroprotective KP, CRH and catalase all co-localize with Aß plaque-like deposits in the pons region from a male AD subject

Benzothiazole Aniline Tetra(ethylene glycol) and 3-Amino-1,2,4-triazole Inhibit Neuroprotection against Amyloid Peptides by Catalase Overexpression in Vitro

Alzheimer’s disease, Familial British dementia, Familial Danish dementia, Type 2 diabetes mellitus, plus Creutzfeldt-Jakob disease are associated with amyloid fibril deposition and oxidative stress. The antioxidant enzyme catalase is a neuroprotective amyloid binding protein. Herein the effects of catalase overexpression in SH-SY5Y neuronal cells on the toxicity of amyloid-β (Aβ), amyloid-Bri (ABri), amyloid-Dan (ADan), amylin (IAPP), and prion protein (PrP) peptides were determined. Results showed catalase overexpression was neuroprotective against Aβ, ABri, ADan, IAPP, and PrP peptides. The catalase inhibitor 3-amino-1,2,4-triazole (3-AT) and catalase-amyloid interaction inhibitor benzothiazole aniline tetra(ethylene glycol) (BTA-EG4) significantly enhanced neurotoxicity of amyloid peptides in catalase overexpressing neuronal cells. This suggests catalase neuroprotection involves breakdown of hydrogen peroxide (H2O2) plus a direct binding interaction between catalase and the Aβ, ABri, ADan, IAPP, and PrP peptides. Kisspeptin 45–50 had additive neuroprotective actions against the Aβ peptide in catalase overexpressing cells. The effects of 3-AT had an intracellular site of action, while catalase-amyloid interactions had an extracellular component. These results suggest that the 3-AT and BTA-EG4 compounds may be able to inhibit endogenous catalase mediated neuroprotection. Use of BTA-EG4, or compounds that inhibit catalase binding to amyloid peptides, as potential therapeutics for Neurodegenerative diseases may therefore result in unwanted effects

Kisspeptin Prevention of Amyloid-β Peptide Neurotoxicityin Vitro

Alzheimer’s disease (AD) onset is associated with changes in hypothalamic-pituitary–gonadal (HPG) function. The 54 amino acid kisspeptin (KP) peptide regulates the HPG axis and alters antioxidant enzyme expression. The Alzheimer’s amyloid-β (Aβ) is neurotoxic, and this action can be prevented by the antioxidant enzyme catalase. Here, we examined the effects of KP peptides on the neurotoxicity of Aβ, prion protein (PrP), and amylin (IAPP) peptides. The Aβ, PrP, and IAPP peptides stimulated the release of KP and KP 45–54. The KP peptides inhibited the neurotoxicity of Aβ, PrP, and IAPP peptides, via an action that could not be blocked by kisspeptin-receptor (GPR-54) or neuropeptide FF (NPFF) receptor antagonists. Knockdown of KiSS-1 gene, which encodes the KP peptides, in human neuronal SH-SY5Y cells with siRNA enhanced the toxicity of amyloid peptides, while KiSS-1 overexpression was neuroprotective. A comparison of the catalase and KP sequences identified a similarity between KP residues 42–51 and the region of catalase that binds Aβ. The KP peptides containing residues 45–50 bound Aβ, PrP, and IAPP, inhibited Congo red binding, and were neuroprotective. These results suggest that KP peptides are neuroprotective against Aβ, IAPP, and PrP peptides via a receptor independent action involving direct binding to the amyloid peptides