The Herp protein pathway is not involved in the pro-amyloidogenic effect of hyperhomocysteinemia

Genomic deletion of GIT2 induces a premature age-related thymic dysfunction and systemic immune system disruption

Recent research has proposed that GIT2 (G protein-coupled receptor kinase interacting protein 2) acts as an integrator of the aging process through regulation of 'neurometabolic' integrity. One of the commonly accepted hallmarks of the aging process is thymic involution. At a relatively young age, 12 months old, GIT2^-/- mice present a prematurely distorted thymic structure and dysfunction compared to age-matched 12 month-old wild-type control (C57BL/6) mice. Disruption of thymic structure in GIT2^-/- (GIT2KO) mice was associated with a significant reduction in the expression of the cortical thymic marker, Troma-I (cytokeratin 8). Double positive (CD4⁺CD8⁺) and single positive CD4⁺ T cells were also markedly reduced in 12 month-old GIT2KO mice compared to age-matched control wild-type mice. Coincident with this premature thymic disruption in GIT2KO mice was the unique generation of a novel cervical 'organ', i.e. 'parathymic lobes'. These novel organs did not exhibit classical peripheral lymph node-like characteristics but expressed high levels of T cell progenitors that were reflexively reduced in GIT2KO thymi. Using signaling pathway analysis of GIT2KO thymus and parathymic lobe transcriptomic data we found that the molecular signaling functions lost in the dysfunctional GIT2KO thymus were selectively reinstated in the novel parathymic lobe - suggestive of a compensatory effect for the premature thymic disruption. Broader inspection of high-dimensionality transcriptomic data from GIT2KO lymph nodes, spleen, thymus and parathymic lobes revealed a systemic alteration of multiple proteins (Dbp, Tef, Per1, Per2, Fbxl3, Ddit4, Sin3a) involved in the multidimensional control of cell cycle clock regulation, cell senescence, cellular metabolism and DNA damage. Altered cell clock regulation across both immune and non-immune tissues therefore may be responsible for the premature 'aging' phenotype of GIT2KO mice.

Evidence of a novel gene HERPUD1 in polypoidal choroidal vasculopathy

Polypoidal choroidal vasculopathy (PCV) is an exudative maculopathy, with clinical features distinct from neovascular age-related macular degeneration (nAMD) which is the leading cause of irreversible blindness in the elderly. Our studies focused on the genetic background and function of a novel gene HERPUD1 in PCV. HERPUD1 has been reported to increase the level of amyloid β (Aβ), which is a component of drusen deposits underlying the retinal pigment epithelium (RPE) layer. To verify the genetic functional associations of HERPUD1 with PCV, exome sequencing of HERPUD1 was performed in unrelated Chinese individuals, including nAMD patients, PCV patients and control subjects. Immunohistochemistry assays for HERPUD1 were performed in the subretinal membranes of PCV patients. The relationship between HERPUD1 and amyloid beta precursor was determined using real-time PCR in HERPUD1-overexpressing RPE cells. The gene expression patterns of angiogenesis cytokines and chemokines in both Aβ-treated RPE cells and in Brown Norway rats that received Aβ subretinal injections were determined. We showed that HERPUD1 rs2217332 is significant associated with Chinese PCV, and HERPUD1 was expressed in PCV subretinal membranes. Besides, Plasma Aβ42 protein was significantly higher in PCV patients compared to nAMD and control subjects. Aβ could upregulate angiogenic factors, chemokines and matrix metalloproteinases both in RPE cells and in a rat model of subretinal Aβ injection. The imbalance of the cytokines may be one of the mechanisms for the formation and development of PCV. Our results strongly suggest that HERPUD1 is highly associated with PCV patients.

Mitochondrial dysfunction: different routes to Alzheimer's disease therapy

Mitochondria are dynamic ATP-generating organelle which contribute to many cellular functions including bioenergetics processes, intracellular calcium regulation, alteration of reduction-oxidation potential of cells, free radical scavenging, and activation of caspase mediated cell death. Mitochondrial functions can be negatively affected by amyloid β peptide (Aβ), an important component in Alzheimer's disease (AD) pathogenesis, and Aβ can interact with mitochondria and cause mitochondrial dysfunction. One of the most accepted hypotheses for AD onset implicates that mitochondrial dysfunction and oxidative stress are one of the primary events in the insurgence of the pathology. Here, we examine structural and functional mitochondrial changes in presence of Aβ. In particular we review data concerning Aβ import into mitochondrion and its involvement in mitochondrial oxidative stress, bioenergetics, biogenesis, trafficking, mitochondrial permeability transition pore (mPTP) formation, and mitochondrial protein interaction. Moreover, the development of AD therapy targeting mitochondria is also discussed.

Is hyperhomocysteinemia an Alzheimer's disease (AD) risk factor, an AD marker, or neither?

Alzheimer's disease (AD) is the most common form of neurodegenerative disease. The vast majority cases of AD are sporadic, without clear cause, and a combination of environmental and genetic factors has been implicated. The hypothesis that homocysteine (Hcy) is a risk factor for AD was initially prompted by the observation that patients with histologically confirmed AD had higher plasma levels of Hcy, termed hyperhomocysteinemia (HHcy), than age-matched controls. Most evidence accumulated so far implicates HHcy as a risk factor for AD onset, but there are also conflicting results. In this review we summarize reports on the relationship between HHcy and AD from epidemiological investigations, including observational studies and randomized controlled clinical trials. We also examine recent in vivo and in vitro studies of potential mechanisms whereby HHcy could influence AD development. Finally, we discuss possible reasons for the existing conflicting data and provide suggestions for future studies.