Translocase of outer mitochondrial membrane 40 (TOMM40) is located in the outer membrane of mitochondria. TOMM40 is essential for protein import into mitochondria. TOMM40 genetic variants are believed to increase the risk of Alzheimer’s disease (AD) in different populations. In this study, three exonic variants (rs772262361, rs157581, and rs11556505) and three intronic variants (rs157582, rs184017, and rs2075650) of the TOMM40 gene were identified from Taiwanese AD patients using next-generation sequencing. Associations between the three TOMM40 exonic variants and AD susceptibility were further evaluated in another AD cohort. Our results showed that rs157581 (c.339T > C, p.Phe113Leu, F113L) and rs11556505 (c.393C > T, p.Phe131Leu, F131L) were associated with an increased risk of AD. We further utilized cell models to examine the role of TOMM40 variation in mitochondrial dysfunction that causes microglial activation and neuroinflammation. When expressed in BV2 microglial cells, the AD-associated mutant (F113L) or (F131L) TOMM40 induced mitochondrial dysfunction and oxidative stress-induced activation of microglia and NLRP3 inflammasome. Pro-inflammatory TNF-α, IL-1β, and IL-6 released by mutant (F113L) or (F131L) TOMM40-activated BV2 microglial cells caused cell death of hippocampal neurons. Taiwanese AD patients carrying TOMM40 missense (F113L) or (F131L) variants displayed an increased plasma level of inflammatory cytokines IL-6, IL-18, IL-33, and COX-2. Our results provide evidence that TOMM40 exonic variants, including rs157581 (F113L) and rs11556505 (F131L), increase the AD risk of the Taiwanese population. Further studies suggest that AD-associated mutant (F113L) or (F131L) TOMM40 cause the neurotoxicity of hippocampal neurons by inducing the activation of microglia and NLRP3 inflammasome and the release of pro-inflammatory cytokines.

Oxidative stress is a key contributor to the pathogenesis of stroke-reperfusion injury. Neuroinflammatory peptides released after ischemic stroke mediate reperfusion injury. Previous studies, including ours, have shown that lipocalin-2 (LCN2) is secreted in response to cerebral ischemia to promote reperfusion injury. Genetic deletion of LCN2 significantly reduces brain injury after stroke, suggesting that LCN2 is a mediator of reperfusion injury and a potential therapeutic target. Immunotherapy has the potential to harness neuroinflammatory responses and provides neuroprotection against stroke. Here we report that LCN2 was induced on the inner surface of cerebral endothelial cells, neutrophils, and astrocytes that gatekeep the blood–brain barrier (BBB) after stroke. LCN2 monoclonal antibody (mAb) specifically targeted LCN2 in vitro and in vivo, attenuating the induction of LCN2 and pro-inflammatory mediators (iNOS, IL-6, CCL2, and CCL9) after stroke. Administration of LCN2 mAb at 4 h after stroke significantly reduced neurological deficits, cerebral infarction, edema, BBB leakage, and infiltration of neutrophils. The binding epitope of LCN2 mAb was mapped to the β3 and β4 strands, which are responsible for maintaining the integrity of LCN2 cup-shaped structure. These data indicate that LCN2 can be pharmacologically targeted using a specific mAb to reduce reperfusion injury after stroke.

Genetic factors may play a role in susceptibility to spontaneous deep intracerebral hemorrhage (SDICH). Previous studies have shown that TNF-α gene variation was associated with risks of subarachnoid hemorrhage in multiple ethnicities. The present case-control study tested the hypothesis that genetic variations of the TNF-α gene may affect the risk of Taiwanese SDICH. We examined the association of SDICH risks with four single nucleotide polymorphisms (SNPs) within the TNF-α gene promoter, namely T-1031C, C-863A, C-857T, and G-308A.

Spontaneous deep intracerebral hemorrhage (SDICH) is a devastating stroke subtype. The causes of SDICH are heterogeneous. Matrix metalloproteinase-9 (MMP-9, Gelantinase B) has been shown to relate to stroke and the development of aneurysm and may increase risks of intracerebral hemorrhage. MMP activities are modulated by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). We analyzed the genetic variants of MMP-9 and TIMP-1 and SDICH susceptibility. Associations were tested by logistic regression or general linear models with adjusting for multiple covariables. Multiplicative terms between genes were applied to detect the interaction effects on SDICH. Permutation testing of 1,000 replicates was performed for empirical estimates. In the group of ≥65 years old (y/o), we found associations of SDICH with rs3787268 (Odds ratio [OR] = 0.48, 95% confidence interval [CI] 0.27 to 0.86, P = 0.01) and haplotype1 (Hap1) (OR = 0.48, 95% CI 0.26 to 0.86, P = 0.014). For TIMP1 gene, rs4898 was associated with SDICH in the elder male group (OR = 0.35, 95% CI 0.15 to 0.81, P = 0.015). In contrast, in the younger male group, there were associations of SDICH with rs2250889 (OR = 0.48, 95% CI 0.27 to 0.84, P = 0.01) and Hap3 (OR = 0.61, 95% CI 0.38 to 0.97, P = 0.04). We found significant genetic interaction between TIMP-1 and MMP-9 in SDICH susceptibility among younger male subjects (P = 0.004). In subjects carrying rs4898 minor allele, carriers with Hap3 had lower SDICH risk than non-carriers (OR = 0.19, 95% CI 0.07 to 0.51, P = 0.001). In addition, this study showed that when young males were exposed to alcohol, Hap3 was a protective factor of SDICH (OR = 0.06, 95% CI 0.01 to 0.27, P = 0.0002). In contrast, when they were exposed to smoke, Hap2 carriers had increased risk of SDICH (OR = 2.45, 95% CI 1.05 to 5.73, P = 0.04). This study showed modest to moderate effects of MMP-9 and TIMP-1 polymorphisms on SDICH risks with significant age differences. MMP-9 may interact with alcohol to play a role in the SDICH risk in young men.

Differences in the incidence of spontaneous intracerebral hemorrhage (ICH) between ethnicities exist, with an estimated 42% of the variance explained by ethnicity itself. Caucasians have a higher proportion of lobar ICH (LICH, 15.4% of all ICH) than do Asians (3.4%). Alterations in the causal factor exposure between countries justify part of the ethnic variance in ICH incidence. One third of ICH risk can be explained by genetic variation; therefore, genetic differences between populations can partly explain the difference in ICH incidence. In this paper, we review the current knowledge of genetic variants associated with ICH in multiple ethnicities. Candidate gene variants reportedly associated with ICH were involved in the potential pathways of hypertension, vessel wall integrity, lipid metabolism, endothelial dysfunction, inflammation, platelet function, and coagulopathy. Furthermore, variations in APOE (in multiple ethnicities), PMF1/SLC25A44 (in European), ACE (in Asian), MTHFR (in multiple ethnicities), TRHDE (in European), and COL4A2 (in European) were the most convincingly associated with ICH. The majority of the associated genes provide small contributions to ICH risk, with few of them being replicated in multiple ethnicities.

With potentially neuroprotective properties, heme oxygenase-1 (HO-1) has been suggested to be the main mediator of cholesterol-independent anti-inflammatory and antioxidant actions of statins. However, we had demonstrated that simvastatin-induced HO-1 increased apoptosis of Neuro 2A cells in glucose deprivation, and iron production from HO-1 activity may be responsible for the toxicity. This study was designed to explore the effect of simvastatin-induced HO-1 on cultured Neuro 2A and C6 cells exposed to lipopolysaccharide (LPS). We found that the HO-1 upregulation was significantly associated with increased nuclear factor kappa B (NF-κB) activation, manifested as IκBα phosphorylation and p65 nuclear translocation, as well as increased production of superoxides. Inhibition of the induced HO-1 by zinc protoporphyrin reduced the increased NF-κB activation and superoxides production. RNA interference with HO-1 siRNA reduced the expression of HO-1 transcripts and protein as well as oxygen radical production. Addition of the iron chelator desferrioxamine to reduce the accumulation of ferric iron from heme by HO-1 resulted in blockade of the aggravated oxygen radical production. There was no significant effect on production of oxygen radicals under these conditions in the presence of a CO donor (RuCO) or a CO scavenger (hemoglobin). In addition, the viable cells were significantly decreased in 48 h in those cells receiving simvastatin pretreatment plus LPS compared to those in control or exposed to simvastatin or LPS alone. This study revealed that simvastatin-induced HO-1 led to increased NF-κB activation and superoxides production in the neuronal cells when exposed to LPS, and iron production may play a role in such a response.