Mahmoud L. Soliman

Acetate reduces microglia inflammatory signaling in vitro

Acetate supplementation increases brain acetyl‐CoA and histone acetylation and reduces lipopolysaccharide (LPS)‐induced neuroglial activation and interleukin (IL)‐1β expression in vivo. To determine how acetate imparts these properties, we tested the hypothesis that acetate metabolism reduces inflammatory signaling in microglia. To test this, we measured the effect acetate treatment had on cytokine expression, mitogen‐activated protein kinase (MAPK) signaling, histone H3 at lysine 9 acetylation, and alterations of nuclear factor‐kappa B (NF‐κB) in primary and BV‐2 cultured microglia. We found that treatment induced H3K9 hyperacetylation and reversed LPS‐induced H3K9 hypoacetylation similar to that found in vivo. LPS also increased IL‐1β, IL‐6, and tumor necrosis factor‐alpha (TNF‐α) mRNA and protein, whereas treatment returned the protein to control levels and only partially attenuated IL‐6 mRNA. In contrast, treatment increased mRNA levels of transforming growth factor‐β1 (TGF‐β1) and both IL‐4 mRNA and protein. LPS increased p38 MAPK and JNK phosphorylation at 4 and 2–4 h, respectively, whereas treatment reduced p38 MAPK and JNK phosphorylation only at 2 h. In addition, treatment reversed the LPS‐induced elevation of NF‐κB p65 protein and phosphorylation at serine 468 and induced acetylation at lysine 310. These data suggest that acetate metabolism reduces inflammatory signaling and alters histone and non‐histone protein acetylation.

Acetate supplementation modulates brain histone acetylation and decreases interleukin-1β expression in a rat model of neuroinflammation

BackgroundLong-term acetate supplementation reduces neuroglial activation and cholinergic cell loss in a rat model of lipopolysaccharide-induced neuroinflammation. Additionally, a single dose of glyceryl triacetate, used to induce acetate supplementation, increases histone H3 and H4 acetylation and inhibits histone deacetylase activity and histone deacetylase-2 expression in normal rat brain. Here, we propose that the therapeutic effect of acetate in reducing neuroglial activation is due to a reversal of lipopolysaccharide-induced changes in histone acetylation and pro-inflammatory cytokine expression.MethodsIn this study, we examined the effect of a 28-day-dosing regimen of glyceryl triacetate, to induce acetate supplementation, on brain histone acetylation and interleukin-1β expression in a rat model of lipopolysaccharide-induced neuroinflammation. The effect was analyzed using Western blot analysis, quantitative real-time polymerase chain reaction and enzymic histone deacetylase and histone acetyltransferase assays. Statistical analysis was performed using one-way analysis of variance, parametric or nonparametric when appropriate, followed by Tukeys or Dunns post-hoc test, respectively.ResultsWe found that long-term acetate supplementation increased the proportion of brain histone H3 acetylated at lysine 9 (H3K9), histone H4 acetylated at lysine 8 and histone H4 acetylated at lysine 16. However, unlike a single dose of glyceryl triacetate, long-term treatment increased histone acetyltransferase activity and had no effect on histone deacetylase activity, with variable effects on brain histone deacetylase class I and II expression. In agreement with this hypothesis, neuroinflammation reduced the proportion of brain H3K9 acetylation by 50%, which was effectively reversed with acetate supplementation. Further, in rats subjected to lipopolysaccharide-induced neuroinflammation, the pro-inflammatory cytokine interleukin-1β protein and mRNA levels were increased by 1.3- and 10-fold, respectively, and acetate supplementation reduced this expression to control levels.ConclusionBased on these results, we conclude that dietary acetate supplementation attenuates neuroglial activation by effectively reducing pro-inflammatory cytokine expression by a mechanism that may involve a distinct site-specific pattern of histone acetylation and histone deacetylase expression in the brain.

Acetate Reduces PGE2 Release and Modulates Phospholipase and Cyclooxygenase Levels in Neuroglia Stimulated with Lipopolysaccharide

Acetate supplementation attenuates neuroglial activation, increases histone and non-histone protein acetylation, reduces pro-inflammatory cytokine expression, and increases IL-4 transcription in rat models of neuroinflammation and Lyme’s neuroborreliosis. Because eicosanoid signaling is involved in neuroinflammation, we measured the effect acetate treatment had on phospholipase, cyclooxygenase, and prostaglandin E2 (PGE2) levels in BV-2 microglia and primary astrocytes stimulated with lipopolysaccharide (LPS). In BV-2 microglia, we found that LPS increased the phosphorylation-state of cytosolic phospholipase A2 (cPLA2), reduced the levels of phospholipase C (PLC) β1, and increased the levels of cyclooxygenase (Cox)-1 and -2. Acetate treatment returned PLCβ1 and Cox-1 levels to normal, attenuated the increase in Cox-2, but had no effect on cPLA2 phosphorylation. In primary astrocytes, LPS increased the phosphorylation of cPLA2 and increased the levels of Cox-1 and Cox-2. Acetate treatment in these cells reduced secretory PLA2 IIA and PLCβ1 levels as compared to LPS-treatment groups, reversed the increase in cPLA2 phosphorylation, and returned Cox-1 levels to normal. Acetate treatment reduced PGE2 release in astrocytes stimulated with LPS to control levels, but did not alter PGE2 levels in BV-2 microglia. The amount of acetylated H3K9 bound to the promoter regions of Cox-1, Cox-2, IL-1β and NF-κB p65 genes, but not IL-4 in were increased in BV-2 microglia treated with acetate. These data suggest that acetate treatment can disrupt eicosanoid signaling in neuroglia that may, in part, be the result of altering gene expression due chromatin remodeling as a result of increasing H3K9 acetylation.

Caffeine, Through Adenosine A3 Receptor-Mediated Actions, Suppresses Amyloid-β Protein Precursor Internalization and Amyloid-β Generation.

Intraneuronal accumulation and extracellular deposition of amyloid-β (Aβ) protein continues to be implicated in the pathogenesis of Alzheimers disease (AD), be it familial in origin or sporadic in nature. Aβ is generated intracellularly following endocytosis of amyloid-β protein precursor (AβPP), and, consequently, factors that suppress AβPP internalization may decrease amyloidogenic processing of AβPP. Here we tested the hypothesis that caffeine decreases Aβ generation by suppressing AβPP internalization in primary cultured neurons. Caffeine concentration-dependently blocked low-density lipoprotein (LDL) cholesterol internalization and a specific adenosine A3 receptor (A3R) antagonist as well as siRNA knockdown of A3Rs mimicked the effects of caffeine on neuronal internalization of LDL cholesterol. Further implicating A3Rs were findings that a specific A3R agonist increased neuronal internalization of LDL cholesterol. In addition, caffeine as well as siRNA knockdown of A3Rs blocked the ability of LDL cholesterol to increase Aβ levels. Furthermore, caffeine blocked LDL cholesterol-induced decreases in AβPP protein levels in neuronal plasma membranes, increased surface expression of AβPP on neurons, and the A3R antagonist as well as siRNA knockdown of A3Rs mimicked the effects of caffeine on AβPP surface expression. Moreover, the A3R agonist decreased neuronal surface expression of AβPP. Our findings suggest that caffeine exerts protective effects against amyloidogenic processing of AβPP at least in part by suppressing A3R-mediated internalization of AβPP.

Caffeine Blocks HIV-1 Tat-Induced Amyloid Beta Production and Tau Phosphorylation

The increased life expectancy of people living with HIV-1 who are taking effective anti-retroviral therapeutics is now accompanied by increased Alzheimer’s disease (AD)-like neurocognitive problems and neuropathological features such as increased levels of amyloid beta (Aβ) and phosphorylated tau proteins. Others and we have shown that HIV-1 Tat promotes the development of AD-like pathology. Indeed, HIV-1 Tat once endocytosed into neurons can alter morphological features and functions of endolysosomes as well as increase Aβ generation. Caffeine has been shown to have protective actions against AD and based on our recent findings that caffeine can inhibit endocytosis in neurons and can prevent neuronal Aβ generation, we tested the hypothesis that caffeine blocks HIV-1 Tat-induced Aβ generation and tau phosphorylation. In SH-SY5Y cells over-expressing wild-type amyloid beta precursor protein (AβPP), we demonstrated that HIV-1 Tat significantly increased secreted levels and intracellular levels of Aβ as well as cellular protein levels of phosphorylated tau. Caffeine significantly decreased levels of secreted and cellular levels of Aβ, and significantly blocked HIV-1 Tat-induced increases in secreted and cellular levels of Aβ. Caffeine also blocked HIV-1 Tat-induced increases in cellular levels of phosphorylated tau. Furthermore, caffeine blocked HIV-1 Tat-induced endolysosome dysfunction as indicated by decreased protein levels of vacuolar-ATPase and increased protein levels of cathepsin D. These results further implicate endolysosome dysfunction in the pathogenesis of AD and HAND, and by virtue of its ability to prevent and/or block neuropathological features associated with AD and HAND caffeine might find use as an effective adjunctive therapeutic agent.

Coexisting tubular adenoma with a neuroendocrine carcinoma of colon allowing early surgical intervention and implicating a shared stem cell origin

High-grade colonic neuroendocrine carcinomas (NECs) are uncommon but extremely aggressive. Their co-existence with tubular adenoma (TA) has rarely been reported. We present a 68-year-old man who was found on routine colonoscopy to have multiple colorectal TAs and an ulcerated lesion in the ascending colon. Microscopically, a poorly-differentiated invasive carcinoma juxtaposed with a TA was identified. Differential diagnosis included a poorly-differentiated adenocarcinoma, medullary carcinoma, high-grade NEC and lymphoma. The immunohistochemical profile showed positive staining for keratins, synaptophysin and chromogranin but negative for LCA, CDX2, CK7, CK20, TTF-1 and PSA, supporting the NEC diagnosis. Upon subsequent laparoscopic right hemicolectomy, the tumor was identified as a 3.0 cm umbilicated and ulcerated mass with an adjacent TA. Both TA and NEC showed positive staining for β-catenin indicating a shared colonic origin. The mitotic counts (77/10 high power fields) and a high proliferation rate (75% by Ki-67) corroborated a high-grade stratification. Mutational analysis indicated a wild-type BRAF and KRAS with mismatch repair proficiency. The AJCC (7th edition) pathologic stage is pT3, pN0, pMx. The patient received adjuvant chemotherapy with cisplatin/etoposides for three cycles and will be followed up for a year to detect recurrence. In conclusion, the co-existence of TA with high grade-NEC in our case allowed early identification and intervention of the otherwise asymptomatic but aggressive tumor. In addition, the finding of a high-grade NEC within a large TA in this case suggests a link between the two lesions and could represent a shared stem cell origin.

Long-Term Survival after Resection of Lung Metastases from Hepatocellular Cancer: Report of a Case and Review of the Literature

Hepatocellular cancer (HCC) is increasing dramatically in incidence in Europe and the United States due mainly to the hepatitis C epidemic and, to a lesser extent, increased body mass index of the population. In the fairly recent past, HCC was largely considered as untreatable due to detection mainly at late stages and lack of effective drugs for treatment. Several advances have led to changes in the prognosis of HCC. Screening of high-risk populations has allowed for earlier detection in some studies. If found at an early stage, liver transplantation not only cures the usual underlying cirrhosis but has cure rates for HCC in the range of 60% in recent series. Larger lesions can sometimes be cured by partial hepatic resection assuming the remaining liver is not too damaged to sustain liver functions after surgery. Vaccination for hepatitis B has led to reduction in the incidence of HCC. Significant improvements in antiviral treatments for both hepatitis B and hepatitis C may be having an impact on the incidence of HCC as well. It is still generally held that a finding of metastases precludes cure of HCC. We here report the case of a patient who presented with a large HCC in the context of occult hepatitis C infection. The primary tumor was resected. Over a year later, he developed a lung metastasis that was resected as well. He has not shown recurrence for 6 years since the metastasectomy. We review the recent literature on resection of lung metastases from HCC.

Dietary Acetate Supplementation Attenuates Neuroinflammation

The innate immune response maintains a vital role in the health of the central nervous system. Within the central nervous system the innate immune response is initiated following the binding of antigen to microglia that activates inflammatory cascades within the cell, recruits other microglial cells to the sight of action, and induces reactive astrogliosis of neighboring astrocytes. Under normal circumstance, once the antigen is cleared both the activated microglia and reactive astrocytes return to their quiescent or ramified states. With many neurological diseases and injury, neuroinflammatory cascades become tonically activated resulting in sustained neuroglia activation that can result in the induction, and/or progression of neurological injury. Because neuroinflammation is a key pathological element found in many neurological disorders it is believed that reducing inflammatory events in the brain can reduce injury and slow disease progression. In this regard, acetate supplementation by increasing the intracellular concentration of the metabolically active intermediate acetyl-CoA imparts both anti-inflammatory and neuroprotective properties. In this review, we summarize the current state of knowledge concerning the metabolism of acetate within the central nervous system and explore potential mechanisms of action by which acetate reduces neuroglial activation and neuroinflammatory signaling.