Stimulatory effect of benzylidenemalononitrile tyrphostins on expression of NO-dependent genes in U-937 monocytic cells

Neuroprotective effects of hawthorn leaf flavonoids in Aβ 25–35 ‐induced Alzheimer's disease model

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by β-amyloid (Aβ) plaques, neurofibrillary tangles, neuronal cell loss, and oxidative stress. Further deposition of Aβ in the brain induces oxidative stress, neuroinflammation, and memory dysfunction. Hawthorn (Crataegus pinnatifida Bge.) leaf, a known traditional Chinese medicine, is commonly used for the treatment of hyperlipidemia, heart palpitations, forgetfulness, and tinnitus, and its main bioactive components are Hawthorn Leaf Flavonoids (HLF). In this study, we investigated the neuroprotective effects of the HLF on the Aβ_25-35 (bilateral hippocampus injection) rat model of AD. The results showed that the oral administration of HLF at a dose of 50, 100, and 200 mg/kg for 30 days significantly ameliorated neuronal cell damage and memory deficits, and markedly increased the enzyme activities of superoxide dismutase and catalase, and the content of glutathione whereas it decreased the malondialdehyde content in the Aβ_25-35 rat model of AD as well as suppressed the activation of astrocytes. In addition, HLF up-regulated Nrf-2, NQO-1, and HO-1 protein expressions. Also, it reduced neuroinflammation by inhibiting activation of astrocytes. In summary, these results indicated that HLF decreased the oxidative stress via activating Nrf-2/antioxidant response element signaling pathways, and may suggest as a potential candidate for AD therapeutic agent.

The Knoevenagel condensation using quinine as an organocatalyst under solvent-free conditions

An organocatalytic Knoevenagel condensation has been developed for the synthesis of electrophilic alkenes using natural quinine under green reaction conditions.

Tyrphostin AG126 exerts neuroprotection in CNS inflammation by a dual mechanism

The putative protein tyrosine kinase (PTK) inhibitor tyrphostin AG126 has proven beneficial in various models of inflammatory disease. Yet molecular targets and cellular mechanisms remained enigmatic. We demonstrate here that AG126 treatment has beneficial effects in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. AG126 alleviates the clinical symptoms, diminishes encephalitogenic Th17 differentiation, reduces inflammatory CNS infiltration as well as microglia activation and attenuates myelin damage. We show that AG126 directly inhibits Bruton's tyrosine kinase (BTK), a PTK associated with B cell receptor and Toll-like receptor (TLR) signaling. However, BTK inhibition cannot account for the entire activity spectrum. Effects on TLR-induced proinflammatory cytokine expression in microglia involve AG126 hydrolysis and conversion of its dinitrile side chain to malononitrile (MN). Notably, while liberated MN can subsequently mediate critical AG126 features, full protection in EAE still requires delivery of intact AG126. Its anti-inflammatory potential and especially interference with TLR signaling thus rely on a dual mechanism encompassing BTK and a novel MN-sensitive target. Both principles bear great potential for the therapeutic management of disturbed innate and adaptive immune functions.

Keap1-Nrf2 signaling pathway: mechanisms of regulation and role in protection of cells against toxicity caused by xenobiotics and electrophiles

The transcription factor Nrf2 governs the expression of a considerable group of genes involved in cell protection against oxidants, electrophiles, and genotoxic compounds. The activity of Nrf2 is sensitive to xenobiotics and endogenous electrophiles. Nrf2 is negatively regulated by specific suppressor protein Keap1, which is also a receptor of electrophiles and adapter for Cul3 ubiquitin ligase. Electrophiles react with critical thiol groups of Keap1 leading to the loss of its ability to inhibit Nrf2. The Keap1-Nrf2 signaling pathway also down-regulates NF-κB transcriptional activity and attenuates cytokine-mediated induction of proinflammatory genes. Pharmacological activation of the Keap1-Nrf2 pathway can be used for treatment and prevention of many diseases. Widely known natural Keap1-Nrf2 activators include curcumin, quercetin, resveratrol, and sulforaphane. The most effective Keap1-Nrf2 activators are synthetic oleanane triterpenoids.

Nitric oxide and redox mechanisms in the immune response

The role of redox molecules, such as NO and ROS, as key mediators of immunity has recently garnered renewed interest and appreciation. To regulate immune responses, these species trigger the eradication of pathogens on the one hand and modulate immunosuppression during tissue-restoration and wound-healing processes on the other. In the acidic environment of the phagosome, a variety of RNS and ROS is produced, thereby providing a cauldron of redox chemistry, which is the first line in fighting infection. Interestingly, fluctuations in the levels of these same reactive intermediates orchestrate other phases of the immune response. NO activates specific signal transduction pathways in tumor cells, endothelial cells, and monocytes in a concentration-dependent manner. As ROS can react directly with NO-forming RNS, NO bioavailability and therefore, NO response(s) are changed. The NO/ROS balance is also important during Th1 to Th2 transition. In this review, we discuss the chemistry of NO and ROS in the context of antipathogen activity and immune regulation and also discuss similarities and differences between murine and human production of these intermediates.