Carnosine Protects against Cerebral Ischemic Injury by Inhibiting Matrix-Metalloproteinases.

Stroke is one of the leading causes of death and disability worldwide. However, treatment options for ischemic stroke remain limited. Matrix-metalloproteinases (MMPs) contribute to brain damage during ischemic strokes by disrupting the blood-brain barrier (BBB) and causing brain edemas. Carnosine, an endogenous dipeptide, was found by us and others to be protective against ischemic brain injury. In this study, we investigated whether carnosine influences MMP activity. Brain MMP levels and activity were measured by gelatin zymography after permanent occlusion of the middle cerebral artery (pMCAO) in rats and in vitro enzyme assays. Carnosine significantly reduced infarct volume and edema. Gelatin zymography and in vitro enzyme assays showed that carnosine inhibited brain MMPs. We showed that carnosine inhibited both MMP-2 and MMP-9 activity by chelating zinc. Carnosine also reduced the ischemia-mediated degradation of the tight junction proteins that comprise the BBB. In summary, our findings show that carnosine inhibits MMP activity by chelating zinc, an essential MMP co-factor, resulting in the reduction of edema and brain injury. We believe that our findings shed new light on the neuroprotective mechanism of carnosine against ischemic brain damage.

Selective inhibition of JAK2/STAT1 signaling and iNOS expression mediates the anti-inflammatory effects of coniferyl aldehyde.

Urgent needs still exist for selective control of excessive inflammation. Despite the therapeutic potential of natural compounds against inflammation-associated chronic conditions, lack of specific molecular targets renders these bioactive compounds difficult for further development. Here we examined the bioactivity of coniferyl aldehyde (CA), a natural phenolic compound found in several dietary substances and medicinal plants, elucidating its efficacy both in vivo and in vitro with underlying molecular mechanisms. IFN-γ/TNF-α-stimulated human keratinocytes and lipopolysaccharide (LPS)-stimulated murine macrophages were used to examine the effect of CA in vitro and to elucidate the underlying mechanisms. In vivo models of phorbol 12-myristate 13-acetate (TPA)-induced ear edema and carrageenan (CRG)-induced paw edema were employed to investigate the topical and systemic anti-inflammatory effects of CA, respectively. CA significantly reduced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in LPS-stimulated macrophages. While nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPKs) pathways, the representative cellular pathways for iNOS induction, were not affected by CA, phosphorylation of Janus kinase 2 (JAK2) and signal Transducers and Activators of Transcription 1 (STAT1) and subsequent nuclear translocation of p-STAT1 were significantly decreased by CA. The effect of CA on JAK2-STAT1-iNOS axis was also observed in human keratinocytes stimulated with IFN-γ/TNF-α. Topical application of CA to mice produced significant protection against TPA-induced ear edema along with suppressed epidermal hyperproliferation and leucocyte infiltration. Systemic administration of CA significantly reduced CRG-induced paw edema in rats, where CRG-induced iNOS expression and STAT1 phosphorylation were decreased by CA. In summary, CA has significant anti-inflammatory properties both in vitro and in vivo, mediated by significant selective inhibition of JAK2-STAT1-iNOS signaling. CA is an attractive novel candidate for treating inflammatory diseases associated with excessive production of NO.

A newly synthesized macakurzin C-derivative attenuates acute and chronic skin inflammation: The Nrf2/heme oxygenase signaling as a potential target.

Impaired immune responses in skin play a pivotal role in the development and progression of chemical-associated inflammatory skin disorders. In this study, we synthesized new flavonoid derivatives from macakurzin C, and identified in vitro and in vivo efficacy of a potent anti-inflammatory flavonoid, Compound 14 (CPD 14), with its underlying mechanisms. In lipopolysaccharide (LPS)-stimulated murine macrophages and IFN-γ/TNF-α-stimulated human keratinocytes, CPD 14 significantly inhibited the release of inflammatory mediators including nitric oxide (NO), prostaglandins, and cytokines (IC50 for NO inhibition in macrophages: 4.61µM). Attenuated NF-κB signaling and activated Nrf2/HO-1 pathway were responsible for the anti-inflammatory effects of CPD 14. The in vivo relevance was examined in phorbol 12-myristate 13-acetate (TPA)-induced acute skin inflammation and oxazolone-induced atopic dermatitis models. Topically applied CPD 14 significantly protected both irritation- and sensitization-associated skin inflammation by suppressing the expression of inflammatory mediators. In summary, we demonstrated that a newly synthesized flavonoid, CPD 14, has potent inhibitory effects on skin inflammation, suggesting it is a potential therapeutic candidate to treat skin disorders associated with excessive inflammation.