Impact of the acute local inhibition of soluble epoxide hydrolase on diabetic skin microcirculatory dysfunction

Inhibition of soluble epoxide hydrolase as a therapeutic approach for blood-brain barrier dysfunction

The blood-brain barrier (BBB) is a protective semi-permeable structure that regulates the exchange of biomolecules between the peripheral blood and the central nervous system (CNS). Due to its specialized tight junctions and low vesicle trafficking, the BBB strictly limits the paracellular passage and transcellular transport of molecules to maintain the physiological condition of brain tissues. BBB breakdown is associated with many CNS disorders. Soluble epoxide hydrolase (sEH) is a hydrolase enzyme that converts epoxy-fatty acids (EpFAs) to their corresponding diols and is involved in the onset and progression of multiple diseases. EpFAs play a protective role in the central nervous system via preventing neuroinflammation, making sEH a potential therapeutic target for CNS diseases. Recent studies showed that sEH inhibition prevented BBB impairment caused by stroke, hemorrhage, traumatic brain injury, hyperglycemia and sepsis via regulating the expression of tight junctions. In this review, the protective actions of sEH inhibition on BBB and potential mechanisms are summarized, and some important questions that remain to be resolved are also addressed.

Role of the soluble epoxide hydrolase in keratinocyte proliferation and sensitivity of skin to inflammatory stimuli

The lipid content of skin plays a determinant role in its barrier function with a particularly important role attributed to linoleic acid and its derivatives. Here we explored the consequences of interfering with the soluble epoxide hydrolase (sEH) on skin homeostasis. sEH; which converts fatty acid epoxides generated by cytochrome P450 enzymes to their corresponding diols, was largely restricted to the epidermis which was enriched in sEH-generated diols. Global deletion of the sEH increased levels of epoxides, including the linoleic acid-derived epoxide; 12,13-epoxyoctadecenoic acid (12,13-EpOME), and increased basal keratinocyte proliferation. sEH deletion (sEH-/- mice) resulted in thicker differentiated spinous and corneocyte layers compared to wild-type mice, a hyperkeratosis phenotype that was reproduced in wild-type mice treated with a sEH inhibitor. sEH deletion made the skin sensitive to inflammation and sEH-/- mice developed thicker imiquimod-induced psoriasis plaques than the control group and were more prone to inflammation triggered by mechanical stress with pronounced infiltration and activation of neutrophils as well as vascular leak and increased 12,13-EpOME and leukotriene (LT) B4 levels. Topical treatment of LTB4 antagonist after stripping successfully inhibited inflammation and neutrophil infiltration both in wild type and sEH-/- skin. While 12,13-EpoME had no effect on the trans-endothelial migration of neutrophils, like LTB4, it effectively induced neutrophil adhesion and activation. These observations indicate that while the increased accumulation of neutrophils in sEH-deficient skin could be attributed to the increase in LTB4 levels, both 12,13-EpOME and LTB4 contribute to neutrophil activation. Our observations identify a protective role of the sEH in the skin and should be taken into account when designing future clinical trials with sEH inhibitors.

Soluble epoxide hydrolase inhibitor, t-AUCB, improves salivary gland function by ameliorating endothelial injury

AIMS

Inhibitor of soluble epoxide hydrolase (t-AUCB) has been used in the experimental therapy of hypertension. This study aimed to investigate whether the secretion of submandibular glands (SMGs) altered in renal hypertensive rats, and to explore whether t-AUCB could improve the salivary secretion.

MAIN METHODS

2-kidney 1-clip Sprague-Dawley rats were used as renal hypertensive animals. t-AUCB treatment was given for 1 week after 8 weeks modeling. Blood pressure, blood perfusion and the secretion of SMGs, and endothelium-dependent relaxation of external maxillary artery were measured to investigate the effects of t-AUCB on the vascular tone and the secretion of SMGs in renal hypertensive rats. SMGs were collected for histological evaluation and the internal arteries were dissected for primary endothelial cells culture.

KEY FINDINGS

The blood perfusion and flow rate of SMGs in the renal hypertensive rats were significantly lower than those in the controls. Endothelium-dependent relaxation of the external maxillary artery and AMPK/Akt/eNOS signaling was impaired in hypertensive rats. The glandular morphology and the concentration of salivary ions did not change obviously. t-AUCB treatment ameliorated the secretion of SMGs, the blood perfusion, and the dysfunction of endothelium-dependent relaxation of the external maxillary artery by activating the AMPK/Akt/eNOS pathway in hypertensive rats.

SIGNIFICANCE

t-AUCB increases the blood perfusion through ameliorating dysfunction of endothelium-dependent relaxation of SMGs arteries and thus improves the hyposecretion of SMGs in hypertensive rats.

Small Molecule Soluble Epoxide Hydrolase Inhibitors in Multitarget and Combination Therapies for Inflammation and Cancer

The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors.