Publications

We examined if lipopolysaccharide (LPS) treatment of mice affected cardiolipin (CL) synthesis. Mice were injected i.p. with LPS, the liver harvested, and CL synthase (CLS) enzyme activity and its mRNA expression examined. Treatment of mice with LPS resulted in a 55% decrease (p < 0.01) in mRNA expression of murine CLS compared to controls, but CLS enzyme activity was unaltered. The pool size of liver CL and other phospholipids were unaltered by LPS treatment. A similar effect was observed in murine epidermal fat pad and in vitro in RAW mouse macrophages and in human HepG2 cells. LPS treatment of HepG2 cells transiently expressing a histidine-tagged human cardiolipin synthase-1 (hCLS1) reduced hCLS1 mRNA and newly synthesized CLS activity indicating that LPS inhibits production of newly synthesized hCLS1 via reduction in hCLS1 mRNA. The results clearly indicate that CLS mRNA levels cannot be correlated with CLS enzyme activity nor CL content in the LPS model of inflammation.

BACKGROUND

Contact dermatitises, including allergic contact dermatitis and irritant contact dermatitis, are among the most common skin disorders in humans. Chinese herbal medicines (CHM) have been used in treating contact dermatitises for centuries. Systemic administration of CHM, including ingredients in huangdang mixture containing Chinese angelica, radix Paeonlae rubra, cat nut, and phelloden dron, rhizoma alismatis, rhizoma smilacis glabrae, and rhizome of swordlike, improves allergic contact dermatitis induced by l-fluoro-2,4-dinitrobenzene. Whether topical applications of these herbal extracts display preventive and/or therapeutic effects on contact dermatitis, thereby avoiding the potential side effects of systemic CHM, remains largely unknown.

AIMS

To determine whether this topical CHM extract exerts preventive and/or therapeutic effects, we assessed its efficacy in both allergic contact dermatitis and irritant contact dermatitis murine models.

MATERIALS AND METHODS

Allergic contact dermatitis and irritant contact dermatitis murine models were established by topical oxazolone and a phorbol ester (12-O-tetradecanoylphorbol-13-acetate; TPA), respectively. Ear thickness was assessed in both dermatitis models.

RESULTS

Our results demonstrate that this topical CHM extract exhibits both therapeutic and preventive effects in acute irritant contact dermatitis but no demonstrable efficacy in murine allergic contact dermatitis.

CONCLUSION

These results suggest that this topical CHM extract could provide an alternative regimen for the prevention and treatment of irritant contact dermatitis.

A major function of the skin is to provide a barrier to the movement of water and electrolytes, which is required for life in a terrestrial environment. This permeability barrier is localized to the stratum corneum and is mediated by extracellular lipid-enriched lamellar membranes, which are delivered to the extracellular spaces by the secretion of lamellar bodies by stratum granulosum cells. A large number of factors have been shown to regulate the formation of this permeability barrier. Specifically, lamellar body secretion and permeability barrier formation are accelerated by decreases in the calcium content in the stratum granulosum layer of the epidermis. In addition, increased expression of cytokines and growth factors and the activation of nuclear hormone receptors (peroxisome proliferator-activated receptors, liver X receptors, vitamin D receptor) accelerate permeability barrier formation. In contrast, nitric oxide, protease-activated receptor 2 activation, glucocorticoids, and testosterone inhibit permeability barrier formation. The ability of a variety of factors to regulate permeability barrier formation allows for a more precise and nuanced regulation.

Ichthyoses, including inherited disorders of lipid metabolism, display a permeability barrier abnormality in which the severity of the clinical phenotype parallels the prominence of the barrier defect. The pathogenesis of the cutaneous phenotype represents the consequences of the mutation for epidermal function, coupled with a "best attempt" by affected epidermis to generate a competent barrier in a terrestrial environment. A compromised barrier in normal epidermis triggers a vigorous set of metabolic responses that rapidly normalizes function, but ichthyotic epidermis, which is inherently compromised, only partially succeeds in this effort. Unraveling mechanisms that account for barrier dysfunction in the ichthyoses has identified multiple, subcellular, and biochemical processes that contribute to the clinical phenotype. Current treatment of the ichthyoses remains largely symptomatic: directed toward reducing scale or corrective gene therapy. Reducing scale is often minimally effective. Gene therapy is impeded by multiple pitfalls, including difficulties in transcutaneous drug delivery, high costs, and discomfort of injections. We have begun to use information about disease pathogenesis to identify novel, pathogenesis-based therapeutic strategies for the ichthyoses. The clinical phenotype often reflects not only a deficiency of pathway end product due to reduced-function mutations in key synthetic enzymes but often also accumulation of proximal, potentially toxic metabolites. As a result, depending upon the identified pathomechanism(s) for each disorder, the accompanying ichthyosis can be treated by topical provision of pathway product (eg, cholesterol), with or without a proximal enzyme inhibitor (eg, simvastatin), to block metabolite production. Among the disorders of distal cholesterol metabolism, the cutaneous phenotype in Congenital Hemidysplasia with Ichthyosiform Erythroderma and Limb Defects (CHILD syndrome) and X-linked ichthyosis reflect metabolite accumulation and deficiency of pathway product (ie, cholesterol). We validated this therapeutic approach in two CHILD syndrome patients who failed to improve with topical cholesterol alone, but cleared with dual treatment with cholesterol plus lovastatin. In theory, the ichthyoses in other inherited lipid metabolic disorders could be treated analogously. This pathogenesis (pathway)-driven approach possesses several inherent advantages: (1) it is mechanism-specific for each disorder; (2) it is inherently safe, because natural lipids and/or approved drugs often are utilized; and (3) it should be inexpensive, and therefore it could be used widely in the developing world.

The two primary barrier functions of skin (permeability and microbial barriers) are provided by lipids and proteins delivered to the extracellular spaces of the stratum corneum by the secretion of lamellar bodies. Owing to their importance in this process, the mechanisms of and the factors regulating lamellar body formation must be better understood. Tarutani et al. (2012) provide data furthering the concept of the importance of the Golgi network in lamellar body formation and the necessity of acidification of the Golgi for normal function.

In terrestrial animals, the epidermal barrier transitions from covering an organism suspended in a liquid environment in utero, to protecting a terrestrial animal postnatally from air and environmental exposure. Tight junctions (TJ) are essential for establishing the epidermal permeability barrier during embryonic development and modulate normal epidermal development and barrier functions postnatally. We now report that TJ function, as well as claudin-1 and occludin expression, change in parallel during late epidermal development. Specifically, TJ block the paracellular movement of Lanthanum (La(3+)) early in rat in vivo prenatal epidermal development, at gestational days 18-19, with concurrent upregulation of claudin-1 and occludin. TJ then become more permeable to ions and water as the fetus approaches parturition, concomitant with development of the lipid epidermal permeability barrier, at days 20-21. This sequence is recapitulated in cultured human epidermal equivalents (HEE), as assessed both by ultrastructural studies comparing permeation of large and small molecules and by the standard electrophysiologic parameter of resistance (R), suggesting further that this pattern of development is intrinsic to mammalian epidermal development. These findings demonstrate that the role of TJ changes during epidermal development, and further suggest that the TJ-based and lipid-based epidermal permeability barriers are interdependent.

Systemic antagonists of the histamine type 1 and 2 receptors (H1/2r) are widely used as anti-pruritics and central sedatives, but demonstrate only modest anti-inflammatory activity. Because many inflammatory dermatoses result from defects in cutaneous barrier function, and because keratinocytes express both Hr1 and Hr2, we hypothesized that H1/2r antagonists might be more effective if they were used topically to treat inflammatory dermatoses. Topical H1/2r antagonists additively enhanced permeability barrier homeostasis in normal mouse skin by the following mechanisms: (i) stimulation of epidermal differentiation, leading to thickened cornified envelopes; and (ii) enhanced epidermal lipid synthesis and secretion. As barrier homeostasis was enhanced to a comparable extent in mast cell-deficient mice, with no further improvement following application of topical H1/2r antagonists, H1/2r antagonists likely oppose mast cell-derived histamines. In four immunologically diverse, murine disease models, characterized by either inflammation alone (acute irritant contact dermatitis, acute allergic contact dermatitis) or by prominent barrier abnormalities (subacute allergic contact dermatitis, atopic dermatitis), topical H1/2r agonists aggravated, whereas H1/2r antagonists improved, inflammation and/or barrier function. The apparent ability of topical H1r/2r antagonists to target epidermal H1/2r could translate into increased efficacy in the treatment of inflammatory dermatoses, likely due to decreased inflammation and enhanced barrier function. These results could shift current paradigms of antihistamine utilization from a predominantly systemic to a topical approach.

A key function of the skin is to provide a permeability barrier to restrict the movement of water, electrolytes, and other small molecules between the outside environment and the internal milieu. Following disruption of the permeability barrier, there is a rapid restoration of barrier function, and one of the key signals initiating this repair response is a decrease in the concentration of calcium in the outer epidermis. In this issue, Borkowski et al. present evidence showing that activation of Toll receptor 3 by double-stranded RNA may be another pathway for activation of permeability barrier repair. These results provide further evidence for a link between innate immunity and the permeability barrier.

OBJECTIVE

To determine whether older adults with diabetes are at increased risk of an injurious fall requiring hospitalization.

RESEARCH DESIGN AND METHODS

The longitudinal Health, Aging, and Body Composition Study included 3,075 adults aged 70-79 years at baseline. Hospitalizations that included ICD-9-Clinical Modification codes for a fall and an injury were identified. The effect of diabetes with and without insulin use on the rate of first fall-related injury hospitalization was assessed using proportional hazards models.

RESULTS

At baseline, 719 participants had diabetes, and 117 of them were using insulin. Of the 293 participants who were hospitalized for a fall-related injury, 71 had diabetes, and 16 were using insulin. Diabetes was associated with a higher rate of injurious fall requiring hospitalization (hazard ratio [HR] 1.48 [95% CI 1.12-1.95]) in models adjusted for age, race, sex, BMI, and education. In those participants using insulin, compared with participants without diabetes, the HR was 3.00 (1.78-5.07). Additional adjustment for potential intermediaries, such as fainting in the past year, standing balance score, cystatin C level, and number of prescription medications, accounted for some of the increased risk associated with diabetes (1.41 [1.05-1.88]) and insulin-treated diabetes (2.24 [1.24-4.03]). Among participants with diabetes, a history of falling, poor standing balance score, and A1C level ≥8% were risk factors for an injurious fall requiring hospitalization.

CONCLUSIONS

Older adults with diabetes, in particular those using insulin, are at greater risk of an injurious fall requiring hospitalization than those without diabetes. Among those with diabetes, poor glycemic control may increase the risk of an injurious fall.

The major function of the skin is to form a barrier between the internal milieu and the hostile external environment. A permeability barrier that prevents the loss of water and electrolytes is essential for life on land. The permeability barrier is mediated primarily by lipid enriched lamellar membranes that are localized to the extracellular spaces of the stratum corneum. These lipid enriched membranes have a unique structure and contain approximately 50% ceramides, 25% cholesterol, and 15% free fatty acids with very little phospholipid. Lamellar bodies, which are formed during the differentiation of keratinocytes, play a key role in delivering the lipids from the stratum granulosum cells into the extracellular spaces of the stratum corneum. Lamellar bodies contain predominantly glucosylceramides, phospholipids, and cholesterol and following the exocytosis of lamellar lipids into the extracellular space of the stratum corneum these precursor lipids are converted by beta glucocerebrosidase and phospholipases into the ceramides and fatty acids, which comprise the lamellar membranes. The lipids required for lamellar body formation are derived from de novo synthesis by keratinocytes and from extra-cutaneous sources. The lipid synthetic pathways and the regulation of these pathways are described in this review. In addition, the pathways for the uptake of extra-cutaneous lipids into keratinocytes are discussed. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.