Distribution of hydrolytic activity catalyzes the biotransformation of prednisolone 21-acetate in human skin

We investigated the distribution of hydrolytic enzymes which metabolize prednisolone 21-acetate (PNA) to prednisolone (PN) in human skin. Km (Michaelis-Menten constant) and Vmax (maximum rate) of hydrolytic enzyme in human skin was 25.1 microM and 0.46 nmol/min/mg protein, respectively. Specific activities of hydrolysis in dermis and epidermis were similar and, in consideration to their thickness, hydrolytic activity in epidermis was 12.1 times higher than in dermis. Moreover, the highest amount of metabolite (PN) was found at 80-120 microm from the skin surface by skin slicing. Therefore, hydrolytic activity which metabolized PNA was distributed in epidermis, especially in the basement membrane area; epidermis borders dermis in this area and the papillary plexus is reached just beneath the dermal papillae. These results suggest that the distribution of hydrolytic activity in human skin may prevent certain substances from entering the systemic circulation in their unhydrolyzed form.

Metabolism of prednisolone 21-acetate in hairless mouse skin

We investigated the hydrolytic activity of prednisolone 21-acetate (PNA) to prednisolone (PN) in an enzyme solution composed of esterase and skin homogenates from hairless mice. The values of the Michaelis-Menten constant obtained from hairless mouse skin and esterase solution were 14.2 and 10.2 microM, respectively; conversely, the value of the maximum rate from hairless mouse and esterase solution were 0.67 and 1,886 nmol/min/mg protein, respectively. To examine the effect of enzymatic inhibitors on hydrolytic activity, five enzymatic inhibitors, 3,4-dichloroisocoumarine (DCIC), N-tosyl-L-phenylalanine chloromethyl ketone, iodoacetamide, p-hydroxymercuribenzoic acid (HMBA) and sodium dodecylsulfate, were added to the enzyme solution. Sixty-eight percent of hydrolytic activity in skin homogenates were not deactivated by DCIC which completely inhibited the enzymatic activity in esterase solution. We also studied the localization of hydrolytic enzyme with a subcellular faction: 66 and 11% of specific activity existed in microsome (Ms) and cytosol (Cp) fractions, indicating that the hydrolytic activity of PNA was included mainly in the Ms fraction. Hydrolytic activity in Ms and Cp fractions was different from sensitivity to enzymatic inhibitor; DCIC inhibited activity in the Ms fraction and, on the other hand, HMBA inhibited it in the Cp fraction. Therefore, Ms and Cp fractions in skin homogenates include a different esterase isoform and the metabolism of PNA to PN in hairless mouse skin is mediated by these isoforms.

The true value of the TRUE Test for allergic contact dermatitis

The development of the thin layer rapid use epicutaneous (TRUE) Test is a history of cooperation between scientists from academia and industry covering several disciplines: medicine, pharmaceutical chemistry, pharmacology, and statistics. The TRUE Test is today a patch test system with documented stability and allergen content. Allergens are incorporated in a dried-in-gel vehicle, which is coated onto a polyester backing to form a patch. Applied to the skin, the allergens are released when the gel becomes moisturized by transepidermal water. This may seem to be a simple technique, but its development required laborious research and solutions to stability and dosage problems. The test has been clinically standardized with serial dilution tests on sensitized patients and validated in comparative multicenter tests. The test is a significant step towards higher reliability of patch testing. Fifteen years of experience and critical investigations are discussed in this article, as are possible improvements such as expansion of the test with new allergens.

A preliminary report of the occupation of patients evaluated in patch test clinics

BACKGROUND

The interplay between the occupational environment and worker's skin can result in contact dermatitis of both irritant and allergic types. Other forms of dermatitis can also be influenced by occupational exposures.

OBJECTIVE

The aim of this study is to compare the occupations and allergens of occupational contact dermatitis cases with nonoccupational contact dermatitis cases.

METHODS

Diagnostic patch testing with allergens of the North American Contact Dermatitis Group and occupational coding by the National Institute for Occupational Safety and Health methods.

RESULTS

Of 2,889 patients referred for evaluation of contact dermatitis, 839 patients (29%) were found to have occupational contact dermatitis. Of the 839 cases deemed occupational, 455 cases (54%) were primarily allergic in nature and 270 cases (32%) were primarily irritant in nature. The remaining 14% were diagnoses other than contact dermatitis, aggravated by work. The occupation most commonly found to have allergic contact dermatitis was nursing. Allergens strongly associated with occupational exposure were thiuram, carbamates, epoxy, and ethylenediamine.

CONCLUSION

Some contact allergens are more commonly associated with occupational contact dermatitis. Nursing and nursing support are occupations most likely to be overrepresented in contact dermatitis clinics.

Alefacept (Biogen)

Alefacept (B-9273) is an LFA-3-Ig fusion protein CD2 antagonist under development by Biogen for the potential treatment of autoimmune diseases, including psoriasis and transplant rejection [270267]. It is in phase III trials for psoriasis [349467]. In October 2000, the company reported that Amevive was on track for regulatory filing in the second half of 2001 [385250], with a possible launch in the second half of 2002 [395628]. The company began a pivotal phase III trial in the US in December 1999, involving patients with chronic plaque psoriasis [349467]. A second phase III trial has also been initiated [362199], [374040]. Results from both trials are expected in mid-2001 [396544]. In April 2001, SalomonSmithBarney confirmed that a regulatory filing was expected in Europe and the US in the second half of 2001 and stated that alefacept would be critical to the future earnings growth of the company [407796]. In June 1999, Merrill Lynch estimated product launch in 2001 [327145], [344773]. Sales in 2001 and 2002 were anticipated to be US $20 million and US $100 million, respectively [327145].

Skin occlusion and irritant and allergic contact dermatitis: an overview

Occlusion, widely used to enhance percutaneous absorption of drugs, also increases penetration of other chemicals and antigens, and hence may exacerbate irritant and allergic contact dermatitis. This overview summarizes the adverse effects of occlusion.

Pitfalls of irritant patch testing using different test chamber sizes

BACKGROUND

Test chambers for irritant patch testing are usually larger than those used in allergic patch testing. In general, larger areas show stronger skin reactions than smaller areas.

OBJECTIVE

This study investigated whether this difference is of practical relevance, when a model irritant is applied in small and large Finn chambers and evaluated by measurement of transepidermal water loss (TEWL).

METHODS

Patch testing was performed with 2 concentrations of sodium lauryl sulfate (SLS) (0.25% and 0.5%) on forearms of healthy volunteers. Large (inner diameter, 12 mm) and small (inner diameter, 8 mm) chambers were used.

RESULTS

A variance analysis (3 factors, 2-tailed) showed that the test outcome, as assessed by TEWL, was strongly dependent on SLS test concentration and test chamber size. The larger chambers gave approximately 30% to 50% higher values than the smaller.

CONCLUSIONS

This may be explained by the fact that with the small chambers, the adjacent small area of nontreated skin was also assessed by the evaporimeter, biasing the results. A formula estimating TEWL value of the large chamber from values of the small chambers has been proposed.

Is contact allergy in man lifelong? An overview of patch test follow-ups

In contradistinction from certain strains of mice, contact allergy in man is hypothesized to be either lifelong or at least to last for years. We examined follow-up studies on contact allergy, as evaluated by patch testing, attempting to quantify its natural history. The allergens include colophonium, gold sodium thiosulfate, nickel, and cobalt. At present, due to technical limitations, we cannot state in quantitative terms whether contact allergy in man is lifelong and whether its clinical manifestations change. Thus, we list some criteria for future studies which may help resolve the above question.

Subclinical, non-erythematous irritation with an open assay model (washing): sodium lauryl sulfate (SLS) versus sodium laureth sulfate (SLES)

Compared to exaggerated hand washing procedures, an open non-exaggerated assay better approximates consumer surfactant use. Our goal was to observe skin surface modifications induced by an open test with regard to discriminating between surfactant solutions. This human in vivo assay provided information about the effect of only three washes at the laboratory and a week of at-home use. Dorsal hand and volar forearm were compared. The results demonstrated that this clinical model permits exploration of subclinical surfactant-induced irritation. Both the volar forearm and the dorsal hand are capable of discriminating between the effects of sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES). Squamometry proved to be a sensitive assessment technique for detecting surfactant-induced subclinical skin surface alterations and for differentiating surfactant effects in this open application assay, in as few as three washes.

Sea water or its components alter experimental irritant dermatitis in man

BACKGROUND/AIMS

Ocean bathing has been considered "healthy" for skin, but its efficacy remains testimonial in nature. Our aim was to evaluate the effects of sea water and its main components on experimental irritant contact dermatitis induced by sodium lauryl sulphate (SLS) cumulative irritation.

METHODS

After open application of 2% SLS for 10 min on volar forearm sites, solutions of sea water, 500 mM NaCl, 10 mM KCl, 55 mM MgCl2, 10 mM CaCl2, or deionized water were separately applied using filter paper discs for 20 min. The procedures were repeated daily for 2 weeks. The effects of the treatment were assessed daily using measurements of transepidermal water loss (TEWL), as an indicator of epidermal barrier function, and capacitance, as a parameter of stratum corneum water content.

RESULTS

Sea water, NaCl, and KCl significantly inhibited the increase of TEWL as compared with deionized water (P < 0.003, P < 0.05, P < 0.05, respectively). Sea water and NaCl inhibited the decrease of capacitance as well (P < 0.03, P < 0.01).

CONCLUSION

The effect of sea water may be attributed to skin barrier preservation by NaCl and KCl, and an emollient effect by NaCl.

Physical and physiological effects of stratum corneum tape stripping

BACKGROUND/AIMS

Tape stripping of human stratum corneum has been performed to measure stratum corneum mass, barrier function, drug reservoir and percutaneous penetration. However, the technique itself requires further development to facilitate interpretation.

METHODS

In this study we quantified stratum comeum (SC) tape stripping and water kinetic parameters utilizing three types of adhesive tapes, in an in vivo randomized clinical trial. Stratum corneum was tape stripped, and the mass of SC removed by each tape was quantified utilizing a protein assay. Transepidermal water loss (TEWL) was measured and barrier disruption and SC water kinetics calculated. Three commonly utilized acrylate adhesive tapes were utilized and a comparison made between them.

RESULTS

Each type of tape successfully stripped the stratum corneum, but the rayon tape did not induce SC barrier disruption. Neither the type of tape nor the site stripped significantly influenced the mass of SC removed. Water kinetic parameters did not differ significantly for the tapes that did induce barrier disruption. Individual variation in barrier disruption to water following tape stripping was demonstrated.

CONCLUSION

The tapes utilized removed a similar amount of SC. The tapes have a different propensity to cause barrier disruption. Some individuals do not demonstrate increased TEWL despite an equivalent mass of SC being removed compared to those who do show a response.

Effects of skin occlusion on percutaneous absorption: an overview

Skin occlusion produces profound changes, including hydration status, barrier permeability, epidermal lipids, DNA synthesis, microbial flora, and numerous molecular and cellular processes. It often, but not always, increases percutaneous absorption of applied chemicals. This overview focuses on the effect of skin occlusion on percutaneous absorption.

An overview of the efficacy of topical corticosteroids in experimental human nickel contact dermatitis

We review controlled trials of corticosteroid effect in experimentally elicited acute nickel contact dermatitis in man, in the hope of clarifying optimal efficacy for clinical use. To maximize discrimination and objectivity, we focus on data with 1 well-characterized allergen, nickel, in studies utilizing bioengineering documentation. Higher potency corticosteroids are effective (unlike in experimental irritant contact dermatitis), but optimum schedules still require definition.

Antipruritic and thermal sensation effects of hydrocortisone creams in human skin

Few studies evaluate the effect of topical corticosteroids on thermal sensation and in alleviation of itch produced by intradermal injection of histamine. We evaluated the antipruritic effect of hydrocortisone (1% and 2.5%) on histamine-induced itch and sensory effects by measuring itch magnitude, itch duration and thermal thresholds using a computerized thermal sensory analyzer (TSA). This was a double-blind, random, comparative, controlled, single-dose and single-center study. Itch was experimentally induced in both forearms by intracutaneous injection of histamine in 18 subjects. Hydrocortisone 1%, 2.5% and placebo were applied to test sites on both forearms. The thermal threshold for warmth sensation, cold sensation, cold and heat pain was measured with the TSA. Itch magnitude was measured each minute after histamine injection for 10 min with a visual analogue scale (VAS). Itch duration was also recorded. In comparison to placebo, 2.5% hydrocortisone significantly (p = 0.03) reduced itch duration from 12.6 +/- 11.0 min (mean +/- SD) to 8.6 +/- 8.2 min (the reducing rate was 32%) as well as itch magnitude (at minutes 3, 6, 7 and overall). Placebo, 1% and 2.5% hydrocortisone significantly altered (p <0.05) the cold sensation threshold. No treatment altered cold or heat pain thresholds. These data suggest that topical application of 2.5% hydrocortisone may be significantly beneficial for the treatment of histamine-induced itch. The correlation between thermal measurements and antipruritic effects warrants further study.

Evidence that the serum inhibitor of hyaluronidase may be a member of the inter-alpha-inhibitor family

A study of the uncharacterized serum inhibitors of hyaluronidase, first described half a century ago, was undertaken. Activity was measured against bovine testicular hyaluronidase using a microtiter-based assay and reverse hyaluronan substrate gel zymography. The predominant inhibitory activity was magnesium-dependent and could be eliminated by protease or chondroitinase digestion and by heat treatment. Kinetics of inhibition were similar against hyaluronidases from testis and snake and bee venoms. The inhibitor had no effect on Streptomyces hyaluronidase, indicating that inhibition was not through protection of the hyaluronan substrate. Inhibition levels in serum were increased in mice following carbon tetrachloride or interleukin-1 injection, inducers of the acute-phase response. Reverse zymography identified a predominant band of 120-kDa relative molecular size, with two bands of greater and one of smaller size. The predominant protein was tentatively identified as a member of the inter-alpha-inhibitor family. Inhibition was also observed using either purified inter-alpha-inhibitor or an inter-alpha-inhibitor-related 120-kDa complex. Inter-alpha-inhibitor, found in the hyaluronan-rich cumulus mass surrounding mammalian ova and the coat of fibroblasts and mesothelial cells, may function to stabilize such matrices by protecting against hyaluronidase degradation. Turnover of circulating hyaluronan is extraordinarily rapid, with a half-life of 2-5 min. Prompt increases in levels of serum hyaluronan occur in patients with shock, septicemia, or massive burns, increases that can be attributed, in part, to suppression of degradation by these acute-phase reactants, the inhibitors of hyaluronidase.

Predicted chemical warfare agent VX toxicity to uniformed soldier using parathion in vitro human skin exposure and absorption

Chemical warfare agents (CWA) are easily and inexpensively produced and are a significant threat to military forces and the public. Most well-known CWAs are organophosphorus compounds, a number or which are used as pesticides, including parathion. This study determined the in vitro percutaneous absorption of parathion as a CWA simulant through naked human skin and uniformed skin (dry and sweated). Parathion percentage dose absorbed through naked skin (1.78 +/- 0. 41) was greater than dry uniformed skin (0.29 +/- 0.17; p = 0.000) and sweated uniformed skin (0.65 +/- 0.16; p = 0.000). Sweated and dry uniformed skin absorption were also different (p = 0.007). These relative dry and sweated uniformed skin absorptions were then applied to VX skin permeability for naked skin (head, neck, arms, and hands) and the remaining uniformed skin over the various regions of the human body. Risk assessment shows VX 50% lethality within the first hour for a soldier wearing a sweated uniform. By 8 h postexposure to naked skin plus trunk area predicted lethality for both dry and sweated uniform, and, at 96 h postexposure, all body regions individually exposed would produce lethality. Military uniform and public clothing provide some immediate protection but absorption through cloth and skin does occur. Immediate safety response to skin and clothing is required.

Influence of age, anatomic site and race on skin roughness and scaliness

BACKGROUND

Variations in skin roughness and scaliness between age groups, anatomic sites and race have been assumed but minimally quantified.

OBJECTIVE

We quantitatively investigated skin roughness, scaliness and stratum corneum hydration as a function of age, anatomic site and race (white and black).

METHODS

Skin roughness, scaliness and stratum corneum hydration were determined in vivo by noninvasive bioengineering and image analysis techniques in 22 female subjects grouped according to age (young and aged) and race (white and black).

RESULTS

Skin roughness, scaliness and stratum corneum hydration varied significantly in different anatomic areas and age groups. There was no racial variation in skin hydration between any anatomic site, nor significant differences in roughness and scaliness between races, except for the preauricular area. Skin roughness was significantly increased in the aged, compared to the young at the preauricle, volar forearm, lower back, thigh and lower leg. Older women demonstrated significantly more scaling at the preauricle than younger women. Stratum corneum hydration correlated with scaliness. No significant correlation between stratum corneum hydration and skin roughness was observed.

CONCLUSION

Age and anatomic site but not race demonstrated a significant influence on skin roughness and scaliness. The desquamation index appears a good indicator of the status of stratum corneum hydration.

The pig as an experimental animal model of percutaneous permeation in man: qualitative and quantitative observations--an overview

The pig has been a well-recognized experimental animal in biomedical research for many centuries. Physiological and anatomical similarities between man and pig made this animal a good model for man in many research areas. Pharmacological and toxicological research on the skin is often based on knowledge of skin absorption and percutaneous permeation. Anatomical, physiological and biochemical similarities are cited and various uses of the pig as a model for man in the investigation of skin permeation are reviewed. Further, several isolated organ models are reviewed. The importance of full details of the experimental animal, namely its age, sex, breed, size (weight) and body region, is emphasized.

Effect of topical antioxidants on UV-induced erythema formation when administered after exposure

BACKGROUND

Photoprotective effects of topically applied antioxidants when applied before ultraviolet radiation (UVR) exposure are well known. Their protective effect when applied after UVR exposure is, however, less established.

OBJECTIVE

In a randomized, double-blinded, placebo-controlled human study the short-term photoprotective effects of different antioxidants and of their combinations were evaluated when applied after UVR exposure.

METHODS

Melatonin (N-acetyl-5-methoxytryptamine), vitamin E (alpha-tocopherol) and vitamin C (ascorbic acid) were topically administered alone or in combination following UVR exposure as single applications (immediately or 30 min after irradiation, respectively) or as multiple applications (three times: 30 min, 1 h and 2 h after irradiation). The erythemal reaction was evaluated visually and noninvasively with bioengineering methods (skin color and skin blood flow).

RESULTS

No significant protective effect of melatonin or the vitamins when applied alone or in combination were obtained when antioxidants were applied after UVR exposure. No improved photoprotective effect was obtained when multiple applications were done.

CONCLUSION

UVR-induced skin damage is a rapid event, and antioxidants possibly prevent such damage only when present in relevant concentration at the site of action beginning and during oxidative stress.

Effects of glycolic acid on light-induced skin pigmentation in Asian and caucasian subjects

BACKGROUND

Topical use of alpha-hydroxy acid (AHA) may increase skin photosensitivity, as demonstrated by increased numbers of sunburst cells. However, effects of AHA on tanning have not been studied.

OBJECTIVE

Our purpose was to study whether short-term use of glycolic acid hastens resolution of pre-existing light-induced pigmentation and whether the skin becomes tan more easily in Asian and Caucasian subjects after such treatment.

METHODS

Six Asian and six Caucasian volunteers received separate irradiations of UVB and UVA to both sides of the lower back. In a double-blind fashion, patients then applied a 10% glycolic acid gel, pH 3.52, to one side of the back, including the irradiated area, and the contralateral extensor forearms once daily for 7 days and then twice daily for 2 weeks. A placebo gel, pH 5.75, was applied to the opposite sides. The subjects returned for measurement of residual tanning with a colorimeter and received additional irradiation to forearms and a second site on the back. Resulting pigmentation was measured immediately after irradiation, at 2 hours, and at 1 week.

RESULTS

Increased UVB-induced skin tanning occurred on the forearm and the lower back in both races in areas pretreated with glycolic acid. UVA also caused increased tanning, but only on the extensor forearms in Asian subjects. Treatment with glycolic acid for 3 weeks had no effect on pre-existing light-induced pigmentation.

CONCLUSION

Short-term topical treatment of glycolic acid caused an increase in UVB tanning as well as in UVA tanning in some subjects, even in the absence of overt irritation. The inclusion of UVB, and even UVA, sunscreen in AHA products may be warranted.

Effect of saline iontophoresis on skin barrier function and cutaneous irritation in four ethnic groups

The effect of saline iontophoresis on skin barrier function and irritation was investigated in four ethnic groups (Caucasians, Hispanics, Blacks and Asians). Forty healthy human volunteers were recruited according to specific entry criteria. Ten subjects, five males and five females, were assigned to each ethnic group. Skin barrier function was examined after 4 hours of saline iontophoresis at a current density of 0.2 mA/cm(2) on a 6.5 cm(2) area in terms of the measured responses: transepidermal water loss (TEWL), skin capacitance, skin temperature and visual scores. There were significant differences in TEWL among the ethnic groups prior to patch application. TEWL at baseline in ethnic groups was in the rank order: Caucasian>Asian>Hispanic>Black. Iontophoresis was generally well tolerated, and skin barrier function was not irreversibly affected by iontophoresis in any group. There was no significant skin temperature change, compared to baseline, in any ethnic groups at any observation point. Edema was not observed. At patch removal, the erythema score was elevated in comparison to baseline in all ethnic groups; erythema resolved within 24 hours. Thus, saline iontophoresis produced reversible changes in skin barrier function and irritation in healthy human subjects.