Topical applications of an emollient reduce circulating pro-inflammatory cytokine levels in chronically aged humans: a pilot clinical study

BACKGROUND

While increased levels of circulating inflammatory cytokines in chronologically aged humans have been linked to the development of ageing-associated chronic disorders (e.g., cardiovascular disease, type II diabetes, osteoporosis and Alzheimer's disease), approaches that reduce circulating cytokines are not yet available. In chronologically aged mice, we recently demonstrated that epidermal dysfunction largely accounts for age-associated elevations in circulating cytokine levels, and that improving epidermal function reduced circulating cytokine levels.

OBJECTIVE

We performed a pilot study to determine whether improving epidermal function reduces circulating pro-inflammatory cytokine levels in aged humans.

METHODS

Thirty-three aged humans were topically treated twice-daily for 30 days, with ≈ 3 mL of an emollient, previously shown to improve epidermal function, while untreated, aged humans and a cohort of young volunteers served as controls. Changes in epidermal function and levels of three key, age-related, plasma cytokines (IL-1β, IL-6 and TNFα) were measured at baseline and after treatment, using Luminex 200™ system.

RESULTS

We also found significantly higher baseline levels of IL-1β, IL-6 and TNFα in aged vs. young humans (P < 0.001), as previously reported. Topical applications of the barrier repair emollient significantly enhanced epidermal permeability barrier function (P < 0.01) and stratum corneum hydration (P < 0.05). In parallel, circulating levels of IL-1β and IL-6 normalized, while TNFα levels declined substantially.

CONCLUSION

The results of this preliminary study suggest that a larger clinical trial should be performed to confirm whether improving epidermal function also can reduce circulating pro-inflammatory cytokine levels in aged humans, while also possibly attenuating the downstream development of chronic inflammatory disorders in the aged humans.

25 Hydroxyvitamin D 1 alpha-hydroxylase is required for optimal epidermal differentiation and permeability barrier homeostasis

Keratinocytes express high levels of 25OHD 1alpha-hydroxylase (1OHase). The product of this enzyme, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), promotes the differentiation of keratinocytes in vitro suggesting an important role for this enzyme in epidermal differentiation. To test whether 1OHase activity is essential for keratinocyte differentiation in vivo we examined the differentiation process in mice null for the expression of the 1alphaOHase gene (1alphaOHase(-/-)). Heterozygotes for the null allele were bred, and the progeny genotyped by PCR. The epidermis of the 1alphaOHase(-/-) animals and their wild-type littermates (1alphaOHase(+/+)) were examined by histology at the light and electron microscopic level, by immunocytochemistry for markers of differentiation, and by function examining the permeability barrier using transepidermal water loss (TEWL). No gross epidermal phenotype was observed; however, immunocytochemical assessment of the epidermis revealed a reduction in involucrin, filaggrin, and loricrin-markers of differentiation in the keratinocyte and critical for the formation of the cornified envelope. These observations were confirmed at the electron microscopic level, which showed a reduction in the F (containing filaggrin) and L (containing loricrin) granules and a reduced calcium gradient. The functional significance of these observations was tested using TEWL to evaluate the permeability barrier function of the epidermis. Although TEWL was normal in the basal state, following disruption of the barrier using tape stripping, the 1alphaOHase(-/-) animals displayed a markedly delayed recovery of normal barrier function. This delay was associated with a reduction in lamellar body secretion and a failure to reform the epidermal calcium gradient. Thus, the 25OHD 1OHase is essential for normal epidermal differentiation, most likely by producing the vitamin D metabolite, 1,25(OH)(2)D, responsible for inducing the proteins regulating calcium levels in the epidermis that are critical for the generation and maintenance of the barrier.

Mice lacking 25OHD 1alpha-hydroxylase demonstrate decreased epidermal differentiation and barrier function

Keratinocytes express high levels of 25OHD 1alpha-hydroxylase (1OHase). The product of this enzyme, 1,25(OH)(2)D, promotes the differentiation of keratinocytes in vitro. To test whether 1OHase activity is essential for keratinocyte differentiation in vivo we examined the differentiation process in mice null for the expression of the 1alphaOHase gene (1alphaOHase(-/-)) by light and electron microscopy, by immunocytochemistry for markers of differentiation, by ion capture cytochemistry for calcium localization, and by function using transepidermal water loss (TEWL) to assess barrier integrity. Levels of involucrin, filaggrin, and loricrin-markers of differentiation in the keratinocyte and critical for the formation of the cornified envelope-were reduced in the epidermis of 1alphaOHase(-/-) mice. Calcium in the outer epidermis was reduced with loss of the calcium gradient from stratum basale to stratum granulosum. TEWL was normal in the resting state, but following disruption of the barrier, 1alphaOHase(-/-) mice had a markedly prolonged recovery of barrier function associated with a reduction in lamellar body secretion and a failure to reform the calcium gradient. Thus 1,25(OH)(2)D is essential for normal epidermal differentiation, most likely by inducing the proteins and mediating the calcium signaling in the epidermis required for the generation and maintenance of the barrier.

Acute barrier perturbation abolishes the Ca2+ and K+ gradients in murine epidermis: quantitative measurement using PIXE

Epidermal permeability barrier homeostasis requires the delivery of lipids and hydrolytic enzymes by lamellar body exocytosis from the uppermost granular cells, a process that is upregulated following barrier disruption. As lamellar body secretion is controlled by ionic concentrations, especially Ca2+ and K+, we used a quantitative technique, microbeam proton-induced X-ray emission, to measure Ca2+, K+, Cl-, and P concentrations before and after acute barrier perturbation by acetone applications. We found a steep gradient of Ca2+ in normal tissue, peaking in the outer stratum granulosum, which disappeared after barrier disruption, and partially reformed as the barrier recovered. A similar gradient, peaking somewhat lower in the epidermis (i.e., at the stratum granulosum-stratum corneum interface), was found for K+. Epidermal concentrations of K+ also decreased after barrier abrogation, although to a lesser extent than Ca2+. In contrast, P and Cl- demonstrated distribution gradients at baseline, which remained unchanged after barrier disruption. These studies quantitate the levels of Ca2+, K+, Cl-, and P within specific epidermal cell layers at baseline, and in relation to changes in permeability barrier integrity. Ca2+ and K+, but not Cl- or P, decrease after barrier disruption, consistent with these two ion's role in barrier repair.

Endotoxin and cytokines decrease serum levels and extra hepatic protein and mRNA levels of cholesteryl ester transfer protein in syrian hamsters

Endotoxin alters the metabolism of lipoproteins, including that of high density lipoprotein (HDL). Cholesteryl ester transfer protein (CETP) facilitates exchange of HDL cholesterol for very low density lipoprotein (VLDL) triglyceride, leading to catabolism of HDL. We investigated the effects of endotoxin and cytokines on CETP in Syrian hamsters. Endotoxin induced a rapid and progressive decrease in serum CETP levels, by 48 h CETP had decreased to < 20% of control levels. Endotoxin also decreased CETP mRNA and protein levels in adipose tissue, heart, and muscle, the tissues with highest levels of CETP mRNA, providing a plausible mechanism for the endotoxin-induced decrease in circulating CETP. Dexamethasone did not mimic the effects of endotoxin on CETP, but the combination of tumor necrosis factor and interleukin-1 did, indicating that these cytokines may in part mediate the effects of endotoxin on CETP. The endotoxin-induced decrease in CETP may help maintain HDL cholesterol levels during infection and inflammation when increased triglyceride levels could drive the exchange of HDL cholesteryl ester for VLDL triglyceride. Maintaining circulating HDL may be important because HDL protects against the toxic effects of endotoxin and provides cholesterol for peripheral cells involved in the immune response and tissue repair.

Source estimation of auditory brainstem evoked potentials: comparison of 3CLT and dipole localization

The generators of auditory brainstem evoked potentials (ABEPs) are generally agreed to be located between the auditory nerve and upper pons. Thus, they are all located within a few cm from the center of the head. Three-channel Lissajous' trajectory (3CLT) provides the amplitude and orientation of a centrally located equivalent dipole of surface recorded activity. Volume conductor theory predicts decreased spatial resolution of source estimation the deeper the source. In this study we compared source estimates obtained with 3CLT, using three orthogonal differential channels, with those obtained with two other source estimation methods: i) setting the generators at their known anatomical coordinates and calculating orientation and magnitude of the source (dipole localization method--DLM); ii) estimation of all source parameters, including the number of sources by wavelet-type decomposition, without assumptions on the location of the sources (multiple source estimate--MSE). 3CLT, DLM and MSE all converged on magnitudes and orientations that were not significantly different from each other, and locations that were within a few cm of each other. In conclusion, although 3CLT can only estimate a single, centrally located equivalent dipole, in the specific case of ABEPs, it provides the same information available from the more demanding source estimate methods. In addition to the considerable saving in recording channels, 3CLT is reference-independent and thus avoids ambiguities resulting from the choice of reference.

Methicillin-resistant Staphylococcus aureus colonization in a new nursing home

Methicillin-resistant Staphylococcus aureus (MRSA) has been detected in nursing homes and long-term care facilities. Studies disagree about the risk of infection with MRSA in colonized patients. MRSA colonization and infection were tracked for one year in all admissions to a 60-bed ward at the Philadelphia VA Nursing Home Care Unit (NHCU) from the time of its opening in June, 1990. Patients and staff were blinded to culture results, and the NHCU followed universal precautions for all patients. Of the first 72 patients, 7 were found to be colonized with MRSA; only one of them was known to have had MRSA prior to NHCU transfer. Three patients died (2 had negative cultures prior to death), and 1 was discharged home. Three patients spontaneously cleared MRSA colonization and lived to the end of the study. Three patients appeared to be colonized by MRSA after admission; subsequent cultures were negative. No patients were infected by MRSA in the NHCU. At the close of the study, one year after the nursing home opened, no patient in the nursing home had a culture positive for MRSA. In conclusion, colonization with MRSA at the time of admission to the nursing home is not uncommon, but patients can spontaneously clear it. Besides, nursing homes that pre-screen only those patients with classic risk factors may be admitting many MRSA-colonized patients. Nonetheless, universal precautions appear to be effective in limiting transmission of MRSA in the nursing home; in this study, MRSA acquisition was sporadic and brief.

Three-channel Lissajous' trajectories of auditory brainstem evoked potentials: contribution of fast and slow components to planar segment formation

Three-Channel Lissajous' Trajectories (3CLT) of Auditory Brainstem Evoked Potentials (ABEP) to clicks were obtained after finite impulse response filtering in three frequency bands. These bands were chosen to replicate the widely used passband (100-3000 Hz) and to selectively enhance the definition of the 'pedestal' (10-240 Hz) or the first, third and fifth components (240-483 Hz). Quantitative measures of 3CLT were calculated to describe apex latencies, planar segment orientations, durations, trajectory amplitude peaks and their latencies. In addition, dipole moments at the latencies of apical points along 3-CLT were calculated. The planarity of ABEP 3-CLT segments persisted after selective enhancement of the 'pedestal' or the first, third and fifth components. These results rule out the suggestion that planarity of ABEP segments results from the interaction of the 'pedestal' with the superimposed faster components. These results demonstrate summation of 3-CLT planar segments ('a' 'c' and 'e' with the 'pedestal') to form new segments (wide-band 'a', 'c' and 'e'). With the exception of 'c', planar segments and the equivalent dipole moments associated with apexes did not change orientations across passbands. The effects of passband on the orientation of planar segment 'c' and the dipole moment of its apex are explained by its superimposition on the 'pedestal' in the wide-band records. A similar analysis of ABEP to clicks as compared to low-frequency stimuli (high-pass masked clicks) revealed no change in planarity nor in plane parameters. These results are compatible with the suggestion that the generators of the first, third and fifth ABEP components are curved fiber tracts. The planarity of the slow 'pedestal' may be due to the summation of slow synaptic potentials in auditory brainstem nuclei. These findings indicate that the generators of ABEP are composites that may be separated by selective lesion studies.

Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and cholesterol synthesis and esterification during the first cell cycle of liver regeneration

The regenerating rat liver provides a unique in vivo synchronized system for study of the interrelationships between mevalonate and sterol metabolism during the cell cycle. The regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, cholesterol synthesis and acyl coenzyme A: cholesterol acyltransferase during the first cell cycle was investigated. At 8 h postoperative and prior to onset of DNA synthesis or S phase, cholesterol synthesis was depressed in the regenerating liver relative to that in sham-operated controls. This suppression was observed whether assayed in vitro with liver homogenates utilizing radiolabeled acetate, mevalonate or water or in vivo with tritium water. In contrast, at this time point, 3-hydroxy-3-methylglutaryl-CoA reductase activity was increased in microsomes prepared both in the presence and absence of NaF. By 24 h, well into S phase and approaching mitosis, reductase activity and cholesterol synthesis both approached levels observed in the sham-operated control animals. There were no detectable changes in acyl-CoA: cholesterol acyltransferase activity at any time point. Thus, at the 8 h time point, the regulation of the three processes appeared uncoupled. The increased levels of in vitro expressed 3-hydroxy-3-methylglutaryl-CoA reductase activity compared with the decrease in the rate of both cholesterol and squalene biosynthesis suggested diversion of mevalonate into products other than squalene or sterols. We propose that this may reflect the needs of the cell for a nonsterol metabolite of mevalonate necessary for entry of cells into S phase.

Studies on the pathophysiological role of thyroidal prostaglandin E (PGE) in Graves' disease

A potential role for prostaglandin E (PGE) of thyroid origin in the pathogenesis of the hyperthyroidism of Graves' disease was investigated in vivo. The venous-arterio prostaglandin E (PGE) concentration gradient across the thyroid was measured in 5 patients undergoing subtotal thyroidectomy for Graves' disease. This gradient (161 +/- 14 pg/ml; mean /+- SE) was significantly greater than that found in 11 patients undergoing surgery for hyperparathyroidism and thyroid nodules (64 +/- 20 pg/ml; P < 0.01). This suggests that there is a net increase in PGE output by the thyroid gland in Graves' disease, but the thyroid cell-type responsible for this increased PGE output is unknown. In contrast to previous reports, thyrotropin (TSH) did not stimulate thyroid cell PGE generation in vitro, providing evidence against a role for TSH in this phenomenon. Administration of maximal doses of indomethacin to two thyrotoxic patients did not significantly alter peripheral thyroid hormone concentrations. These data suggest that thyroidal PGE has a function other than to stimulate thyroid hormone secretion in Graves' disease.