Recommendations for rosacea diagnosis, classification and management: update from the global ROSacea COnsensus 2019 panel

Background

A transition from a subtyping to a phenotyping approach in rosacea is underway, allowing individual patient management according to presenting features instead of categorization by predefined subtypes. The ROSacea COnsensus (ROSCO) 2017 recommendations further support this transition and align with guidance from other working groups.

Objectives

To update and extend previous global ROSCO recommendations in line with the latest research and continue supporting uptake of the phenotype approach in rosacea through clinical tool development.

Methods

Nineteen dermatologists and two ophthalmologists used a modified Delphi approach to reach consensus on statements pertaining to critical aspects of rosacea diagnosis, classification and management. Voting was electronic and blinded.

Results

Delphi statements on which the panel achieved consensus of ≥ 75% voting ‘Agree’ or ‘Strongly agree’ are presented. The panel recommends discussing disease burden with patients during consultations, using four questions to assist conversations. The primary treatment objective should be achievement of complete clearance, owing to previously established clinical benefits for patients. Cutaneous and ocular features are defined. Treatments have been reassessed in line with recent evidence and the prior treatment algorithm updated. Combination therapy is recommended to benefit patients with multiple features. Ongoing monitoring and dialogue should take place between physician and patients, covering defined factors to maximize outcomes. A prototype clinical tool (Rosacea Tracker) and patient case studies have been developed from consensus statements.

Conclusions

The current survey updates previous recommendations as a basis for local guideline development and provides clinical tools to facilitate a phenotype approach in practice and improve rosacea patient management.

What's already known about this topic?

A transition to a phenotype approach in rosacea is underway and is being recommended by multiple working groups.

New research has become available since the previous ROSCO consensus, necessitating an update and extension of recommendations.

What does this study add?

We offer updated global recommendations for clinical practice that account for recent research, to continue supporting the transition to a phenotype approach in rosacea.

We present prototype clinical tools to facilitate use of the phenotype approach in practice and improve management of patients with rosacea.

Linked Comment: Elewski. Br J Dermatol 2020; 182:1090–1091.

Plain language summary available online

Applying the phenotype approach for rosacea to practice and research

BACKGROUND

Rosacea diagnosis and classification have evolved since the 2002 National Rosacea Society expert panel subtype approach. Several working groups are now aligned to a more patient-centric phenotype approach, based on an individual's presenting signs and symptoms. However, subtyping is still commonplace across the field and an integrated strategy is required to ensure widespread progression to the phenotype approach.

OBJECTIVES

To provide practical recommendations that facilitate adoption of a phenotype approach across the rosacea field.

METHODS

A review of the literature and consolidation of rosacea expert experience.

RESULTS

We identify challenges to implementing a phenotype approach in rosacea and offer practical recommendations to overcome them across clinical practice, interventional research, epidemiological research and basic science.

CONCLUSIONS

These practical recommendations are intended to indicate the next steps in the progression from subtyping to a phenotype approach in rosacea, with the goals of improving our understanding of the disease, facilitating treatment developments and ultimately improving care for patients with rosacea.

Propionic acid and its esterified derivative suppress the growth of methicillin-resistant Staphylococcus aureus USA300

Previously, we demonstrated that Propionibacterium acnes, a human skin commensal bacterium, ferments glycerol into short-chain fatty acids, including propionic acid. Propionic acid suppressed the growth of Staphylococcus aureus USA300, a community-acquired methicillin-resistant bacterium, in vitro and in vivo. In this study, it is demonstrated that the anti-USA300 activity of propionic acid persisted after buffering the acid with 4-(2-hydroxyethyl)-1- piperazineethanesulfonic acid. This suggests that the growth suppression of USA300 mainly resulted from the antimicrobial activity of propionic acid per se and not from the acidity of the medium. In addition, proprionic acid significantly reduced the intracellular pH of USA300 and exhibited broad-spectrum antimicrobial activity against Escherichia coli and Candida albicans. P. acnes showed a higher tolerance to propionic acid. Next, an esterified derivative of propionic acid was synthesised. Propionic acid and the esterified derivative were equivalent in their efficacy to suppress the growth of USA300 in vitro. The esterified derivative thus provides an alternative to propionic acid as an antimicrobial agent against S. aureus.

Porphyrin metabolisms in human skin commensal Propionibacterium acnes bacteria: potential application to monitor human radiation risk

Propionibacterium acnes (P. acnes), a Gram-positive anaerobic bacterium, is a commensal organism in human skin. Like human cells, the bacteria produce porphyrins, which exhibit fluorescence properties and make bacteria visible with a Wood's lamp. In this review, we compare the porphyrin biosynthesis in humans and P. acnes. Also, since P. acnes living on the surface of skin receive the same radiation exposure as humans, we envision that the changes in porphyrin profiles (the absorption spectra and/or metabolism) of P. acnes by radiation may mirror the response of human cells to radiation. The porphyrin profiles of P. acnes may be a more accurate reflection of radiation risk to the patient than other biodosimeters/biomarkers such as gene up-/down-regulation, which may be non-specific due to patient related factors such as autoimmune diseases. Lastly, we discuss the challenges and possible solutions for using the P. acnes response to predict the radiation risk.

Induction and exacerbation of psoriasis with Interferon-alpha therapy for hepatitis C: a review and analysis of 36 cases

BACKGROUND

Interferon-alpha (IFN-α) therapy is used to treat hepatitis C infection. The exacerbation and occurrence of psoriasis in hepatitis C patients treated with IFN-α is increasingly recognized, but the distinct associated features, aetiology and management have not been reviewed.

OBJECTIVE

To review all published cases of hepatitis C patients who developed psoriasis while receiving IFN-α therapy.

METHODS

The review was conducted by searching the PubMed database using the keywords 'hepatitis C' AND 'psoriasis.' In addition, references to additional publications not indexed for PubMed were followed to obtain a complete record of published data.

RESULTS

We identified 32 publications describing 36 subjects who developed a psoriatic eruption while receiving IFN-α therapy for hepatitis C. Topical therapies were a commonly employed treatment modality, but led to resolution in only 30% of cases in which they were employed solely. Cessation of IFN-α therapy led to resolution in 93% of cases. Hundred per cent of those who developed psoriasis while on IFN-α therapy responded to systemic therapy and were able to continue the drug.

CONCLUSION

Further studies and analysis of IFN-α-induced lesions are necessary to clarify the role of IFN-α and the hepatitis C virus in the development of psoriatic lesions.

A randomized controlled double-blind investigation of the effects of vitamin D dietary supplementation in subjects with atopic dermatitis

BACKGROUND

Subjects with atopic dermatitis (AD) have defects in antimicrobial peptide (AMP) production possibly contributing to an increased risk of infections. In laboratory models, vitamin D can alter innate immunity by increasing AMP production.

OBJECTIVE

To determine if AD severity correlates with baseline vitamin D levels, and to test whether supplementation with oral vitamin D alters AMP production in AD skin.

METHODS

This was a multi-centre, placebo-controlled, double-blind study in 30 subjects with AD, 30 non-atopic subjects, and 16 subjects with psoriasis. Subjects were randomized to receive either 4000 IU of cholecalciferol or placebo for 21 days. At baseline and day 21, levels of 25-hydroxyvitamin D (25OHD), cathelicidin, HBD-3, IL-13, and Eczema Area and Severity Index (EASI) and Rajka-Langeland scores were obtained.

RESULTS

At baseline, 20% of AD subjects had serum 25OHD below 20 ng/mL. Low serum 25OHD correlated with increased Fitzpatrick Skin Type and elevated BMI, but not AD severity. After 21 days of oral cholecalciferol, mean serum 25OHD increased, but there was no significant change in skin cathelicidin, HBD-3, IL-13 or EASI scores.

CONCLUSIONS

This study illustrated that darker skin types and elevated BMI are important risk factors for vitamin D deficiency in subjects with AD, and highlighted the possibility that seasonality and locale may be potent contributors to cathelicidin induction through their effect on steady state 25OHD levels. Given the molecular links between vitamin D and immune function, further study of vitamin D supplementation in subjects with AD is warranted.

Cathelicidin protects against Helicobacter pylori colonization and the associated gastritis in mice

Cathelicidin, an antimicrobial peptide of the innate immune system, has been shown to modulate microbial growth, wound healing and inflammation. However, whether cathelicidin controls Helicobacter pylori infection in vivo remains unexplored. This study sought to elucidate the role of endogenous and exogenous mouse cathelicidin (CRAMP) in the protection against H. pylori infection and the associated gastritis in mice. Results showed that genetic ablation of CRAMP in mice significantly increased the susceptibility of H. pylori colonization and the associated gastritis as compared with the wild-type control. Furthermore, replenishment with exogenous CRAMP, delivered via a bioengineered CRAMP-secreting strain of Lactococcus lactis, reduced H. pylori density in the stomach as well as the associated inflammatory cell infiltration and cytokine production. Collectively, these findings indicate that cathelicidin protects against H. pylori infection and its associated gastritis in vivo. Our study also demonstrates the feasibility of using the transformed food-grade bacteria to deliver cathelicidin, which may have potential clinical applications in the treatment of H. pylori infection in humans.

Intrarectal administration of mCRAMP-encoding plasmid reverses exacerbated colitis in Cnlp(-/-) mice

Cathelicidin is a pleiotropic host defense peptide secreted by epithelial and immune cells. Whether endogenous cathelicidin is protective against ulcerative colitis, however, is unclear. Here we sought to delineate the role of endogenous murine cathelicidin (mCRAMP) and the therapeutic efficacy of intrarectal administration of mCRAMP-encoding plasmid in ulcerative colitis using dextran sulfate sodium (DSS)-challenged cathelicidin-knockout (Cnlp(-/-)) mice as a model. Cnlp(-/-) mice had more severe symptoms and mucosal disruption than the wild-type mice in response to DSS challenge. The tissue levels of interleukin-1β and tumor necrosis factor-α, myeloperoxidase activity and the number of apoptotic cells were increased in the colon of DSS-challenged Cnlp(-/-) mice. Moreover, mucus secretion and mucin gene expression were impaired in Cnlp(-/-) mice. All these abnormalities were reversed by the intrarectal administration of mCRAMP or mCRAMP-encoding plasmid. Taken together, endogenous cathelicidin may protect against ulcerative colitis through modulation of inflammation and mucus secretion.

Skin microbiota: a source of disease or defence?

Microbes found on the skin are usually regarded as pathogens, potential pathogens or innocuous symbiotic organisms. Advances in microbiology and immunology are revising our understanding of the molecular mechanisms of microbial virulence and the specific events involved in the host-microbe interaction. Current data contradict some historical classifications of cutaneous microbiota and suggest that these organisms may protect the host, defining them not as simple symbiotic microbes but rather as mutualistic. This review will summarize current information on bacterial skin flora including Staphylococcus, Corynebacterium, Propionibacterium, Streptococcus and Pseudomonas. Specifically, the review will discuss our current understanding of the cutaneous microbiota as well as shifting paradigms in the interpretation of the roles microbes play in skin health and disease.

Who is really in control of skin immunity underphysiologicalcircumstances - lymphocytes, dendritic cells or keratinocytes?

Our views of the skin immunity theatre are undergoing constant change. These not only reflect paradigm shifts in general immunology and skin biology, but also have profound clinical implications, which call for strategic changes in dermatological therapy. Nowhere can this be witnessed at a greater level of instructiveness and fascination than when addressing the question posed by this new Controversies feature. Thus, after a very long period of dominance by T cells and Langerhans cells as 'lead actors' on the skin immunity stage, the lowly keratinocyte has recently made an astounding theatrical appearance as a key protagonist of the innate skin immunity system, which may control even acquired skin immune responses. Further enhancing dramatic complexity and tension, the mast cell has entered as an additional actor claiming centre stage, and the epidermal Langerhans cell has slipped in a surprise appearance as the chief agent of immunotolerance. May you, esteemed reader, enjoy the spectacle offered here by selected immunodermatology authorities who double as 'stage managers' pushing their respective favourite actors into the limelight. You get everything you may expect from a good performance - complete with the impresario's overture that lures you into the theatre and sets the stage, competing divas, recently discovered new talents and even the critic's digest while the performance is still ongoing. By the time the curtain drops, you will have reached your own, independent conclusions on how to answer the title question of this play - at least for the time being...

Antimicrobial peptides: an essential component of the skin defensive barrier

The skin is positioned at the interface between an organism's internal milieu and an external environment characterized by constant assault with potential microbial pathogens. While the skin was formerly considered an inactive physical protective barrier that participates in host immune defense merely by blocking entry of microbial pathogens, it is now apparent that a major role of the skin is to defend the body by rapidly mounting an innate immune response to injury and microbial insult. In the skin, both resident and infiltrating cells synthesize and secrete small peptides that demonstrate broad-spectrum antimicrobial activity against bacteria, fungi, and enveloped viruses. Antimicrobial peptides also act as multifunctional immune effectors by stimulating cytokine and chemokine production, angiogenesis, and wound healing. Cathelicidins and defensins comprise two major families of skin-derived antimicrobial peptides, although numerous others have been described. Many such immune defense molecules are currently being developed therapeutically in an attempt to combat growing bacterial resistance to conventional antibiotics.

Characterization of the expression and function of N-methyl-D-aspartate receptor in keratinocytes

The N-methyl-D-aspartate (NMDA) receptor is expressed on neural tissue where it gates calcium ion entry upon stimulation. Using immunohistochemistry, it has been demonstrated in this study that the NMDAR1 receptor is also expressed on keratinocytes (KCs) in normal human skin and inflamed psoriatic skin in vivo. Furthermore, the NMDA receptor was functional as demonstrated by the ability of this receptor to trigger Ca++ influx in KCs. Incubation of cultured, human KCs with MK-801 decreases the cell growth and induces an increase in apoptosis. These findings demonstrate that the KC expression of NMDA receptor is a mechanism through which the influx of Ca++ into the cell can be regulated and suggest that the expression of this receptor may play a role in the regulation of KC growth and differentiation.

Cathelicidin antimicrobial peptides are expressed in salivary glands and saliva

The expression of antimicrobial peptides at epithelial surfaces such as skin, lung, and intestine is thought to provide protection against infection. Cathelicidin antimicrobial peptides are essential for the protection of skin against invasive bacterial infection. To determine if cathelicidins are also present in the oral cavity, we examined the expression of both mRNA and protein in mice and human saliva. The murine cathelicidin (CRAMP) was detected in the adult by reverse-transcription/polymerase chain-reaction (RT-PCR), and in embryonic, newborn, and adult tissues by in situ hybridization and immunohistochemistry. CRAMP mRNA and protein were localized to the salivary glands, specifically in acinar cells of the submandibular gland and palatine minor glands, as well as in lingual epithelium and palatal mucosa. In man, the human cathelicidin LL-37 was detected in human saliva by Western blotting. These results indicate that cathelicidins are present in the salivary system, in some oral epithelia, and in saliva, contributing to broad-spectrum defense of the oral cavity.

Innate antimicrobial peptide protects the skin from invasive bacterial infection

In mammals, several gene families encode peptides with antibacterial activity, such as the beta-defensins and cathelicidins. These peptides are expressed on epithelial surfaces and in neutrophils, and have been proposed to provide a first line of defence against infection by acting as 'natural antibiotics'. The protective effect of antimicrobial peptides is brought into question by observations that several of these peptides are easily inactivated and have diverse cellular effects that are distinct from antimicrobial activity demonstrated in vitro. To investigate the function of a specific antimicrobial peptide in a mouse model of cutaneous infection, we applied a combined mammalian and bacterial genetic approach to the cathelicidin antimicrobial gene family. The mature human (LL-37) and mouse (CRAMP) peptides are encoded by similar genes (CAMP and Cnlp, respectively), and have similar alpha-helical structures, spectra of antimicrobial activity and tissue distribution. Here we show that cathelicidins are an important native component of innate host defence in mice and provide protection against necrotic skin infection caused by Group A Streptococcus (GAS).

Processing site and gene structure for the murine antimicrobial peptide CRAMP

Cathelicidins are a mammalian gene family notable for the presence of an antibiotic peptide encoded at the carboxy-terminal domain of the nascent pre-pro-protein. Following proteolytic release, this peptide has direct antimicrobial activity. To understand the function and regulation of cathelicidin we investigated the peptide processing site and gene structure of the mouse cathelicidin CRAMP. Amino acid sequencing of the purified native 5 kDa peptide identified the functionally critical amino terminal sequence of mature CRAMP. Characterization of the CRAMP gene (Cnlp) showed homology in structure and sequence identity in several potential transcription factors binding sites found in the human cathelicidin LL-37. Overall, CRAMP shows striking similarities with LL-37, making it a useful model for study of human cathelicidin function and regulation.

Cutaneous injury induces the release of cathelicidin anti-microbial peptides active against group A Streptococcus

Cathelicidins are a family of peptides thought to provide an innate defensive barrier against a variety of potential microbial pathogens. The human and mouse cathelicidins (LL-37 and CRAMP, respectively) are expressed at select epithelial interfaces where they have been proposed to kill a number of gram-negative and gram-positive bacteria. To determine if these peptides play a part in the protection of skin against wound infections, the anti-microbial activity of LL-37 and CRAMP was determined against the common wound pathogen group A Streptococcus, and their expression was examined after cutaneous injury. We observed a large increase in the expression of cathelicidins in human and murine skin after sterile incision, or in mouse following infection by group A Streptococcus. The appearance of cathelicidins in skin was due to both synthesis within epidermal keratinocytes and deposition from granulocyctes that migrate to the site of injury. Synthesis and deposition in the wound was accompanied by processing from the inactive prostorage form to the mature C-terminal peptide. Analysis of anti-microbial activity of this C-terminal peptide against group A Streptococcus revealed that both LL-37 and CRAMP potently inhibited bacterial growth. Action against group A Streptococcus occurred in conditions that typically abolish the activity of anti-microbial peptides against other organisms. Thus, cathelicidins are well suited to provide defense against infections due to group A Streptococcus, and represent an important element of cutaneous innate immunity.

Anti-microbial activity and cell binding are controlled by sequence determinants in the anti-microbial peptide PR-39

PR-39 is a member of the proline-rich group of cathelicidin peptides, a class of anti-microbial peptides found in skin and in leukocytes. In addition to their innate defense function, these proline-rich peptides influence a number of mammalian cell processes, including inflammation, development, differentiation, and metastatic transformation. To characterize the mechanism further, through which proline-rich cathelicidin peptides may exert their numerous effects, we altered various conserved peptide sequence motifs using a biologically active fragment of PR-39 [PR-39(15)] as the template: We altered the N-terminal charge of its SH3 binding motif, substituted tryptophan for a conserved intervening leucine, and modified a proline-arginine stretch (residues 10-13). These peptide variants were tested for binding known targets of PR-39 and for biologic activity in mammalian and bacterial systems. We found that the N-terminal arginines are crucial for protein binding and that modification in this domain results in loss of affinity and specificity in binding to generalized and SH3-containing targets. The N-terminal charged residues are also required for NIH 3T3 syndecan induction and anti-microbial activity. In addition, modification of more C-terminal residues eliminates anti-bacterial activity while having less of an effect on peptide interactions in mammalian cell assays. This study shows that the presence of a charged N-terminus is important for peptide activity in both mammalian and bacterial systems whereas the C-terminal alterations of PR-39(15) more definitively affect anti-bacterial activity.

Proteoglycans and cutaneous vascular defense and repair

Proteoglycans are hybrid molecules composed of a core protein and covalently attached glycosaminoglycan chain(s). The structure, location, and processing of these molecules enables them to encode specific information that is used in multiple physiologic processes. Endothelial cells in the skin are influenced by proteoglycans through binding interactions between glycosaminoglycans and extracellular matrix, growth factors, cytokines, adhesion receptors, enzymes, and enzyme inhibitors. In wound repair, proteoglycans such as the syndecans are induced by antimicrobial peptides and can control growth factor responsiveness. The glycosaminoglycans further signal endothelial cells to increase expression of ICAM-1 and other molecules important for leukocyte adhesion. Thus, proteoglycans represent a powerful central regulatory element in skin that influences a wide variety of events and participates in host defense and tissue repair.

Dermatan sulfate activates nuclear factor-kappab and induces endothelial and circulating intercellular adhesion molecule-1

Proteoglycans (PGs) can influence cell behaviors through binding events mediated by their glycosaminoglycan (GAG) chains. This report demonstrates that chondroitin sulfate B, also known as dermatan sulfate (DS), a major GAG released during the inflammatory phase of wound repair, directly activates cells at the physiologic concentrations of DS found in wounds. Cultured human dermal microvascular endothelial cells exposed to DS responded with rapid nuclear translocation of nuclear factor-kappaB (NF-kappaB), increased expression of intercellular adhesion molecule-1 (ICAM-1) mRNA, and increased ICAM-1 cell surface protein. Heparan sulfate and chondroitin sulfates A and C had no effect on activation of NF-kappaB or induction of ICAM-1. Inhibition of NF-kappaB activation blocked the effect of DS. The increase in cell surface ICAM-1 did not involve TNF-alpha or IL-1 release by endothelial cells, but it was facilitated by autocrine factors whose release was initiated by DS. The ICAM-1-inductive activity of DS was confirmed in vivo. Injection of DS, but not heparin or other chondroitin sulfates, into mice greatly increased circulating levels of soluble ICAM. These data provide evidence that DS, but not other GAGs, initiates a previously unrecognized cell signaling event that can act during the response to injury.

Antimicrobial peptides: an emerging concept in cutaneous biology

Antimicrobial peptides are part of the host defense systems of plants, insects, fish, amphibia, birds, and mammals. These small proteins were previously thought of as an evolutionarily ancient system of immune protection with little relevance to the normal function of human skin. Recent developments have found that mammalian skin expresses these gene-encoded peptide antibiotics during inflammatory events such as wound repair, contact dermatitis, and psoriasis. The presence of these peptides in the skin forms a barrier for innate host protection against microbial pathogenesis. Furthermore, antimicrobial peptides also act on animal cells by stimulating them to change behaviors such as syndecan expression, chemotaxis, and chloride secretion. The combination of effects on host cells with antimicrobial action in a single molecule represents an efficient defense and response system against injury. Understanding the action of antimicrobial peptides in skin may yield further insight into the mechanism of innate cutaneous disease control and provide new approaches to therapy of wounds and inflammatory dermatitis.

PR-39, a syndecan-inducing antimicrobial peptide, binds and affects p130(Cas)

PR-39 is a proline-arginine-rich antimicrobial peptide and an important component of innate immunity. In addition to its antimicrobial effects, PR-39 can alter mammalian cell gene expression and behavior. To determine the mechanism through which PR-39 affects mesenchymal cells, we identify a number of binding targets for PR-39 using a biologically active fragment of PR-39 (PR-39(15)). We found that PR-39 binds NIH 3T3 in a saturable manner consistent with the existence of a binding target. Similar to full-length PR-39, PR-39(15) interacts with lipid bilayers. After interacting with the membrane, PR-39(15) rapidly enters human microvascular endothelial cells and binds a number of cytoplasmic proteins. PR-39 selectively binds recombinant SH3-containing proteins and was also found to bind a native SH3-containing protein, p130(Cas). PR-39(15) treatment of endothelial cells results in altered p130 localization. These results show that PR-39(15) binds an SH3-containing signal transduction molecule that has the potential to explain a myriad of effects PR-39 has on mammalian cell behaviors.

Dermatan sulfate released after injury is a potent promoter of fibroblast growth factor-2 function

Proteoglycans have been shown in vitro to bind multiple components of the cellular microenvironment that function during wound healing. To study the composition and function of these molecules when derived from an in vivo source, soluble proteoglycans released into human wound fluid were characterized and evaluated for influence on fibroblast growth factor-2 activity. Immunoblot analysis of wound fluid revealed the presence of syndecan-1, syndecan-4, glypican, decorin, perlecan, and versican. Sulfated glycosaminoglycan concentrations ranged from 15 to 65 microgram/ml, and treatment with chondroitinase B showed that a large proportion of the glycosaminoglycan was dermatan sulfate. The total glycosaminoglycan mixture present in wound fluid supported the ability of fibroblast growth factor-2 to signal cell proliferation. Dermatan sulfate, and not heparan sulfate, was the major contributor to this activity, and dermatan sulfate bound FGF-2 with Kd = 2.48 microM. These data demonstrate that proteoglycans released during wound repair are functionally active and provide the first evidence that dermatan sulfate is a potent mediator of fibroblast growth factor-2 responsiveness.

Reduced expression of syndecan-1 in human hepatocellular carcinoma with high metastatic potential

Syndecans comprise a gene family of transmembrane proteoglycans that regulate cellular behavior through interactions with various effectors, including heparin-binding growth factors and insoluble matrix components. Syndecan-1, the most extensively studied, localizes in epithelial cells and has been shown to present in normal hepatocytes. However, little is known about the change of syndecan-1 expression in human hepatocellular carcinoma (HCC). We investigated syndecan-1-protein expression by immunohistochemistry in 57 HCC tissue samples. Syndecan-1 gene expression was also determined. Syndecan-1 protein was expressed in cytoplasm and cell membrane of the hepatocytes and in the bile duct epithelial cells of liver with underlying hepatitis and cirrhosis. Conversely, among 57 HCC tissues, 39 HCC (68.4%) showed negative staining; 50% of well-differentiated HCC showed positive staining, whereas 82.4% of poorly differentiated HCC were negative. Loss of syndecan-1-protein expression was more prevalent in HCC with intra-hepatic metastasis (85.2%) than those without metastasis (48.0%). Similarly, syndecan-1 expression was significantly reduced in HCC with extra-hepatic metastasis (91.7%) as compared with the HCC without extra-hepatic metastasis (62.2%). The gene expression of syndecan-1 was significantly lower in HCC tissue than that in non-tumoral liver tissue. In 2 human HCC cell lines with poorly differentiated phenotype, HLE and HLF, syndecan-1 expression was markedly decreased both at the mRNA and the protein levels. These results suggest that the loss of syndecan-1 expression is a characteristic feature of HCC with high metastatic potential.

Reduced expression of syndecan-1 in human hepatocellular carcinoma with high metastatic potential

Syndecans comprise a gene family of transmembrane proteoglycans that regulate cellular behavior through interactions with various effectors, including heparin-binding growth factors and insoluble matrix components. Syndecan-1, the most extensively studied, localizes in epithelial cells and has been shown to present in normal hepatocytes. However, little is known about the change of syndecan-1 expression in human hepatocellular carcinoma (HCC). We investigated syndecan-1-protein expression by immunohistochemistry in 57 HCC tissue samples. Syndecan-1 gene expression was also determined. Syndecan-1 protein was expressed in cytoplasm and cell membrane of the hepatocytes and in the bile duct epithelial cells of liver with underlying hepatitis and cirrhosis. Conversely, among 57 HCC tissues, 39 HCC (68.4%) showed negative staining; 50% of well-differentiated HCC showed positive staining, whereas 82.4% of poorly differentiated HCC were negative. Loss of syndecan-1-protein expression was more prevalent in HCC with intra-hepatic metastasis (85.2%) than those without metastasis (48.0%). Similarly, syndecan-1 expression was significantly reduced in HCC with extra-hepatic metastasis (91.7%) as compared with the HCC without extra-hepatic metastasis (62.2%). The gene expression of syndecan-1 was significantly lower in HCC tissue than that in non-tumoral liver tissue. In 2 human HCC cell lines with poorly differentiated phenotype, HLE and HLF, syndecan-1 expression was markedly decreased both at the mRNA and the protein levels. These results suggest that the loss of syndecan-1 expression is a characteristic feature of HCC with high metastatic potential.

Endothelial cell surface alkaline phosphatase activity is induced by IL-6 released during wound repair

Phosphatase activity on endothelial cell surfaces is responsible, in part, for the conversion of adenosine nucleotides to adenosine, a potent vasodilator and anti-inflammatory mediator that can protect tissues from the ischemic damage that results from injury. To evaluate whether phosphatases are actively induced by a soluble factor released following injury, the effect of tissue fluids collected from porcine or human skin wounds was tested on primary cultures of endothelial cells. Phosphatase activity increased approximately 50-fold following 48-h culture in the presence of wound fluid. Inductive activity was present only in fluids collected during the inflammatory phase of wound repair. The phosphatase activity metabolized adenosine monophosphate to free phosphate and was the liver/bone/kidney alkaline phosphatase isoenzyme: activity was temperature- and levamisole-sensitive, 1-phenylalanine-resistant, and linked to the cell surface via phospholipid, and migrated at a size identical to this isozyme. interleukin-6 was identified as the phosphatase-inducing factor in wound fluid and the related cytokines, leukaemia inhibiting factor, and oncostatin M, caused a similar degree of alkaline phosphatase induction. Therefore, following injury, accumulation of interleukin-6 can lead to production by alkaline phosphatase of adenosine and subsequent protection from ischemic injury.

Identification of CRAMP, a cathelin-related antimicrobial peptide expressed in the embryonic and adult mouse

Cathelicidins are the precursors of potent antimicrobial peptides that have been identified in several mammalian species. Prior work has suggested that members of this gene family can participate in host defense through their antimicrobial effects and activate mesenchymal cells during wound repair. To permit further study of these proteins a reverse transcriptase-polymerase chain reaction approach was used to identify potential mouse homologs. A full-length 562-base pair cDNA clone was obtained encoding an NH2-terminal prepro domain homologous to other cathelicidins and a unique COOH-terminal peptide. This gene, named Cramp for cathelin-related antimicrobial peptide, was mapped to chromosome 9 at a region of conserved synteny to which genes for cathelicidins have been mapped in pig and man. Northern blot analysis detected a 1-kilobase transcript that was expressed in adult bone marrow and during embryogenesis as early as E12, the earliest stage of blood development. Reverse transcriptase-polymerase chain reaction also detected CRAMP expression in adult testis, spleen, stomach, and intestine but not in brain, liver, heart, or skeletal muscle. To evaluate further the expression and function of CRAMP, a peptide corresponding to the predicted COOH-terminal region was synthesized. CD spectral analysis showed that CRAMP will form an amphipathic alpha-helix similar to other antimicrobial peptides. Functional studies showed CRAMP to be a potent antibiotic against Gram-negative bacteria by inhibiting growth of a variety of bacterial strains (minimum inhibitory concentrations 0.5-8.0 microM) and by permeabilizing the inner membrane of Escherichia coli directly at 1 microM. Antiserum against CRAMP revealed abundant expression in myeloid precursors and neutrophils. Thus, CRAMP represents the first antibiotic peptide found in cells of myeloid lineage in the mouse. These data suggest that inflammatory cells in the mouse can use a nonoxidative mechanism for microbial killing and permit use of the mouse to study the role such peptides play in host defense and wound repair.

Structure-function relations in the inhibition of murine contact hypersensitivity by amiloride

Topical application of amiloride, a potent inhibitor of the Na+/H+ antiport, inhibits cutaneous inflammation induced by ultraviolet radiation or contact hypersensitivity in mice. Amiloride analogues with greater and lesser inhibition of the Na+/H+ exchange were tested to determine whether anti-inflammatory effects correlate with this activity. Structural analogues of amiloride without significant activity at the Na+/H+ antiport (pyrazine, pyrazinamide, and chloropyrazine) failed to inhibit contact hypersensitivity. N-amidino-3-amino-5-dimethyl amino-6-chloropyrazinecarboxamide (DMA) has a 23-fold greater affinity for the Na+/H+ antiport compared to amiloride, but failed to inhibit contact hypersensitivity in this assay. 3,5-diamino-6-chloropyrazine-amido-guanidine (DCG), which has only 7% of the affinity of amiloride for the antiport, suppressed contact hypersensitivity as well as amiloride. Experiments examining the ability of these agents to diffuse through mouse skin revealed amiloride to be superior to both DCG and DMA, which were approximately equal. DMA, with greater inhibition of the Na+/H+ antiport but lesser ability to inhibit contact hypersensitivity, inhibited protein synthesis and induced cell death more than amiloride or DCG. Amiloride and DCG hold promise as topical anti-inflammatory agents. Their anti-inflammatory properties do not correlate with affinity for the Na+/H+ antiport, ability to penetrate murine skin, or inhibition of protein synthesis.

Syndecans, cell surface heparan sulfate proteoglycans, are induced by a proline-rich antimicrobial peptide from wounds

Cell surface heparan sulfate proteoglycans, such as the syndecans, are required for cellular responses to heparin-binding growth factors and extracellular matrix components. Expression of syndecan-1 and -4 is induced in mesenchymal cells during wound repair in the mouse, consistent with a role for syndecans in regulating cell proliferation and migration in response to these effectors. Here we show that wound fluid contains inductive activity that mimics the in vivo induction in time of appearance, specificity for mesenchymal cells, and selectivity for syndecan-1 and -4. We have purified and synthesized a 4.8-kDa proline-rich protein from wound fluid that reproduces this induction of syndecan-1 and -4 in cultured cells. This peptide, identical to the antibacterial peptide PR-39, is released into the wound by the cellular infiltrate and induces syndecan expression at the same peptide concentrations that lyse bacteria. These results indicate that wounds contain a multifunctional protein that induces mammalian cells to express cell surface heparan sulfate proteoglycans as part of the wound repair process and that kills bacteria as part of a nonimmune defense mechanism.

Members of the syndecan family of heparan sulfate proteoglycans are expressed in distinct cell-, tissue-, and development-specific patterns

The syndecans are a gene family of four transmembrane heparan sulfate proteoglycans that bind, via their HS chains, diverse components of the cellular microenvironment. To evaluate the expression of the individual syndecans, we prepared cDNA probes to compare mRNA levels in various adult mouse tissues and cultured mouse cells representing various epithelial, fibroblastic, endothelial, and neural cell types and B cells at various stages of differentiation. We also prepared antibody probes to assess whether the extracellular domains of the individual syndecans are shed into the conditioned media of cultured cells. Our results show that all cells and tissues studied, except B-stem cells, express at least one syndecan family member; most cells and tissues express multiple syndecans. However, each syndecan family member is expressed selectively in cell-, tissue-, and development-specific patterns. The extracellular domain of all syndecan family members is shed as an intact proteoglycan. Thus, most, if not all, cells acquire a distinctive repertoire of the four syndecan family members as they differentiate, resulting in selective patterns of expression that likely reflect distinct functions.

Deficient antigen presentation by Langerhans cells from athymic (nu/nu) mice. Restoration with thymic transplantation or administration of cytokines

Epidermal Langerhans cells (LC) are a unique subtype of I-A+ dendritic cells able to present Ag for CD4-dependent immune responses. To investigate whether cutaneous Ag presentation is regulated by thymic elements or soluble factors produced by thymus-derived cells, we compared LC function in athymic nude mice and euthymic normal controls. Examination of the ability of LC to present alloantigens to T cell-enriched responder populations, and insulin to an insulin-specific T cell hybridoma, demonstrated that this function is deficient in LC from inbred and outbred strains of congenitally athymic (nu/nu) mice compared with euthymic litter mates. Adoptive transfer of thymic tissue from euthymic to athymic mice reconstituted the ability of LC derived from athymic mice to present alloantigens. To investigate whether an altered local cytokine microenvironment was responsible for the diminished LC function in athymic mice, various cytokines were administered in vivo and in vitro before determination of alloantigen presentation by epidermal cells from athymic and euthymic mice. Continuous intraperitoneal infusion of granulocyte-macrophage colony stimulating factor (GM-CSF) or TNF-alpha, but not IL-1 alpha or IL-2, restored alloantigen presenting ability in athymic LC. In vitro preincubation of LC in GM-CSF or TNF-alpha but not in other cytokines tested also reconstituted alloantigen presentation by LC from athymic mice in most, but not all, of the experiments performed. Furthermore, analysis of cytokine production by epidermal cells in athymic and euthymic mice revealed that epidermal cells from athymic mice produce less GM-CSF and more TNF-alpha, but normal amounts of various other cytokines. However, reconstitution of athymic mice with thymic tissue did not result in normalization of GM-CSF or TNF-alpha production by epidermal cells. These data suggest that LC Ag presenting ability is regulated by thymic factors and that adequate function of cutaneous APC in situ may require the continuous presence of sufficient amounts of cytokines including GM-CSF and TNF-alpha.

Deficient antigen presentation by Langerhans cells from athymic (nu/nu) mice. Restoration with thymic transplantation or administration of cytokines

Epidermal Langerhans cells (LC) are a unique subtype of I-A+ dendritic cells able to present Ag for CD4-dependent immune responses. To investigate whether cutaneous Ag presentation is regulated by thymic elements or soluble factors produced by thymus-derived cells, we compared LC function in athymic nude mice and euthymic normal controls. Examination of the ability of LC to present alloantigens to T cell-enriched responder populations, and insulin to an insulin-specific T cell hybridoma, demonstrated that this function is deficient in LC from inbred and outbred strains of congenitally athymic (nu/nu) mice compared with euthymic litter mates. Adoptive transfer of thymic tissue from euthymic to athymic mice reconstituted the ability of LC derived from athymic mice to present alloantigens. To investigate whether an altered local cytokine microenvironment was responsible for the diminished LC function in athymic mice, various cytokines were administered in vivo and in vitro before determination of alloantigen presentation by epidermal cells from athymic and euthymic mice. Continuous intraperitoneal infusion of granulocyte-macrophage colony stimulating factor (GM-CSF) or TNF-alpha, but not IL-1 alpha or IL-2, restored alloantigen presenting ability in athymic LC. In vitro preincubation of LC in GM-CSF or TNF-alpha but not in other cytokines tested also reconstituted alloantigen presentation by LC from athymic mice in most, but not all, of the experiments performed. Furthermore, analysis of cytokine production by epidermal cells in athymic and euthymic mice revealed that epidermal cells from athymic mice produce less GM-CSF and more TNF-alpha, but normal amounts of various other cytokines. However, reconstitution of athymic mice with thymic tissue did not result in normalization of GM-CSF or TNF-alpha production by epidermal cells. These data suggest that LC Ag presenting ability is regulated by thymic factors and that adequate function of cutaneous APC in situ may require the continuous presence of sufficient amounts of cytokines including GM-CSF and TNF-alpha.

Cyclosporin increases granulocyte/macrophage colony-stimulating factor (GM-CSF) activity and gene expression in murine keratinocytes

Keratinocytes produce multiple cytokines in response to a variety of stimuli. The release of interleukin 1 (IL-1) from keratinocytes may be significant in initiation of cutaneous inflammation, and the presence of granulocyte/macrophage colony-stimulating factor (GM-CSF) is thought to be important in the regulation of antigen-presenting function by epidermal Langerhans cells. Because cyclosporin inhibits interleukin 2 release from T cells, it has been suggested that cyclosporin may function as an anti-inflammatory agent within the epidermis through inhibition of keratinocyte cytokine release. This investigation examined the direct effect of cyclosporin on the production of GM-CSF by murine keratinocytes and the keratinocyte cell line PAM 212. GM-CSF bioactivity increased in cell supernatants from keratinocytes exposed in vitro to 1 microgram/ml cyclosporin for up to 24 h. GM-CSF and IL-1 mRNA levels in keratinocytes cultured under similar conditions or in the presence of lipopolysaccharide also increased. The lack of inhibition of GM-CSF expression following cyclosporin treatment is consistent with recent observations in T cells and is opposite to the effect of cyclosporin on interleukin 2.

Regulation of GM-CSF and IL-3 production from the murine keratinocyte cell line PAM 212 following exposure to ultraviolet radiation

Ultraviolet radiation (UVR) exposure induces profound changes in the synthesis and secretion of various cytokines both in vivo and in vitro. Little is known regarding the mechanism of these responses. This investigation evaluated the effects of UVR on the ability of a murine keratinocyte line (PAM 212) to produce interleukin 3 (IL-3) and granulocyte-macrophage colony stimulating factor (GM-CSF). Subconfluent rapidly dividing PAM 212 cells were shown by RNA slot-blot hybridization studies to have increased levels of mRNA for both IL-3 and GM-CSF within 1 h of UVR exposure. However, only GM-CSF-specific bioactivity, as determined by antibody neutralization studies, was shown to increase above baseline in cell supernatants. Cells grown to confluence responded differently to UVR. Under these culture conditions an apparent decrease in bioactivity was detected after UVR exposure for both growth factors, and no change in mRNA levels was detected. In addition to culture density, removal of extracellular calcium or sodium during irradiation, treatment with amiloride, or inhibition of new mRNA synthesis with cordycepin was shown to influence the UVR-induced alteration in release of IL-3 or GM-CSF bioactivity from both confluent and subconfluent PAM 212 cells. These results demonstrate that UVR influences the release of the colony stimulating factors GM-CSF and IL-3 from keratinocyte, and suggests that the state of cell growth and conditions of membrane ion transport influence the mechanisms regulating secretion of those factors.

Tumor antigen presentation by murine epidermal cells

The ability of epidermal Langerhans cells to present Ag for CD4-dependent immunity is well documented, and it has been hypothesized that Langerhans cells participate in the generation of immunity against incipient epidermal neoplasms by presentation of tumor-associated Ag in situ. This study examined the ability of murine epidermal cells (EC) to present tumor-associated Ag for the induction of in vivo antitumor immunity. Murine epidermal cells were deleted of Thy-1-bearing cells, cultured in 50 U/ml granulocyte-macrophage-CSF for 14 to 18 h, and pulsed with tumor fragments (TF) derived from S1509a-fibrosarcoma cells. These TF-pulsed EC were injected s.c. into syngeneic recipients at weekly intervals for a total of three immunizations and challenged with viable S1509a tumor cells 1 wk after the last immunization. Control animals received TF-pulsed allogeneic EC or EC treated identically but not pulsed with TF. EC that were pulsed with tumor cell fragments were able to induce protective immunity to tumor growth in vivo and to immunize for a significant delayed-type hypersensitivity response to injected tumor cells. The induction of antitumor immunity with TF-pulsed EC was genetically restricted, and culture of EC in granulocyte-macrophage-CSF was required for development of significant immunity. Furthermore, deletion of I-A+ cells by antibody and complement-mediated lysis eliminated the generation of immunity. Thus, I-A+ epidermal cells are capable of presenting S1509a tumor Ag for the generation of protective antitumor immunity in vivo.

Tumor antigen presentation by murine epidermal cells

The ability of epidermal Langerhans cells to present Ag for CD4-dependent immunity is well documented, and it has been hypothesized that Langerhans cells participate in the generation of immunity against incipient epidermal neoplasms by presentation of tumor-associated Ag in situ. This study examined the ability of murine epidermal cells (EC) to present tumor-associated Ag for the induction of in vivo antitumor immunity. Murine epidermal cells were deleted of Thy-1-bearing cells, cultured in 50 U/ml granulocyte-macrophage-CSF for 14 to 18 h, and pulsed with tumor fragments (TF) derived from S1509a-fibrosarcoma cells. These TF-pulsed EC were injected s.c. into syngeneic recipients at weekly intervals for a total of three immunizations and challenged with viable S1509a tumor cells 1 wk after the last immunization. Control animals received TF-pulsed allogeneic EC or EC treated identically but not pulsed with TF. EC that were pulsed with tumor cell fragments were able to induce protective immunity to tumor growth in vivo and to immunize for a significant delayed-type hypersensitivity response to injected tumor cells. The induction of antitumor immunity with TF-pulsed EC was genetically restricted, and culture of EC in granulocyte-macrophage-CSF was required for development of significant immunity. Furthermore, deletion of I-A+ cells by antibody and complement-mediated lysis eliminated the generation of immunity. Thus, I-A+ epidermal cells are capable of presenting S1509a tumor Ag for the generation of protective antitumor immunity in vivo.

A controlled trial of intralesional recombinant interferon-gamma in the treatment of keloidal scarring. Clinical and histologic findings

Interferon-gamma (IFN-gamma) suppresses the synthesis of collagen by fibroblasts in vitro and the synthesis of collagen in vivo in animal models. Therefore, recombinant human IFN-gamma was examined for its ability to clinically modify keloids. Subjects were treated by injection of either 0.01 or 0.1 mg of recombinant human IFN-gamma into one lesional site and diluent alone into another lesional site three times per week for 3 weeks. Keloids were measured and photographed before beginning therapy and weekly thereafter. Three days after the final injection, biopsies were performed on treated and control sites. Six of eight subjects who finished the course of treatment demonstrated reduction in size at the treated site with an average reduction in height of 30.4% vs 1.1% for control sites. Lesions treated with recombinant human IFN-gamma demonstrated alterations in both the epidermis and dermis. The epidermis showed thinning of the suprapapillary plates, compact hyperkeratosis, focal or diffuse parakeratosis, exocytosis of lymphocytes, and an increased quantity of mucin. The dermis contained a diminished quantity of thickened collagen bundles and active fibroblasts and an increased number of inflammatory cells and quantity of mucin. These results suggest the feasibility of using IFN-gamma in the treatment of abnormal fibrosis. Dose-ranging studies are required to establish whether IFN-gamma can fulfill a true clinical need in the treatment of keloidal scarring.

Mechanism for 193-nm laser radiation-induced effects on mammalian cells

The cellular sites for damage in mammalian cells caused by 193-nm radiation from an argon fluoride excimer laser were investigated. The ability of Chinese hamster ovary cells to reduce a tetrazolium dye (MTT) was decreased to 37% of unirradiated control by 2.5 x 10(3) J/m2 of 193-nm radiation when measured either 4 or 24 h after irradiation. In contrast, inhibition of MTT reduction by 254-nm radiation which primarily causes DNA damage was not measurable using this assay at 4 h after exposure; at 24 h 45 J/m2 inhibited MTT reduction to 37% of control. An increase in plasma membrane permeability, detected by 51Cr release, was observed within 15 min of exposure to 193-nm radiation, whereas exposure to 254-nm radiation did not cause this immediate release of 51Cr. In control experiments, the mitochondrial poison, carbonyl cyanide m-chlorophenyl hydrazone, did not cause 51Cr release in the dark, indicating that the 193-nm radiation-induced increase in plasma membrane permeability was not subsequent to loss of mitochondrial function. [3H]-Arachidonic acid was released from C3H10T1/2 cells using low 193-nm fluences, whereas release of [3H]arachidonic acid using UVB (290-32 nm) radiation required cytotoxic fluences. DNA does not appear to be a major site of 193 nm-induced cellular damage because alkali-labile sites were not detected in cells exposed on ice to up to 2 x 10(4) J/m2 of 193-nm radiation. These results indicate that 193-nm radiation produces primary damage on the level of the plasma membrane.

Ultraviolet radiation induces a change in cell membrane potential in vitro: a possible signal for ultraviolet radiation induced alteration in cell activity

The regulation of a transmembrane ionic gradient, reflected by the cellular membrane potential, has been shown in several cell systems to be involved in the regulation of cell function. This investigation presents evidence that biologically relevant doses of ultraviolet radiation (UVR) will alter the membrane potential of keratinocytes in vitro. Estimation of the relative change in the steady-state membrane potential of the murine keratinocyte cell line PAM 212, the murine myelomonocytic cell line P388D1, and normal human keratinocytes in culture, were made through the use of the lipophilic cationic membrane potential sensitive probe; triphenylmethylphosphonium. Our observations indicate that UVR composed primarily of UVB (280-320 nm) radiation at doses as low as 100 J/m2 can induce a depolarization in the murine cell lines and a hyperpolarization in human keratinocytes. Evidence suggests that this difference in the direction of the membrane potential response reflects a difference in Na+/K+ ATPase activity following UVR. These results suggest a possible mechanism for modulation of keratinocyte activity induced by UVR.

Inhibition of allergic contact dermatitis and ultraviolet radiation-induced tissue swelling in the mouse by topical amiloride

Amiloride is known to inhibit membrane sodium transport and has been shown in vitro to inhibit cell activation and proliferation in several model systems. These effects occur at relatively high local concentrations of amiloride. We studied the cutaneous response to the topical application of amiloride hydrochloride. Our observations demonstrated that topical application of amiloride was potent in its ability to inhibit murine tissue swelling and inflammation in response to contact sensitizing agents and ultraviolet radiation. These observations might suggest a role for amiloride or its analogues as topical anti-inflammatory or antiproliferative drugs.

Lysophosphatidylcholine cell depolarization: increased membrane permeability for use in the determination of cell membrane potentials

Current techniques for the determination of cellular membrane potentials based on the uptake of a radiolabeled lipophilic cation, [3H]triphenylmethylphosphonium, and the cyanine dye, DiOC5(3), were analyzed in terms of the proportions of these probes which are accumulated due to potential-dependent and potential-independent forces. Measurements were made of probe uptake in two model systems: rabbit type II pneumocytes and human promyelocytic HL60 cells. For both cell types, the membrane potential-independent component of triphenylmethylphosphonium uptake was found to be a function of several variables, including the length of exposure of the cells to the transport facilitator tetraphenylboron, the concentration of tetraphenylboron, and the integrity of the cell membrane. To accurately determine the magnitude of the potential-independent component of probe uptake by type II and HL60 cells, the cell-permeabilizing agent lysophosphatidylcholine was used. The ability of lysophosphatidylcholine to depolarize cell membranes and accurately predict membrane potential-independent accumulation was found to be equal to or superior to several other techniques commonly used to achieve membrane depolarization (e.g. gramicidin, valinomycin plus high external potassium). Lysophosphatidylcholine cell treatment was found to be a simple, rapid, and accurate technique to increase cell membrane permeability and allow equilibration of intra- and extracellular ions. The method is shown to be useful for determining membrane potential-independent accumulation of both radiolabeled and fluorescent probes of membrane potential.

Characterization of the plasma and mitochondrial membrane potentials of alveolar type II cells by the use of ionic probes

The lipophilic cation triphenylmethylphosphonium (TPMP+) and the potassium analog Rb+, were used to monitor the membrane potential (delta psi) of freshly isolated rabbit type II alveolar epithelial cells. Type II cells were found to accumulate TPMP+ rapidly at 37 degrees C in Hanks' balanced-salt solution with 5 microM tetraphenyl boron, but this accumulation was partially due to non-membrane potential dependent binding of TPMP+ to the cell. Lysophosphatidylcholine (lysoPC) was found to abolish delta psi and permitted correction for bound TPMP+ or Rb+. TPMP+ remaining in the cell following correction for binding represents the sum of mitochondrial and plasma membrane potential dependent accumulation. The accumulation of Rb+ by the type II cell was found to be independent of the mitochondrial membrane potential and indicated a trans-plasma membrane Rb+ distribution potential of -62.9 +/- 4 mV. A similar value was obtained by estimating the plasma membrane potential dependent accumulation of TPMP+ in type II cells whose mitochondria were depolarized with carbonylcyanide m-chlorophenylhydrazone (CCCP). The release of TPMP+ due to CCCP treatment also permitted an estimation for the trans-mitochondrial membrane potential of -141.8 +/- 10 mV. These techniques of membrane potential measurements were found to be sensitive to changes in delta psi induced by a number of inhibitors and ionophores. The ability to measure the membrane potential of the type II pneumocyte, and the changes caused by various agents, should be useful in characterizing the functional responses of this pulmonary surfactant producing cell.