Mary S. Ross

Topical application of a selective cyclooxygenase inhibitor suppresses UVB mediated cutaneous inflammation

Ultraviolet B (UVB) radiation causes much of the cutaneous damage after both acute and long-term exposure, and is also the most important etiologic agent in human skin cancer. UVB exposure initially induces an inflammatory response characterized by edema, dermal infiltration of leukocytes, sunburn cell formation, as well as the induction of cyclooxygenase-2 (COX-2) gene expression and subsequent increase in the production and release of prostaglandins. This process of inflammation induced by UVB exposure has been linked to tumor formation. Recently, a specific COX-2 inhibitor, Celecoxib, was developed, which inhibits COX-2-induced inflammation without inhibiting the cytoprotective function of cyclooxygenase-1 (COX-1). The present study compared the effects of topical treatment with Celecoxib (a specific COX-2 inhibitor) and Ibuprofen (a nonspecific COX inhibitor) on the acute UVB-induced cutaneous inflammatory response. We show that the specific inhibition of COX-2 effectively reduced many parameters of UVB-mediated inflammation, including edema, dermal neutrophil infiltration and activation, prostaglandin E2 (PGE2) levels and the formation of sunburn cells. By inhibiting this inflammatory response, topical Celecoxib treatment may ultimately be effective in preventing UVB-induced tumor development in the skin.

Ibuprofen-induced inhibition of cyclooxygenase isoform gene expression and regression of rat mammary carcinomas.

A single dose of 75 mg/kg 7,12 dimethylbenz[a]anthracene was administered to 50-day-old virgin female Sprague-Dawley rats and 100 days later, animals were randomized and provided with Teklad rodent chow mixed with a dose of 25 mg/rat/day ibuprofen for 35 days. Ibuprofen treatment reduced tumor volume (P < 0.05) and significantly inhibited gene expression of both cyclooxygenase- and cyclooxygenase-2 (P < 0.02). These results indicate that ibuprofen induced significant regression of established mammary carcinomas which was associated with inhibition of expression of isoforms of the gene responsible for prostaglandin production.

Inhibition of ultraviolet light B-induced cutaneous inflammation by a specific cyclooxygenase-2 inhibitor.

Ultraviolet B (UVB) radiation is responsible for the majority of cutaneous damage following both acute and long-term exposure, and is believed to be the most important etiologic agent in human skin cancer. UVB carcinogenesis initially induces an inflammatory response characterized by edema, dermal infiltration of leukocytes, as well as the production and release of prostaglandins, which may be critical to the observed damaging effects of UVB light on skin. Recently, a specific cyclooxygenase-2 (COX-2) inhibitor, Celecoxib, was developed, which inhibits COX-2-induced inflammation without inhibiting the cytoprotective function of cyclooxygenase-1 (COX-1). Studies have demonstrated that oral administration of Celecoxib decreased the incidence of skin and colon tumors. Recently, the process of inflammation has been linked to tumor formation. The present study examined the effects of a topical application of Celecoxib on the acute UVB-induced cutaneous inflammatory response. We show that topical Celecoxib treatment effectively reduced many parameters of UVB-mediated inflammation, including edema, dermal myeloperoxidase activity, neutrophil infiltration,and prostaglandin E2 (PGE2) levels. By inhibiting this inflammatory response, topical Celecoxib treatment could ultimately be effective in preventing tumor development and progression in the skin, which is known to result from long-term UV exposure.

Temporal sequence of pulmonary cytokine gene expression in response to endotoxin in C3H/HeN endotoxin-sensitive and C3H/HeJ endotoxin-resistant mice.

Although previous studies suggested that tumor necrosis factor alpha (TNF‐α) was a critical cytokine responsible for the inflammation observed after exposure to endotoxin, other mediators may also play an important role in the regulation of systemic inflammatory responses independent of TNF‐α. The present study compared the temporal sequence of endotoxin‐induced TNF‐α, interleukin‐1α (IL‐1α), and interleukin‐10 (IL‐10) gene expression and cellular localization of cytokine proteins in pulmonary tissue of two strains of mice that have a genetically based differential sensitivity to endotoxin. Lung tissue and plasma were harvested from endotoxin‐sensitive C3H/HeN and endotoxin‐resistant C3H/HeJ micé at 15 min, 30 min, 1 h, 2 h, 4 h, 6 h, 12 h, and 24 h after intraperitoneal (i.p.) injection of 5 mg/kg endotoxin (Escherichia coli–derived lipopolysaccharide, serotype 0111:B4). There were significant elevations in both TNF‐α gene and IL‐2α expression immediately (15 min) after endotoxin injection in C3H/HeN mice. Although levels of TNF‐α mRNA in the two mouse strains were similar at 1‐2 h, the IL‐1α gene expression in pulmonary tissue isolated from endotoxin‐resistant mice was not comparable to the levels detected in C3H/HeN endotoxin‐sensitive mice at the same times. The most dramatic difference in endotoxin‐induced cytokine gene expression between the two strains of mice was in IL‐10 mRNA levels in pulmonary tissue isolated from endotoxin‐sensitive mice, compared to the lack of detectable increase in IL‐10 gene expression in C3H/HeJ endotoxin‐resistant mice above baseline at any time point examined. Quantitation of neutrophil infiltration into pulmonary tissue using immunochemical detection of CR‐1, a myeloid differentiation‐specific antibody, demonstrated that there was a significantly decreased inflammatory infiltrate in pulmonary tissue isolated from C3H/HeJ mice following endotoxin administration, which correlated with decreased levels of proinflammatory cytokine immunoreactive protein within pulmonary cells. Pulmonary cytokine synthesis and immunoreactive protein production did not directly correlate with either the magnitude or the temporal sequence of increases in plasma cytokine levels, suggesting that systemic levels of cytokines may not accurately reflect the cytokine response within the local tissue milieu. The present observations demonstrate that the differential synthesis and production of immunosuppressive cytokines as well as proinflammatory cytokines may be important variables in the determination of the extent of infiltration of inflammatory cells into the local pulmonary site in response to endotoxin and may significantly contribute to the determination of sensitivity or resistance to endotoxin in this murine model.

Inhibitory effects of pentoxifylline on ultraviolet B light–induced cutaneous inflammation

It is now recognized that ultraviolet (UV) radiation is a potent environmental insult capable of interfering with immunity to skin cancers and modifying certain immunologic reactions within both locally irradiated skin and distant, unexposed sites. Exposure to UVB light (290–320 nm) induces a potent cutaneous inflammatory response that involves the infiltration of leukocytes into the dermis as well as the production of proinflammatory cytokines by both resident epidermal keratinocytes and dermal cells. Tumor necrosis factor‐α (TNF‐α) is a proinflammatory cytokine that has been shown to be a major mediator of UVB light effects on cutaneous immunity. Recent studies have demonstrated that pentoxifylline (PTX), a xanthine‐ derived phosphodiesterase inhibitor, has the ability to inhibit synthesis of TNF‐α. To examine the effects of PTX on UVB‐mediated cutaneous inflammation, Skh/hr hairless mice were injected intraperitoneally with either phosphate‐buffered saline or 50 μg/g PTX 1 h before exposure to 2240 J/m2 UVB. Reverse transcription–polymerase chain reaction and immunohistochemical techniques were used to demonstrate that 24 h to 1 wk after UVB‐light irradiation, PTX inhibited UVB‐induced TNF‐α gene expression, inhibited the increase in epidermal TNF‐α protein synthesis, blocked the increase in epidermal proliferation observed after exposure to UVB light, and decreased production of myeloperoxidase by neutrophils infiltrating into the dermis. These studies demonstrated that PTX modifies epidermal responses after acute UVB light exposure and suggest that PTX treatment may be used clinically to modulate the deleterious effects of long‐term UVB‐light irradiation. Mol. Carcinog. 22:16–25, 1998.

Interleukin‐1α gene expression during wound healing

Interleukin‐1α is known to be constitutively produced by epidermal keratinocytes under normal conditions, and injection of this cytokine enhances wound reepithelialization. However, no studies have characterized the temporal sequence of interleukin‐1α gene expression over the time course of wound healing, and the cellular sources of this cytokine have not been identified. In the present studies, levels of interleukin‐1α messenger RNA in wound tissue isolated from SKH‐1 hairless mice were characterized and the cells that produced interleukin‐1α immunoreactive protein over a 10‐day time course of wound healing were defined. A time‐dependent upregulation in interleukin‐1α gene expression occurred immediately (4 hours) after a full‐thickness wound was made, which represented a four‐fold increase over levels of cytokine gene expression detected in nonwounded skin. Upregulation of cytokine gene expression correlated with an immediate increase in plasma interleukin‐1α levels and was followed by an increase in interleukin‐1α immunoreactive protein localized to keratinocytes within the leading edge of the wound and epidermis, as well as to neutrophils within the dermis. The rapid increase in local and systemic interleukin‐1α levels correlated with the infiltration of a significant number of neutrophils into the wound site and with the proliferation of both basal keratinocytes and dermal fibroblasts. Given the known ability of interleukin‐1α to regulate proliferation and migration of epidermal keratinocytes and to indirectly induce leukocyte chemotaxis, the results of the present studies suggest that interleukin‐1α may be an important cytokine with both local and systemic actions that are linked to the initiation of critical cellular events early in wound healing.

Inhibition of Cutaneous UV Light–induced Tumor Necrosis Factor‐α Protein Production by Allotrap 1258, a Novel Immunomodulatory Peptide

Peptides derived from the heavy chain of the HLA Class‐I molecules have been shown to modulate immune responses both in vivo and in vitro. Using a computer‐aided rational drug design approach, novel immunomodulatory peptides were designed based on peptide 2702.75–85, derived from HLA‐B2702. Several peptides were identified which had increased immunomodulatory activity, including peptides RDP1258 and its d‐isomer the peptide Allotrap 1258. The present study using Skh/hr hairless mouse skin model evaluated the in vivo effects of Allotrap 1258 on acute UVB‐induced skin inflammation. Here we demonstrate that intraperitoneal administration of Allotrap 1258 1 h prior to UV exposure resulted in significantly diminished levels of UV‐induced tumor necrosis factor (TNF)‐α protein production in the epidermis but had no effect on other parameters of the acute UV‐induced inflammatory response. By virtue of its ability to suppress TNF‐α protein production, Allotrap 1258 could prove to be an effective modulator of inflammatory responses.

Inhibition of ultraviolet light B-induced cutaneous inflammation by a specific cyclooxygenase-2 (COX-2) inhibitor

Ultraviolet B (UVB) radiation is responsible for the majority of cutaneous damage following both acute and long-term exposure, and is believed to be the most important etiologic agent in human skin cancer. UVB carcinogenesis initially induces an inflammatory response characterized by edema, dermal infiltration of leukocytes, as well as the production and release of prostaglandins, which may be critical to the observed damaging effects of UVB light on skin. Recently, a specific cyclooxygenase-2 (COX-2) inhibitor, Celecoxib, was developed, which inhibits COX-2-induced inflammation without inhibiting the cytoprotective function of cyclooxygenase-1 (COX-1). Studies have demonstrated that oral administration of Celecoxib decreased the incidence of skin and colon tumors. Recently, the process of inflammation has been linked to tumor formation. The present study examined the effects of a topical application of Celecoxib on the acute UVB-induced cutaneous inflammatory response. We show that topical Celecoxib treatment effectively reduced many parameters of UVB-mediated inflammation, including edema, dermal myeloperoxidase activity, neutrophil infiltration, and prostaglandin E2 (PGE2) levels. By inhibiting this inflammatory response, topical Celecoxib treatment could ultimately be effective in preventing tumor development and progression in the skin, which is known to result from long-term UV exposure.