Different photoinactivation mechanisms in Propionibacterium acnes for near-ultraviolet and visible light

Light as a Broad-Spectrum Antimicrobial

Antimicrobial resistance is a significant and growing concern. To continue to treat even simple infections, there is a pressing need for new alternative and complementary approaches to antimicrobial therapy. One possible addition to the current range of treatments is the use of narrow-wavelength light as an antimicrobial, which has been shown to eliminate a range of common pathogens. Much progress has already been made with blue light but the potential of other regions of the electromagnetic spectrum is largely unexplored. In order that the approach can be fully and most effectively realized, further research is also required into the effects of energy dose, the harmful and beneficial impacts of light on eukaryotic tissues, and the role of oxygen in eliciting microbial toxicity. These and other topics are discussed within this perspective.

Energy-Based Devices in Treatment of Acne Vulgaris

BACKGROUND

Acne vulgaris is a chronic dermatologic complaint with a multifactorial cause. Traditionally, antibiotics and retinoids have been used to manage the condition; patient compliance has been an ongoing issue. A variety of energy-based devices have been reported to be effective in the treatment of acne vulgaris.

OBJECTIVE

To review and summarize the current literature specific to treatment of acne vulgaris with energy-based devices.

METHODS

A review of the current literature of energy-based devices used for the treatment of acne vulgaris.

RESULTS AND CONCLUSIONS

Although limited randomized controlled trials for the treatment of acne have been performed, significant clinical improvement of acne vulgaris, especially of inflammatory lesions, has been demonstrated with a variety of energy-based devices. Newer approaches may lead to even better results.

Efficacy of Intense Pulsed Light Therapy in the Treatment of Facial Acne Vulgaris: Comparison of Two Different Fluences

BACKGROUND

Acne vulgaris is the most common disease of the skin affecting adolescents and young adults causing psychological distress. The combination of antibiotic resistance, adverse effects of topical and systemic anti acne medications and desire for high tech approaches have all led to new enthusiasm for light based acne treatment. Intense pulse light (IPL) therapy has three modes of action in acne vulgaris i.e., photochemical, photo thermal and photo immunological.

AIMS

(1) to study efficacy of IPL therapy in facial acne vulgaris. (2) To compare two fluences - one normal and other subnormal on right and left side of face respectively.

METHODS

(Including settings and design and statistical analysis used). Total 45 patients in age group 16 to 28 years with inflammatory facial acne vulgaris were included in prospective study. Baseline data for each patient was recorded. All patients were given 4 sittings of IPL at 2 weeks interval and were followed for 2 months every 2 weeks. Fluence used was 35J/cm(2) on right and 20J/cm(2) on left side. Percentage reduction in lesion count was calculated at each sitting and follow up and graded as mild (0-25%), moderate (26-50%), good (51-75%) and excellent (76-100%). Side effects were noted. The results were analysed using Mann-Whitney Test.

RESULTS

On right side, excellent results were achieved in 10(22%), good in 22(49%) and moderate in 13(29%) patients. On left side excellent were results achieved in 7(15%), good in 19(42%) and moderate in 16(43%) patients. There was no statically significant difference noted in efficacy of two fluences used in treatment of facial acne vulgaris.

CONCLUSIONS

IPL is a effective and safe option for inflammatory acne vulgaris with minimal reversible side effects. Subnormal fluence is as effective as normal fluence in Indian skin.

Efficacy of Red or Infrared Light-Emitting Diodes in a Mouse Model of Propionibacterium acnes-Induced Inflammation

Background

Laser/light-based devices may provide an alternative to conventional acne therapeutics in some patients with nonresponsive acne.

Objective

We investigated the efficacy of red or infrared light-emitting diode (LED) devices in a mouse model of Propionibacterium acnes-induced inflammation through clinical examination and histopathological and immunohistochemical studies.

Methods

A human-derived Propionibacterium acnes suspension (10⁹ colony-forming units /µl) was injected into the back of an HR-1 mouse. Then, a 28.9 J/cm² 650-nm red LED or 9.3 J/cm² 830-nm infrared LED was applied to the mouse with P. acnes-induced inflammation once daily for 2 weeks. Two weeks after treatment, histological findings with hematoxylin and eosin staining and expression levels of inflammatory biomarkers (integrin α6, neutrophils, interleukin [IL]-1β, and matrix metalloproteinase [MMP]-2/9) were evaluated in tissue specimens using immunohistochemical staining.

Results

Mice treated with red and infrared LED showed clinical improvement in inflammatory nodules compared to mice in the control group. Red LED was much more effective than infrared LED. Epidermal hyperplasia, comedone-like cysts, and integrin α6 expression improved to a similar extent in the red and infrared LED treatment groups and control group. Neutrophil, IL-1β, MMP-2, and MMP-9 expression after treatment with red and infrared LED decreased considerably compared to expression in the control group.

Conclusion

In a mouse model of P. acnes-induced inflammatory nodules, red and infrared LED devices may be an alternative to conventional acne therapies. In addition, a mouse model of P. acnes-induced inflammatory nodules is helpful for laboratory research of acne.

Intense pulsed light versus photodynamic therapy using liposomal methylene blue gel for the treatment of truncal acne vulgaris: a comparative randomized split body study

Acne vulgaris is an extremely common skin condition. It often leads to negative psychological consequences. Photodynamic therapy (PDT) using intense pulsed light has been introduced for effective treatment of acne. The objective was to study the effect of PDT in truncal acne vulgaris using liposomal methylene blue (LMB) versus IPL alone. Thirty-five patients with varying degrees of acne were treated with topical 0.1 % LMB hydrogel applied on the randomly selected one side of the back, and after 60 min the entire back was exposed to IPL. The procedure was done once weekly for three sessions and patients were re-evaluated 1 month after the third session by two independent dermatologists. Acne severity was graded using the Burton scale. Patient satisfaction using Cardiff Acne Disability Index (CADI) was recorded before and after treatment. On LMB-pretreated side, inflammatory acne lesion counts were significantly decreased by 56.40 % compared with 34.06 % on IPL alone. Marked improvement was seen on LMB-pretreated side in 11.5 % of patients compared with 2.8 % on IPL alone. There was a correlation between CADI score and overall improvement. Our study concluded that LMB-IPL is more effective than IPL alone, safe with tolerable pain in the treatment of acne vulgaris on the back. LMB-IPL is more effective than IPL alone, safe with tolerable pain in the treatment of acne vulgaris on the back.

The response of human skin commensal bacteria as a reflection of UV radiation: UV-B decreases porphyrin production

Recent global radiation fears reflect the urgent need for a new modality that can simply determine if people are in a radiation risk of developing cancer and other illnesses. Ultraviolet (UV) radiation has been thought to be the major risk factor for most skin cancers. Although various biomarkers derived from the responses of human cells have been revealed, detection of these biomarkers is cumbersome, probably requires taking live human tissues, and varies significantly depending on human immune status. Here we hypothesize that the reaction of Propionibacterium acnes (P. acnes), a human resident skin commensal, to UV radiation can serve as early surrogate markers for radiation risk because the bacteria are immediately responsive to radiation. In addition, the bacteria can be readily accessible and exposed to the same field of radiation as human body. To test our hypothesis, P. acnes was exposed to UV-B radiation. The production of porphyrins in P. acnes was significantly reduced with increasing doses of UV-B. The porphyrin reduction can be detected in both P. acnes and human skin bacterial isolates. Exposure of UV-B to P. acnes- inoculated mice led to a significant decrease in porphyrin production in a single colony of P. acnes and simultaneously induced the formation of cyclobutane pyrimidine dimers (CPD) in the epidermal layers of mouse skin. Mass spectrometric analysis via a linear trap quadrupole (LTQ)-Orbitrap XL showed that five peptides including an internal peptide (THLPTGIVVSCQNER) of a peptide chain release factor 2 (RF2) were oxidized by UV-B. Seven peptides including three internal peptides of 60 kDa chaperonin 1 were de-oxidized by UV-B. When compared to UV-B, gamma radiation also decreased the porphyrin production of P. acnes in a dose-dependent manner, but induced a different signature of protein oxidation/de-oxidation. We highlight that uncovering response of skin microbiome to radiation will facilitate the development of pre-symptomatic diagnosis of radiation risk in a battlefield exposure, nuclear accidents, terrorist attacks, or cancer imaging/therapy.

The role of pulsed light and heat energy (LHETM) in acne clearance

BACKGROUND

Propionibacterium acnes synthesize and store a large amount of porphyrins. Once the porphyrin is exposed to visible light it becomes chemically active and transfers to an excited state, resulting in the formation of singlet oxygen, which combines with cell membranes to destroy the P. acnes. This process is dependent on the rate of production of excited porphyrin molecules, which is influenced by the concentration of porphyrins, the concentration of photons, the temperature, and the wavelength of the photons.

METHODS

Nineteen patients with mild to moderate acne underwent bi-weekly treatments for 4 weeks using the ClearTouch system. During each treatment, pulses of light and heat were applied. Each pulse used an average energy density of 3.5 J/cm(2), a pulse width of 35 ms, and a wavelength between 430 and 1100 nm.

RESULTS

At the end of the eighth treatment, acne clearance for the non-inflammatory and inflammatory lesions was 63 +/- 21% and 50 +/- 32%, respectively. One month after the last treatment, the acne clearance for non-inflammatory and inflammatory lesions was 79 +/- 22% and 74 +/- 20%, respectively, with further improvement in acne clearance at 2 months after the last treatment (85 +/- 17% and 87 +/- 25%, respectively).

CONCLUSION

ClearTouch pulsed light and heat energy (LHE) technology is effective and safe for the treatment of acne vulgaris.

Optical treatments for acne

Light-based treatments for acne are becoming increasingly commonplace in dermatology. This article reviews various light approaches in acne therapy. Methods are discussed from an anatomical and a functional perspective. The emphasis is on the practicality of treatment as well as the pros and cons of various devices. Also, a review of the recent literature is presented. The article is intended to give the reader a panoramic view of this still-young and developing area. Most likely, light-based acne treatment will receive more popularity as dermatologists learn how to integrate this type of therapy within the context of more established drug agents.

The temperature dependence of porphyrin production in Propionibacterium acnes after incubation with 5-aminolevulinic acid (ALA) and its methyl ester (m-ALA)

Topical PDT treatment of the common skin disease acne vulgaris is now in clinical use. Propionibacterium acnes (P. acnes) is known to play an important role in acne. 5-Aminolevulinic acid (ALA) supplementation leads to an enhanced porphyrin production in the bacteria. Subsequent illumination with light of the proper wavelengths can reduce the number of bacteria and this might at least partly explain the PDT effect on acne. We have assessed the effects of temperature on P. acnes washed cell suspensions incubated for 4 h with ALA or ALA methyl ester (m-ALA). The effect on porphyrin production of both the cell suspension incubation temperature as well as the initial growth temperature of the cultivated cells prior to harvesting and use in suspension experiments was investigated. The bacterial porphyrin content was estimated from fluorescence emission spectra. It was found that incubation with ALA or m-ALA at a temperature 42 degrees C resulted in an approx. 100% and 33% increase in the total amount of PDT-relevant porphyrins produced as compared to incubation at 37 degrees C. These results support increasing the skin temperature during incubation with ALA or m-ALA in the clinic. The initial growth temperature, prior to the incubation, had no apparent effect on the ALA or m-ALA induced porphyrins. Activation energy studies indicate slightly higher temperature dependence in the case of ALA produced porphyrins as compared to m-ALA produced porphyrins (77 and 65 kJ mol(-1), respectively).

Light Therapy in the Treatment of Acne Vulgaris

BACKGROUND

Over the past decade, lasers and light-based systems have become a common modality to treat a wide variety of skin-related conditions, including acne vulgaris. In spite of the various oral and topical treatments available for the treatment of acne, many patients fail to respond adequately or may develop side effects. Therefore, there is a growing demand by patients for a fast, safe, and side-effect-free novel therapy.

OBJECTIVES

To address the role of light therapy in the armamentarium of treatments for acne vulgaris, to discuss photobiology aspects and biomedical optics, to review current technologies of laser/light-based devices, to review the clinical experience and results, and to outline clinical guidelines and treatment considerations.

RESULTS

Clinical trials show that 85% of the patients demonstrate a significant quantitative reduction in at least 50% of the lesions after four biweekly treatments. In approximately 20% of the cases, acne eradication may reach 90%. At 3 months after the last treatment, clearance is approximately 70% to 80%. The nonrespondent rate is 15% to 20%.

CONCLUSIONS

Laser and light-based therapy is a safe and effective modality for the treatment of mild to moderate inflammatory acne vulgaris. Amelioration of acne by light therapy, although comparable to the effects of oral antibiotics, offers faster resolution and fewer side effects and leads to patient satisfaction.

Porphyrin sensitization and intracellular calcium changes in the prokaryote Propionibacterium acnes

Photosensitization induces intracellular free calcium changes ([Ca2+]i) in some eukaryotic cell systems which either contribute to or protect against cell inactivation. We have investigated whether or not similar changes can be induced in prokaryotes. The skin bacterium Propionibacterium acnes was sensitized using protoporphyrin IX (PP IX) or 5-aminolevulinic acid (ALA). Exogenous ALA resulted in either a preferential accumulation of protoporphyrin (ALA-PP) or of coproporphyrin and/or uroporphyrin (ALA-CP/UP) in P. acnes. For PP IX or ALA-PP sensitization, exposure to broad-band red light resulted in an increase in [Ca2+]i. For ALA-PP sensitization, this increase was transient and [Ca2+]i returned to basal levels within 5-10 min after irradiation. However, the elevated [Ca2+]i levels obtained after PP IX sensitization were maintained for at least 1 h after irradiation. In both cases, the reduction in the external calcium concentration led to an enhancement in the cell survival, indicating that induced [Ca2+]i changes may participate in photoinactivation. Sensitization by hydrophilic coproporphyrin and/or uroporphyrin (ALA-CP/UP) did not affect the [Ca2+]i levels, but higher levels of cell inactivation were obtained. It therefore appears that damage to membrane-associated components is at least partly responsible for [Ca2+]i alterations after photosensitization.

Intracellular pH changes induced in Propionibacterium acnes by UVA radiation and blue light

The intracellular pH changes induced in the Gram-positive skin bacterium Propionibacterium acnes by blue light and UVA radiation were studied. Two methods (31P nuclear magnetic resonance (NRM) spectroscopy and fluorescence spectroscopy using a pH-sensitive fluoroprobe (2',7'-bis-(2-carboxyethyl)-5-(and -6-)-carboxyfluorescein)) were used to determine the intracellular pH. The pH changes induced by irradiation were found to be a function of cell survival. These changes as a function of cell survival followed the same pattern for blue light and UVA radiation. A reduction of the pH gradient across the cell membrane (inside alkaline) was found for lethal doses (less than 15% survival). This reduction corresponded to a decrease in intracellular pH and may indicate a proton influx. An increase in the pH gradient, which corresponded to an increase in the intracellular pH, was observed for sublethal doses. This increase appears to be reversible. Thus two separate mechanisms, which appear to be the same in UVA and blue light regions, may be responsible for the irradiation-induced pH alterations.

The microaerophily and photosensitivity of Propionibacterium acnes

The effect of oxygen on the in vitro propagation of Propionibacterium acnes was investigated under defined culture conditions. This micro-organism is the predominant bacterial resident within the pilosebaceous follicles of sebum-rich areas of human skin. The organism was grown in continuous culture in defined synthetic medium with glucose as the main carbon-energy source at various air saturation concentrations and in the presence and absence of light. Steady state continuous cultures were achieved at very low oxygen tensions in the presence of light, and at higher levels of oxygen when non-illuminated. Culture biomass yields were higher than those of anaerobic cultures. Bacterial cells were inactivated in the presence of light at high oxygen concentrations because of photosensitization reactions involving excess oxygen and microbial porphyrin species.

Near-UV-induced radicals in Propionibacterium acnes, studied by electron spin resonance spectrometry at 77 K

Suspensions of Propionibacterium acnes were UV irradiated and the induced radicals were measured at 77 K by electron spin resonance (ESR) spectrometry. Two types of radical were formed during irradiation and stabilized in the frozen suspensions. The relative yield of each radical was studied as a function of irradiation wavelength. The first radical, which was a singlet with a peak-to-peak width of 20 G, was insensitive to the deoxygenation of the samples and to the exchange of solvent water by heavy water. The action spectrum was similar to the absorption spectrum of NADPH. The second type of radical was not formed in deoxygenated samples and the shape of the ESR spectrum was characteristic of the superoxide radical. This radical was only formed at wavelengths below 340 nm.