Hirohiko Akamatsu

The inhibitory effects of thiopental, midazolam, and ketamine on human neutrophil functions.

We investigated the effect of thiopental, midazolam, and ketamine (at clinically relevant concentrations and at 0.1 and 10 times these concentrations) on several aspects of human neutrophil functions. The three intravenous (IV) anesthetics significantly decreased chemotaxis, phagocytosis, and reactive oxygen species (ROS) (O2-, H2 O2, OH) production of neutrophils in a dose-dependent manner. At clinically relevant concentrations, thiopental and midazolam significantly depressed these neutrophil functions. However, ketamine at the clinical plasma concentration did not impair chemotaxis or ROS production, except phagocytosis. In contrast, the three anesthetics had no effect on the levels of ROS production by a cell-free ROS generating system. In addition, intracellular calcium concentrations in neutrophils stimulated by N-formyl-L-methionyl-L-leucil-L-phenylalanine were dose-dependently decreased in the presence of each of the three anesthetics. The suppression of an increase in intracellular calcium concentrations may be responsible for the inhibition of neutrophil functions by the IV anesthetics. Implications: Neutrophils play an important role in the antibacterial host defense system and autotissue injury. We found that thiopental and midazolam (but not ketamine), at clinically relevant concentrations, impaired the neutrophil functions.

Propofol inhibits human neutrophil functions

Neutrophils play important roles in the antibacterial host defense mechanism and in the pathogenesis of tissue injury.Propofol has been reported to impair the production of reactive oxygen species from neutrophils. We examined the effect of propofol (2,6-diisopropylphenol), at clinically relevant concentrations and at 10 and 100 times this concentration, on several aspects of human neutrophil functions using an in vitro system. Propofol significantly inhibited chemotaxis, phagocytosis, and reactive oxygen species (ROS) (O2-, H2 O2, OH) production of neutrophils in a dose-dependent manner. At clinically relevant concentrations, propofol suppressed these neutrophil functions, but it did not decrease ROS generation by the cell-free (xanthine-xanthine oxidase) system. Increase in intracellular calcium concentrations in neutrophils stimulated by N-formyl-L-methionyl-L-leucyl-L-phenylalanine was dose-dependently attenuated by propofol. This decreasing effect on [Ca2+] (i) in neutrophils may represent one of the mechanisms responsible for the inhibition of neutrophil functions by propofol. Implications: Neutrophils play a pivotal role in the antibacterial host defense system and tissue injury. We found that at clinically relevant concentrations, propofol impaired neutrophil functions. Further studies may determine whether this impairment, observed in vitro, leads to clinical immunological suppression. (Anesth Analg 1998;87:695-700)

Human skin stem cells and the ageing process

In healthy individuals, skin integrity is maintained by epidermal stem cells which self-renew and generate daughter cells that undergo terminal differentiation. Despite accumulation of senescence markers in aged skin, epidermal stem cells are maintained at normal levels throughout life. Therefore, skin ageing is induced by impaired stem cell mobilisation or reduced number of stem cells able to respond to proliferative signals. In the skin, existence of several distinct stem cell populations has been reported. Genetic labelling studies detected multipotent stem cells of the hair follicle bulge to support regeneration of hair follicles but not been responsible for maintaining interfollicular epidermis, which exhibits a distinct stem cell population. Hair follicle epithelial stem cells have at least a dual function: hair follicle remodelling in daily life and epidermal regeneration whenever skin integrity is severely compromised, e.g. after burns. Bulge cells, the first adult stem cells of the hair follicle been identified, are capable of forming hair follicles, interfollicular epidermis and sebaceous glands. In addition, -- at least in murine hair follicles -- they can also give rise to non-epithelial cells, indicating a lineage-independent pluripotent character. Multipotent cells (skin-derived precursor cells) are present in human dermis; dermal stem cells represent 0.3% among human dermal foreskin fibroblasts. A resident pool of progenitor cells exists within the sebaceous gland, which is able to differentiate into both sebocytes and interfollicular epidermis. The self-renewal and multi-lineage differentiation of skin stem cells make these cells attractive for ageing process studies but also for regenerative medicine, tissue repair, gene therapy and cell-based therapy with autologous adult stem cells not only in dermatology. In addition, they provide in vitro models to study epidermal lineage selection and its role in the ageing process.

Inhibitory effect of azelaic acid on neutrophil functions: a possible cause for its efficacy in treating pathogenetically unrelated diseases

SummaryIt has been shown that acne, hyperpigmentation and lentigo malignant are more or less related pathogenetically to reactive oxygen species (ROS). It has recently been reported that azelaic acid is effective in treating these conditions and that it possesses anti-enzymatic and anti-mitochondrial activity, including cytochrome-P450 reductase and 5α-reductase in microsomal preparations with nicotinamide adenine dinucleotide phosphate (NADPH). We therefore investigated the effects of azelaic acid on human neutrophil functions, such as chemotaxis, phagocytosis and ROS generation. ROS generation in a cell-free system was also assessed. The results revealed that neutrophil chemotaxis and phagocytosis as well as ROS generated in a xanthine — xanthine-oxidase system were not significantly changed in the presence of azelaic acid. However, azelaic acid markedly decreased O2−and OH generated by neutrophils. It may be concluded that the reported clinical effectiveness of azelaic acid is partly due to its inhibitory action on neutrophil-generated ROS, leading to a reduction both in oxidative tissue injury at sites of inflammation and in melanin formation.

Establishment of grading criteria for acne severity

For the epidemiological surveys and evaluations of therapy, it is essential to evaluate the severity of diseases. There are several reported methods of assessment for acne severity including lesion counting, comparison of the patients to a photographic standard and comparison of the patients to a text description. But all of these are based on opinions of specialists. In this study, we attempted to make an evidence‐based grading criteria for acne severity, which was expected to yield consents from most dermatologists. The dermatologists consulted classified the global severity of acne patients without any standard and then counted the numbers of eruptions. Three independent expert dermatologists graded the photographs of these patients. We compared the verdicts of the consulted dermatologist and three experienced dermatologists, and analyzed the relationships between these classifications and numbers of eruptions. Our results showed that most of the dermatologists have similar latent recognitions of acne severity. We selected representative photographs as standards, which would contribute to making adjustments for judgments. Global classifications of dermatologists correlated with numbers of inflammatory eruptions (papules plus pustules), but did not with numbers of comedones. The appropriate divisions of inflammatory eruptions of half of the face to decide classifications were: 0–5, “mild”; 6–20, “moderate”; 21–50, “severe”; and more than 50, “very severe”.

The inhibition of free radical generation by human neutrophils through the synergistic effects of metronidazole with palmitoleic acid: a possible mechanism of action of metronidazole in rosacea and acne

SummaryMetronidazole is clinically effective in treating not only rosacea but also acne inflammation. Yet it is generally considered not to be very effective in inhibiting the growth of anaerobic Propionibacterium acnes. We report here our investigation into the synergistic effects of metronidazole and palmitoleic acid on the anaerobic growth of P. acnes as well as on human neutrophil functions, including the generation of reactive oxygen species (ROS). Both metronidazole and palmitoleic acid, when used alone, only slightly inhibited the growth of P. acnes, and no significant decrease in human neutrophil functions, including the generation of ROS, was observed. But metronidazole used in the presence of palmitoleic acid markedly inhibited the anaerobic growth of P. acnes and decreased ROS generation by neutrophils. However, ROS generated in the xanthine-xanthine oxidase system were not affected. Metronidazole was shown to be clinically effective by decreasing neutrophil-generated ROS at the sites of inflammation with the aid of palmitoleic acid, which is generally present in human skin. By inhibiting oxidative tissue injury under in vivo conditions, treatment with metronidazole results in remarkable improvement of rosacea and acne.

Novel mutations in GJB2 encoding connexin‐26 in Japanese patients with keratitis–ichthyosis–deafness syndrome

Summary Background Germline missense mutations in the GJB2 gene that encodes connexin‐26 (Cx26) have recently been found to be the cause of the keratitis–ichthyosis–deafness (KID) syndrome.

The Effects of Clonidine and Dexmedetomidine on Human Neutrophil Functions

UNLABELLED Neutrophil functions are inhibited by various anesthetics. Clonidine and dexmedetomidine, alpha2-agonists, are often used as adjuncts to anesthesia. Thus, we conducted the current study to determine the effect of clonidine, dexmedetomidine, and xylazine at clinically (or veterinary anesthetically) relevant concentrations (and 10 and 100 times these concentrations) on several aspects of human neutrophil functions using an in vitro system. The three alpha2-agonists had no effects on chemotaxis, phagocytosis, or superoxide anion (O2-) production of neutrophils, except that the highest concentration of clonidine inhibited chemotaxis. Increases in intracellular calcium concentrations in neutrophils stimulated by chemotaxin were not influenced by clonidine, dexmedetomidine, or xylazine. Unchanged calcium concentrations may contribute to failure to modulate the neutrophil functions. In addition, these drugs did not scavenge O2- generated by the cell-free (xanthine-xanthine oxidase) system. This is the first report concerning the effect of clonidine or dexmedetomidine on human neutrophil functions. Our findings suggest that we may not have to take extra precautions in using the alpha2-agonists in patients with infection, but that we cannot expect these drugs to be prophylaxis against autotissue injuries whose pathogenesis includes activation of neutrophils. IMPLICATIONS Neutrophils are involved in the antibacterial host defense system and autotissue injury. We found that clinically relevant concentrations of clonidine and dexmedetomidine do not affect chemotaxis, phagocytosis, or superoxide production by human neutrophils. These findings indicate that it may not be necessary to take special care in using alpha2-agonists in patients with infection, sepsis, or systemic inflammation.

Effects of a Single Exposure to UVB Radiation on the Activities and Protein Levels of Copper‐Zinc and Manganese Superoxide Dismutase in Cultured Human Keratinocytes

Abstract— Ultraviolet B irradiation has been believed to decrease or impair the activity of reactive oxygen species (ROS) scavenging enzymes such as superoxide dismutase (SOD) in the skin. It has been recently reported that two isozymes of SOD, namely copper‐zinc SOD (Cu‐Zn SOD) and manganese SOD (Mn SOD), exist in mammalian cells and that the two enzymes play different roles in living systems. The aim of this study was to investigate changes in SOD activities and protein levels in cultured human keratinocytes after acute UVB irradiation. In addition, the protein levels of Cu‐Zn SOD and Mn SOD were quantified separately. A single exposure to UVB irradiation produced an increase in SOD activity and protein level that peaked immediately after UVB irradiation, after which a decline was observed, with subsequent recovery to baseline levels 24 h after irradiation. In individual assays of Mn SOD and Cu‐Zn SOD, the amount of Mn SOD protein decreased and then gradually recovered 24 h after irradiation. In contrast, the amount of Cu‐Zn SOD protein increased immediately after UVB irradiation, and then gradually declined. To evaluate the mechanisms of these changes, we examined the effects of the cytokines, interleukin‐1α (IL‐1α) and tumor necrosis factor‐α (TNF‐α), which can be secreted from keratinocytes after UVB irradiation, on the SOD activity and protein levels in keratinocytes. Interleukin‐la and TNF‐α enhanced both the SOD activity and protein level of Mn SOD, while these cytokines had no effect on Cu‐Zn SOD protein levels in cultured human keratinocytes after incubation for 24 h. Furthermore, when neutralizing antibodies against IL‐1α and TNF‐α were added separately or together to the culture medium before UVB irradiation, the recovery of total SOD activity and Mn SOD protein level were markedly inhibited 24 h after irradiation. Our results suggest that significant increases in SOD activity and protein level occur as a cutaneous antioxidant defense mechanism that protects against the cytotoxicity as a result of UVB irradiation, and that this increase in SOD is attributed to Cu‐Zn SOD. The Cu‐Zn SOD and Mn SOD protein levels changed in a different manner after UVB irradiation. The former may participate in an early phase and the latter in a late phase defense mechanism directed against oxidant cytotoxicity through UVB irradiation. In addition, the recovery of Mn SOD to baseline levels 24 h after UVB irradiation seems to be mediated through cytokines such as IL‐1α and TNF‐α, which are secreted from keratinocytes.

Kojic acid scavenges free radicals while potentiating leukocyte functions including free radical generation

The effects of kojic acid, a compound that suppresses melanogenesis and is widely consumed in the Japanese diet with the belief that it is beneficial to health, were investigated on several aspects of leukocyte function. Kojic acid significantly decreased the levels of reactive oxygen species (ROS) (O2−), H2O2, OH) generated by neutrophil and by a cell-free ROS-generating system. In contrast, it significantly enhanced neutrophil phagocytosis and ROS generation, and lymphocyte proliferation stimulated by phytohemagglutinin. In addition, calcium concentration, [Ca2+]i in human neutrophils was increased in the presence of kojic acid. These results suggest that kojic acid is a favorable agent in terms of host defense in that it enhances a number of activities of leukocytes, but scavenges ROS excessively released from cells or generated in the tissues or blood vessels that are potentially injurious to host tissues.