Platinum and palladium nanoparticle-containing mixture, PAPLAL, does not induce palladium allergy

The Antioxidant PAPLAL Protects against Allergic Contact Dermatitis in Experimental Models

PAPLAL, a mixture of platinum (nPt) and palladium (nPd) nanoparticles, is widely used as a topical agent because of its strong antioxidant activity. Allergic contact dermatitis (ACD) is one of the most common occupational skin diseases worldwide. However, the role of oxidative stress in ACD remains unclear. In the present study, we investigated the protective effects of topical PAPLAL treatment on 2,4-dinitrofluorobenzene (DNFB)-induced ACD. DNFB treatment increased 8-isoprostane content; upregulated Xdh, Nox2, and Nox4, pro-oxidant genes; and downregulated Sod1, an antioxidant gene, indicating oxidative damage in the ear skin. PAPLAL therapy significantly reduced ear thickness associated with the downregulation of inflammatory cytokine-related genes. PAPLAL also significantly increased the expression of the stress-response-related genes Ahr and Nrf2, as well as their target genes, but failed to alter the expression of redox-related genes. Furthermore, Sod1 loss worsened ACD pathologies in the ear. These results strongly suggest that PAPLAL protects against ACD through its antioxidant activity and activation of the AHR and NRF2 axes. The antioxidant PAPLAL can be used as a novel topical therapy for ACD that targets oxidative stress.

Systemic allergic contact dermatitis to palladium, platinum, and titanium: mechanisms, clinical manifestations, prevalence, and therapeutic approaches

Contact dermatitis (CD) is an inflammatory skin disease of eczema that is elicited by chemicals or metal ions that have toxic effects without eliciting a T-cell response (contact elicitation) or by small reactive chemicals that modify proteins and induce innate and adaptive immune responses (contact allergens). The clinical condition is characterized by localized skin rash, pruritus, redness, swelling, and lesions, which are mainly detected by patch tests and lymphocyte stimulation. Heavy metals such as palladium (Pd), platinum (Pt), and titanium (Ti) are ubiquitous in our environment. These heavy metals have shown CD effects as allergic agents. Immunological responses result from the interaction of cytokines and T cells. Occupational metal CD accounts for most cases of work-related cutaneous disorders. In this systematic review, the allergic effects of heavy metals, including Pd, Pt, and Ti, and the mechanisms, clinical manifestations, prevalence, and therapeutic approaches are discussed in detail. Furthermore, the therapeutic approaches introduced to treat CD, including corticosteroids, topical calcineurin inhibitors, systemic immunosuppressive agents, phototherapy, and antihistamines, can be effective in the treatment of these diseases in the future. Ultimately, the insights identified could lead to improved therapeutic and diagnostic pathways.

Two palladium (II) complexes derived from halogen-substituted Schiff bases and 2-picolylamine induce parthanatos-type cell death in sensitive and multi-drug resistant CCRF-CEM leukemia cells

The use of cisplatin and its derivatives in cancer treatment triggered the interest in metal-containing complexes as potential novel anticancer agents. Palladium (II)-based complexes have been synthesized in recent years with promising antitumor activity. Previously, we described the synthesis and cytotoxicity of palladium (II) complexes containing halogen-substituted Schiff bases and 2-picolylamine. Here, we selected two palladium (II) complexes with double chlorine-substitution or double iodine-substitution that displayed the best cytotoxicity in drug-sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells for further biological investigation. Surprisingly, these compounds did not significantly induce apoptotic cell death. This study aims to reveal the major mode of cell death of these two palladium (II) complexes. We performed annexin V-FITC/PI staining and flow cytometric mitochondrial membrane potential measurement followed by western blotting, immunofluorescence microscopy, and alkaline single cell electrophoresis (comet assay). J4 and J6 still induced neither apoptosis nor necrosis in both leukemia cell lines. They also insufficiently induced autophagy as evidenced by Beclin and p62 detection in western blotting. Interestingly, J4 and J6 induced a novel mode of cell death (parthanatos) as mainly demonstrated in CCRF-CEM cells by hyper-activation of poly(ADP-ribose) polymerase 1 (PARP) and poly(ADP-ribose) (PAR) using western blotting, flow cytometric measurement of mitochondrial membrane potential collapse, nuclear translocation of apoptosis-inducing factor (AIF) by immunofluorescence microscopy, and DNA damage by alkaline single cell electrophoresis (comet assay). AIF translocation was also observed in CEM/ADR5000 cells. Thus, parthanatos was the predominant mode of cell death induced by J4 and J6, which explains the high cytotoxicity in CCRF-CEM and CEM/ADR5000 cells. J4 and J6 may be interesting drug candidates and deserve further investigations to overcome resistance of tumors against apoptosis. This study will promote the design of further novel palladium (II)-based complexes as chemotherapeutic agents.

Citrate-Coated Platinum Nanoparticles Exhibit a Primary Particle-Size Dependent Effect on Stimulating Melanogenesis in Human Melanocytes

Hypopigmentation disorders due to an underproduction of the pigment melanin by melanocytes cause uneven skin coloration, while in hair follicles they cause grey hair. There is a need for novel materials which can stimulate melanogenesis in the skin and hair for personal care use. While titanium dioxide, gold and silver nanoparticles have been extensively used for applications in cosmetic and personal-care products (PCP), the use of relatively inert platinum nanoparticles (PtNPs) has remained underappreciated. PtNPs have been reported to be a mimetic of the enzyme catechol oxidase with small size PtNPs reported to exhibit a higher catechol oxidase activity in a cell-free system, but no testing has been conducted in melanocytes to date. Herein, we have investigated if PtNPs of two sizes (SPtNP: 5 nm; LPtNP: 50 nm) might have an effect on melanogenesis. To this end, we have used MNT-1 human melanoma cells and primary human melanocytes from moderately-pigmented skin (HEMn-MP). Both SPtNP and LPtNP were nontoxic over a concentration range 6.25–25 μg/mL, hence these concentrations were used in further experiments. Both PtNPs stimulated higher extracellular melanin levels than control; SPtNP at concentrations 12.5 and 25 μg/mL significantly stimulated higher levels of extracellular melanin as compared to similar concentrations of LPtNP in MNT-1 cells, in the absence of ROS generation. The effects of PtNPs on melanin secretion were reversible upon removal of PtNPs from the culture medium. The results of primary particle size-specific augmentation of extracellular melanin by SPtNPs were also validated in HEMn-MP cells. Our results thus provide a proof-of-principle that SPtNP might hold potential as a candidate for the treatment of white skin patches, for sunless skin-tanning and for use in anti-greying hair products in cosmetics.