Combined Treatment With H1 and H4 Receptor Antagonists Improves Th2 Inflammatory Responses in the Nasal Mucosa of Allergic Rhinitis Rats

Opportunities and challenges in the therapeutic exploitation of histamine and histamine receptor pharmacology in inflammation-driven disorders

Inflammation-driven diseases encompass a wide array of pathological conditions characterised by immune system dysregulation leading to tissue damage and dysfunction. Among the myriad of mediators involved in the regulation of inflammation, histamine has emerged as a key modulatory player. Histamine elicits its actions through four rhodopsin-like G-protein-coupled receptors (GPCRs), named chronologically in order of discovery as histamine H1, H2, H3 and H4 receptors (H1-4R). The relatively low affinity H1R and H2R play pivotal roles in mediating allergic inflammation and gastric acid secretion, respectively, whereas the high affinity H3R and H4R are primarily linked to neurotransmission and immunomodulation, respectively. Importantly, however, besides the H4R, both H1R and H2R are also crucial in driving immune responses, the H2R tending to promote yet ill-defined and unexploited suppressive, protective and/or resolving processes. The modulatory action of histamine via its receptors on inflammatory cells is described in detail. The potential therapeutic value of the most recently discovered H4R in inflammatory disorders is illustrated via a selection of preclinical models. The clinical trials with antagonists of this receptor are discussed and possible reasons for their lack of success described.

Desloratadine via its anti-inflammatory and antioxidative properties ameliorates TNBS-induced experimental colitis in rats

BACKGROUND

Intestinal mucosal immune cells, notably mast cells, are pivotal in ulcerative colitis (UC) pathophysiology. Its activation elevates tissue concentrations of histamine. Inhibiting colonic histamine release could be an effective therapeutic strategy for treating UC. Experimental model like 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats mimic human IBD, aiding treatment investigations. Drug repurposing is a promising strategy to explore new indications for established drugs. Desloratadine (DES) is second-generation antihistamine utilized for managing allergies by blocking histamine action in the body. It also has reported anti-inflammatory and antioxidant actions.

OBJECTIVE

DES was investigated for its repurposing potential in UC by preclinical screening in TNBS-induced colitis in Wistar rats.

METHODS

Therapeutic efficacy of DES was evaluated both individually and in combination with standard drug 5-aminosalicylicacid (5-ASA). Rats were orally administered DES (10 mg/kg), 5-ASA (25 mg/kg), and DES + 5-ASA (5 mg + 12.15 mg) following the induction of colitis. Parameters including disease activity score rate (DASR), colon/body weight ratio (CBWR), colon length, diameter, pH, histological injury, and scoring were evaluated. Inflammatory biomarkers such as IL-1β, TNF-α, along with reduced glutathione (GSH), and malondialdehyde (MDA) were assessed.

RESULTS

Significant protective effects of DES, especially in combination with 5-ASA, against TNBS-induced inflammation were observed as evidenced by reduced DASR, CBWR, and improved colon morphology. Drugs significantly lowered plasma and colon histamine and, cytokines levels. GSH restoration, and decreased MDA content were also observed.

CONCLUSION

DES and DES + 5-ASA demonstrated potential in alleviating colonic inflammation associated with TNBS-induced colitis in rats. The effect can be attributed to its antihistamine, anticytokine, and antioxidative properties.

Neuroimmunology and Allergic Disease

The prevalence of allergic diseases is rising globally, inducing heavy quality of life and economic burdens. Allergic reactions are mediated by the complex bi-directional cross-talk between immune and nervous systems that we are only beginning to understand. Here, we discuss our current understanding of the molecular mechanisms of how this cross-talk occurs in the skin, gut, and lungs. An improved understanding of the communication between the immune and nervous system may lead to the development of novel therapies for allergic diseases.

Characteristics of allergen profile, sensitization patterns and Allergic Rhinitis in SouthEast Asia

PURPOSE OF REVIEW

To highlight the characteristics of allergic rhinitis, local allergic rhinitis (LAR), and importance of allergens in Southeast Asian countries.

RECENT FINDINGS

The Asia-Pacific region is very diverse with disparities in the epidemiological data between countries as well as in the unmet needs. The prevalence of allergic rhinitis has markedly increased in the past decades, with a high variation between countries, ranging from 4.5--80.3%. In terms of LAR, the reported prevalence in Southeast Asia is similar to that of other Asian countries (3.7-24.9%) but lower than that in western countries. House dust mites, cockroach, pollens, and molds are major allergens that are known triggers for of allergic rhinitis in this region, whereas the association with helminth infection requires further investigation.

SUMMARY

There are gaps and high variation between countries in Southeast Asia regarding the prevalence of allergic rhinitis and LAR. Further studies are needed to fully elucidate the association between allergens and allergic rhinitis in Southeast Asia.