Monoterpenes as therapeutic candidates to induce fetal hemoglobin synthesis and up-regulation of gamma-globin gene: An in vitro and in vivo investigation.

Pharmacologically induced production of fetal hemoglobin (HbF) is a pragmatic therapeutic strategy for the reduction of globin chain imbalance and improving the clinical severities of patients with β-hemoglobinopathies. To identify highly desirable new therapeutic HbF-inducing agents, we screened functionally diverse ten monoterpenes, as molecular entities for their potent induction and erythroid differentiation ability in human erythroleukemia cell line (K562) and transgenic mice. Benzidine hemoglobin staining demonstrated six compounds to have significantly induced erythroid differentiation of K562 cells in a dose and time-dependent manner. This induction paralleled well with the optimal accumulated quantity of total hemoglobin in treated cultures. The cytotoxic studies revealed that three (carvacrol, 3-carene, and 1,4-cineole) of the six compounds with their maximal erythroid expansion ability did not affect cell proliferation and were found non-toxic. Four compounds were found to have high potency, with 4-8-fold induction of HbF at both transcriptional and protein levels in vitro. Subsequently, an in vivo study with the three active non-cytotoxic compounds showed significant overexpression of the γ-globin gene and HbF production. Carvacrol emerged as a lead HbF regulator suggested by the increase in expression of γ-globin mRNA content (5.762 ± 0.54-fold in K562 cells and 5.59 ± 0.20-fold increase in transgenic mice), accompanied by an increase in fetal hemoglobin (F-cells) levels (83.47% in K562 cells and 79.6% in mice model). This study implicates monoterpenes as new HbF inducing candidates but warrants mechanistic elucidation to develop them into potential therapeutic drugs in β-thalassemia and sickle cell anemia.