Depressant effects of ambroxol on lipopolysaccharide- or fMLP-stimulated free radical production and granule enzyme release by alveolar macrophages

Ambroxol reduces LPS toxicity mediated by induction of alkaline phosphatases in rat lung

Alkaline phosphatases (APs) have been suggested to detoxify lipopolysaccharide (LPS) by dephosphorylation. Ambroxol, a bronchial expectorant, is known to accelerate the secretion of pulmonary surfactant particles including AP molecules as a pharmacological action. In the present study, some beneficial effects of ambroxol on LPS toxicity in the rat lung were investigated. In an experiment using the rat lung organ culture, AP activities were enhanced in a time-dependent manner by incubation with 25 microM of ambroxol in both the tissue and the medium. Western blot analysis indicated that AP activity was elevated by the treatment with ambroxol, due to the induction of surfactant proteins (SPs) and AP molecules. In the in vivo experiment, the serum LPS content was markedly increased after LPS administration to rats by intratracheal instillation of 20 mg/kg. However, when the rats were pretreated with oral ambroxol (1.0 mg/kg) at 1 h before LPS challenge, the area under the concentration--time curve (AUC) of serum LPS was significantly decreased. These results suggest that ambroxol inhibits the translocation of LPS from the lung into the circulation as well as its detoxification effect via the elevation of AP activity. Bromhexine, another expectorant, is less effective than ambroxol as an LPS detoxificant. Maintenance of high AP activity level in the lung suggests APs to have physiological significant effects against the inflammatory events induced by LPS.

Depressant effects of ambroxol and erdosteine on cytokine synthesis, granule enzyme release, and free radical production in rat alveolar macrophages activated by lipopolysaccharide

The present study examined the effects of ambroxol and erdosteine, bronchial expectorants, on the cytokine synthesis, granule enzyme release, and free radical production in rat alveolar macrophages activated by lipopolysaccharide. Ambroxol and erdosteine significantly decreased the production of tumour necrosis factors-alpha, interleukin-1beta, and interleukin-6 in alveolar macrophages activated by lipopolysaccharide. These drugs significantly reduced the production of superoxide anion, hydrogen peroxide, and nitric oxide and the release of acid phosphatase and lysozyme in lipopolysaccharide-activated macrophages. Ambroxol and erdosteine showed no scavenging effect on superoxide anion and hydrogen peroxide, whereas both drugs effectively decomposed nitric oxide. The results show that ambroxol and erdosteine may inhibit the responses, including cytokine synthesis and free radical production, in rat alveolar macrophages activated by lipopolysaccharide. Unlike the production of reactive oxygen species, the inhibitory effect of ambroxol and erdosteine on the production of nitric oxide in lipopolysaccharide-activated alveolar macrophages may be accomplished by a scavenging action on the species and inhibition of the respiratory burst.

Ambroxol inhibits platelet-derived growth factor production in human monocytic cells

Several growth factors, including platelet-derived growth factor (PDGF), have been implicated in the mechanism of lung and airway remodeling. We investigated the effect of ambroxol, trans-4-[(2-amino-3,5-dibromobenzyl) amino] cyclohexanol hydrochloride, on the lipopolysaccharide-induced PDGF production in human monocytic cells, THP-1. Ambroxol inhibited the lipopolysaccharide-induced PDGF-AB production via PDGF-A mRNA expression. Lipopolysaccharide activated p44/42 extracellular signal-regulated kinase (ERK), and ambroxol attenuated the lipopolysaccharide-induced p44/42 ERK activation. Furthermore, mitogen-activated protein kinase kinase (MEK)-1-specific inhibitor, 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one (PD 98059), blocked the lipopolysaccharide-induced p44/42 ERK activation and PDGF production. These findings indicate that ambroxol inhibits the lipopolysaccharide-induced PDGF production due to the suppression of p44/42 ERK activity.

Depressant effect of ambroxol on stimulated functional responses and cell death in rat alveolar macrophages exposed to silica in vitro

The present study examined the effect of ambroxol on free radical production, granule enzyme release, and cell death in silica-activated rat alveolar macrophages. The action of ambroxol was assayed by measuring changes in the activities of protein kinase C (PKC) and tyrosine kinase (PTK) and in the intracellular calcium level. Ambroxol attenuated the production of superoxide, hydrogen peroxide, and nitric oxide and the release of acid phosphatase and lysozyme in macrophages activated by silica. Staurosporine, genistein, EGTA, and trifluoperazine inhibited the silica-induced free radical production and granule enzyme release. Silica induced the increase in PKC and PTK activities and the elevation of intracellular calcium level in macrophages, which was decreased by ambroxol. Silica induced a cell death and increased the caspase-3 activity in macrophages in a concentration-dependent manner. Ambroxol decreased the silica-induced cell viability loss in macrophages. The results show that ambroxol decreases the stimulated responses and cell death in rat alveolar macrophages exposed to silica, which may be accomplished by inhibition of activation processes, protein kinases, and calcium transport. The inhibitory effect of ambroxol on silica-induced cell death appears to provide the protective effect on pulmonary tissues against the toxic action of silica.

Differential regulation of protein tyrosine kinase on free radical production, granule enzyme release, and cytokine synthesis by activated murine peritoneal macrophages

The present study examined the regulatory effect of tyrosine kinase inhibitors (genistein, tyrphostin, and 2,5-dihydroxycinnamate) on the free radical production, granule enzyme release, and synthesis of interleukin (IL)-8 and granulocyte macrophage-colony stimulating factor (GM-CSF) in murine peritoneal macrophages exposed to different stimulators [10 ng/mL of IL-1, 1 microgram/mL of lipopolysaccharide (LPS), and 1 microM N-formyl-methionyl-leucyl-phenylalanine (fMLP)]. Protein tyrosine kinase (PTK) inhibitors attenuated the stimulated superoxide, hydrogen peroxide, and nitric oxide production in macrophages stimulated with IL-1, LPS, or fMLP. N,N-Dimethylsphingosine (DMS) alone stimulated superoxide and hydrogen peroxide production by intact macrophages, but at 45 microM the stimulatory effect on superoxide production was not found. In contrast, DMS attenuated nitric oxide production by macrophages. High concentrations of DMS, tyrphostin, and 2,5-dihydroxycinnamate showed cytotoxic effects. PTK inhibitors did not exhibit a significant effect on granule enzyme release induced by IL-1, whereas they attenuated the effect of LPS and fMLP on degranulation. Genistein and tyrphostin decreased the production of IL-8 and GM-CSF in macrophages activated by IL-1, whereas 2,5-dihydroxycinnamate did not affect it. The results suggest that tyrosine kinases exposed to IL-1, LPS, and fMLP may exert different modulatory actions on macrophage responses. The IL-1-activated macrophage responses, particularly degranulation, appear to be differently regulated by tyrosine kinases compared with the responses activated by LPS and fMLP.

Ambroxol as an inhibitor of nitric oxide-dependent activation of soluble guanylate cyclase

The influence of ambroxol on the activity of human platelet soluble guanylate cyclase and rat lung soluble guanylate cyclase was investigated. Ambroxol in the concentration range from 0.1 to 10 microM had no effect on the basal activity of both enzymes and slightly enhanced it at 50 and 100 microM. Ambroxol inhibited in a concentration-dependent manner the sodium nitroprusside-induced activation of both enzymes. The IC(50) values for inhibition by ambroxol of sodium nitroprusside-stimulated human platelet soluble guanylate cyclase and rat lung soluble guanylate cyclase were 3.9 and 2.1 microM, respectively. Ambroxol did not influence the stimulation of soluble guanylate cyclase by protoporphyrin 1X. Thus, it is possible that the molecular mechanism of the therapeutic action of ambroxol involves the inhibition of nitric oxide (NO)-dependent activation of soluble guanylate cyclase.